Starting Problem !!!!

**ROLLIN1200** · 08-11-2007, 08:55 AM

I have a starting problem that is kind of complicated to exlain but it is something like this. When my truck is cold (after sitting overnight) it starts fine. When my truck is running and i shut it off and start it right back up it starts fine. But the problem is when after driving my truck and letting it sit from 15 minutes to 4 hours it just cranks and barely starts, when it does start i have to give it gas to keep it running until the idle smoothes out. The problem may have began after washing my engine bay with a hose. Any help or ideas would be greatly appreciated.(99 silverado w/ 5.3L)

**newtechnova** · 08-11-2007, 07:22 PM

it sounds like the fuel pressure regulator is leaking fuel into the vacuum line that attached to it causing your truck to run rich on warm start-up. pull the vacuum line off the regulator after run the engine and see if it has gas in it

**SeVeReDiStOrTiOn** · 08-11-2007, 07:46 PM

Are you getting any codes? When you say you have to smoothout the idle...does it feel like it's missing? Does it run fine otherwise after having to give it gas to smooth out the idle? I'm thinking it might be a pre-cat o2 sensor since the cold starts are good (front o2's are bypassed in open-loop)...could also be a leaking injector causing a miss after sitting. Also how many cranks does it take to start up when warm?

Just FYI but when I wash my engine I cover the electronics with plastic grocery bags...so the whole throttle body, PCM, alternator, EGR, fuse block and I remove the MAF.

**ROLLIN1200** · 08-12-2007, 07:03 PM

I actually am getting a coide that indicates a faulty precat o2 sensor but i did not think that could affect starting. When it starts it seems like it may be starving for fuel, but i am unsure. For now I am going to get an O2 sensor and pull the vaccuum line. Thanks for your advice and I'll repost with the results.

**Naf** · 08-18-2007, 08:50 AM

WAIT A SECOND HERE!!!!!

there are some serious issues that need attendin to. I washed my engine plenty of times and i NEVER had any runnin issues...I did have TB problems due to imporper sealing, sparkplug burnin out due to leanin...

Plus a few spashes of water is acceptable, you have to remember, when it rains the engine is exposed to high pressure of water and it still runs great, till you kinda start to submerge it...Then it hickups...but a few puffs of air and its all good...

There could a number of problems...I know for a fact that the trailblazers have an issue with starting up in hot climate after runnin for a while...This is due to a data issue. My thoughts are your MAF might be broken, or your MAP...Temperture is your enemy with electronics, and if you did wash your car when it was hot you probably broke one of the components...

**ROLLIN1200** · 09-21-2007, 06:06 PM

I just pulled the vacuum line off the fuel pressure regulator the other day and fuel did spill out. So I went and bought a new one and replaced today and the problem is solved, so big thanks to NEWTECHNOVA, my truck finally starts like new again.