neilcase

I just finished a ground up resto of a 1990 IROC convertible 5.0 TPI with a 700r. It ran perfect for about 100 miles and the very day I delivered it to the customer it started to stall when shifting from park to drive. Its gotten progressively worse to the point that it will now stall after a minute or so of idle (in closed loop) without shifting into gear. This does not happen in open loop when the car is cold. Only after closed loop. The O2 sensor is a brand new Delco. The TPS, IAC, timing and valves are all set dead on correct. No vacuum leaks either.

The biggest clues here are that it only happens AFTER the ECM starts making adjustments in closed loop and that the car runs fair but lack of power at RPM higher than idle.

And one last possible clue. Bosch III injectors. These are significantly better spray pattern and more efficient injectors then the stock Multec turds. The BLM readings are pegged at 160 at all times. I wonder if the ECM is adding fuel and fouling out the engine at low RPM?

Pro

So if you unplug the brand new O2 sensor when everything is warmed up, does it run better?

ULTM8Z

Ahhhh... Bosch-III's strike again. Is the car stock except for the injectors?

Any rate, sounds like you need to get the Bosch-III fix in place before messing with anything else.

When my friend's 5.0L TPI was displaying the same symptoms, I put in the following values for the Injector Pulse Width vs Battery correction attached here.

The other thing to do is to zero out the Low Pulse Width Injector Offset vs BPW table (for the reasons you specified...i.e., the Bosch-III's are more efficient at low pulse widths).

Lastly, ensure the battery voltage and the switched igntion voltage are the same. In the ALDL datastream, the ignition voltage is often referred to as Fuel Pump Voltage). I was struggling with driveability issues for a while before I discovered I had nearly a 1V discrepancy between the switched ignition voltage and the battery voltage (there was a large voltage drop across the igntion switch that I had to fix). The ECM relies on both voltages, and when they're significantly different it can cause problems.

neilcase

[QUOTE=ULTM8Z;6219544]Ahhhh... Bosch-III's strike again. Is the car stock except for the injectors?

Way beyond my paygrade. Yes the engine and total car is bone stock. I'll send you my PROM for you to fix?

neilcase

That's a very good question?point to make. I really never thought of that. I'l give it a try.

ULTM8Z

There are guys on this board who specialize in modified memcals.

recommend getting in contact with them. Or maybe one or more of them will reply to this thread.

neilcase

Just tried that. Still dies off after 3-4 minutes of idle. One other curiosity is that using an IR thermometer everything on the odd side exhaust is 350-450 degrees and everything on the even side is well below 300 after 3-4 minutes of running. That can't be right?

I'm starting to suspect a wonky ECM. Not controlling the even side properly or is that even a possibility here?

Pro

I dont think thats a possibility. The fuel injection is controlled as a whole, all 8, not individually like in later models. So if you had a bad injector on the passenger bank, but drivers bank is running fine, the O2 sensor is on the drivers bank so it wouldnt see the issue with the passenger side.
You could do a fuel injector pressure drop test on each cylinder. I had one on cyl 5 that would stick open, and one on cyl 8 sticking closed. Since the O2 is on drivers side, it picked up the rich condition, so BLM would go down and down and down. And with the ECM removing fuel because of that issue on the drivers bank, cyl 8 on passenger side was running even more lean than before the adjustment. After I replaced all injectors the issue went away. BTW I replaced with the bosche injectors and didn't need to burn a new chip.

neilcase

Did you use Bosch II or Bosch III? Lots of chatter about Bosch III being a superior injector but our ECMs cant adjust for them.

Pro

III
I only drive like 1000 miles a year but so far what little testing i have done with them in both the truck and camaro they do fine.

ULTM8Z

Even if the Bosch-III's are not the source of the problem here, it'll behoove you to get the right values into the ECM for the tables I mentioned above.

neilcase

OK. Here's what I've done since my last post. New EGR. it wasn't suspect but since I had to pull the TPI apart to swap the Bosch III's for Bosch II's I replaced the EGR. New IAC as well.

So to recap. I have pulled the battery long enough to erase all the learned tables. I am a very early beginner with tuning so don't even know if I'm using the correct terms there. In addition to new EGR and swapping the injectors.

1. I have set the timing at 6 BTDC
2. Reset the new IAC via the grounding the ALDL for 30 seconds
3. Set the TPS to exactly .57 volts
4. Set the idle screw so that it idles at 800-1000 in park
5. checked for vacuum leaks (doesn't mean there still isn't one I didn't find)

I connect TunerPro and all I can do at this stage in my understanding of TP is to just watch the readings. The IAC is all over the place at idle in park but tends to settle between 10-20. TPS is around .60 BLMS 142 Integrator 128.

Seems to idle OK in park other than some erratic IAC readings. BUT ..... as soon as I shift into gear I see the IAC fall to zero and it dies.

HELP!

neilcase

SOLVED. Before I tell you the solution I want to encourage everybody to return to their posts and tell us when you have found your solution. Most of the posts I read just leave us all hanging. Anyway, mine is solved.

I actually had 2 problems that produced similar symptoms. After completing a ground up restoration I drove the car for about a week and it ran really well. The day I delivered it to the buyer it started stalling when shifted from park to gear and as time went on it starting stalling at stop lights too. And THEN it started konking out even in park after idling for 3-7 minutes. All seemed to be one problem that was progressively getting worse and more and more evidence pointed the finger at the Bosch III injectors. I ordered a set of Bosch II. Immediately noticed the car would idle in park and had much more power throughout its entire band. But it still stalled at stop lights!! Foiled again!

Did a little more reading. Called my Transmission guy based on a hunch I had that it might be the TCC solenoid. He says yank the connector and drive it all you want. I did and the stalling stopped immediately. Bad TCC solenoid!

And there ya have it. Runs like a new car now. The lesson? TCC will cause stalling in gear at stops. And even the really great guys at SouthBay insist the Bosch III's are compatible I say dont use Bosch III injectors. BTW the guys at SouthBay are amazing people. All they care about is that your car runs the way it should. He allowed me to send the Bosch III back after I had them for about 6 months. Great people over there!

ULTM8Z

If the BLM's are at 142, the customer may not notice the difference during normal driving since the ECM has room to correct the lean condition via closed loop fueling corrections.

But that perpetually high BLM s an indicator that the injectors are not properly tuned for, and the non-closed loop fueling will be negatively impacted- like open loop start up, power enrichment and accelerator enrichment.

Like I said, the customer may not notice the difference, but if he reports hesitation or lack of power, etc, the bin file may need to be touched to correct for the injector swap.

tduffy703

I am having the same type of problem with my 87 IROC, well actually it will idle but when you put it in gear it will stall out.....unless you stomp on it then it will smoke the tires....
you said you unplugged the tcc. did you have to pull the pan off of the trans to do that? or did you just unplugg the trans?