whiteturbo87

Ok so from the beginning.I bought an 88 iroc with no engine or trans.I bought a used drivetrain from an 89 iroc.So the only difference is no cold start.Got everything together and running.Only problem is its very hard to start.Cranks strong but wont start.I have to crank it a little,shut it off,crank it a little,shut it off,etc....and i do this for like a minute until it finally starts.I was guessing because of no cold start.When it gets started it runs great....until it starts getting warm.The longer it runs,the worse it runs until after about 4-5 minutes its running like complete crap.It seems to develop a miss.And its at any RPM.I can hold it at 800 or 3000 and its the same.When i installed the engine i put in new plugs,wires,cap,rotor and module.I checked the timing and its dead on 6*.I checked fuel pressure key on engine off and its 43psi.Running its at 40psi.I did an injector balance test and all 8 injectors went from 43psi down to 30psi.Fuel pressure does not bleed off.I hooked a scan tool up and watched all the computer info.Everything seems to be within spec.I thought maybe was bad CTS but doesnt seem to be the case.Im thinking either the distributor or something fuel related.I did notice the reluctor wheel in the dist. was rusty.Any help would be great

,Tom

BigBadLou

Howdy Tom, welcome to the club.

Good troubleshooting.
Hopefully we can get her running straight!

When you swapped in the new drivetrain, did you put in a different ECM or EPROM? Or did you keep the original one from 1988?
When cold, did you try spray extra fuel into the intake to get it started? Did it help?
When you plugged in the scanner, did you check the temp sensor readings and O2 sensor voltage?

Lou

whiteturbo87

I left the original computer alone.I did however drop the computer and check the PROM.it appears to be stock.I actually completley forget what the O2 readings were,but it was functioning.And the coolant temp sensor readings were correct from before i started until i shut it off.No funny readings.As ive been working on the car I definatley noticed it was "hot rodded" in its previous life.One of the elec. fan relays was jumped to run key on.I see where someone torched a bit of the lower control arm mounts for header clearance.It has tubular rear control arms and some engine parts were still in the back of th car w/an intake gasket set.So is it pssible someone messed with the PROM?Theres no markings on it other than factory

whiteturbo87

I also did not try to spray anything in the intake.Ill try that.If it does start with stuf sprayed in the intake i would assume its a fuel issue?

BigBadLou

Yes, if extra fuel in the intake helps the start, you can suspect a fueling issue (the cold-start injector was in there for a reason).
The older ECM did not know to add more fuel during cranking because that's what the cold-start injector was doing. The new ECM knows to do that. But since you are using the old one, your engine might be starving for fuel at start time. So try to eliminate that with some brake parts cleaner or any other decently flammable liquid in the intake.

If the PROM appears to be stock (did you happen to write down the 4-letter code on it?), it is most likely stock. The old EPROMs are not easy to reprogram, they are so old that they won't accept new programming. So if you wanted to reprogram your EPROM, you'd use a newer EEPROM and you could tell it from the original chip easily.

Let us know what you find.
Lou

whiteturbo87

Ok i finally got time to mess with it again.Yes spraying starter fluid in the intake first allowed it to start right up.I figured the cold start not being there would be a problem.I really dont feel like spending the time or money on getting all the cold start stuff for the engine.And i obviously cant throw an 89 prom in there due to vats.I did find a guy that sells a "piggy back" chip.it goes under your original and it incorporates the 89 injector sequence.I did look at my computer again.Number on the computer says 1227165.Numbers/letters on the prom are AKXX and 3269 with a piece of cork glued to it and has WB written on it.I did notice that the prom was not fully seated like someone may have messed with it?I pushed it down and ran the car.
I let the car run for about 10 minutes or so.Still runnin like crap.When I shut it off and tried to restart it I had to open the throttle.It sounded almost as if it was rich and needed more air to start.

BigBadLou

Hi Tom,
sorry for the late reply, it has been a busy weekend.
It really sounds like you just need to get the piggy back chip to get the cold start taken care of. As for the rough running when warm, I'd look at the scan tool again. What are the O2 or AFR readings? Any indication of a rich or lean condition? Does timing look stable from the ECM readings?

Lou

IROC-T

Your fuel pressure may be a little low,it should be about 48# with the vac hose off and plugged. Also check your IAC.

whiteturbo87

Installed new injectors and the piggy back chip.Car starts right up and runs great.Thanks for the help

BigBadLou

Thank you for posting the outcome, Tom.
It is always good to know whether the advice worked or not.

Good job.

Lou