OK, so I've been having a rough idle problem the last few weeks. No codes. Changed all the usual tune-up type stuff. No improvement. Since I get a discount because my daughter works at a dealer, I finally broke down and took it in.

What I get told is fuel injectors are dirty and need to be cleaned. Fine. MAP sensor is way out of range. OK, fine. He says all the plugs like fine. I know, I just changed them, but the old ones looked fine too. He says the rest of the basic stuff looks good. Then he tells me my compression is at about 150 PSI, but he's pretty sure my cam has some flat spots on it. Huh? I've only had the truck since last July, and it's run great until this rough idle thing started a few weeks ago. I of course have no way of knowing how the truck was treated before. I'm assuming it was used to either tow or haul some fairly heavy weight considering the overload leafs AND the coil-over shocks on the back.

Has anyone else had a problem with cam lobes flattening out, but the engine still seems to run OK? I guess I'm just going to have to see if the MAP sensor and cleaning the injectors smooth out the idle.

 

I thought they went to roller cams by 95. Only older chevs wear out cams. It would probably start popping out the exhaust or intake if you started to round a lobe.

 

No popping or anything like that. It has just been shaking at idle. Actually, even while driving when the RPM's are under 1500 or so you can still feel it. Anything over that and it's just as smooth as ever.

I thought the engines were roller by '95 also. Does anyone know for sure?

 

Well if it smoothes out you know it's not the cam.Rollers don't wear out and I'm pretty sure thats what you have.

 

Well, so now they say the cam is fine, but I have a vacuum leak in the intake manifold gasket.

And no, the MAP sensor and cleaning the fuel injctors didn't help at all.

 

The best way to check for a "wiped" cam lobe is to pull the valve
covers, and watch the valves open. If you have a "wiped" cam
lobe, you will see the valve barely open....