user123

Guys, please help me. Limited budget (like everybody else on here...)

Vehicle:

Armored (bullet proof) 1999 Suburban, 350 V8, 110K miles, company vehicle, routine plug, tune ups, not exactly religiously followed. Will be sent to auction in 6 months. Do not want to rebuild the engine/etc for this problem...need it to run reliably for six months till I offload it. This vehicle weighs probably twice what a normal Suburban weighs.

Problem:

When driving up a steep hill, the engine coughs and sputters but when I push the pedal further to the floor it will "cough thru" the problem and spin back up to normal speeds. It gave the sensation (before I observed it closer) that the tranny was slipping, but RPMS do not fluctuate all over the place, they drop down slower as the engine coughs, which appears to be what it should be doing. It does burn SOME tranny fluid tho, FYI

On level street or downhill it runs fine. I attribute this to the fact that no load/stress is being placed on the engine.

Also, when you are parked or neutral (tranny not an issue in park...), if I floor it, it will run rough from say 1000 thru 2000 RPM then run strong. If I immediately pull my foot off the gas from high RPM, the engine will suddenly drop to idle (seems to drop a little quicker than I would prefer) to the point I think it will stop running....however it just drops back to idle and runs fine. It will often release a "pop" from the engine compartment (exhaust type sound) when I suddenly pull my foot off the pedal at high RPM.

This problem does not happen all the time, only on a hot summer day. Same hill in the morning, no issues. I will also state that with a full tank (heavy weight in back) this problem is more common than 1/4 tank of gas.

I also believed it was bad gas, but 10 tanks later, that is not the problem. Some fuel system cleaner dumped in tank kinda-sorta fixed the problem, but not really.

I also pulled the top of the air filter cover off, installed a new filter, and I drove it like that (no upper filter housing to cover filter, air filter exposed), and it ran somewhat better but still the problem exists.

I need a sub $500 fix for this. I am leaning toward new fuel filter, new PCV valve. Neither have been changed in history of vehicle so its prob not a bad idea anyway.

NOTE: Local Chevy house checked the fuel pump, pressure is fine. Due to a full garage I was not able to get a full diagnostic done

thanks guys

EvansBlue

It wouldn't hurt at all to do a standard tune-up. if the fuel filter has never been changed at 110K miles, I'd safely say its due

An Armored vehicle is an interesting find. Municipal/Government or Security Contractors auction I'm assuming?

user123

Bank vehicle

in2pro

110k miles 10 years old, my guess would be injectors need to be cleaned, try 2 or 3 bottles of techron in a tank and see if it improves for a bit...if so the poppets and injectors probably need cleaning/replacing

chrisbmo2000

its deffinatly a fuel/ ignition problem...............armored huh???? whats the mileage like?

user123

like 5 to the gallon city 10 highway

LRB

I have the same problem with my '98 Suburban with teh 5.7 Under load I start to loose power and the RPM's stay around 2400. The check engine light starts to flash then stays on. And after the hill it runs fine. My mechanic has hooled up the reader and I get random misfire code. This has happened many times, various cylinders, and sometimes multi cylinders. The reades shows thousnads of misfires when it happens.

What can be done to help this out?

73shark

Welcome to the forum. Did you try in2pro's suggestion?

LRB

Thanks for the welcome.

I spent some time going deeper into the posts here and have seen another thread regarding the injectors. Looks like its time to replace them. 148K miles so far. Been a good ride to date.

Also looks like I need to use spell check before posting threads.

73shark

Good luck and let us know how it turns out.