rough idle

[elgineddie]

I have a wicked rough idle that I've been coping with for over a year.

In fact, I can't remember how long it's been, but it's been too long. I know I've tried everything to fix it.

New fuel filter, plugs, wires, injectors. Sea Foam. Checked all connections. Even a Westers Tune (I told my wife I needed the "computer reprogrammed" to help fix the bad idle!!).

I've checked the stored codes (although it never lights the MIL light) and found only generic lean condition code faults.

 

I've done the idle relearn procedure a few times and that hasn't fixed it. I read online that there is a "Crankshaft Position Variation Learn Procedure" (see below). Anyone done this? Is this applicable to Chevy's?

 

Are there any other recommendations y'all can share for me to check?

Someone once told me it sounded like a bad intake manifold gasket but how the h&ck do ya check that?

 

Many thanks!

Ed

 

 

CKP variation is only relearned with a scan tool. It does not relearn “by itself.”

 

1. Make sure no DTCs are set. If DTCs

are set, service them before performing the procedure.

2. The service brake must be firmly applied and the transmission in Park for an automatic or Neutral for a manual.

3. A/C must be “OFF” and the hood closed.

4. At this point, use the scan tool and select CASE Learn:

5. Open the accelerator to the CASE fuel cutoff speed and release it as soon as the PCM cuts off the fuel and the engine begins to decelerate.

6. The scan tool will identify when the procedure is complete.

[GM-Tech]

I read online that there is a "Crankshaft Position Variation Learn Procedure" (see below). Anyone done this? Is this applicable to Chevy's?

 

It's applicable, but a crankshaft variation relearn isn't going to correct any sort of rough running or driveability problem. All that does is give the PCM a point of reference so it can detect misfires. It doesn't CAUSE misfires or rough running.

[elgineddie]

...a crankshaft variation relearn isn't going to correct any sort of rough running or driveability problem...

 

Hmmm, OK. I can follow that. Thanks.

 

Let me ask you this... What would be the first couple of things you would check if someone brought in a 2001 Suburban 6.0L K2500 with 110,000 miles that just replaced all those items and still had a bad idle?

[devin16]

could be an o sensor

[sxmax]

Are all of your sensors within range? O2, map, fuel pressure regulator? Maybe even a clogged cat?

[elgineddie]

Are all of your sensors within range?  O2, map, fuel pressure regulator?  Maybe even a clogged cat?

 

Good questions. I am not sure.

So to check sensor ranges, I'd need to get a scan tool that reads and displays that sort of data? (I know, dumb question.) My code reader is just that, a reader and doesn't display sensor readings.

[sxmax]

Correct. I reputable shop either a GM shop or the guy down the street with some $$ invested in tools can hook up and watch all these. I use the Vertronix Mastertech at our shop. It is simply amazing what you can do with one of these things, even rev the engine if needed!!!

[willieboy]

Correct.  I reputable shop either a GM shop or the guy down the street with some $$ invested in tools can hook up and watch all these.  I use the Vertronix Mastertech at our shop.  It is simply amazing what you can do with one of these things, even rev the engine if needed!!!

 

<{POST_SNAPBACK}>

 

 

 

That is what my local shop uses as well. It is pretty impressive...