Okay, this is a hard problem to describe. My truck idles like I have a racing cam in it. I don't. Now, while it's idling rough, I've noticed that the lights will dim as the rpm's get lower, and brighten as it smooths out. When I put it in reverse, it idles even rougher and almost dies. I shift to drive and it idles smooth, but when I accelerate, it bogs down so bad it is right on the verge of death... Acceleration is really slow up to about 15mph. Once I hit that mark, it smooths out a little and runs okay, as long as I'm accelerating. Once I hit a cruising speed, be it 35mph or 70mph, the truck, well, loses power. That's the only way I know to describe it. What it does is, say I'm cruising at 35mph. The tach reads 1000 let's say, but, if you watch it, it will drop to about 600 for a split second and back up to a grand. You can feel it "lurching" as it does it.

Now, back story. About a year ago, I had a cracked intake manifold gasket, and replaced it. I called a Chevy dealership to get the torque specs for the manifold bolts and they told me 75 foot lbs per bolt. Snapped one off. Called a different dealer. 60 foot lbs. Snapped another. Called yet another dealer. 35 foot lbs. As the third bolt snapped, I threw one hell of a temper tantrum. I called a custom hot rod builder I knew and he told me 22 INCH lbs. Doesn't seem like that's enough, but, I didn't snap a bolt. But, because of the other crap, I ended up cracking the lower manifold and just replaced it, thinking that it was the cause of the rough idle. It wasn't apparently. SO, now I'm thinking that either I screwed up and put my plug wires back on wrong, didn't get a good connection on one, switched a fuel injector nozzle on the spider, or maybe got my timing off just a hair. I'm at a loss. And if you have ever had to remove the lower intake, you'll understand this next part. When I pulled the distributor assembly, I bumped it and broke part of the flange off of it. So now, the only thing sealing the hole it seats in is the gaskets. I don't have alot of money, and I am FAMILIAR with the 4.3l Vortec, I am not, however, a master mechanic. I know enough to get me in trouble.

If you know anything about this problem, PLEASE contact me asap so I can get my Beast back on the road!! I am so frustrated that I am almost considering large amounts of C4 to remedy this problem!!! Thank you!

 

Have you actually tested compression? Your problem could be caused by a clogged EGR valve or a MAF sensor problem amongst numerous other sensor issues that could cause this driveability concern. Are there any codes present?

 

I'm going tonight to see if we can get a good code reading. As for checking compression, I'm not exactly sure how to do that. I'm a self-taught shadetree mechanic. I know I have several problems with it, and I'm hoping that it's something relatively cheap. I'm always broke. My wife and kid take all the money I have.... I know I have a problem with the oil pickup valve, possible my spider is going bad, the catalytic converter is shot... I'm thinking that C4 would be the best answer, but I love 'er too much to blow her up or trade her off on a newer, less dependable car. I'll find out what codes it throws tonight and post tomorrow.

 

You test compression by first picking up a compression tester. It will be a gauge with a hose and fittings that will screw into the heads in place of the spark plug. You should pull the fuel pump relay and all 6 plugs, then test each cylinder individually, recording the pressure readings each gives.

 

Okay, I had the compression tested yesterday and it read okay. My friend tested it for me, he is very touchy about his tools so I didn't get any of the readings. I took it and had a diagnostic run and it says I have a mis-fire, but did not give the cylinder. SO, I'm going to start in the most obvious place and check the routing of my plugwires. Hopefully that's it. If it is, I'm gonna kick myself.... If that's not it, I'm going to check my plugs and then finally, my fuel injection spider. I'm honestly praying that it's the plugwires. Thanks for your input. I REALLY appreciate it!!

 

Well, the plugs nor crossed fuel injector lines seem to be the problem. Going to change the plugs tomorrow and if that doesn't help, well, I guess I'm going to order a new spider. yay.... The problem almost seems electronic though. It's like I'm having constant "brown outs" The rpms fluctuate and lights flicker while idling, kinda like it's having a hard time keeping a smooth flow of energy. I don't know if this is the engine, or maybe something electronic....

 

Well, latest update.... I am starting to believe that my timing is off by maybe one tooth. Going to pull the distributor and decrease the timing hopefully today. I did alot of work to it over the weekend and this week and nothing has changed. I took it out after dumping some fuel injector cleaner into it and nothing changed. I did notice however, that at 70mph it ran fine. Even jumped to 85 and 90 easily. But, once I hit a stop sign, the engine tried to die again. Rough idle, flickering lights, the whole bit. I'll post again once I adjust the distributor...