1996 XJ 4x4 with the 4.0. 146k miles. Fresh fluids, new distributor/wires/plugs. New O2 sensors.

Two days ago my Jeep had an issue with starting. It would crank and crank but only catch when I gave it gas. Then after it started it didn't have any issues the rest of the day. Fast forward to yesterday and I took it on a Jeep-venture a couple miles up some logging roads - pretty well maintained, no wheeling, just exploring. I pulled over to let a truck pass me and when I stopped the engine died. The Jeep then would crank but not catch. I let it cool for about thirty mins and then it started up and ran perfectly home. However, it did throw a check engine light.

Once I got it home I used some carb cleaner to clean my IAC. It wasn't too dirty but its housing was. While cleaning the IAC the screw/spring/nipple assembly came apart. ****. So I seated everything again and gently screwed the screw into the body of the sensor to keep pressure on the spring and stay seated. Reinstalled.

I then tried to read the engine code. I plugged my scanner in, turned the ignition to on, and then told the tool to scan. Loading bar...loading bar.... Failed to connect. ****. Tried it muleiple times and it wouldn't connect. Checked the ground for the OBDII plug for the Jeep and it was good.

I havent started the Jeep yet after cleaning the IAC. I'm expecting that I ruined the sensor when it came apart. I'm thinking my IAC or CPS is bad. Or both. Any ideas on all this? And the trouble with the scan tool not connecting?

 

Have you tried disconnecting the IAC and CPS to see if you get your OBD2 comms back? Start there. Sometimes, when the CPS sensor fails, it has a way of knocking out the OBD2 bus. If you disconnect the CPS and get your OBD2 comms back, that is a strong indicator that the CPS or its connector/wiring are in need of attention.

 

Those IAC arent suppose to come apart. I was told that if the pintle comes off, its junk and should be replaced. Maybe youll get lucky, dont know. Never took one apart to see.

 

I tried removing the CPS and IACv but still get the check engine light and no communication to the scan tool.

However, the Jeep starts and idles just fine so far. So maybe my IACv isn't broken after all? I just took it on a drive and no issues whatsoever. Idle is normal, power is great, no sputters/backfires etc. Started right up after each stop (3-4x).

I have a 400 mile trip coming up in it so I may buy a new IACv and CPS prior to that just for peace of mind.

 

The internals of the IAC are quite delicate and should be cleaned very carefully with only a toothbrush, not moving the pindle or having it rotate. Once it comes off, it's trash. Inside is a stepper motor that controls it's movement to control air flow at idle. Carbon deposits can restrict it's movement and airflow around it, thus making idle speed hard to control. If it hasn't been cleaned very often, it's best to just replace it. Aftermarket one seem to work for a while, but if you want reliability, buy Mopar. I'd use throttle body cleaner to protect the internal circuitry from the harsh chemicals involved with cleaning gasoline varnish in carb cleaner. JMHO.


It sounds like the CPS is still fine.

 

I drove it today and it was completely fine. Started perfectly, idled perfectly. I'll probably still end up replacing it but it runs normal, even after the IACv fell apart and I put it back together

 

Well, that was just my opinion, but if you're facing a long trip, I'd change it.

 

No real experience here, done some reading though. Never energize an IAC that's out. If the motor on the screw runs the pintel all the way out, guess that's bad. That said luck does happen. I don't think its exactly "nailed", but needs to be within parameters the puter can work with. There is for sure stuff in the FSM. Somebody screwed it on there right once before! Gonna check crusier 54.com right now for that..ow ,ouch 96 FSM...there might not be an FSM for 96. Yea, no 96, to late and tired for me to download the 97. Pretty sure there is something there though.

 

What's the consensus on aftermarket sensors like NTK? Should I get OEM from the dealer? Rockauto doesn't carry MOPAR.

EDIT: I bought a SMP IACv and am going OEM with the CPS. Dealership is charging me through the roof on it but from what I've gathered I just need to sack up because OEM is worth it in this case.

 

You can find Mopar stuff on Rockauto by getting the part number and doing a part number search. They will often have listings that won't show up under the Year/Make/Model search. They may or may not have what you're looking for, but it's always worth a shot.
Also you can find Mopar parts on Amazon and at other retailers, the key seems to be searching for the mopar part number rather than the specific vehicle.

 

If you have the OEM part #, type that into the 'Part Number Search' on Rockauto, and choose Mopar from the list. thats all you need. If they have it, it will pop up. Most Mopar parts dont show up using the 'Parts Catalog' like the other stuff.

I just checked and Rockauto sells both the IAC and CPS for 96. There are different part numbers given for each in the description and went thru them to find yours. I found the IAC using part #4798377, and part #4897321AA for the CPS. before you buy them, what shape is your CPS connector? Early 96 had a squared connector, and the later had an oval. Rockauto shows the square connector. If yours is oval, dont buy the one i found. It wont fit. I believe part # 56026921 is the oval connector. Rockauto has it, but no photo.

 

Wow. Dealership was going to charge me $140 for the CPS. You just saved me a ton of money. Thank you!

 

Well, color me confused because I have the oval connecter with round pins. From what I understand and have read, this connecter is OBDI. This would explain why my OBDII scan tool is not connecting with my Jeep.... Though I have a DLC in my driverside footwell near my hood release! I thought only the OBDII connections were there and OBDI were in the engine bay?

At any rate, I have the oval connecter with the round pins so I will order that CPS. There seems to be a lot of misinformation surrounding CPS part numbers and such though.

 

The CPS connector type doesn't necessarily indicate OBD1 or OBD2. Your OBD2 connection problem may or may not be related. Most 96s built late in that model year had the rectangular connector as the 97 connector upgrades started being used. But the 96 can be a mixed bag, as they used up the components from earlier and started to transition to the newer components. For example, I have a 95 fuse box, a 97 CPS connector, and a power distribution center layout that doesn't match anything found online!

If you have an OBD2 connector under your left knee, my bet would be that you have OBD2. Many scan tools have a problem with vehicles this old, so it could just be the scanner. What is the brand?

 

I bought part number 56026921 from Rock Auto so I hope that's the correct one!

To be honest I'm not sure of the brand. I borrowed it from a neighbor. It isn't fancy or high quality