First off i did search and came up with no real solid answers to this outside what i have all ready done.

Info: 91 cherokee HO AW-4 with NP231. 92k on original motor.

Things i've done so far. Plugs, wires, cap, rotor, Air/Fuel filters, IAC, TPS. Now cold start rpm is about 700 and after warm it drops to about 500 and seems to bounce/surge a little between 500/450. Coolent temp runs between 200/210. I really don't know where to go next. I have cleaned TB and IAC port as best as i could with out taking it off. There has been NO changes in RPMs after each of these things has been done. All help would be greatly appreciated.

 

Bump??Anyone?

 

have you checked the fuel pressure?it is possible it could be low,should be around 40lbs.

 

Cat could also be stopping up.
Have you cleaned the Throttle body?
Look at it at night in a darkened room to check for spark jump.
How many miles on that fuel pump?
Just a few suggestions and questions.

 

I haven't check fuel pres. yet but will do this weekend. I have read somewhere it should be a steady 49 psi. Is this correct? I have cleaned the TB as best as i could with out taking it off, but have decided to do that as well this weekend. As far as i know it's the orig. fuel pump with 92k on it. Could my MAP or MAT have anything to do with this? I hate to throw parts at it. The last few thing i've done haven't helped. How do i check these?

 

for a 91 the fuel pressure should be 39psi

 

39 psi.... Cool i'll need to check that. Now i have a few questions about the MAP sensor. I unplugged the vac line to it and the idle runs up to 1500 rpms or so. Plug it back and back down to 475. Now if i unplug the the connection plug it goes up to 750 at idle and put it in drive and it really wants to die but stays at idle about 400 or less. Does this point to a bad MAP? Also shoud there be any change in idle when the ICT sensor (aka MAT sensor)? I have pulled the plug to this as well with no change in idle only CEL.

 

Get a Haynes or Chilton Manual. It describes how to test a MAP sensor. Also I have never heard of an ICT or MAT sensor. Did you mean the IAC(Idle Air Control) valve thats located on the tb?

 

IAT- Intake air temp sensor.. sorry for any confusion this may have caused.

MAT- Manifold air temp sensor.

I called the dealer on this one and the name they have for it is IAT sensor. The sensor that is right next to where the MAP vac hose connects to the manifold. As far as the MAP goes i went to JY and grabbed 2 and there was no change in idle. Guess i need to go buy a Fuel test gauge.. .

 

Yeah, its known as an IAT sensor. Its honestly in a horrible location and would do better relocated to the intake hose before the throttle body.