Never had this happen with my last XJ, so this issue is new to me.

XJ starts fine from cold. Drive along fine. My commute to work is about 45 min local driving. Once I start with stop and go, the Jeep will stall unless I pay attention to the tach and keep the revs up. Once it dies, its hard to get started again. It will restart eventually and drive as if nothing happened.

This has happened about 6 times thus far, both before I changed the plugs, cap, rotor, & wires and after. Engine temps are fine, no strange noises that would appear to give any clues to what may be wrong either. This ONLY happens when coming to stops after driving. It runs fine on the highway, no stalling (thus far).

I’ve also noticed the XJ either idles fine or high (about 1100-1300). This also varies and corrects itself eventually with the stalls and restarts.

I’ve read a few threads regarding CPS, CSS, etc……

Anyone able to provide some insight into what’s wrong here?

Thanks

 

I expect that others will jump in here as there could be several things that cause this, but when I suffered similar issues, replacing the IAC seems to have allieviated the issue for me.

Rather inexpensive and not a hard job.

Keith

 

Hi Keith.....

IAC.....idle air control valve? Location on vehicle?

Thanks.

 

IAC would cause the high idle, crankshaft pos. sensor would cause the stalling.

 

I'm going to be a PITA now.....

Can you tell me what each is actually doing?

IAC I assume controls the air/fuel mix to maintain proper idle? Any chance an AC vac line leak would have an effect on this?

CPS - what's this do?

Thanks!

 

The purpose of the IAC valve is to allow the ECU to control an additional amount of air to enter the engine without touching the throttle. It's basically an electronically-controlled vacuum leak that allows the ECU to control idle speed. The IAC valve consists of a stepper motor and a pintle. The stepper motor is controlled by the ECU, and the motor moves the pintle towards or away from a seat. The further the pintle is from the seat, the more air is being allowed into the engine. The ECU can raise the idle speed when the engine is cold, or maintain a given idle speed when an AC compressor turns on by allowing more air into the engine. To get the IAC motor to work best for you, the blades on the throttle body should be set so that the IAC valve is barely open while idling. This will allow the IAC valve all the room to open up that it will ever need.

CPS is a sensor that tells the ecm where #1 cylinder is. It reads the position and/or speed of an engine as it is rotating.

When crankshaft is turning, the sensor will provide a signal to the PCM. The PCM will then allow the engine to start by providing spark and fuel.
It reads the rotational position of the crankshaft.

 

Thx Diesel......going to try to inspect some of these items when I get home from work tonight. I'm hoping my issue is something like loose connector or something clogged or dirty before I start dumping money on sensors.

Engine bay is pretty filthy for an XJ with only 127K on the clock. It wasn't taken off-road by the prior owner either.....just plain dirty.

At 180K, you could eat off my old XJ's engine.......was spotless.

 

Another thought.......how many miles are you guys getting from a fuel tank? Talking stock (or close to stock), non-lifted Jeep with I6 and manual trans?

 

17 highway, 14 city.

 

Just found some info on Edmunds.

Says 20 gal tank, about 303 city / 404 highway.

I think I'm pretty far off from this numbers........does this help further identify my issue?

 

CPS.

 

Really? Any other signs to look out for that would confirm this?

Think my mile to the tank were around 215 - 230. This included highway driving also.

 

by CPS you mean crankshaft position sensor or CAM position sensor ?
i get always confused and I have the same kind of pb
thanks

 

Ride home tonight was interesting.

At traffic lights, before I can take off, I have to give a little extra gas before releasing the clutch to take off. Otherwise, I would stall. So, no stalling the whole ride home.

Go to pick my son up a little later (all highway driving). No issues to report other than some odd acceleration bucking a couple of times as I attempted passing lane changes.

Get to my inlaws, hang for a few minutes before leaving with my son. Jeep started right up.

Go around the corner to get some gas (been putting in only highest grade for a few fill-ups). Shut the Jeep off, fill up, pay, go to start and its just cranking without starting. After about a minute or so of trying, its starts and all is fine.

In addition to these symptoms, the idle seemed to hang a little higher, very gradually dropping to normal level after being stopped at a traffic light for at least 20-30 seconds.

After dinner tonight, I had a little bit of time to go inspect things under the hood.

All tune-up stuff is fine.....no loose wires. I disconnect the CPS, ICV, and a few other plugs and apply some electric grease. Checked for any kinked hoses.......all looked good.

Took for another test drive and it "seemed" a little smoother. Let it get to operating temp, shut it off and it started right up again. Idle "appeared" better, but not perfect yet.

So........guess I will try the commute again tomorrow and see if it acts up or not.

I still think I may need to replace something......we'll see tomorrow I guess.

Based on the above recap (sorry for the length), are you guys still thinking CPS?

 

CPS always refers to Crankshaft position sensor.

Stator or Sync Pulse generator would be cam shaft pos. sensor.

GS-CPS.