My 95 XJ is acting up. The crankshaft position sensor went out 2 days ago. Yesterday I put a new one on. Now it will start and drive, but has a rough idle and bucks and backfires on the road, especially at low RPMs. I have swapped for a good O2 sensor, IAC, TPS, changed plugs and wires. Has a new rotor and cap. It will not throw a code.
The only problem I had before the crank sensor went out was a hot weather bucking and backfire. This only happenned on a 100 degree day in traffic ir after idling for a few minutes, but as soon as you got back to 60-70 mph, it would stop and run fine.

Any help would be appreciated
Amy

 

reuse the original bolts? I hear different lengths can cause problems with the cks

 

did ya do both 02's? one is half the battle... assuming you have two...???

 

check your wires. make sure none of them are getting too close to the block or the manifold. That could account for it acting up in the heat.

 

x2.........

i think ive got a short in my wiring... cant pin it to a sensor or a computer (we are retesting the computer in a few days, to be sure..) so the wiring is our next adventure...

 

only has 1 O2, used original bolts in cks, no wires are touching or real close to block or exhaust manifold.

 

Hey, might sound silly cuz its stuff we tend to think we are sure we did right that sometimes comes back and we say "doh!"

anyway, when you did the plugs and wires.....100% sure each plug gapped correctly?
100% each plug you are sure they are nice-n-tightly inserted to the block?

100% sure the plug wire "boot" on each plug had a "click" feel when you re-installed each one?
Did you inspect your NEW wires for cracks or defects before putting them on? ( I bought new set recently and no BS, the NEW # 1 wire was trashed physically, I mean split everywhere and even no connector inside boot to attach to plug, yes missing.)

is it possible there is an error in the firing sequnce, i.e. wrong wire on wrong plug? (yeah i know, thats a stretch, but hey).......

and one last really dumb question......when your gas tank is say down to about a quarter full (on a hot day mind you.....) do you smell gas fumes while driving?
[I ask cuz my vapor canister was shot and whenever it was hot outside , say 100+ and i got below say 1/3 or 1/4 tank of gas the smell was horrendous. I put a new one in and no more problem, with that.]

also maybe verify ALL your vacuum lines are ok (no splits, loose, etc),
I'm just sayin.

apologies for the rambling...........
hope it helps,
Best of luck!

cpnwrench

 

I FIXED IT!! thanks for all the replies. It was installer error. I never thought to check the cks after installing it. I was checking the vacuum lines and moved the cks wire out of the way and heard a clink sound. I shook the wire again and the cks was loose. Started the Heep, pulled the wire tight, and it ran perfect. I had to put a washer on the bolts because not every cks plate is the same thickness. The boltholes are appearantly only so deep so the bolts will bottom out if the cks plate is too thin. I hope this can help someone else if they are evr in the same situation.

Thanks Again,
Amy

 

I knew I was on the right track! :-p sorry, couldn't resist.