1995 3.8 V6 - Engine problem

[Rodaxx]

Hello everyone, I need help or advice on where the problem might be. Pontiac Trans Sport 1995, 3.8 V6. I apologize for the translator, but I'm from the Czech Republic ...

The cold start of the engine is absolutely fine, but as the engine warms up, as if running on only 4-5 cylinders, the engine speed fluctuates and the engine shuts off. The orange engine warning light on the dashboard illuminates. Can you advise where to look for a problem? Thank you all for any help.

[Jeffrv]

Is there anyway you can get access to a scan tool to find out the trouble code that made the orange light ( with engine symbol) come on? otherwise it is going to be rather difficult hit and miss to track down the problem. Perhaps check for vacuum leaks, proper fuel pressure, and spark from all 3 coils. Use an inductive timing light to see if one coil quits when it heats up.
Good luck
Jeff

[Virgis007]

Hi, and welcome.

Good advise from Jeffrv, but I think that it could be the ignition coils or ignition coil plugs and cables. If they are good, then it may be that the ICM (ignition control module) is faulty. Best would be to connect to the diagnostic port and to check.
On 1995 TS the paper clip test won't probably? Paper clip test was a real savior for me.

[Blue Bowtie]

What will make it even more difficult is that 1994/95 vehicles did not need to conform to the OBD-II standards, so scanners are fairly specific to vehicle brands.

[Rodaxx]

Thank you very much, diagnostics is a problem, the staple test cannot be performed. Cables and plugs are new. Fuel pressure OK. So I'll try to replace the ignition coils.

[Blue Bowtie]

Instead of replacing all the ignition coils, fundamental diagnostics should be able to reveal whether ANY of the coils have problems, and identify the coil(s) involved.

An important item is to verify good grounding of the Ignition Control Module (ICM). The cam position sensor (CPS), the crank position sensor (CKP), and the ignition coils all rely upon the ICM base for a good ground reference. Since the bracket which holds the ICM and cols is aluminum, if can suffer corrosion. It is a good idea to remove the ignition coils, remove the ICM, and clean the aluminum bracket. It is also good to clean the bolts holding the bracket to the engine to insure a reliable ground.

When the bracket is cleaned a polished to a bright surface finish, install the ICM, connect the sensors, and install the ignition coils.

When the engine is running and at normal operating temperature, carefully remove one spark plug wire from an ignition coil and note any changes in idle quality or speed (RPM). Insulated spark plug wire pliers are helpful for this. Do this for all cylinders, one at a time. Replace the spark plug wire in its original position, and remove the next spark plug wire from the adjacent coil terminal and monitor the idle speed and quality.

If removing a spark plug wire does NOT affect the idle quality, it is a fair assumption that the cylinder with that disconnected spark plug has some problem. If removing two wires from the same coil causes no change in idle, that coil may have a problem.

If a coil is suspected as having a failure, exchange that ignition coil with one from another position and see if the problem remains with those two cylinders or has moved with the coil. If a coil is verified as having a problem, replace that coil and test again.

[Rodaxx]

Originally Posted by Blue Bowtie

Instead of replacing all the ignition coils, fundamental diagnostics should be able to reveal whether ANY of the coils have problems, and identify the coil(s) involved.

An important item is to verify good grounding of the Ignition Control Module (ICM). The cam position sensor (CPS), the crank position sensor (CKP), and the ignition coils all rely upon the ICM base for a good ground reference. Since the bracket which holds the ICM and cols is aluminum, if can suffer corrosion. It is a good idea to remove the ignition coils, remove the ICM, and clean the aluminum bracket. It is also good to clean the bolts holding the bracket to the engine to insure a reliable ground.

When the bracket is cleaned a polished to a bright surface finish, install the ICM, connect the sensors, and install the ignition coils.

When the engine is running and at normal operating temperature, carefully remove one spark plug wire from an ignition coil and note any changes in idle quality or speed (RPM). Insulated spark plug wire pliers are helpful for this. Do this for all cylinders, one at a time. Replace the spark plug wire in its original position, and remove the next spark plug wire from the adjacent coil terminal and monitor the idle speed and quality.

If removing a spark plug wire does NOT affect the idle quality, it is a fair assumption that the cylinder with that disconnected spark plug has some problem. If removing two wires from the same coil causes no change in idle, that coil may have a problem.

If a coil is suspected as having a failure, exchange that ignition coil with one from another position and see if the problem remains with those two cylinders or has moved with the coil. If a coil is verified as having a problem, replace that coil and test again.

THANK YOU VERY MUCH, I will try everything, but how do I perform the basic diagnostics on the 1995 model?

[Virgis007]

Originally Posted by Rodaxx

THANK YOU VERY MUCH, I will try everything, but how do I perform the basic diagnostics on the 1995 model?

These are the basic diagnostics that Blue Bowtie wrote you about. Simple tests that may indicate your problem.

[Rodaxx]

Originally Posted by Virgis007

These are the basic diagnostics that Blue Bowtie wrote you about. Simple tests that may indicate your problem.

Understand, very thanks all!