RRC rough at idle

[kjg48359]

I've tried a few different things, but the bottom line is that when the RRC (a '90) is warmed up, it just runs rough until a O2 sensor misfires and then i'm stuck with the dreaded error 52.

I realized that there was a leak on the fuel line into the back of the fuel rail, and failing to source a new rubber line (with the male adapter on the end), I went back to a generic auto parts store and bought a set of ferrules
/olives and placed one into the connection and used a new hose clamp on the line coming from the chassis rail.

I closed the leak, but after running it for a while it still doesn't seem to run much better. I'm thinking it's not a fuel delivery issue. But a recent experience with my 'tin can' gets me to think about the EGR system. On my tin can, I actually had a gummed up EGR valve and cleaning that out with a brake cleaner seemed to fix that issue (otherwise the dealership would have probably changed $100 for a new EGR value, and another $100 in labor for something I just cleaned in about 30 minutes).

So, it gets me thinking. What could starve an engine of low air at idle, could it be a problem with the "idle air control" mechanism? When I first got the vehicle a couple of years ago, I remember thinking that there might have been a problem with that, so I took it off, wiped it down and replaced the washer. Hard a hard time replacing the washer, I'm wondering, if that replacement were too thick, could that cause an issue?

I just looked through the RAVE CD for "EGR" and it only finds one on the diesel, not the 3.9.

Any thoughts from someone? Thanks.

 

[carlosz]

lots of variables with out a baseline.... indeed the rover gas engines do not have egr's... how long since last tune up?... fuel filter replacement, any codes, vacuum leaks...function of tps, iac, fuel pressure, timing,maf... etc.

 

[kjg48359]

Yes, there is a constant signal for '52' for the oxygen sensor, but that only pops on when the idle gets rough and the vehicle shakes. The vehicle is in such rough shape (not paint for instance on the hood and roof) that, and tailgate frame so rusted, that I just keep on charge now in a garage. I only take it out infrequently when I can 'tinker.'

Last tune up was a couple of years ago (but I've put less than 500 miles on it since then). I've done all the fluids within that 500 miles.

What gets me thinking it's not actually a sensor issue is that the sensor that keeps faulting was replaced about the time the last tune up happened. And it's the original engine, I have a replacement engine that has a damaged cylinder (think the ring is bad, or was told by the previous owner). So the engines have been swapped out a couple of times and I can't help but think something might not have been put back together properly. As always this would seem to me to be a proper suspicion.

Just looking for some ideas. Thanks

 

[singingcamel]

Most rough idle issues consist of vaccum leaks , distibutor issues. This is where I would start.

 

[p m]

There's no EGR on your truck.
IAC stepper motor is an easy thing to get out and clean, or replace with a Chevy one. It may or may not improve your idle. A vacuum leak will affect the idle quality - I'd look for PCV circuit and make sure the brake booster (your should have a vacuum one, right?) doesn't leak.

 

[kjg48359]

Thanks PM. And no, this has ABS, no vacuum on the brakes (right?). Thought that change was like 88 or so...

 

[rover4x4]

It needs to be driven, fill it up with a tank of v-power, clean the throttle body and DRIVE it.

 

[singingcamel]

Sea Foam the damn thing, clean the throttle body valve and clean the stepper motor.