I think my truck is shot

TUFFTRUX · January 18, 2006

Have a 2000 GMC SAVANA 2500 Cargo Van with a 5.0L V8 and 4L60E, 220K miles and 1 tranny rebuild in commercial service. During a return trip from Boston to NYC, the truck would suddenly lose power and I would need to use 2nd gear to bring it back up to speed and then shift back to 3rd or 4th. This happened a few times on my way back. By the time I got back to the city the engine could no longer idle by itself whether in gear or in park. It would run really rough and shake a lot and I would need to keep my foot on the gas to keep it running. After letting it sit for the night, it is really hard to start and I still need to keep my foot on the gas to keep it running, there is some black smoke when I start it and a lot of moisture and emissions coming from the exhaust, and also the brakes don't work right. The brake and antilock lights are on and the pedal is really hard to push down still have some brakes though (I am assuming I lost vacuum assist). The engine Oil and oil pressure are both normal. The transmission oil smelled burnt and looked brownish so I'm assuming the tranny is gone but what about the engine? Is the transmission causing my engine to stall? Thanks in advance for any assistance.

By the way, I am using all synthetic lubes, for the engine, tranny, and rear end. Maintenance has been kept up regularly with a tune-up that was supposed to be done this week.

Thanks,

Luke

RyanZ71 · January 20, 2006

I would first start out by checking the basics. Check the charging system, battery condition (don't go by that stupid pointless little eye on the battery) then onto the alternator. Check that because a faulty charging system can cause problems with the onboard computer. Next would have to be the wires, plugs, fuel filter, maybe the fuel pump is going out? That kind of milage it could be anything but do the basics first. I don't believe your engine is going out. Will it rev easily when it is in park and you step on the gas?

mmmikkke · January 20, 2006

I think you could have a leak in your vacuum dashpot for your power brakes, which is of course affecting the drivability of the engine because if the vacuum leak is bad enough, the engine won't run.

Try disconnecting the vacuum line to the power brakes, and plugging it, and see how that affects your idle.

kdm101 · January 20, 2006

The vacuum leak sounds plausible to me too. I know that when I've pulled brake booster line from my own truck, it wanted to stall immediately. Amazing how such a "little" thing makes such a big difference in how it runs.

I doubt the trans is causing the engine problems (not that it's helping at all either). In park, the transmission is essentially disconnected, and if the engine won't idle then either, I would think you can factor it out.

For my "worst case scenario", excessive loss of power might also be caused by damaged (plugged) catalytic converters. I once borrowed a Savanna that had cat damage. Power would suddenly drop even with the pedal floored. Once you let completely off the gas, you'd end up with a quick surge of power as the back pressure released, then you could get back on the gas and go again for a little while (the guy that owned it was notorious for poor vehicle maintenance - it was practically a rolling wreck!). However, I would assume that this would throw a code in the computer and give you the "Service Engine Soon" message. A simple test would be to disconnect the exhaust at the headers and try running the engine. It'll be loud and you'll definitely throw a code because the O2 sensors won't be picking anything up, but you should have your answer fairly quick.

TUFFTRUX · January 21, 2006

Thanks for the replies, I too think it is a vacuum leak and will check it out tomorrow. The truck can rev up easily its just that it runs loud and rough. It is also tough to start. As for the vehicles on board computer, it hasn't given any code or SES light so I'm assuming something is probably wrong with that too.