i have a 99 with the 4.3L that is running rough and also running very rich, i have recently done a tune up (plugs,wires,cap) , and checked it with code scanner and it said the O2 sensors were bad, so i changed them, it is still running rough and the check engine light is not on either but it is stillhard to start and running rough and rich.anyhelp would begreatlyapreciated

 

I would start by cleaning the throttle body (and the IAC - idle air control valve bore) and the EGR valve with some sensor safe carbon cleaner. Also clean the MAF sensor (very carefully) with some MAF specific cleaner. A clogged EGR valve can cause an engine to run rough and rich.

After that, if none of those items change anything, you may want to look into doing a fuel pressure test, paying particular attention to the fuel pressure after you turn the key off. If it drops, you have a leak somewhere. You can follow the procedure found in the DIY section for testing to narrow down the cause if necessary.

 

i am not very good with all these sensors on new cars,could you tell me where the EGR valve is possibly located

 

The EGR valve is on the front of the intake; cylinder looking thing with a 4 or 5 pin connector on the end. The end that bolts to the intake is in a bit of a "Y" shape, two bolts.

A piece of carbon could be in the EGR valve, keeping it open when it should be closed. Very common problem. Very easy to fix. Just unbolt the EGR, and carefully remove it and look at the end of it. I have not worked on a '99, but on my '95 I had to remove the belt and then a brace between the water pump and the alternator. I think yours are opposite from mine, so you may have a clear view of the EGR. You may have to replace the EGR gasket....$2 at the parts store.

Good luck

 

thanks for the info, i will try these things and hope one of them works

 

You will definitely want to get a new gasket. There is an EGR gasket available that has an integrated screen on the supply side of the valve. This greatly reduces the chances of getting a chunk of carbon in the valve, keeping it from closing.

You should not have to remove anything but the valve. It will take a ratchet with a 10mm socket and at least a 6" extension to remove it.

 

ok i know its been a while since i asked about this rough idle problem but just now got around to working on it, cleaned the EGR valve and replaced gasket but its still running rough. any tips on how to get the idle air control valve off easily without having to remove all the hoses and wires that are in the way ?