Any Ideas?

[Jess]

I'm not getting much help in OE Tech and I'm almost at my wits end with this issue. Every time I think I've got it fixed the problem is still there.

http://naxja.org/forum/showthread.php?t=1030038

Thanks

 

[KPTHEMP]

I had this problem on my 01 and it was a fuse in the PDC,

Shrek had this on his 93? and it was the Coolant Temp Sensor.

if that helps any

 

[katuah]

as KGP sez, I would def look at sensors that would have greatly changed parameters after the engine warms up. temp sensors come to mind, probably O2 as well. I don't have specs handy but I'm sure somebody on here can tell you what you should see off a meter when testing. my 98 had an issue with a BAD miss at running temp, traced it to one of the O2 sensors, but it took blowing the engine with a shop fan to do troubleshooting :-(.

i'm also thinking it could be a solenoid in the starter - I've not worked with that part of my XJ so this is all sort of secondhand, but I had this problem on a Honda CRX and it was related to a solenoid circuit that would swell and short out when heated, but when allowed to sit & cool would shrink back and let the car start again. if it takes you a few minutes to get the starter fluid out, open the hood, spray it in, etc, it may just be that the engine cools enough in the interim to "fix" the short.

next time, open the hood, let it cool for a while, then see if it will restart without the fluid.

 

[Jamescad04]

I have been having a very similar issue with mine I think my cat is bad. I unplugged the precat o2 sensor and the jeep would start and run great so i replaced it and it ran great for a lil while but now its starting to act up again. So im going to take my exhaust off and replace the cat Im 99% sure that this is my problem and I ran through alot of the same things you did as well.

 

[Jess]

shortdoug and I have been working on it to no avail most of the day. This morning it would not start at all and I noticed the starter was smoking while trying to start. I pulled the starter and it checked good, but I replaced it with a reman under warranty. We changed the cps back to the original one and it showed no changes. When we tried to start it would turn for a while and then hydrolock on the gas in the cylinders which destroyed the plugs, so we replaced the plugs...and still no luck. I had a spare coil, so we changed it and still had no luck.
There is both gas and spark. The spark it not great, but should be enough to start.

Right now, the only possible fix I can think of is a new CPS.

As a side note, we also swapped a good ecu into it and it still didn't run.

The problem seems to be spark now. There is spark, but it is not very hot.

To answer all questions:
It is now doing it while cold now, so I'm not sure it could be temp related-although I did think it was before.

Replaced the starter today.

No cat.

Any further help would be greatly appreciated.
Thanks

 

[Ghost]

shortdoug and I have been working on it to no avail most of the day. This morning it would not start at all and I noticed the starter was smoking while trying to start. I pulled the starter and it checked good, but I replaced it with a reman under warranty. We changed the cps back to the original one and it showed no changes. When we tried to start it would turn for a while and then hydrolock on the gas in the cylinders which destroyed the plugs, so we replaced the plugs...and still no luck. I had a spare coil, so we changed it and still had no luck.
There is both gas and spark. The spark it not great, but should be enough to start.

Right now, the only possible fix I can think of is a new CPS.

As a side note, we also swapped a good ecu into it and it still didn't run.

The problem seems to be spark now. There is spark, but it is not very hot.

To answer all questions:
It is now doing it while cold now, so I'm not sure it could be temp related-although I did think it was before.

Replaced the starter today.

No cat.

Any further help would be greatly appreciated.
Thanks

Posted in your first thread.
I'd test the CPS per the FSM. You can check it's resistance or volt spike when cranking IIRC. It has been a while since I read the procedure. I think its posted in the OEM section.

 

[jeepgeek2002]

maybe the fuel pump is fine but the regulator tube has a hole in it.
On xj's its easy to check. No dropping tank.
Start from the tank and work your way up.
its not complicated usually.. if its not the fuel pump or regualator then check fuel filter if not check fuel line.. then work your way to rail and injectors.
If its not fuel then its CPS or ACV.. 93 could be TPS maybe?
If not check electric.. wires.. distributor cap. coil..etc..
i have a fuel pressure gauge if you need one..

mark

 

[Maxcfm]

Seems odd but check all your ground points for rust and make sure there tight I've seen bad grounding cause weak spark or no spark problems

 

[Jess]

After Doug left last night, I decided to go ahead and replace the CPS. After installed I was checking one of the plugs for fire and noticed it was firing on the compression stroke.
I was stupid and not paying attention when I changed the cap and got all the wires one off. I changed all the wires to the correct location and it fired right up.

Later, I remembered the coil I used to test was still hanging under the hood, so I disconnected it and re-hooked the original. Then a few minutes later I went to leave and it just cranked. I reconnected the test coil and it fired right up.

So........it appears I not only had weak fuel pressure but also weak spark which got progressively worse with heat. Since last night I have put close to 60 miles on it with several hot starts and everything seems perfect. There is no more slow starts and it seems to run better than before. Today it turned over 293K.

Thanks for all the help!

 

[jeepgeek2002]

Thats Weak!

mark