I'm changing the plugs soon in my 4.5. I have an ACCEL super coil, MSD cap and rotor, and MSD 8.5mm wires all feeding my current AutoLite double platinum plugs. They only have 20K miles on them but I'm having a 'stumbling upon acceleration' issue and I cant find anything wrong with the fuel system so now I'm on to the ignition....
I'm not trying to start a 'my plugs are better than your plugs' debate.:stirpot: Im just curious what everyone is running in their 4.x and how satisfied are you with your choice of spark plugs?
Today I put in new plugs - AC Delco standards. managed to do it from above this time by removing the heater hoses. Anyways, no more hard starts! But I didnt have hard starts before I switched to Allante injectors..wtf? All the old plugs(Autolite Double Platinum) had a cherry red coating on one side just like I described in my thread about red o2 sensors. All looked the same except #4 which had a silvery coating on top of the ground electrode. It had the appearance of lead or zinc like a galvanized bolt. Strange.....
Before I did the plugs I checked the mileage. I started with 12.3 gallons and drove until I had 6.3. So 6 actual gallons consumed but the 'Fuel Used' said 4.4. That's 1.9 gallons unaccounted for and that's all on the new allante injectors. I'm stumped. In those 6 gallons I went 87.7 miles which comes out to 14.62mpg. Dont know what's going on. I'll fill up and check again on these new plugs.
On these new plugs there is still an integrator difference of around 10 counts. After the plug change I recorded this:
IDLE 600rpm, temp 195, in Park
121 LINT
113 RINT
108 L B/L
108 R B/L
10 L CROSS
11 R CROSS
L OXY VOLTS .11 to .73 <---perfect
R OXY VOLTS .53 to .85 <---rich but I shouldnt have seen ANY cross counts if .53v is the lowest value. It has to cross .45 to make a cross count. Interesting...
Also, while driving, the integrator counts are now very close from L to R - within 5 counts or so. At 1800 rpm steady cruising they both read 133. Looks pretty good to me.
So time for a fill up and another mileage calculation on the new plugs and then I'll go from there.
Don't have any idea how the computer uses miles traveled compared to fuel flow to get MPG, but it sounds like it's messed up somehow. Must be a transducer in there someplace to measure fuel flow.
It knows how much fuel is sprayed for a given pulse width and then adds up all those pulse widths. Usually the discrepancy indicates leaking injectors because each leaking drip isnt accounted for by the computer because that leaking fuel wasnt commanded to go into the engine. The fuel used according to the fuel sender in the tank and the 'Fuel Used' on the DIC should be VERY close. The system divides miles traveled by fuel used to give you mpg.
Also I spoke too soon about the hot starts.... I got 4 normal starts after the plugs, one cold and 3 hot. Posted the follow-up then went to go get dinner 2 hours later and its consistently hard starting just like before. :bighead:
I still have no concrete evidence that the hard starts and the fuel data inaccuracy have anything to do with my rich running and fuel imbalance! This is madness!
Fuel data accuracy has improved after the new plugs but it is still too far off to be normal and hard starts continue.
Begin 17.1 gallons
End 8.7
DIC Fuel used: 7.1
ACTUAL Fuel Used: 8.4
Difference: 1.3 gallons
Miles traveled: 126.6
DIC Avg Econ: 17.7
Actual Calculated Econ: 15.0
I see an improvement here. The DIC used to say 21.4mpg when the calculated mpg was 14.6.
Mileage Accuracy difference before the plugs: 6.8mpg After the plugs: 2.7
So the new plugs have made an improvement.. I dont know how but at this point I dont care.
And check this out... Went to replace my FPR hose today and noticed a hissing sound from the TB. One of the 'new' Allante injectors is leaking loudly and there is fuel down in the TB. Bastards. That explains the sudden hard start issue after I put them in. I guess it wasnt bad enough to notice before. Now I'm getting set up to R n R the rail and injectors for the FIFTH time and put the Bosch III's back in. I cant have my crankcase full of gasoline.. good thing its about time for an oil change.
Sooooo after I let the car cool for a while I turned the key to ON to check for the leaking sound and there was none. Interesting. Then I swapped my Bosch III's in and went to the gas station to fill up. The car ran good with no apparent issues and the avg econ says 20.8 after a 12 mile trip.
Now I hear the spraying sound again from inside the manifold but this time it's coming from the other throttle bore. $#@!. So it looks I had a leaker the whole time but only when hot. At the beginning of this thread I said that none of the injectors visibly leak because I had the rail pulled up with pressure on it. But when I did that, the engine was COLD! Son of a bitch. So I now have 2 full sets of bad injectors and when I get the money I'm due for a SIXTH RnR of the fuel rail and injectors.
On the plus side, no more hard starts and no more stumble on acceleration which was likely the plugs. I've located some parts to build my own injector test bench so I can pressure test all my injectors both cold and hot. It will consist of a fuel pump, mustang fuel rail, and a small aquarium. I also have a couple commercial hand-dryers that I'll use to simulate hot-soak conditions on the injectors. It will come in handy as long as I dont burn the house down... I cant wait to get started on it... just need to win a few ebay auctions.
Oh and it gets better! I just lost the instrument panel cluster and DIC today. Turns out the power supply for the vacuum florescent lights burned out. This power supply is built into the board of the IPC so I need a whole new unit.:mad2: No speedo, gas gauge, odometer, nothin. And worst of all, no onboard diagnostics so no more mileage calculations for my wonderful fuel problem. Luckily I found a used unit on Ebay for $50 but unfortunately odometer mileage is store in the IPC so I'll have to calculate it based on my last recorded odometer reading. The madness never ends with this car!
A brief update - I swapped the IPC with the ebay unit and sure enough, mileage stayed the same so who knows? Unfortunately the ebay IPC display has dimmed quite a bit since I put it in but as long as it stays lit I'm happy. (knock on wood) I swapped the ECM with an original unit from a 91 deville and no improvement.... mileage accuracy is still way off, mileage still around 14, still bogs and stumbles on acceleration. I've almost got everything I need to build my fuel injector test bench. I still need to get an aquarium and figure out what I'm going to do for 12v bench power. I've got several computer PSU's that I may use but I dont know if they can handle a fuel pump... What do they pull? 20 amps? That may be a lil high for what I have.... Meanwhile I've ordered a pulse width generator and a set of injector clips and am still waiting for them to arrive. Gonna hit the pet supply places tomorrow after work for an aquarium and then I can start construction. Once I get leaking injectors out of the equation I'm going to start compression testing both static and dynamic. At this point I wouldnt be surprised if there was something internally wrong with this engine.
I'm right there with you with this WHOLE thread. I've been fighting injector bs for a year now and I really feel it blew my headgasket. I've pulled fuel rails some 5 or 6 times myself.
Yeah I've seen that page. I've actually had more trouble with non oem injectors. With the originals, one simply shorted out with the rest close behind so I pulled them out and that was the end of them. Then I bought a reman set of bosch III's from Ebay, ran them for 4 months until they started to leak(but i didnt know it then because they only leaked when hot) Then onto a set of Allante injectors that leaked even worse only when hot. Now I'm back to the bosch's simply because they dont leak as bad but I'm still getting 14mpg. All of this is because the price of new injectors is so ridiculous.
I just got the MSD injectors in the mail and they have the Rochester Products (RP) logo on the side; which is OEM replacement, right? I know they all get lumped into one company Delphi, Rochester, and Multec and I hope they work for a little while...:ill:
ive been reading this entire thread...i think your fueling problem could be a small vacuum leak in your throttlebody gasket...spray some carb cleaner at the base of the throttlebody all the way around it, see if the engine idle drops a little when you do that....
also, this constant business with changing out injectors, changing spark plugs, etc...the issue is elsewhere. have you checked to see if you are getting a constant 12v to your power steering input on the ecm? if not, it will cause a constant rich condition but not set any codes...the power steering switch cuts the 12v only when there is power steering cramp at idle and the ecm richens the fuel mixture to compensate so you can turn yoru steering weheel easier at idle... BUt if the switch is bad, and doesn't allow the 12volts through during normal driving conditions, the ecm will constantly think the power steering is cramped...the computer doesn't always throw a code either when this happens....
also, your reman computer might be for a 91 or later deville/seville, since they have the same part number, but different memcal(chip)... i would take the chip out of your orgiginal stock computer and put it into the new computer....
also, have you considered the fact that maybe you have bad compression on one or more of the cylinders? there is alot of ground you have not covered.. but you keep changing the variables by just changing out parts... you need to go back and start over with the basics...
ive been reading this entire thread...i think your fueling problem could be a small vacuum leak in your throttlebody gasket...spray some carb cleaner at the base of the throttlebody all the way around it, see if the engine idle drops a little when you do that....
also, this constant business with changing out injectors, changing spark plugs, etc...the issue is elsewhere. have you checked to see if you are getting a constant 12v to your power steering input on the ecm? if not, it will cause a constant rich condition but not set any codes...the power steering switch cuts the 12v only when there is power steering cramp at idle and the ecm richens the fuel mixture to compensate so you can turn yoru steering weheel easier at idle... BUt if the switch is bad, and doesn't allow the 12volts through during normal driving conditions, the ecm will constantly think the power steering is cramped...the computer doesn't always throw a code either when this happens....
I have not seen any evidence to support that on this vehicle. The PS switch just tells the computer to bump the idle up via the idle speed control motor.
also, your reman computer might be for a 91 or later deville/seville, since they have the same part number, but different memcal(chip)... i would take the chip out of your orgiginal stock computer and put it into the new computer....
also, have you considered the fact that maybe you have bad compression on one or more of the cylinders? there is alot of ground you have not covered.. but you keep changing the variables by just changing out parts... you need to go back and start over with the basics...
I havent been keeping up to date on my work in the boards so there are gaps, holes, and things I forgot to mention. I havent been following this thread because the engine is now in a whole different state of parts, testing, tweaking, etc etc... The only ground I havent covered is a compression test and possibly going through the o2 sensor grounds.
I believe the stumbling issue that this thread was about was simply a heavily worn distributor cap... I cant remember. Perhaps I should be a little more diligent about noting my progress on these boards as they sort of serve as a diary/history of events. I did however have 2 bad sets of injectors one 'new' and another 'rebuilt' which caused the hard hot starts and seriously compromised the diagnostic journey.
Anyways the car is running quite well on 19# injectors albeit with poor mileage. I havent had the green to spend on a set of the CORRECT 16# injectors. I had a set of BMW 16.6# injectors but for some reason it pinged like a sonofabitch on those. When I decide to dig into that issue I'll start a new thread.
Well I'm going to jump in here, I have had these problems with my 90 Deville. Stumble, running rich, stalling etc. Someone informed me after the fact that the 4.5 uses 16# injectors not 19# mentioned here. The 19# injectors just aggravate your problems. In addition I had installed a new Bosch O2 sensor which was operating but not correctly, this also aggravated the problems. After changing the plugs 4 times and changing pretty much the intire ignition system and all of the injectors (new 19# aftermarket) I put new OEM AC plugs and O2 sensor the old original injectors and the car runs like it should. I also had the instrument cluster and speedometer fail just after this work, battery goes dead and the car blows fuse #7 repeatedly, natuarally this being a Cadillac this was caused by the AC compressor clutch coil failure. Old school logic just does not work, you will be chasing your own tail on these cars. Try OEM parts or the old stuff you removed and see what happens, it worked for me.
stumble is MAT sensor, manifold air tempurature. Located beside the alternator in the intake manifold. Had same issue with my 91 deville and buddies 89 deville.
Heh, looking back this thread makes me laugh. I was so frustrated, lol... Too many variables popping up during diags, and on top of that, using the car everyday for work. I think the answer was a combo of heavy 19# injectors, too much timing, and mostly a well worn distributor cap due to my MSD 6A eating the contacts. Now I regularly sand them clean.
I have the correct injectors now and fuel data is accurate again. Current config is 12deg BTDC and copper core plugs @ one heat range colder than stock (Autolite 104). The MSD 6a provides spark through a brass cap instead of aluminum... I also relocated the MAT sensor to the filter box which seems to have corrected a 'flat spot' in the fuel delivery. Cause of that is unknown as everything is at spec in the fuel system... Having the sensor report a colder air temp results in more initial fuel when accelerating. Just enough to correct the problem without affecting gas mileage. Good enough for me. Motor is happy.
I have no future plans for it now that the trans is really showing its age at just 95K miles. Seems the pump was damaged some time ago after switching to Dex 6. It got really noisy and stayed that way after switching back to regular fluid. An autopsy of the trans filter revealed aluminum shavings presumably from the inside of the pump housing.
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