deepstage69

Ive got a 90 cherokee 4.0 and aw4, ive swapped into a 90 wrangler. The problem is that it runs well, except for idleing. On cold starts, it starts doesnt idle high but for a sec then idle slows way down and fluctuates up and down and eventually stalls out. After its warm, driving and come to a stop it idles down and eventually stalls.

Ive already changed Map, Tps , Iac, O2 sensors (new) adjusted tps as well, and swapped know working Mat and Coolant sensor (used)

Thanks

My375hp302

Mine did the same thing when the vacuum line to the MAP sensor got cracked. Check to see that it is hooked up and then to see if there is actually a vacuum signal on the line. If that checks out ok check the wiring to and from the MAP, it may not be hooked up correctly or you may have a broken wire.

truckntractorhick

yup, check all ur vacuum lines!

redrunner

Mine just started the same thing about a month ago. I have done the same things to mine. I checked the tps and adjusted it with a volt/ohm meter. Checked all the senors with the volt/ohm meter, replaced a bad knock senor that was broken not bad, replaced the Idle Air Control, replace a couple of vacuum lines. Still the same problems you having please let me now if you get any good ideas, I sure would like to fix these problems!

redrunner

Anyone thought about a CPS. Mine will not start some days until I unplug and plug the CPS in again. I have checked it with an ohm meter and it tests good. I know that they sell a patch for that issue, we put one in my kids 89, just never got one in mine. It almost seams to loose electrical quick than kicks back in.....what does everyone think?

superj

only one way to find out amigo

mike albo

Have you checked the pick up(stator) in the distibutor?

deepstage69

Ok update, couldnt find a vacuum leak.

Also on cold startup it doesnt idle high, it idles up for a sec then drop straight down.

My375hp302

Remove the vacuum line from the MAP and take it for a drive. If it drives the same you know it's the MAP. If it gets worse you know your MAP is working. Let us know

deepstage69

take off map, it runs like crap. New theory, the motor is rebuilt and im thinking the cam is something aftermarket. Because im only getting about 12 inches of vacuum at idle. Im thinking this is screwing with the map sensor.

My375hp302

That would definatly mess with the MAP and put you into a rich condition. I would check for other issues before thinking it was a big cam tho. Could be a vacuum leak in a hose, or even the intake gasket, or worn/burned valves. I would do a compression check and then a leak down test to determine the condition of the engine. You'll want to take the valve cover off to do the leak down test so you could check the cam then.

deepstage69

Checked for vacuum leaks with propane, never found any. Motor is freshly rebuilt 100 miles max, head was redone as well. Cam is unknown and lopes a little.