I have a 97 XJ6L that I bought used about 3 years ago. Last fall she threw a code 1409 if I remember correctly, EGR valve. Shortly after, the car started running pretty rough. The tech said the valve looked fine, but that all of the coils and plugs were done in. They replaced them and reset the codes. He said let them know if the light came back on. It never did, but I don't really drive the car a lot. So last week I took her for emissions testing. She failed for readiness. They said "go drive it".

I hit the highway and opened her up. It didn't take long, she threw another code. Different code, but still the EGR valve. They checked it out and said it was fine, but very dirty in the system and they ran a cleaner through it. Took it for a run, reset the computer and passed emissions.

I picked her up, and came home, then later set out for the store. I'm sitting idling at a light and the car... mostly from the center to the back started rocking like a boat on water. Not hard... not jerking, really, just back and forth swaying.

So I come home and sit in her for a bit. A/C on... off, in park, in drive, in reverse. Idle, engine rev. etc.

Revving the engine makes it go away. The engine is running smooth. There are no rattles or vibrations from under the car. It almost seems to "pulse" with the sound of the exhaust. I put a treatment in and filled her up.

This didn't ever happen before the EGR valve cleaning. Any thoughts? The place I took her was close to home, but they irritated me something terrible by quoting me one price then trying to have me pay a lot more, so I don't really want to go back there again.

 

This is not a tech reply, others are better than me.

But are all your engine/gearbox mounts etc OK. The rubber perishes over time and at low revs things can move around in harmony with the engine.

Speaking of harmony, IIRC I seem to remember seeing posts about harmonic balancers going AWOL.

Others will chime in.

 

Thanks for your response. I can have those things checked, but it's strange that it started after the "Fuel/Air Induction Service" and EGR port cleaning.

Today I headed out to the store and she threw another code. I didn't have time to take it to be checked, I'll take it in the morning. If it's another EGR code I'm not going to be a happy camper.

If it is I think I'll have no choice but to take it back to the local mech and claim they didn't do something right, and I don't think they want to see me again after the fit I pitched yesterday over the excess bill.

 

OK, I sucked it up and called the shop that did the induction service. Had a nice long chat about it. They said bring it in, let the see if it was their error and they would make it right.

Just dropped it off, the code was a misfire. They said the chemical they used fouled the plugs and they would take care of it and let me know when it was ready.