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HT4100 4.1, 4.5, 4.9 Discussion, Spark Plugs: What do YOU run? in Cadillac Engine Technical Discussion; Originally Posted by drewsdeville Well, I'd say that pretty much rules that out then. Like ehall stated, the stumble and ...
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    Re: Spark Plugs: What do YOU run?

    Quote Originally Posted by drewsdeville View Post
    Well, I'd say that pretty much rules that out then.

    Like ehall stated, the stumble and the mpg issue are EGR symptoms and the OBD1 system CEL's aren't exactly a reliable indicator of proper EGR operation. These engines use a positive back pressure type EGR valve, so testing the EGR will require you to create backpressure to raise the lower diaphragm to test if the upper diaphragm will hold vacuum. You'll also need to check for proper EGR controller operation. I'm sure your FSM has the info on that.
    Yes, I did all the tests on the EGR. Even the one where you put something in the exhaust pipe and run it to 2000 then override the ECM to open the valve. It all tests good. Not to mention the stumble remained even with zero possible EGR however I didnt leave the plate on long enough to measure the mileage.

    I think the DIC and fuel guage data being so grossly different is the biggest indicator of the problem. Whatever is going on, the engine is seeing more fuel than the ECM knows about. It relies on pulse width at a given pressure. It's as if my injectors suddenly went from 19lb up to 24# all at the same time. The fuel pressure tests ok in my garage but I'd like to see it at all operating conditions.

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    Re: Spark Plugs: What do YOU run?

    Quote Originally Posted by Sevillian273 View Post
    Yes, I did all the tests on the EGR. Even the one where you put something in the exhaust pipe and run it to 2000 then override the ECM to open the valve. It all tests good. Not to mention the stumble remained even with zero possible EGR however I didnt leave the plate on long enough to measure the mileage.

    I think the DIC and fuel guage data being so grossly different is the biggest indicator of the problem. Whatever is going on, the engine is seeing more fuel than the ECM knows about. It relies on pulse width at a given pressure. It's as if my injectors suddenly went from 19lb up to 24# all at the same time. The fuel pressure tests ok in my garage but I'd like to see it at all operating conditions.

    Fuel pressure gauge taped to the windshield?

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    Re: Spark Plugs: What do YOU run?

    When I decided to clean up my 85 I spent a couple of years chasing down problems. One of them was intake gasket that seems to have been the source of a perpetual oil consumption problem. Another was a hairline crack in the throttle body at the butterfly valve that was allowing unmetered air into the engine causing lean/rich cycles. I wouldn't be surprised if you have some kind of structural problem like this.

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    Re: Spark Plugs: What do YOU run?

    Quote Originally Posted by Sevillian273 View Post
    Wow thats a rare thing to hear! Most forums frown upon those plugs but I've never seen any real evidence as to why they 'are no good'. Most praise AC Delcos as gospel and conversely I haven't seen any evidence as to why.... But I do think that recommendations come from real experience and that is tangible enough for me so when I'm done blindly throwing parts at the fuel system, my next set will be Delcos. Changing plugs on a transverse V8 is no fun otherwise I'd take my chances with the +4's but I've heard alot more negative rhetoric about them than positive... Whether it be fuel or spark, I still feel I'm in a no-win situation.

    And to add insult to injury, my latest calculation on my most recent tank of gas has revealed 14.4 mpg while the DIC says 21.1mpg...
    Hmm. Well, I'm afraid I don't really have the knowledge to answer your specific issue, but I can tell you there definitely was a positive difference with the tune up, but that was the whole deal including cap, rotor, and wires, (which were 10.8 mm Accel wires that I find they discontinued. Anyways, I had to cut and terminate the ends and in researching the proper tool was told that the core was same as the 9.8mm wires.)

    One thing to note with the four prongs of the Bosch plugs are that they are thin. It is possible that people having negative experience with them have accidentally bent them upon installation. That would definitely throw things off.

    I have been using the Bosch IR Fusion plugs in another car I work on, but would not hesitate to try them in the Cadillac if it were in operation. (My mom kept having accidents until I told her better get a smaller car to drive around, so the Cadillac is just sitting in our front driveway for now with a busted front right half shaft.) You aren't kidding about it being difficult to change some of the plugs, as I remember lying on the top of the engine getting some of the back ones in. Just have to be patient and gentle I guess to get good results from them.

    It's funny you note 14.4 mpg, as that was about what the DIC was saying on ours, either 14.x or very low 15s max that is.

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    Re: Spark Plugs: What do YOU run?

    My '85 indicates from 24 to 27 MPG, but the indicated average seems OK at 18.6, mostly, and sometimes 19, depending on highway or city/highway driving. Maybe it's not accurate, but it's acceptable.
    I rebuilt the TBI a few years ago because the regulator housing was seeping fuel, but no change in mileage etc.
    I don't usually run any other plugs than the ACs in the daily drivers. In my performance cars I use Accel plugs, which are actually Nippendenso U-groove types.

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    Re: Spark Plugs: What do YOU run?

    Put in the new Kemparts FPR today- No changes. Wasn't really expecting anything either. The old one was pretty rusty inside but still held vacuum. So thats one thing off the list... One thing I noticed while monitoring the fuel integrator is that around 2500rm at 45mph or so, the car surges with power and the integrator goes way down below 60! That means the computer is taking ALOT of time off the pulse width under those conditions. Still have no idea what is going on.

    Next random part: Allante fuel injectors! I found a set of new (doubt it) OEM replacements on ebay for 142 w/ shipping. http://cgi.ebay.com/ebaymotors/ws/eB...AQ:MOTORS:1123 Not sure what the flow rate is on those but at least they are for a 4.5. They'll go in next weekend. Meanwhile I'm still getting around 14mpg. Sucks.

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    Re: Spark Plugs: What do YOU run?

    Got the Allante injectors in the mail - They came in factory sealed packaging and not a scratch on them. I installed them and she runs. The stumble is gone and integrator counts are a bit higher but now I have an extended crank issue when hot... Every hot start is an extended crank now Fuel psi is in spec during the hot start and FPR is brand new and does not leak.

    Also the integrator differs from left to right now. I dont recall if there was a difference from L to R with the previous Bosch III's but I had 89 counts at idle which was rich. I now have 111 for the left and 98 for the right. Both should read the same. Something still isnt right but I suspect that the lesser flowing stock injectors have alleviated the driveability issue. As for the extended crank, I'm clueless. I'll give it some more time while I calculate the new mileage before I go for a new computer.

    I dont see what else could cause one side to run richer than the other. The only kind of sensor that is specific to each bank is the O2's. Other than that you have injectors and sparkplugs. The rest of the system affects both banks the same. Fuel pump, rail, FPR, MAP, MAT, ISC, TPS, ECT - none of those can influence just one side of the engine.

    Usually when things just dont make sense it's the computer. And I have a hunch... When one of my OEM Multec injectors crapped out it was on that side of the engine, #6 if I recall. It read just 1.2 ohms when It showed symptoms and I probably drove home about 5 miles before I removed it. I wonder if the heat from such low resistance did damage to the injector driver circuit in the ECM? I'm clutching at straws here...

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    Re: Spark Plugs: What do YOU run?

    The integrator counts are only a short term fuel trim, so may vary at different conditions. Recording the values at different conditions could help pinpoint the problem. Have you checked it during varying conditions? Idle, low/high rpm, low/load?

    What are the values for the block learn? Does the ECM go into closed loop like it's supposed to?

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    Re: Spark Plugs: What do YOU run?

    Each differing condition ( acceleration, cruise, deceleration) sets the integrator back to 128 and from there (in my case) it dials the fuel back lower than 128, correcting for richness. This happens for both sides but the right bank integrator goes lower indicating that it runs richer than the left. L and R differ by 10 to 20 counts at any condition. The difference is most pronounced at idle. Block learn is 118 at present.

    It does reach closed loop. That's when the ECM starts to dial the integrator back from 128.

    The new FPR does perform better than the old one. A hard stab on the gas in D would shoot the pressure to 50psi for a second with the old unit. The new unit hardly lets the needle move at all.

    The new injectors have definitely helped out the richness and there is more available power. I'm an idiot for not taking readings before removing the bosch III's. I cant remember if there was a L to R difference with those. Getting sick of pulling the rail but now I can RnR it in under an hour.

    After I run through a tank of gas and calculat mileage and fuel data accuracy, I'm putting in new plugs. If the rear plugs look anything like the oxy sensor did, then they could use a change. If the mileage is still horrible, then I will get a new ECM.

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    Re: Spark Plugs: What do YOU run?

    Quote Originally Posted by Sevillian273 View Post
    Each differing condition ( acceleration, cruise, deceleration) sets the integrator back to 128 and from there (in my case) it dials the fuel back lower than 128, correcting for richness. This happens for both sides but the right bank integrator goes lower indicating that it runs richer than the left. L and R differ by 10 to 20 counts at any condition. The difference is most pronounced at idle. Block learn is 118 at present.
    so if I'm reading that correctly, the integrator is normal during all conditions except idle?

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    Re: Spark Plugs: What do YOU run?

    No, the integrator just resets to 128 and then counts back to dial in the mix for that particular driving condition. I think each condition is called a cell - not sure. For instance, if I sit and idle in P the integrator counts down to 89, shift into D and instantly back to 128 again and then counts back. So if I sit at a light in D it counts down and when the light goes green and I hit the gas its back to 128 and then counts down while I accelerate. During acceleration when it gets to around 70 to 60 counts there is a surge of extra power which makes sense because by then the fuel mix is close to where it should be.

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    Re: Spark Plugs: What do YOU run?

    Well out of curiousity, on my way to work earlier this afternoon, I checked my own block learn and integrator counts to compare to the info you gave. They were both the same at all times, not differing bank to bank. The block learn values were slightly above 128, in the low 130's but I wonder if this is due to the fact that I'm using a set of Ford 19# injectors...

    ANYWAY, on to your problem Sevillian, something occured to me while I was chugging away at work (I think about anything and everything at my physically active, but mind-numbing job). This might not be your problem, but is one of the only theories I can attempt to help you with.

    The lower integrator values you are stating don't necessarily say if the car is running rich or not. Only the O2 sensors can tell you that and a O2 code would be tripped if that was the case. A cars fuel management is always trying to achieve the correct stoichiometric ratio, right? That's what your car is doing by adjusting the values per bank. Your car isn't running rich right now. If it was, you'd have major driveability symptoms that, from what I understand, you really aren't getting. It's running "correctly", as in the air/fuel mixture is correct, but it's using more fuel to achieve that.

    So what does that mean?

    Well, the integrator is calculated from the engine management gadgets you listed, with large emphasis on the MAP and O2 sensors. The MAP is a global measurement while the O2's are per bank. What this tells us is that the O2 on the effected bank is detecting a lean condition, and the computer is adjusting the integrator accordingly to compensate.

    How is there a lean condition on one bank?

    VACUUM LEAK!!! My money is on an intake gasket leaking vacuum on whatever bank has the low integrator counts.

    One thing I'm curious about is to what it takes to set a E046 code, because you'd think something like this would set that. Perhaps the banks don't differ enough yet to set it?

    If I remember correctly, you have an FSM (I never got one yet otherwise I'd do this homework for you as I'm interested in this). Does it have diagnostic charts for the E046? If so, take a look to see what it uses trip this. Does it use integrator values? Then follow the chart and see if it leads you to an intake gasket leak diagnosis. If so, I'd consider that to the true confirmation that this is the problem.

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    Re: Spark Plugs: What do YOU run?

    There is no lean condition on either bank. Both are richer than they should be. Any integrator count lower than 128 means the ecm is correcting for a rich condition. Less integrator means time is taken off of the pulse width to achieve stochiometric mix. If I had a lean condition, integrator counts would be higher than 128 meaning time is added to the pulse width. Im OK with higher or lower integrator counts because they designed this system to be able to operate at all possible conditions(sea level, high altitude, hot weather, cold weather etc) but what makes me uncomfortable is that there is a fueling difference between both banks.

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    Re: Spark Plugs: What do YOU run?

    DOH

    My bad

    I suck

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    Re: Spark Plugs: What do YOU run?

    I wish you were right, I really do. i would gladly change the intake gaskets 50 times than go through these mental gymnastics... I will report back after I calculate fuel mileage and change the plugs. I'm starting to really miss driving my Ford. Thanks for taking an interest in this madness, lol. It's nice to see that your values are the same for both banks. I seem to remember mine being the same also back before I started having issues.

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