Jeep Cherokee Talk banner
1 - 20 of 20 Posts

·
Registered
Joined
·
20 Posts
Discussion Starter · #1 ·
I am having an odd problem with my 89 XJ, it was running fine but got very bad gas mileage (roughly 250k a tank) but about a year later it started doing weird things, such as bogging down to the point where you cant even accelerate and would just backfire out the intake (restart was a temp fix but replacing the ignition control module seemed to fix it) then a few weeks later, I started it up, and it ran like crap, less power then if it was running on 4 cylinders, and was really rough, and shook the whole vehicle quite a bit, but it still ran...
it was a few weeks later that it stalled after it shook more then usual, went to restart it, but it wouldn't start, it really was trying to, as it sputtered/sorta ran, but it would not actually start. The day after is when I bought a second XJ (1990) for parts, I suspected that it had something to do with the timing, so I swapped the whole distributor over and set the engine to TDC and made it so the distributor rested at 5 o'clock, (Ok yes, I messed it up and didn't put it in on the compression cycle (180 off I guess), which blew my muffler to bits after excessive cranking, fixed it and it ran) I swapped over a few other sensors afterwards (just because I knew they worked and mine were questionable, cps, iac, ait, tps, fuel sending unit) however there was so little power that I had to floor it to get it to move out of the driveway, took it around the block and it stalled 3 or 4 times, the last time is when it died, I have been unable to get it to start since, its getting 150-175 compression on all cylinders, its getting spark, good fuel pressure, injectors are pulsing properly, its getting air, the valves are moving properly and the seals looked good, the timing chain is strong and is lined up properly, yet it will not start. the wire harness seems OK, I couldn't find any broken wires, and I refreshed the grounds, so its not that, it really makes no sense whatsoever.

If anyone could shed some light on this, that would be amazing, replacing parts will not be a problem as I have the parts jeep, hell I even plan on replacing the engine and harness after I rebuild it, but that wont be till the fall, so I need this to work till then.
Thanks.
 

·
Registered
Joined
·
20 Posts
Discussion Starter · #4 ·
I have replaced the fuel sending unit, with a good one from the parts jeep (it ran perfectly and the pump seems to be fairly new I think it was walbro or something like that) I have a new ICM and swapped over the coil from the working jeep (tested with both ICM and coil) - nothing. I got a orange/blue spark when I tested it from the #4 cylinder (#3 gave me nothing) so its possible that its a problem with spark, but even if 1 cylinder is getting spark, then the engine should at least try and do SOMETHING, but there's just nothing. I was talking to the P/O a few days ago, he said that in 95 the transmission and TCM were replaced due to some kind of problem (he didn't go into detail as time was limited), I remember that when I got the thing on the road there was alot of rust in the place that the tcm mounts, if there is a problem with the tcm, is it possible that it could prevent the PCM from allowing the engine to start? (just a hunch, as I have checked just about everything else at this point)
 

·
Registered
Joined
·
20 Posts
Discussion Starter · #7 ·
Hmm, I was unaware that a bad O2 sensor would prevent it from running, I have a few others (from renix XJs) I will swap it out, as well as the ECM
 

·
Registered
Joined
·
20 Posts
Discussion Starter · #8 ·
I was digging around a bit today, I found out that I'm not actually getting spark, I am getting about 2.2-2.7 volts from the cps, I will swap it out tomorrow and see what happens
 

·
Registered
Joined
·
20 Posts
Discussion Starter · #10 ·
TCM swap didn't seem to do anything, however I had the cps unplugged and reattached a few times (when testing voltage) from searching online, I believe that .2 volts is too low to generate spark (should be closer to .5) I will post if it changes anything, however it seems odd that it was working fine on one xj and registered too low voltage when reinstalled.
 

·
Registered
Joined
·
20 Posts
Discussion Starter · #11 ·
I think I may have narrowed down the problem, I am getting spark from the coil to the distributor, but it does not seem to be going from the cap to the plug wires, it may be caused by improperly indexing the distributor, however I don't know why it would have ran for a few hours then died, I will try and re-index it properly and see what happens
 

·
Registered
Joined
·
20 Posts
Discussion Starter · #12 ·
I found the problem! turns out, the coolant temp sensor wire had a bare section and was grounding to the intake manifold, I guess the computer got a weird reading from it and decided to prevent the engine from starting.

for some reason it pops out the intake a few times when I floor it, nothing major though.
 

·
Registered
Joined
·
20 Posts
Discussion Starter · #14 ·
Yeah, I was just backtracking wires, and found the short.

However, an old problem that I forgot about (had hoped tearing things apart and resembling might fix) resurfaced. Every time I start it cold, it will idle fine (sometimes a bit erratic, but that's because the brake booster is shot and causes a vacuum leak) but if I try and give it some throttle, it will bog down severely, and backfire (enough to blow the muffler to bits) if I do it too long. it just bogs down and won't go, also since I got it running again, if I floor it from a dead stop, it will pop out the intake 4-5 times (only when floored from a dead stop, and a few seconds afterwards) Not too sure whats causing this, but until I find a fix, I cant drive it.
 

·
Registered
Joined
·
20 Posts
Discussion Starter · #16 ·
It it possible that its caused by the TPS I suppose, I replaced mine cause it failed, but I just stuck it on there, I didn't adjust it or anything, so its possible that that is the cause. I tried running it with the brake booster vacuum line plugged, and it made no difference in the bogging down, I have a replacement that I intend to put in when I swap the engine, but right now I am just looking for cheap and temporary "band-aid" fixes till I get that done. I will adjust the tps and see what happens.
 

·
Registered
Joined
·
20 Posts
Discussion Starter · #17 ·
The vacuum leak coming from the brake booster is pretty bad, is it possible that a large vacuum leak could over time cause the jeep to accelerate poorly? or is it just the tps?
 

·
Registered
Joined
·
20 Posts
Discussion Starter · #19 ·
I replaced the brake booster today. Its going to take some time getting used to assisted braking XD

I was able to adjust the tps according to cruisers guide and got it spot on, it certainly runs better and accelerates smoother.
however it still misses under 2k rpm and shakes the whole vehicle, I determined this to be a problem with the #2 cylinder, as unplugging the injector their does not change the pitch of the engine, and the spark plug always comes out wet and fouled (regardless of swapping the wire and plug), I've known about this for a while, and is not that important, but what really needs to be fixed is the bogging down when trying to accelerate from a cold start. It honestly feels like its just dumping so much gas when it does anything other then idle that it almost kills it. I will swap out the CTS and see what happens (it was the cause of the previous problem, and I have a spare, so why not) I also swapped the O2 sensor, and will swap the MAP, but I just what to know what your thoughts are.
 

·
Registered
Joined
·
20 Posts
Discussion Starter · #20 · (Edited)
I'd also like to point out that I went probably no more then 40k since I got it running and used about 1/3 of a tank of gas, it worked out to be something like 4mpg

This is bad.
 

·
Registered
Joined
·
20 Posts
Discussion Starter · #21 ·
I figured out that the problem only occurs on a COLD start and lasts until its warmed up, it will not accelerate anything above idle for the 10-15 minutes that it takes to warm up, its just bogs down and backfires but wont actually stall. I swapped pretty much every sensor from a known good running 90 xj and the problem still happens, so its either something in the wiring harness or something mechanical. its not the MAP, as running it with unplugged is just about impossible, and its got a good vacuum line, what else could cause it to run really good at idle, but bog down and with enough gas to almost kill it?
something is causing the ECM to send so much fuel that it almost kills until its warmed up.

any ideas?
 

·
Registered
Joined
·
20 Posts
Discussion Starter · #23 ·
I'm pretty sure is oil, (although there was gas on it because it wasn't burning it) I ran a compression test a few times and got 150 on all cylinders, except #2, it got 175 first time and 160 second time, so its probably valve related. I'm not too concerned about it right now as I have a rebuilt engine to put in (when I rebuild it XD) so the current engine only has to last a few more months.

The only reason I brought up the bogging down issue is because its a PITA to have to wait ~15 minutes to be able to go anywhere, not to mention I'm only getting 5 mpg...
 

·
Registered
Joined
·
20 Posts
Discussion Starter · #25 ·
You are absolutely right, I swapped the fuel rail and all the injectors, and it fixed the problem with #2. Also, they must have given me an ICM for the wrong year, I swapped it outand it starts and runs perfectly now, the thing probably runs better then it has in a year and a half! anyway, thanks for the help.
 

·
Registered
Joined
·
20 Posts
Discussion Starter · #26 ·
it was the fact that the tach was jumping all over the place when it would bog down that made me think ICM, turns out, I was right.
 

·
Registered
Joined
·
20 Posts
Discussion Starter · #29 ·
having a problem with my headlights now though, often times they will simply be super dim, and overtime (sometimes) get brighter, however recently they have started to flash on and off (dash/interior lights unaffected) so I was wondering where the headlights themselves grounded to? I think it could be a bad ground causing these issues
 

·
Registered
Joined
·
20 Posts
Discussion Starter · #31 ·
Ok, I will take a look there, it could be a loose connector, as when I'm driving they flicker on and off quite frequently, so it might just need a good cleaning.
 
1 - 20 of 20 Posts
Top