Cold start issue 2007 Tahoe

[zorrro]

Our 2007 Tahoe has a cold start issue in the cold weather. It starts happening around 40F and gets worse through -10F (coldest so far). Its getting to the point where we are going to be stranded soon if I don't get it whipped.

 

On a cold morning or after sitting a few hours engine seems to fire right up them immediately drops off in rpms (you think it stalls) then ramps back up and stumbles for about 15 seconds then is fine. More and more frequently it actually dies right after initial fire-up then becomes much harder to start.

 

I've checked fuel pressure during one of these episodes: Fuel pressure starts at 0 psi, immediately goes to 60psi upon turning the key, engine starts and stumbles and FP stays at a steady 60 while engine stumbles around 700-1000 rpm for about 15 secs.

 

I've sprayed starting fluid around intake manifold to test for intake leaks and no change in engine rpm or any other evidence of intake leaking.

 

We run 87 fuel most of the time 10% ethanol (pump rating). We have alsways used this grade of fuel. At least for the last 140k miles. No check engine light or codes stored in computer.

 

Car has near 200K miles, we have owned it sense 60K it has always started slightly abnormal when extremely cold but nothing to be concerned with. Now I am concerned and confused...

 

Whatcha think? Thanks much......Z

 

 

 

[zorrro]

It is a flex-fuel rig. We tried e85 one time about 5 years ago. It ran bad and got horrible milage. I'll never touch the stuff again..

[zorrro]

After reading my Haynes book, staying at 60 psi after the engine starts might be the issue. It claims, the pressure should drop to 45 psi once the engine starts. Mine stays at 60 all the time......

[BlackZ71Silverado]

After reading my Haynes book, staying at 60 psi after the engine starts might be the issue. It claims, the pressure should drop to 45 psi once the engine starts. Mine stays at 60 all the time......

 

That is correct! The initial start-up pressure should be higher than the idle pressure. That 60psi being constant may be the issue.