Stumbles on cool start up

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Aug 17, 2019 | 06:53 AM

#21

Twisted sisal

Thread Starter

Junior Member

Joined: Jul 2018

Posts: 18

It will do it at anytime with a full tank of gas or a qrt tank I did a fuel pressure test I had 55lbs of pressure and my leak down test I lost 10lbs in 10min

Aug 28, 2019 | 08:35 AM

#22

HumbleAg

Senior Member

Joined: Nov 2009

Posts: 174

Quote:

Originally Posted by hummerz

Have you performed an induction service?
I'm currently doing my annual service on mine right now, got the tank from penray rep(pic below). Add a 1/2 can of seafoam, adjust the flow( a slow drip) and run at 1800rpm until the tank empties. Seafoam also carries a spray can with a long hose attached that you can try:

Well, this seemed to work. Used the spray can and followed the video procedures. Still got quite a few misfires right afterwards, but drove around a bit and they stopped. Have cold started a couple of times since then and no misfires reported.I think that indicates it was a sticking valve issue, just need to see if it comes back. Since the Hummer isn't a daily driver, sitting up seems to cause it to misfire more.

Thanks for the help!

Sep 4, 2019 | 03:40 PM

#23

hummerz

Senior Member

Joined: Jul 2012

Posts: 8,999

From: C-Town

Quote:

Originally Posted by HumbleAg

I only average around 3k miles per year, however I only use top tier fuel, I also keep the oil clean with a quality full synthetic oil, and keep the air filter clean. If you ever experience a performance issue in the future, you now know where to start.