Just picked up a 95 Jimmy SLT, 4.3. It was running fine but failed emissions test for bad egr and fuel cap. Replaced both and it passed the emissions easily. The next day, we drove it about 4 miles, when slowing for town, it ran rough without throttle, and smelled like a hot cat converter, which cant be bad since it passed emissions. After half an hour being parked, it started and idled rough with the engine light on. It ran fine at highway speeds and only ran rough at idle.
After that, it ran and idled fine for a few days with no engine light. Last night back to square one with the light and idle.
I know the simple answer is to have it scanned for the codes, but does this sound familiar to anyone?
Ive searched but havent found much so I posted.
Thanks for any tips or idead.

 

Based off your description and symptoms, it is possible your EGR is bad again. Did you replace it with a new or used part? Sounds like the pintle may be sticking. Or their could be a circuit issue. Your EGR is kind of like a controlled engine leak. At idle it should be closed. At highway speeds it will open a certain percentage based off of input from the VCM. By feeding burnt exhaust gasses into the engine it reduces combustion temperatures at highway speeds. I would first go to an auto parts store and have any codes pulled. But next time it idles rough you could shut off the engine and gently remove the EGR to see if it the pintle is stuck in an open position. I say gently because if it is sticking working on removing it could jostle the pintle loose and it would close giving you a false result ( that might happen anyway). If the code you retrieve is a P0404, that along with your symptoms would probably narrow your problem down to either the EGR valve or its circuit. Take a look at the wires going to it also. Since the first one was bad, and now this one may be bad, you could have some type of short. Look for rubbed through or damaged wires. On my 98 there are five wires. I don't know yet about a 95. Also, does your engine have A.I.R. system on it ("smog pump")?

 

I need to know how many wires are going to the plug on the EGR Solenoid to pull a wiring diagram. Two, three or four?

 

Thanks for the response! My wife has the rig at work until 8pm so cant check how many wires.
It ran perfect before the smog check, and the engibe light never lit up until the smog tech ran it for a while and plug his computer stuff in.
Also, against my advice, the wife ordered a ridiculously priced egr off of amazon, which is probably a very cheaply made from overseas unit Id imagine. Id never heard of the manufacturer and the box was pretty much just a white box with a bar code.
Im fairly mechanically inclined when it cones to carbs and points (older stuff), but never mess with fuel injected, electonicly controlled rigs.

 

It just dawned on me that 95 was a transition year. You might have five wires. Do you know if your system is OBDI or OBDII? I think that year had a mix of both. I'm three hours ahead of you, so I may not see your wire response until tomorrow evening (EST).

 

I txted her and had her ck to see if she could count the wires. She says theres 4 that she can see coming out of the plug. Blue, black, green and she thinks yellow.
And im not even sure what odbi is. 😳

 

Your solenoid is what is known as a non-linear type and engine vacuum is used to bring the gases into the combustion chamber. So if the valve is sticking, basically you have a vacuum leak (basically). At highway speeds you wouldn't notice it, since that is when the EGR valve would be opening anyway. At idle you would definitely notice it. Unlike a normal vacuum leak where your engine would probably race or surge, the already burnt gasses being drawn into the combustion chamber are inert and don't burn like drawn in air would. So the fact that the engine is running rough leads me to think that something with the EGR valve or circuit is not right.

 

Does your EGR Valve Solenoid look like the attached?