Bangkok Dean

Current problem with my 1990 L98 engine.
Symptoms, in closed loop the engine stalls and runs erratic even when applying the brake and trying to keep the revs up, it bucks and will stall.

What I have tried today is installing a different IAC, following the instructions provided by Lars and Tech tips. All went well after setting the IAC and the TPS to .54volts.

The car did idle at 750 in gear at a stop light. So I took the car on the high way for about 1.5 miles, came to a stop and all seamed good till I went to turn on to the highway too go home and it stalls in the turn.
Now after putting it in neutral and restarting it does not want to run, so I used the pedal and the brakes to limp home. That was a chore.

In the driveway I turned the motor of and then restarted and checked the fuel pressure and it was a steady 42 lbs but after a few seconds it stalls.

This has been giving me fits for a long time and it is getting worse.

The temps hold between 185 and 192 when hot.

What am I missing?

thurman_merman

There are still a few things you can check. First, check for codes in the ecu using a jumper wire. Put a timing light on all of your plug wires and make sure they are firing. Check your map sensor the same way you checked your tps, just pull the vacuum off for voltage change. Egr could be faulty or clogged, you can check spark plugs, you could have a wiring problem, try moving your wires around under the hood while it's acting up. FSM should have a procedure for stalling and checking the ecm. You could try a known good computer if you have access to one.

Bangkok Dean

I don't have a FGR and don't have codes available. I have been running the engine for 4 year now and it has been a struggle keeping it running as it should. Sometimes it is good and lately it is a mess.I will bring it to a shop on a slider truck that has a scanner to try to see what is the problem. Maybe the map is the problem?

aklim

What EXACTLY has been done to that motor?

esham

Are the fuel injectors original?

Bangkok Dean

The motor is stock, with about 10,000 miles on it

The injectors are Accell

aklim

Accel? What size? Were they too large or small for the ECM you were using? Are the other values right or just plausible?

Bangkok Dean

3 year ago I had a custom EPROM made for the setup In the motor.

All was good till a couple of weeks ago when everything went crazy.

I really dont drive it much, maybe 10 miles a week. Last month I took it on a trip 400 miles and it ran mostly good but when I stopped for a short time and started it, the motor died and ran funny. I thought the problem was heat related but now I don't know.

Question will the 02 sensor, he MAP cause the problem?

Bangkok Dean

Cold starts the motor idles OK fuel pressure 42 lbs.

As soon as it warms up it immediately stalls. even trying to give it gas.

aklim

Any way you can get an IAC count when warm and a fuel pressure reading

Bangkok Dean

The fuel pressure hold true at 42 lbs. I will try to get data when it is at my friends shop and post it. Many thanks

I am thinking it is an electrical problem maybe the coil when it is hot. But usually when the coil is bad it is gone.

cv67

Wonder if your coolant temp sensor is taking a dump on you?

aklim

Fair enough. Lets try that. When the problem comes, pull out a wire and stick a new spark plug in it and ground the threads. If you get a steady blue sparking, you are not broken there.

Bangkok Dean

Are you saying that the coolant temp sensor would cause the problem?

aklim

It could cause problems. Way I understand it is that the ECM throws a code if the sensor reports way out data that isn't plausible. So if the sensor reports say 400 degrees, sure. OTOH if the sensor reports 20 degree temps but it is actually 70, it might not know enough to cross check with the oil temp.

If you get a scanner, you can see if the value is correct. So if the ECM sees 100 degrees, you hit the sensor with an infrared thermometer and it should be around that temp. If not, replace.

Bangkok Dean

Tomorrow is a holiday here so the scanner will be next week, thanks again

aklim

Don't forget the infrared thermometer