I had the ECM replaced a while back. The car had to be towed to the dealer. It has not idled well since getting it back. I drove it for a few days to let everything relearn new settings -fuel trims, etc. I reinstalled the Diablo tune. Performance was down a bit and the idle was poor. It had an intermittent miss and rough idle. It drove like it had a small cam in it. The idle was rough and caused enough of an rpm variance that easing up to a red light or slowly creeping along in traffic made the poor adle even more obvious. I removed the Diablo tune. It made no difference.
I talked with the dealer tech that installed the ecm and he said sometimes it takes several tries to get the crank TDC to "properly take". Does any one have experience with the Tech 2 tool and what it involves to install an ecm and get the settings correct? Highway travel is still good and no cel or codes. What issues would be created with an issue with the crank TDC being off? Can the crank tdc position even be "off"?

Please no "replace the plugs". Plugs and wires had less than 2000 miles on them before the ecm replacement and they have been replaced since the ecm install.

 

did you install a new pcm? if so was it the right year for the car. some differences lie between the ebcm that may stop the car from seeing that you`re holding the brake pedal to do the relearn correctly

 

Sounds like your dealer is FOS. I changed the ECM in my car to one from Chuck CoW and I didn't have any problems like that. It was literally a plug and play deal.
The ECM will typically throw a DTC and light up the CEL for crank relearn reset. I had one after changing my cam, and the only how I got rid of it was one day when accidentally overrevved the car in first gear when I was dialling in the trans tune. Apparently, you need to rev the motor until it reaches the fuel cut off point to reset it.
Other than the CEL, the car had no other symptoms from the crank relearn code, and it idled exceptionally well, even with the new cam.
I don't think you have a crank TDC relearn problem or you would have a DTC. Can't remember what the code was exactly.
I would get a competent tuner's opinion on this. Dealers are invariably the worst people to take advice from on modified or tuned vehicles anyways.
Good luck with getting it sorted out.

 

Thank you. There's lots of was you can do it..... and NO it isn't really necessary.

Our AutoCal Device can do the crank learn procedure on most vehicles and computers.

Not necessary to go to the dealer....

Call me nay time if you need help.
Chuck CoW

 

Well... The typical answer in this section is "Did you check your grounds?"

 

HOLY COW!!! Chuck, you still alive??? Haven't heard from you in ages - thought you had packed it in! How you doing man?

 

So true! It's like you were in court or something...

 

I had a similar with a computer changed by a dealer my best conclusion after many years of experience now is the stealership installed someone removed faulty computer into my car and keep the guarantee money.

No you don't have to worry about crank learn procedure take the car to another dealer.

 

If the ECM was replaced they are supposed to follow the procedures below.

If the engine control module (ECM) is replaced, the following procedures must be performed:

The ECM Reprogramming--Refer to Service Programming System (SPS) .
The CKP Variation Learn--Refer to Crankshaft Position System Variation Learn .
The Theft Deterrent Programming--Refer to Immobilizer System Component Programming .
The Clutch Pedal Position Sensor Learn--Refer to Clutch Pedal Position Sensor Learn .
The Throttle Learn procedure--Refer to Throttle Learn .
Engine Oil Life Remaining--When available, use a scan tool to rest the Engine Oil Life Remaining back to the original percentage recorded.
Transmission Fluid Life Remaining--When available, use a scan tool to reset the Transmission Fluid Life Remaining back tot he original percentage recorded.

I would be willing to bet they didn't perform the throttle learn. Procedures below:

Throttle Learn
With Scan Tool - Reset Procedure

Ignition ON, engine OFF, with a scan tool, perform the Idle Learn Reset in Module Setup.
Start the engine, monitor the TB Idle Airflow Compensation parameter. The TB Idle Airflow Compensation value should equal 0 percent and the engine should be idling at a normal idle speed.
Clear the DTCs and return to the diagnostic that referred you here.

Without Scan Tool - Learn Procedure
Important: Do NOT perform this procedure if DTCs are set. Refer to Diagnostic Trouble Code (DTC) List - Vehicle.

Start and idle the engine in PARK for 3 minutes.
With a scan tool, monitor desired and actual RPM.
The ECM will start to learn the new idle cells and Desired RPM should start to decrease.
Ignition OFF for 60 seconds.
Start and idle the engine in PARK for 3 minutes.
After the 3 minute run time the engine should be idling normal.
Important: During the drive cycle the check engine light may come on with idle speed DTCs. If idle speed codes are set, clear codes so the ECM can continue to learn.

⇒ If the engine idle speed has not been learned the vehicle will need to be driven at speeds above 70 km/h (44 mph) with several decelerations and extended idles.

After the drive cycle, the engine should be idling normally.
⇒ If the engine idle speed has not been learned, turn OFF the ignition for 60 seconds and repeat step 6.

Once the engine speed has returned to normal, clear DTCs and return to the diagnostic that referred you here.

 

Thanks for all the help and ideas. The idle RPM was fine when I got the car back from the dealer about 3 months ago. I paid for a new ECM. Pretty sure I got a new one, the original ECM was toasted. I know the parts people and service writer. They are good people.
Back to the issue with the engine. I replaced the mass air flow sensor. New AC Delco unit, same as original, #15865791, $34. I found a GM bulletin addressing weak mass airflow sensors. Worth a shot. The engine idles decent until everything gets hot. Idle begins to get rough. When the ECM was failing I got some backfires out the exhaust and intake while just trying to get to an exit around midnight. I'm ready to pull the intake and look for a vacuum leak. Engine runs great up to the 1-2 and 2-3 shift points of about 6000 rpm. Only issue is idle and just off idle speeds.