: Moron Asks: Timing and Fuel Economy?

04-29-05, 09:11 PM
Okay, well, um. Most of you know I love to complain, right? This isn't so much a complaint as an outline of my situation and some questions. Searching the forum has helped a bit but I need someone who can explain things to the three-year-old inside those of us who lack mechanical knowledge or potty training. (I'll get the hang of it...so far I just haven't WANTED to!)

I bought my 1989 Brougham from a local, trusted, high-school-friend-of-my-dad's used collector car dealer. He bought this car for himself to use during the months his camper would be mounted to his pickup. He never did put the camper on his truck so the car just sat there and he decided to sell it. That's his story.

I bought it for $3500, a good price for a car in showroom condition. After a week or so, I had to replace a "universal lockup solenoid." $40 because I didn't have to pay for labor. This was done at a reputable tranny shop. It was shifting harshly, shifting late, pulling the engine down at stop lights. Solenoid replaced--problem solved. Everything was fine until my Check Engine light came on a week later, after having an alarm installed. My MPG went from 15 around town to 9. It went to my dad's mechanic, in the biz since '68 and he works on classic cars. The ALDL port wasn't working, I verified this myself before. He works on it for a couple hours and discovers that the ECM seems to have been disconnected in a deliberate manner; he says, "It looks like the damned thing was never even hooked up in the first place! How the heck have you been driving around with it like that?" I shrug, not knowing the answer myself. $235. Two other mechanics seemed to have missed this, or didn't think to look for it.

So the computer was fixed and I drove on my merry way. I began to notice that my lockup solenoid was acting up a bit, again. At stops, it lugs down and lurches a bit. After a tank of gas, I found my MPG hadn't increased at all. I took it back in and he, for the low-low hourly rate of nearly $80, adjusted my timing and some voltage or something-or-other and my carb. He adjusted the timing from 16 degrees (where it's been since I bought the thing, I guess) down to the factory 10 degrees. I immediately notice a substantial loss of power during accelleration; so substantial as to make driving it a concern. On the one hand, I can now burn 87 octane gas, which was my goal...along with the hope of reaching the 15 MPG rating I had before.

SO, one of my questions is: now that the timing is at 10 degrees, should my MPG increase? What of this substantial and potentially dangerous lack of power during upshifts? Could THAT be related to the solenoid?

Remember, the first solenoid replacement was done without the ECM connected. Could having the ECM connected after the fact have caused the solenoid to malfunction? The tranny shop will replace it for free on Monday. I won't tell them about the ECM. Or is it more likely that the ECM is malfunctioning and causing the solenoid to lock-up at the wrong times? Could that be why the ECM was disconnected in the first place, to bypass this problem?

And what of running it at 10 degrees? Will this really improve fuel economy? Is the horrible loss of power permanent? Would adjusting it to 12 degrees make enough of a difference?

What say you? You all seem to have much more experience than I do. I've relied on this group a lot, that much is obvious. LOL Anything anyone has to contribute is very welcome. It's to the point now where if I have to keep sinking a few hundred here and there into this car, I'll sell it and cut my losses. I'd hate to do that, though...

04-29-05, 11:17 PM
Highest timing doesn't always mean best efficiency. Althought on many engines it does.

Jim Hand's 455 Pontiac runs around 28-30 degrees timing and runs low 11's. My 400 in my T/A has such low compression I can run 30 degrees INITIAL and 55-60 total!! Similar heads, but very different cams and pistons.

Often a bump up in timing does bring in some more power. The timing is set rather conservative based on fuel quality, ambient air temps, engine temperature, barometric pressure, etc. You can often increase timing some and increase your octane to make use of it.

As for getting 9 mpg, that sounds like there is something else wrong. My 1980 T/A with a 70 455 got 11 mpg city and 16 highway. That with 10:1 compression and a crappy running QJet (Carter made, alum in bad shape) that would overflow the fuel on the carb when you got higher in the revs.

I would look at other things. I have found that the settings on the E4MC Q-Jet on the CCC cars (your 89 Brougham is a CCC car) are cruicial to proper operation. This QJet is an excellent peice provides great drivablility and fuel economy. You should be seeing more like 16 city and 24 highway on that car as long as you keep your foot out of it.

Checking that timing is set properly, spark plugs are ok, wires ok, cap, rotor and carbon button are in good shape.

04-29-05, 11:57 PM
That's just it, I have no idea what the timing should be. My guy says 10, so that's where he set it. And yet the computer can adjust that on the fly depending upon conditions. If the ECM were bad or the spark-knock sensor or something else, I'm thinking it could affect my MPG as well. I'm wondering what other 1980's Brougham drivers are getting.

So, to clarify, when it was at 16 degrees, the timing had been advanced. This means the distributor fires faster? And fuel economy does...what? Now that it's at 10 degrees, will fuel economy improve over the previous setting? Or does timing ultimately have little to do with fuel economy? Does the ECM need time to adjust to the new baseline of 10 degrees? I understand, according to my shop manual, that the timing may be set as high as 20 degrees. What benefit/detriment does advancing the timing provide? I need a, "Basics of Automotive Mechanics for Dummies" book.

I'm retarded and so is my timing, huh?

04-30-05, 07:17 AM
Time to find a new mechanic. The ECM being disconnected should be a sure sign that there was a problem that someone attempted to solve via disconnecting it. The problem I have with someone saying the computer was disconnected is this:

1. If it was truely disconnected, functionality of the lock-up solenoid would not have changed after replacement since it is controlled by the computer.
2. If the computer was disconnected, how did you get a Check Engine Light?
3. If the computer was disconnected, how did the car run?

The current mechanic adjusting your base timing to 10 degrees shows he has no clue since as I recall it should be up around 20 degrees. He was probably looking at the wrong timing spec since the FWD engines should be at 10 degrees. Thank Cadillac for confusing people by having FWD and RWD Fleetwoods at times. Get a new mechanic, get the timing set back to the proper spec, and have them go through the car (mainly the CCC system) and make sure everything's to spec. The CCC system is a great system and will run great as long as you don't have someone screw it all up on you.

04-30-05, 02:44 PM
Those cars will run with the ECM not functioning. M/C solenoid stays up, (full rich), EST module goes to bypass and timing is fixed. Nothing else is needed.

Check under the hood, the spec is there for timing. I seem to recall it is upwards of 20 degrees. I think I got away with around 22 with mine without pinging.

The Olds 307's never got knock sensors, but the input on the ECM is there. I just never got around to seeing if the input worked or any software was written for it. The Buick 3.8's all had knock sensors, you might be able to get the knock sensor module (ESC) from the Buick 3.8's in the G Bodies and adapt it and run more timing and get away with it. You don't want to go too high, as the ECM pulls out excessive amounts of timing to compensate with a ping.

04-30-05, 04:39 PM
So how come my shop manual shows where the knock sensor is and how to diagnose it and remove it, etc.? I tend to think the computer was disabled because someone was having trouble with it. Perhaps that was at a time when a replacement ECM was still $600. They can be had, remanufactured, for about $120 now. I'm not really gonna give up on my mechanic just yet. If he screwed up the timing, he owes me one and that's a nice chip to have in the game. I'm not sure he did the work or if someone else did, but IF the timing should be 20 degrees, yeah, somebody dropped the ball. I'll go check under the hood here to see if I find anything. VERY interesting, though, fellas. Thanks for the discussion. Keep it going. =-)

Oh, yeah, what would have caused my CE light to come on if the computer wasn't up?

04-30-05, 05:27 PM
I just did some part number checking and you are correct, they did. I have never seen one with it. I guess once Cadillac got ahold of the engine they implemented that feature. I always felt that the engine would be so much better with it.

What I wondered is if I could add the module to a non knock sensor 307 and have it work, is there eprom software or is it something simply on the ECM PCB that does it (i.e. knock present, pull out 5 degrees, fixed value) I just never got around to messing with it.

04-30-05, 07:07 PM
So the car was running fine when you bought it, except the lockup solenoid needed to be replaced, and was. Everything was fine until you had an alarm installed, and then the CE light came on. So did the place that installed your alarm unplug the computer? Obviously there would be no way to prove they did, but have you gone and talked to them?

I had problems with my computer on my 85 Parisienne (305 Chevy). It was also causing lock-up of the converter, but only as soon as I removed my foot from the brake. It would unlock when I hit the brake with my foot. I simply left the computer in place, and wired a toggle switch into the pink lead to the transmition telling the converter to lock up. That way, I could flip the switch and get lockup whenever I wanted. I changed carburetors though as well, to a non-computer controlled Edelbrock. This isn't an option for you, but I would suggest you go and talk to the people who installed the alarm and see if they know anything about the computer being unplugged. Good luck!


04-30-05, 10:09 PM
I talked with Car Toys about all of that, considering how my CE light came on RIGHT after they started the car after working on it. I mean, BOOM, it was on. No-one, not Car Toys, not 3 mechanics, could see anything that Car Toys did that was out of the ordinary. As far as everyone knows, Car Toys did EXACTLY what they should have done.

Katshot brought up an interesting question. Will the lock-up solenoid function if the ECM is disabled? I can understand the ECM going into a fail-safe mode if there's a problem, but if there was NO power to it, not even wired to the fuse panel, can the solenoid still function?

Setting the timing from 10 degrees to 20 will do what? I'll notice an increase in power, I expect, but what of spark knock? What of fuel economy? The problem I have with acceleration seems to come and go, and lately it's not so bad. Maybe the ECM has compensated?

This is so danged technical, yet nothing like the Northstar, etc. In fact, I won't buy a Northstar engine unless I have to. They're great when the work but MAN, what a pain to have fixed.

So if someone knows what relationship timing has with fuel economy, power, etc., please explain it so I can try to figure out what's going on. At 10 degrees, I'm not noticing any pinging. I had about a third a tank of 92 and mixed with 87. We're off the oxygenated stuff so that helps...but no pinging at 10 degrees. Will it ping at 20 degrees? Probably...Will I have more power? Better or worse fuel economy?

According to a Toyota manual I found online, which talks all about timing and its effects, retarding the timing will waste fuel because it's not burning efficiently. Having been set at 16 instead of 20, it was already a little retarded. (NOTE: I may not be using the correct terminology. I don't know the difference between advanced and retarded timing. All I know is that it was at 16 degrees and now it's 10, whatever that means.) But I doubt it was enough to cause my MPG to drop from 15 to 9! So now if it's at 10 degrees, my mileage will get WORSE, not better...right? The higher the timing, the more likely it will ping but the better fuel economy I get...at the risk of damaging my engine if it's too high. So then I'd WANT to set it back to the baseline 20 degrees to improve fuel economy...but that in itself didn't seem to be the cause of the problem since it was at 16 degrees before and my MPG sucked!! Are we sure the base timing should be 20? Aren't there different shades of timing? Oh dear, I've gone cross-eyed. GRRRRR.

05-01-05, 12:17 AM
I can't seem to find any articles to have you read up, so I will wing it best as I remember. Although this article may be helpful. http://www.angelfire.com/on/geebjen/timing.txt

Timing is measured in degrees before top dead center (BTDC). The closer to TDC you are the more efficient the fuel event is. A very efficient chamber design will often get timing around 28-30 degrees for peak power. This is not where it pings at, this is where it makes best power at. Often with most average cyl heads on a SB Chevy, peak power is obtained around 36 degrees. A Pontiac often makes best power around 32 degrees. Jim Hand has seen best 1/4 mile times with his around 28-30 with his cyl heads ported by "Hand". Best power (at WOT mind you, not at part throttle where we drive) at whatever timing is most efficient at WOT. But what is it at 20% throttle? And factory specs on timing may be a comprimise for cold start or emissions, or they may yet be the perfect ones for fuel economy. But not at WOT, or maybe at WOT. We don't really know. Testing would help.

So, does more timing give you better fuel economy? You'll need to experiment. As BBob has said, and I agree, fuel economy testing is difficult at best. And there is very little good info on designing an engine for fuel economy.

We can come up with litterly hundreds of tests to try. For example:
I would start at the peak timing your engine can tolerate without pinging. Fill the tank to as consistent as you can fuel level. Drive as consistent as you can for a specified distance. Refuel to the same as before, calculate fuel usage. Then make 1 change, say, drop timing 2 degrees, and drive the exact same drive. Measure again. It will take time and dilligence to get it where you have some decent repeatable results. You will need to hit each timing level at least 3 times to get a value you can trust and consider a value data point. Then change say thermostat to 180, then do it all over again. See what data you get. Then change fuel grade, or fuel type, (ethenol or non ethenol) and run through all data points again, including both thermostat 180 and 195. It takes a tremendos amount of time and dedication. Sit down and research some theories on what you think might help or hurt fuel economy. And devise a way to test them. I am working on my statistical green belt, so if you need help crunching data, I have excellent tools to do that and will be glad to help.

I have had many questions on power vs fuel economy and none have ever been answered. No one knows. I think I need to do some chassis dyno testing at part throttle to find out some of them, but that is $$ and still hard to do consistently.

05-01-05, 12:22 AM
Something else to test. Spark plugs. I would, if it was me, would remove all 8 plugs at the end of each test group and "read" them. See what they look like under a magnifing glass or a microscope if you have one (up to 6x is all you need).

Some things here to ponder too: http://www.dapa.org/jhpages/jhandracing7.htm and http://www.dapa.org/jhpages/jhand15.htm

much of what Jim comments on here that improves 1/4mile times also will improve fuel economy. Again, we are not racing dyno's, or down the track, we are driving daily. I know much on what affects what as I drive 500-600 miles a week to get to work and back. So I get some play time in.

05-01-05, 03:10 AM
So "advancing" it 20 degrees would be the factory setting? It will ping with regular unleaded; I'd need the use the premium stuff. However, I'd gain more power and reliable acceleration. I could, potentially, gain some fuel economy as well. Unfortunately, none of this seems to explain why I was (and maybe still am) only getting 9 MPG. The lockup solenoid may play a hand in that, though it WAS working until recently; I was only getting 9 MPG with a working solenoid anyway.

This mileage problem may have started around the same time I put on a Flowmaster, although I was doing a lot of other things to it (stereo, alarm, solenoid, etc.) around then.

I'm just upset that other people are getting 17 MPG around town and I'm clearly not. So if I can't figure this out, you all are going to have to start lead-footing it to lower your fuel economy to make me feel better. =P

05-01-05, 07:29 AM
Those cars will run with the ECM not functioning. M/C solenoid stays up, (full rich), EST module goes to bypass and timing is fixed. Nothing else is needed.
Ya know, as I was writing that, I was thinking to myself whether they would or wouldn't run. Couldn't remember for sure so figured I'd go with the more conservative theory. OOPPSS! :o
As for knock sensor, I sure don't remember any knock sensors in the CCC system.
As for the timing vs. performance vs. economy question, they all have to vary depending on load and rpm. Low advance will net less power, but better emissions at idle (old trick for getting cars through inspection). It will also increase engine temp as well.
Bumping up the timing gives you better performance but it will sacrifice ecomony due to it causing greater amounts of unburned fuel to go down the tailpipe. The factory settings are usually a good balance but are generally a little on the "fat" side as far as A/F ratio since that setting protects the engine. Contrary to popular belief, 9 times out of 10 slightly better performance can be had by creating a slightly LEANER A/F ratio as compared to stock. The problem with that is standard O2 sensors aren't sufficient for keeping tabs on it. A wide-band setup is needed and even at that point detonation is even MORE tedious to control.

05-01-05, 10:57 AM
hey cmgrafmc. when i first got my car last june, i started out at about 9 mpg. i have slowly gotten it up to 11.5-12mpg. but would still like to see more, so you arent the only one

05-01-05, 09:58 PM
So when he says he set it to 10 degrees, does it SHOW 20 degrees on the crank? So is that what this 20 degrees stuff is about? I guess I won't know until I talk with him tomorrow morning. I want as advanced timing as possible whilst avoiding detonation. If the timing is set to factory specs, I should not have any problem running 87 octane fuel; the knock sensor SHOULD compensate under engine strain. If it's knocking at factory specs, something else is wrong. Adjusting timing or using premium fuel is only a Band-Aid solution.

So my lousy fuel economy must be linked to something else; possibly excessive vacuum advance or a bad sensor or ECM. The lock-up solenoid can affect mileage and cause the loss of power during upshifts.

I notice a noise after I let off the accelerator that ticks for a while until my engine RPMs decrease, then it goes silent. It's not piston slap because it happens even after the engine is warm. It's hard for me to pinpoint since I can't be in two places at once. It SOUNDS, at times, like it might be coming from the alternator..?

You all are providing some great info. I just wish I could talk to the mechanic without the strain of using up his time. I'm still not sure what he meant when he said it WAS set at 16 degrees. 16 at the crank or not? Just so danged complicated. =P I'm gonna watch Family Guy and settle down.

05-01-05, 11:12 PM
GOOD...LORD. No offense to the Lord or anything, I hope He knows that.

I just took it for a spin around the freeway. On the way out, it was okay, decent acceleration, though not like it used to be. On the way home, however, it was pretty bad. From a stop, acceleration was terrible, I had to floor it to try to get up to speed. It would pulse as it increased in RPMs until the next shift point, where the lugging and pulsing would pick up all over again. On the hill up to my place, I had to throw it into 1st, and I made about 10 MPH when normally I could do 20. So it seems that it has to warm up a bit before it acts up...could the lock-up solenoid be responsible for this, as well? Since it lurches forward and drags the engine down at stop signs, I assume it's causing late shifts.

I would have thought that EARLY shifting would be more likely to cause that effect as the RPMs wouldn't be high enough, causing the engine to lug down and struggle. I guess I'll know tomorrow since I'm having the solenoid replaced in the morning. At least it'll narrow down the possibilities if the problem isn't repaired.

The Ape Man
05-02-05, 12:02 AM
Do yourself a favor and find a mechanic who has worked on these cars. Katshot was right. It's bad enough trying to figure out an original problem and worse when someone has fooled around with things.

05-02-05, 02:02 AM
Yeah, I'm thinking that, too. The only places I know of who have the most experience with these is one of the dealerships...and God help me if I have to go there! They charge $600 to replace the computer, I GUESS because they're required to replace it with a "new" one, not a rebuilt one...or so I'm told by other mechanics. Now, I like the people at the dealership and we've dealt with them for years but it's a DEALERSHIP. And it's not like I live in LA so finding specialized mechanics isn't all that easy. I'll call around, though...I'm almost $400 into these "repairs" and I'm farther away than I was.

ONE more question, then I promise to leave you guys alone for a while. After driving on the highway for a bit, I got home and opened the hood to sniff around and noticed that my coolant in the overflow tank came up to the "Add" line and not above. Is that normal for a hot engine? I never really had to pay attention to this stuff with my last cars. Thanks in advance.

05-02-05, 07:57 AM
have you had your carb rebuilt. you should try doing that, or having someone do that. could help your mileage and the way it runs

05-02-05, 08:01 AM
and what you are describing when you slow down. does it seem to stay in a higher gear too long and then when it downshifts, its jerky and almost stalls. then when you accelerate and it shifts the rpms go way low and it lugs. if that is what is happening, it is very likely that it is the lock-up solenoid. i have yet to get mine replaced and thats what it acts like once the car is warmed up and the TCC has a chance to lock up

The Ape Man
05-02-05, 09:28 AM
Your overflow tank is doing what it was designed for.
DONT take your car to the dealership. They may land up taking your shirt and your car will still not run.
Find a garage that uses some older mechanics who have been in the business all along and not retired janitors.
You want someone with experience, test equipment and honesty. Find out how the mechanic is paid. Is it on comission? If anyone suggests throwing parts at the job without testing the originals then move on. There are exceptions to this as certain parts test by substitution.
AND if anyone tries to quote $600.00 for a computer then laugh in their face.

05-02-05, 09:58 AM
the sluggish take-offs from a stop light and the lugging and lurching at stops are most likely your govenor sticking, let me ask you does it run fine sometimes, good power and smoth timely shifts and then all the sudden for no reason when you stop start lugging and at the last moment surge forward? then when you go to take off it acts like it is in 3rd gear , no power just flat on it's face? what is probably happening is your govenor is sticking holding 2nd gear to long as you stop and when it is just about to stall it the ecm gives it some fuel and that causes it to lurch, then when you take off the govenor again malfunctions and up shifts to quick or erratically does this sound like your problem? as to the timing issue you have to disconnect the distributor lead to set the timing to 10deg when you hook up the lead it will read 20deg, i have a 1985 and at least it is that way on mine.

05-02-05, 08:38 PM
Well, I had the solenoid replaced today and it's still doing the same thing. Unfortunately, there seem to be several possibilities as to what is really causing this problem. The first is that the MAP sensor is out of whack. An uneducated but hopeful guess. This can cause late shifts. Another, more sinister possibility is that the torque converter clutch is going...in which case I'm looking at a rebuild. I'm going to get a second opinion, somehow...So far I've been quoted $1100 for a rebuild, which, according to a few sources, is a darned good deal for this transmission. I'm also told that the way they are rebuilt these days means it will last forever and I can put a 403 on it if I so choose, down the line.

However, I'm not convinced that I NEED a new transmission. (That whining is normal, right? LOL) All of this happened after the ECM was reconnected...a hell of a coincidence. I think the only way to know for sure is to check the voltage of all the sensors to know if they're within spec. Speaking of spec, I had the timing REadjusted to where it SHOULD be, 20 degrees BTDC. Quite a bit more power now, thank you very much, but my MPG still seems lousy. I'll give it time.

I'm not sure exactly what I'll do now. The EASY solution is to get a rebuild, since I'll need one eventually. But I can't help feeling screwed. I wouldn't have paid what I did if I'd thought that a couple months later it would need a transmission job. That's the nature of used cars, I suppose. And considering that these babies with rebuilt trannys in as good shape as mine can fetch upwards of $6,000-10,000 on the market, I may still have gotten a good deal. I just can't afford the deal. =P

I noticed in another thread that someone with a similar car had gone from 24-26 MPG highway down to about 10. He's experiencing the same spongy acceleration accompanied by the same boost in power I get. I'm gonna head over there and comiserate.

[EDIT] As for the overflow tank, I think the manual says that, after running the egine, the tank level should be at "Hot," whereas mine reads, "Add." This is what has confused me a little.

And about the governor, well now, that is very similar to my problem, yes! I'll do some more research, thanks a TON!

Oh, a carb rebuild...no, I've not had that done, but I've only had the car a couple of months. And maybe only for a couple more. =P

05-14-05, 08:35 PM
Transmission is fine, lock-up solenoid is doing it's job, torque converter clutch is a-ok. I disconnected the ECM and I'm not experiencing that lug-down at stop signs anymore. Mileage is still terrible, naturally. I'll reconnect the ECM fuse and see if the tranny problem pops back up. It's not the solenoid, though. I'm thinking the PROM might be telling it to shift at the wrong times? I have no idea about all that. I'll let the mechanic know Monday to see what he comes up with.

Otherwise, everything tests fine.

Oh, since I can't confirm that Car Toys did anything to the ECM, they aren't going to pay for my repairs so far. I didn't expect them to, since I can't prove anything. But the manager is going to give me discounts on my next purchases since I'm a good customer. I guess I could always use a nav system at cost. LOL (I'd rather have a moon roof, though.)

So anyone have any PROM experience? And not the kind that ends up with a drunken grope-fest.

05-17-05, 01:15 PM
You can try this:

Pull the PROM and drive it. It will default to Limp Home Mode. See if that improves anything.

I am wondering if the ECM has a bad TCC driver transistor. Anything from my post here: http://cadillacforums.com/forums/showthread.php?t=40197