Hi, I have a hummer h2 supercharged I just got, that when I try to start it with the engine cold, it cranks a little before it actually starts.
If I try to crank it after the engine is hotter, it cranks as it should.

Battery is fine.
I have checked fuel pressure and it's ok.
I switched the MAF with another H2 and the problem remains.
There are no errors showing up (no engine light on).


When I start it cold, it cranks a little and it starts with low RPMS (on other good working H2s, usually the RPMS peak a little then it idles) on this H2 when it starts it doesn't give that little peak.

Any suggestions on what it could be?

 

You likely have a fault in the IAC or TPS.

You would have to get into the settings on the ECM and check the settings and or check for faults.

It MIGHT be entirely possible to reset each by disconnecting the battery for a few mins and then doing a throtttle re-learn.

Tim

 

 

With a Tech2.... I think some of the expensive higher end scan tools that mechanics have from Snap On / Mac Tools, etc also have the programming to do a throttle relearn. I'm not sure there is any other way.

 

I talked to the shop that is trying to fix this problem, and they said they already tried switching the throttle body from another h2 I left there, to the one that has the problem and it behaved the same, it didn't fix anything.

That should eliminate the possibility of it being a IAC or TPS problem, right?

 

NO because the ecm doesn't know that the part has been changed.

Check google for the relearn procedures or atleast disconnect battery for a few mins and see it it will adjust itself.

Tim

 

 

I did the throttle relearn process but nothing changed.
Here is a video I made today of a cold engine start, maybe someone can identify something from the video.

 

You need to take it to a tuner and see where the temperature based idle rpm is at. Its hard to trouble shoot without having it on a computer to see where everything is at. You might go over the LS1.com board and read some tuning info and or pose the same question over there. I'm far from a tuning expert but know enough to get by.

Tim