thefallofjeffrey

Okay so I'm installing a new crank position sensor on my 99 Cherokee 4.0 auto. It did not come with a spacer but I keep hearing about this wonderful spacer that you need. Side by side the sensors are exactly the same dimensions. But when I install the new one, it runs like crap. Put the old one back on and it runs fine. Until it gets hot, then it fails and causes the engine to die.

Do I need this spacer or not? If so where can I get it??

scottmphoto

My '91 doesn't have a spacer. Did you clear the computer (if you can on yours)?

thefallofjeffrey

I should probably mention that I returned the CPS I bought, got a different one, and had the same issue.
I cleared the computer, but even if I didn't it wouldnt have mattered, due to the fact that it would run and idle fine with the old CPS in there.
Im going to return the CPS I got and just go to the Jeep dealer in the morning and get one from them, I've heard you should just suck it up and get the MOPAR one from them, but I'm tight on cash of course, so I just picked one up from advanced auto parts. I'll report back tomorrow after I install MOPAR replacement.

BimmerJeeper

In the BMW world, there is one rule for buying parts.
NEVER buy (cheap) non-OEM sensors.
In fact, most never buy non-OEM anything.

Why are you replacing the CPS if it works fine? Prev. Maint?

thefallofjeffrey

no, when it gets hot, it fails. I can be driving along just fine, and then it will just start bucking, misfiring, barely maintaining idle, then it will die. Wont restart until it cools down, then once it gets back up to temp, dies. I read somewhere that these are common CPS symptoms.

I just replaced the TPS, distributor, coil, cap, rotor, wires and plugs. Holy cow did it run smooth then! What lead me to replace all this was the whole dieing thing. Plus it needed it. Bad. Dist seal was all gone to hell, rusted out and corroded all the contacts on the rotor and cap, plug wires were all shot.

So hear I am again, with a dead jeep. But since I have narrowed it down by replacing all of the above, I figured this MUST be the source of my problem.

tjwalker

Go directly to your Jeep dealer and buy a crank sensor from them.

I buy plenty of aftermarket parts, but the crank sensor is absolutely, positively one part I will ONLY buy from a Jeep dealership.

Even if the part you buy from XYZ parts store tests okay electrically, this a "hall effect" sensor and spacing is extremely important. That is where many aftermarket crank sensors fall short.

Please, please, please people.....I beg of you.......buy only MOPAR crank sensors from Jeep! Will some aftermarket sensors work? Sure....but plenty of others will give you heartburn. Don't take the chance as MOPAR crank sensors work perfectly. Every time.

I work on Jeeps and I will NOT install anything but a Mopar crank sensor. Period. I've had people come to me with their no name crank sensor asking me to install it? Won't do it. No way.

BimmerJeeper

Well, it seems like you isolated the faulty new CPS. I would go install an OEM CPS. Anyone know who makes the OEM CPS?

Never buy cheap sensors. You'll do the job twice. Please update this thread.

BimmerJeeper

What are other parts you'd NEVER buy as aftermarket?

98XJ40K

One misconception proved untrue for me... the aftermarket CPS' were all around $90-$110. The Mopar CPS from my local dealer was $74, I always thought the dealership was higher.

I have read that many people have trouble with the aftermarket CPS... something like 50-60% are dead right out of the box. The CPS is one thing you should always get from Jeep. I think O2 sensors may fall into this category as well, but definitely not cheaper at the dealer.

tjwalker

As a general rule, I buy my thermostats and most engine management sensors directly from Jeep. As shown, they are not always more expensive. My crank sensor cost me about $60 from moparonline parts. Most aftermarket crank sensors will be more than this. Link to this great parts resource HERE:

https://www.moparonlineparts.com/

The exception would be oxygen sensors, where I can sometimes get the same OEM sensor cheaper than the dealer from places like Rockauto, etc. But I always check moparonlineparts. NTK is the OEM oxygen sensor for 91-01 and Bosch is the OEM oxygen sensor for 87-90.

peep

I second the motion on the Bosch O2 sensor.
gotta admit I'm generally leery of the Bosch brand, (due to 40 year old phobia with Bosch plugs on my 71 skidoo, 1 kid, dark night, and a long cold walk out of the bush, yes my spares were bosch too) However, the quality and reliablility of their O2 sensors has me sold again and again.
I'm also having success to date on couple of Bosch starter motor jeep applications.

thefallofjeffrey

Okay so I installed my new cps from dealer, works great.

But it still dies on me. I'm almost thinking a temp sensor of some kind is causing it to cut out and die. Once I let it sit and cool down for a little bit it will start back up and run fine until it gets heat built back up in it, then it dies. The idle drops wayyy down. I had overheating issues with it when I first got it because the previous owner took out the thermostat. Put a new 165* one in there and it ran great again. But it's almost the same feeling that it was when it would die then. I'm going to go ahead and get a 195* tstat anyways because why not.

What do you guys think? The needle reads fine, but the hoses feel rather hot to the touch...

BimmerJeeper

Why would you overheat without a thermostat? Wouldn't it initially just run too cold and then be fine?

wrenchhead82

Thermostat causes a flow restriction in the cooling system. Without this restriction, the coolant flows too fast and does not transfer heat properly. Yes, it can and very likely will overheat without a thermostat.

BimmerJeeper

Ahh, that makes sense. The coolant returns from the radiator too quickly and it's still hot. Looks like too slow or too fast is bad. Goldilocks wins again!