Posted: 6/9/2004 8:14:56 AM EDT
|
I have a 95 chevy silverado 4x4. I recently rebuilt the motor. It seems to run great on flat ground. I seem to loose power when going up long hills. I am also loosing about 100 miles per gas tank fill. AND heres the really bad part. I am cracking exhaust manifolds. I acuatlly cracked 1 of them in the last couple months. This means I am running rich right?? I checked all ther wireing. Everything is hooked up as far as I can tell. I changed the o2 sencesor. Any help would be greatly appreciated. AND, Before I rebuilt the motor this crap was happening with the old motor also. I think I cracked 2 exhaust manifolds before . So I am at a total of 3 at this point. Any ideas Thanks Brian |
|
You're running LEAN. Atomized gas at 14:1 air/fuel is a propellant. Add more air, and it becomes EXPLOSIVE. So instead of the fuel burning at a relatively cool temperature, producing a steady 'push' of combustion-gasses, it's BLOWING UP -> combusting very quickly & very HOT, producing less power & more waste heat (as a side note, this is why it's so easy to kill an engine with NOx or poorly-done forced induction. You run lean & burn things up)... This means higher exhaust temps & busted stuff... Usually valves, manifolds & exhaust hardware... It can damage your cylinders/pistons if it goes on long enough, too... Check fuel pump, fuel filter, injectors... Either that, or you have a plugged catylitic converter... Silverado is what, a 350/5.7? |
|
Sounds like a lean running engine, which is also causing detonation(ping), this will destory your engine, need to fix it soon ... If your injectors are clean and functioning properly, then the computer is getting some bad signals and telling the engine to go lean. |
|
i agree with redhorseman. lean = hot, usually burned valves and in extreme cases burned pistons (trust me, i've done chernobyl on everything from harleys to small blocks). rich = washed down cylinder walls, accellerated cylinder/ring wear, smoking (black smoke). i'm wondering if you haven't cooked a head gasket or cracked a head? checked the oil and coolant? any cross contamination? hows your cyl. head temp running? check the cooling system for plugged galleries (was the block boiled out prior to rebuild?)? radiater flowing freely? water pump working efficiently? how are you torguing your fasteners? evenly...sneaqking up to torque spec? have you checked for twisting the headers as you draw them up? i'm just tossing out suggestions... |
|
If you're getting no codes(check engine) then it PROBABLY not a sensor related issue. In saying that, I'd look at fuel like everyone else says. Your running lean, meaning not enough fuel, start there. A plugged CAT is a good place to start as well. Just remembered something: I have a first Gen Vortec 4.3 and it has the infamous injector leak alot of people know about. One of my mechanic buddies claims that alot of the injectors in the 350 are starting to fail as well. This could be your issue and would explain alot of the problems you are having. When the injector leaks, crazy things can happen due to the computer thinking it getting everything it needs but in reality, its not getting enough fuel and fuel leaks down into the valve/chamber area when its not supposed too. Dependig on the leak, it can cause a lean or a rich condition, which dragracer pointed out, either can cause exteme heat in your exhuast system. A lean condition will cause higher temps inside the engine, but a rich condition will yield higher temps to the exhuast sytem when compaired to a lean. CATS will get eaten alive if unburnt fuel gets in them. |
|
It could be several things... Lean makes high cylinder temps = high EGT's(exhaust gas temps) = glowing exhaust manifolds Extreme rich condition will put excess fuel into the exhaust manifold where it continues to burn = high EGT's = glowing exhaust manifolds Retarded timing starts combustion too late, and continues while exhaust valve opens = high EGT's = glowing exhaust manifolds... Maybe a tooth off when you dropped the distributor back in, or got the timing chain a tooth off. There's three things for you to look at. 
|