4.0 idle issue

[southcarolinaguy]

this started about a week ago and i have been trying everything that i know to do. i take care of the truck, every 3000 for the oil and i check everything regularly. not the greatest engine person but i do have a general idea of how it all works.
problem: horrible idle but worse with it in gear. i doesn't seem to loose any power when i get on the freeway and i don't notice it missing or anything. no smoke. cranks fine. ran some gas treatment and injector cleaners through the engine. got a check engine so i had my OBDII read and it said i had a #1 cylinder misfire, so i started with the wires, plugs, rotor, cap, and coil and they all checked good. so then i thought it wasn't getting fuel, so i checked for voltage at the injector and they all had about the same voltages. did a compression check and that was good too. didn't know what to do next so i took it to a dealership so they could run it on the equipment they had and they said it was a bad injector. i replaced #1 and 2 injectors and the problem is still there.
any help is appreciated
thanks

[89ltd]

a bad egr valve could make it idle rough if it is opening to early, try unplugging the vacum to the egr and plug the line to see if it helps. What year is it?

[vividd]

I believe it is the tps , my jeep revs high at times and then low , try taking it out and soaking it then clean it......... i cleaned mine and idle was great for two weeks , they are about 200.00 in canada

[southcarolinaguy]

it is a 97 model cherokee. i checked the tps and it seems to be good. i looked for the egr valve but was unable to find it, i don't believe that mine has one but if someone knows that it does, could you please tell me where to find it. another question, if the OBD system was giving me a #1 misfire most of the time and sometimes a multiple misfire with the #1 misfire, wouldn't that knock out the chance of it being the tps or egr or anything related to vaccum lines or even the throttlebody being dirty? or could it be giving this code because the computer doesn't know what is going on in the engine? new to this using OBD to solve problems

[89ltd]

i thought the missfire codes were taken care of when you replaced the injectors...

[southcarolinaguy]

no, the codes still come back after i have them cleared

[southcarolinaguy]

re-did the compression check and this is what i got
1 120psi
2 165psi
3 160psi
4 160psi
5 160psi
6 125psi

read up on some camshaft stuff and it said that it could be a bad exhaust lobe on the cam. anyone have any ideas? guess i'm gonna measure the lobe lift next

[mrcake]

I have a 96 cherokee with the 4.0 I've got the same codes, PO300 and PO301. (multiple misfire, an #1 cylinder). They have only tripped a couple times in the last few months. It idles a little rough, but from what I have read here - it's to be expected. Went and got the jeep smogged, and it failed on the NOx, but barely. (pass was 546, i had 567).
I just replaced the 02 & TPS sensors. Didn't seem to help much. I've been reading that it may be the valves or the CPS (cam position sensor).... god I hope not...

[fredjacksonsan]

Suggesting a search in this forum for "multiple misfire". More info there.

[citizen@large]

I didn't see where you mentioned the year of your Jeep, but a simlar idle issue in my '89 was solved with a new (to me) idle stepper motor/idle air controller(IAC), and a good hearty cleaning of the throttle body.
-good luck...

[AlohaBra]

I would take a second look at the spark plug. Hopefully you used Champions.