My 89 has 120k on it. Today it developed a low rpm stumble with a rough idle (in gear). In park, when you slowly advance the rpms, it clears up right at 3000, and seems to run smooth then. When driving around the hood, it's definitely noticeable.

I suspected a faulty MAF a couple years ago (rough idle, but not like this), but never replaced it. It's really only been intermittently noticeable, mostly during the summer with the A/C running.

Also, I did replace the injectors a few years ago with new Bosch ones (about 45k ago)- I'm wondering if an injector is bad again?? How can you troubleshoot injectors to see if a cylinder is making power?

Any ideas?

Thanks for the input.

 

same thing happens with my car, but once it gets over about 1.1k rpms it runs fine and sounds great, but below that it stumbles and has a rought idle, anyone got some ideas whats going on? how to fix?

 

broken exhaust manifole studs???

 

I have broken exhaust manifold studs but it runs like a top, just loud as all get out. Maybe it's different for others tho.

 

sounds like a bad injector to me. pretty strange for injectors with 45k mi. on them to fail, or for that matter, the stock ones with 80k mi. anyway, pull wires 1 at a time while engine running to check and see which cylinder is missing (missing cylinder won't have an effect on the idle rpm). when you find it, check for spark, faulty wire, and compression check on that cylinder. if all those tests pass, 99% chance of injector failure.

 

Based off the AC comment, does this happen more when the lights are on, or some other power is being drained?

 

not tryin to post steal here but mine gets way worse when i am using more power, such as music, ac, head lights, o and i had 2 broken exaust studs, just had it fixed the other day, so so so much quiter, but still running bad

 

my money is on injectors.
look for one or more cylinders not firing

 

I don't think it's an exhaust issue- the exhaust system is stock, and it sounds perfectly fine. I don't hear any excess noise under the hood either. Thanks for the injector t-shooting tips. I'm going to try that today...

 

I am experiencing the same problems and I can tell you that it is not the manifold since I got mine repaired a month ago and the problem still remains. I assume it is the injectors since when I use higher octane gas it does not do it as much. I will wait a while and fix this over the summer as it is still cold here in Quebec.

 

Mine does the same and it is either the injector or the injector harness can go bad.

 

Take a look at the connectors on the injectors themselves - they like to corrode somtimes... clean them up and see what happens

 

they call me a noobie and i can't start a thread but someone says broken exhaust manifold threads????? how can he be serious?

 

for a bad plug wire to cause low rpm miss but come out of it when revved up.