So, long story short -- I purchased a '87 GTA with a 350 TPI that had not been running since 1998 (currently a 25k mile car). Have done a LOT of work and am running into a snag now that has my head scratching.

First and foremost, this is all that has been done to the car to put it in the state it is in now:

- New Fuel pump
- Cleaned fuel tank
- New fuel filter
- New fuel injectors
- New TPS sensor
- Checked / replaced vacuum and coolant hoses as needed
- Intake was removed and reinstalled with new gaskets
--NOTE: Distributor was removed / reinstalled due to intake removal
- New thermostat
- Fresh oil change
- New plugs, wires, cap, rotor
- Fresh coolant


Current Prognosis:
- With everything plugged in, the car will fire but immediately die. If you pedal it, you can keep it running somewhat, but is not a linear correlation and will backfire and diesel.
- Remove the air cleaner snorkel (btw throttle body and MAF), car will fire up and stay running (~1500rpm). If you try and give it gas, the car will just die (due to MAF not sensing additional air).


Things checked so far:
- New TPS sensor
- Swapped MAF with known good unit and no change
- Checked voltages off of MAF and had the 5V source and 12V source upon ignition. Did not check the output voltage off the circuit yet.
- Moved Distributor advanced and retard and appears that current position is 'best', but have not used a timing light to confirm. Others will not allow car to even catch during crank.

Since the car will 'run' with the snorkel off and holds a good constant RPM, have been able to rule out the various vacuum lines and all appear good from what we can tell.

Due to the correct MAF source voltages, I think the related Relays are probably good -- but this really screams a MAF related issue to me since it will not run w/ it in the air system and when it is not plugged you cant give it any more gas or it will die.

Thoughts???

 

First, stop guessing and get a timing light. Then go from there.

R&R intake manifold.....vacuum leaks?

New TPS....is it set correctly?

Why was the car parked?

 

Well .. the background on the car was that it was broken into and the OCD prior owner was upset it wasnt 'perfect' anymore and put it in storage to deal with at some point. Fast forward 16 years later .. car is finally getting back on the road. The break in broke the steering column which has since been replaced as well.

I will check the timing tonight or tomorrow and get it dailed in if I can with the current setup.

The TPS was installed, but not calibrated. I will check this and get addressed at the same time.

The IAC has not been removed .. would it make sense to go ahead and pull it and clean?

 

As another note -- I was unable to get the dash to throw any codes. Is there any trick with the digital dash cars compared to analog? Supposed to jump 6/12 pins right?

EDIT: I just found the correct pins to jump. Guess I was trying the wrong thing!

http://sethirdgen.org/dtc.htm

 

As a general rule of thumb, you should make sure that any external "adjustments" (there aren't that many) like the ignition timing and the TPS are adjusted properly and obvious things like vacuum leaks, etc. are addressed before starting to mess with your MAF, IAC, etc.

Establish a firm baseline first. Otherwise, you're just wasting your time with the shotgun approach.

 

So even though the car will only run in limp mode and not allowing throttle, I should be able to set the timing? It is running at something like 1500rpm instead of a normal idle. I understand your point, but since there are other things not working I didnt think it was a step 1 item.

 

Have an update ..

The other day I was able to get the ECM to throw some codes and I was getting the following:

22 - TPS voltage low
34 - MAF reading low
42 - EST / IAC Short

I calibrated the TPS as required, cleared the codes and tried it again. Still wont start. However, only one code remained -- 42. One diagnosis said to replace the IAC, so I put on the spare I had and no difference.

Going to run through this diagnosis chart tonight to rule things out:

http://chevythunder.com/est_code_42.htm

Beginning to wonder if this was a bad distributor and the pickups aren't good. This would explain why it will fire and then die. Until the engine hits over 600RPM (aka more than cranking), the timing is set by the ICM. After that point, it is sending signal back to the ECM to then respond with the timing based on engine RPM.

I do have a second distributor, but doesnt look to be in good shape. May try a new unit to see if that makes a difference if all of the diagnostics check out.

 

I have to ask since it wasn't mentioned. Did you try and fire the thing up first to see if it would run or did you just start replacing things on the engine because it had been sitting for 16 years???

 

Dude, your distributor is 180* out. Flip it around, set base timing and enjoy driving your car.

You will throw code 42 when you unplug the EST wire (search) to set your initial timing of 6* (as per your chart under the hood)

All the stuttering, backfiring, dieseling, and being able to feather the throttle to keep it going while is a dead giveaway. I only know because of how many times I have done it.

PS
I assume you put new gas in it....

 

You need to set the TPS..... It will not run right until your set it.

 

Thanks all for the suggestions - will pull the dist out and reinsert 180 off and see if that makes an dramatic improvements. ICM from under distributor was tested good. TPS has been calibrated to .54V. I have not pulled the IAC to check it.

To the question about replacement parts -- the answer is -- the previous owner started doing all of it and i received it with things torn apart and already replaced.

 

If you set your TPS.... unplug the battery... reconnect it after a few minutes and try to fire it. You may be good to go from there!

If it still doesn't start/run right... unplug the MAF and try to fire it. IF the MAF is bad, it should start just fine and run with the MAF unplugged.