What would make an ECM sensitive to temperature?
Thread Starter
On The Tree
Joined: Jan 2002
Posts: 104
Likes: 0
From: Raleigh, NC
What would make an ECM sensitive to temperature? I'm working on a 99 Z28 and have run across a strange problem. When the ECM gets warm, the car will lean out to the point that it won't run. If I put a fan on the ECM and cool it down, the car runs normally.
I can watch the fuel trims with HPT and see them respond to the ECM warming up or being cooled down.
I have installed another computer with no change in symptoms.
One confusing thing, is that the ECM seems to be very temperature sensitive. If I put a thermometer on the ECM housing, I start to see the lean issue arise around 100-110 degrees F. As I cool the ECM down, the problem completely resolves itself as the ECM falls below 100 degrees.
The ECM should be able to easily handle 110 degrees, and I've had the same problem with 2 ECM's. I was wondering if anyone had come across some kind of issue that caused the ECM's to be so sensitive to temperature?
I've heard that running a large injector can cause the injector driver to heat up inside the ECM, but I've never actually seen that happen. This car is running stock impedance 80 lb injectors.
The car is a single turbo set up, running a speed density tune.
Any help is greatly appreciated.
I can watch the fuel trims with HPT and see them respond to the ECM warming up or being cooled down.
I have installed another computer with no change in symptoms.
One confusing thing, is that the ECM seems to be very temperature sensitive. If I put a thermometer on the ECM housing, I start to see the lean issue arise around 100-110 degrees F. As I cool the ECM down, the problem completely resolves itself as the ECM falls below 100 degrees.
The ECM should be able to easily handle 110 degrees, and I've had the same problem with 2 ECM's. I was wondering if anyone had come across some kind of issue that caused the ECM's to be so sensitive to temperature?
I've heard that running a large injector can cause the injector driver to heat up inside the ECM, but I've never actually seen that happen. This car is running stock impedance 80 lb injectors.
The car is a single turbo set up, running a speed density tune.
Any help is greatly appreciated.
Teching In
Joined: Oct 2007
Posts: 34
Likes: 0
From: Mount Airy, MD
I'm working on a 99 Z28 and have run across a strange problem. When the ECM gets warm, the car will lean out to the point that it won't run. If I put a fan on the ECM and cool it down, the car runs normally.
I can watch the fuel trims with HPT and see them respond to the ECM warming up or being cooled down.
I have installed another computer with no change in symptoms.
One confusing thing, is that the ECM seems to be very temperature sensitive. If I put a thermometer on the ECM housing, I start to see the lean issue arise around 100-110 degrees F. As I cool the ECM down, the problem completely resolves itself as the ECM falls below 100 degrees.
The ECM should be able to easily handle 110 degrees, and I've had the same problem with 2 ECM's. I was wondering if anyone had come across some kind of issue that caused the ECM's to be so sensitive to temperature?
I've heard that running a large injector can cause the injector driver to heat up inside the ECM, but I've never actually seen that happen. This car is running stock impedance 80 lb injectors.
The car is a single turbo set up, running a speed density tune.
Any help is greatly appreciated.
I can watch the fuel trims with HPT and see them respond to the ECM warming up or being cooled down.
I have installed another computer with no change in symptoms.
One confusing thing, is that the ECM seems to be very temperature sensitive. If I put a thermometer on the ECM housing, I start to see the lean issue arise around 100-110 degrees F. As I cool the ECM down, the problem completely resolves itself as the ECM falls below 100 degrees.
The ECM should be able to easily handle 110 degrees, and I've had the same problem with 2 ECM's. I was wondering if anyone had come across some kind of issue that caused the ECM's to be so sensitive to temperature?
I've heard that running a large injector can cause the injector driver to heat up inside the ECM, but I've never actually seen that happen. This car is running stock impedance 80 lb injectors.
The car is a single turbo set up, running a speed density tune.
Any help is greatly appreciated.
Checked and verified clean grounds?
Chris
Thread Starter
On The Tree
Joined: Jan 2002
Posts: 104
Likes: 0
From: Raleigh, NC
The injectors are 13.8-14.0 ohms. I don't have a super expensive meter, so those probably aren't accurate to the 9th degree, but I believe its accurate enough to show that they are the correct impedance for the stock ECM.
All the grounds have been taken off, cleaned, and re-attached.
I think we may have found the problem. One of the wiring harness legs is pinched between the down pipe and the shock tower. The shop that put the turbo kit together left the wiring in that location, wrapped in header wrap and then reflective tape.
Next round of diagnostics will include removing the harness and correcting that issue. Hopefully, that resolves the problem.
All the grounds have been taken off, cleaned, and re-attached.
I think we may have found the problem. One of the wiring harness legs is pinched between the down pipe and the shock tower. The shop that put the turbo kit together left the wiring in that location, wrapped in header wrap and then reflective tape.
Next round of diagnostics will include removing the harness and correcting that issue. Hopefully, that resolves the problem.
Teching In
Joined: Oct 2007
Posts: 34
Likes: 0
From: Mount Airy, MD
O2 sensor heater circuits and the 5 volt referece voltage for sensor operation come directly from the pcm. If those get pinched hard enough for a short to be intermittant. In some cases those circuits will overdraw if the load is big enough. What happens is the 12v power buss inside the pcm gets "pulled down" and it overheats the driver circuits in the pcm.
Good you found a possible fault area. Report back. It contributes to the knowledge base.
Chris
Good you found a possible fault area. Report back. It contributes to the knowledge base.
Chris
