Hello friends,
My 1997 has been idling real rough lately, paired with a piston 1 misfire that may or may not be related. I spent a bunch of money at a shop trying to fix it, they replaced plugs and wires(1st spark plug was cracked), rebuilt the valve cover gasket, replaced a bad injector, and replaced the exhaust manifold because it was cracked. The problem was not fixed. The rough idle comes and goes, also it actually seems to have gotten slightly better with the colder weather this week. I am going to replace the MAP sensor, since maybe the cracked manifold could have affected it. I also ordered an idle air control valve and a throttle position sensor as they seem easy to replace and, from what I've read, are likely culprits. Also, I have a shake at 50-60mph that has recently gotten much more noticeable, and my alternator was recently replaced as well, and I was thinking maybe they didn't install it right. I can't really go spend more money at a shop, so any help is greatly appreciated. Thanks!

 

Make sure the plug wires are fully seated. Did they replace the distributor cap and rotor? I always replace those when doing plugs and wires. What plugs did they use? The recommended plug for a 97 is Champion RC12LYC, gapped to .035. Which injector did they replace? I assume #1, but you didnt specify. Did they check compression? #1 could be low. Could be anything, really.

And have you, or the shop, checked for codes? If the CEL is off, i would still check. For stored codes.

 

I've checked, the wires are fully seated. They did not replace the distributor, I haven't done that in a while. Also, unsure about plugs, but I know they said they did gap them to the right amount. And I'll call and ask which injector. Compression was checked, all good. And my OBD2 reader only reads a cylinder 1 misfire

 

You have to concentrate on the cylinder 1 misfire, if still there and it sounds like it is. If you resolve that, it may cure your idle issue. You don't have to replace the entire distributor, just the distributor CAP, along with the rotor. Use quality parts here.

Don't throw any more parts at this without some validation, some of the aftermarket parts available are actually of lower quality than the original parts on your Jeep. That can add variables to the equation that might make you chase your tail. Let testing guide the way to the root cause of your issues.

You need to verify that the injector for cylinder #1 is good and also that you are getting an injector PULSE to that fuel injector which comes from the computer. A simple "noid light" available at most stores can tell you if you have injector pulse.

What did the shop tell you when you picked up your Jeep? If the misfire wasn't fixed, they should have a plan to diagnose it or this is a shop that I wouldn't be going back to. Any good technician worth their salt should be able to diagnose a single cylinder misfire on the 4.0 liter engine.

Post any and all codes here for comment, not just a description of the code but the actual codes themselves POXXXX, etc.