87roc-it

Ok, I have an 87 Iroc that was a 5.0 Tpi that I pulled in favor of a stock rebult Jasper 5.7. It all went together well and the car runs and drives but the spark plugs in the drivers side head always foul out. the plugs in the passanger side head are fine. I have replaced all the intake gaskets several times, swapped the injectors out for new ones, adjusted the fuel pressure regulator many times, and tried many other thing I can't remember at the moment and it still does it.

Does anyone have any Ideas as to what could be causeing this? I have been fighting with it for 3 years now.

Thanks, Ron

jzajac1

Are they fouling from fuel or oil? If it's oil and you've been battling it since the engine exhange then the valve guides or seals were not done right. If it's fuel, you'll have to determine if you're getting enough spark for some reason to that bank. The TPI system feeds fuel to all cylinders at one time so it doesn't seem to be ecm related. Have you taken any type of readings using a TECH1 or hook a scope to it and watch you're firing lines on each cylinder.

87roc-it

I can't tell if it's oil or fuel. The car runs extremely rich so I assume its fuel. I have a Mac Tools scanner I have used on it but it don't individualize each cylinder.

I replaced all the ignition componets, cap ,rotor, wires, ignition module (all Accel), coil and box are Crane Fireball HI-6. Ran it both with and with out the Crane box.

Plugs get changed every 75 or so miles from fouling.

90rocz

Could you have damaged the harness on that side? Have you checked the injectors with a "Noid" light, so you can see how long they're opening etc..

87roc-it

My scanner has an injector pulse width reading.

Forget what the #'s are right now though.

90rocz

The problem with that tho, is your reading the ECM driver, not seeing whats happening at the injector itself...

xeroxed

did you reprogram your prom chip and hopefully you went with bigger injectors meant for a 350 tpi. i think the 350 needs like 22# injectors going a little bigger wouldnt hurt it leaves room for improvement. but if you havent had your prom programed for running the bigger motor itll cause all sorts of problems and running rich is just one of the problems.

97WS6SCharged

Does the car smoke or anything? Does it use any oil? It might be worth it to change out the valve seals on that head and see if that helps.

87roc-it

I have a Gm performance parts chip in the ecm, also switched back and forth to stock with same problem.

Injectors currently in the car are #19's from the 305. TPI Specialties recomends those with slighly increased fuel pressure. originaly I had #24's in the motor and also have switched them back and forth with no change.

I'm begining to think maybe it is the valve seals. the motor only has 11000mi now but it may have been messed up leaving the machine shop.

xeroxed

id say put the 24# injectors back in then find someone with a lap top and the prom burning software (a speedshop might be able to do it) and have them tune your fuel curve because thats what it sounds like to me. i know a guy that had the same problem and he ended up burning his own prom chip and it fixed the problem his car was burning really rich blowing clouds of black smoke out of the exaust. this is just another reason i hate computer controlled motors you cant just swap to a bigger motor and leave everything unchanged. what you might be able to do and save some money is find someone selling an ecm and prom for a tpi 350 out of car the same year as yours and put in the stock sized injectors and you shouldnt have any problems then as long as the prom hasnt been changed.

also your ecm is reading that its working properly but its working properly for the 305. i would hold off on valve seals if you know its burning rich youll smell unburnt gas and there will be black smoke all the time. valve seals usually leak on start up and quit leaking after its warmed up. if your valve seals were leaking itd be a blueish grey smoke and with 11,000 miles im doubting there totally shot.

this is why i sold my tpi and got rid of the ecm and harness less problems tuning with just a carb and hei ignition. lol

87roc-it

Ok, I understand what you saying but I called the Gm dealer and they said the the Ecm's are the same for both 305's and 350's. the differance is the prom chip. Now if you look in the GM performance parts catalog their chip say it can be used for either motor. It does run rich, It'll gag ya if your behind the car, but the plugs on the passenger side never have any problems. Only time I had to change them was when I left the drivers side go too long. As long as I kept the drivers side changed regularly I never had to touch the passenger side.

I think when I get some extra $$$ I'll take it somewhere to get a custom chip burned like you said. I want to keep the TPI and I don't get along with carbs very well

jzajac1

#1 - Your stock 19# injectors are fine for your application, 19 # will support up to 350 hp.
#2 - If you're doubting your PROM - Go to the dealer and purchase a 1988 prom for a corvette, the prom has the correct pulse width and timing applications needed if you are running 22# injectors but the 19# pulse width is the same.
#3 - I agree with the earlier suggestion to make sure each injector is getting a steady signal and it is not intermittent.

Has your scanner recorded any codes? I've used 19# injectors for 3 years on a modified 350 (350hp) and a 88 corvette stock prom, NO fuel or driveability issues ever arose. Can't say for sure what your problem is but it does seem like possibly electrical harness to the injectors. I'm a former ASE Chevy tech and am familiar with the 87-89 tpi system but this one is strange. I'll ask around some other techs and see if anyone has run across this before.

raul.garcia

Shouldn't be to hard to swap the injector bank harnesses. If the passenger side spark plugs begin to foul then the problem is in the left bank harness, or injector drivers in the ECM.

If the fouling doesn't follow the harness swap then it could be mechanical problems in the left cylinder head

90rocz

Just went thru some wiring diagrams and each bank has separate drivers and power wires, either your wiring is bad on that bank or the driver in the ECM for that bank. (even tho it's a bach fire..)My cousin had a similar problem with his SFI set up, but only fouled 1 cylinder, his ECM was bad(bad injector driver), we went thru the harness, compresion etc,etc, but then he tried a new ECM and it ran perfect!...

jzajac1

I agree with 90rocz, it seems the problem is electrical in nature if you are sure it is fuel on your plugs. I did talk to a couple of driveability techs today at the the dealer I frequent and they agreed that it is probably wiring or ecm. So validate whether you have oil or gas on your plugs and go from there........