94 Cherokee 4.0 starting/ timing issue
06-04-2011, 07:22 PM
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94 Cherokee 4.0 starting/ timing issue
Hello new to this forum. Just so you all know, I am a mechanic with over 35 years of expirence working on cars. I know a lot about cars but this one really has me stumped. Im having an issue with a 94 cherokee country with the 4.0 engine in it. I need some advice from some experts with the 4.0 engine.
I bought this jeep about 4 weeks ago for only $300. It has 180,000 miles on it. It had been sitting for about 2 years. I aired up the tires, put in a new battery, & drove it home. It is in very good condition & even has Mickey Thompson wheels & BFG All Terrian T/As on it!
Since I am a mechanic, the first thing I did was clean it up & go over it to see what it would need to be reliable. I did a full tune up (plugs, cap, rotor, wires), changed the oil, changed the trans filter & fluid, changed the fuel filter, & put in a new air filter. I also cut the old battery connectors of & put new ones on so it would get a good connection.
I fixed a few other issues with the lights, put new fog light on, & checked the brakes. They were all new, so I didnt have to do them. The front end has been rebuilt at some time, so I greased all the zerts & checked the front end. It was tight.
I have been driving it ever since then & it has ran great! A few days ago I noticed it was dripping oil, so I checked it out & found out the distributor was leaking. I pulled out the distributor to replace the gasket underneath, & found oil inside of it. I decided to purchased a reman distributor & put it in.
I put it in & cranked it, but it did not start, so I got out to look to see if I had done something wrong. I could smell fuel, so I knew it was getting fuel. Then I saw I had forgotten to put in the rotor
! so I removed the cap & put it in. When I turned the key again, it went BOOM! & backfired through the exhaust! It was so loud & thought I blew up the muffler, but when I looked, it was ok, so I cranked it again. It sounded like it wanted to start, but wouldnt, so I removed the cap & realized I had put the distributor in 180 degrees off. I re-installed the distributor correctly & WAH-LA it started right up! I was happy because I thought I had hurt something when it backfired. It idled normally, so I was going to let it run for a few minutes to be sure everything was ok.
After about 30 seconds, it died like someone had shut off the key. I started it & it started right back up, & idled normally. After about 30 seconds it died again.
I got in it this time & started it & gave it some gas. It started right up & would stay running if I gave it gas, but didnt sound right. I revved it up & let it run for a couple of minutes, then got out to look at it. The first thing I noticed was the exhaust manifold was glowing red hot. Then it died again. I thought that maybe the distributor was off a tooth, so I removed the distributor & re-timed it. same thing. Removed & retimed again. Same thing. Again. Same thing.
I thought that maybe the distibutor was wrong or bad, so I went & compaired it to another new one. They were alike. I compaired it to my old one. They were the same. I installed my old one back in the engine to see what would happen. Same result. I removed it & installed the new one again. Same result.
Then I got on the internet to try to find out what was causing this. I read that the cam sensor is in the distributor, so mine was new, plus it still did it with the old distributor. I aslo read that maybe the crank sensor could be the cause or the exhaust was plugged up. Put in a new crank sensor. Same thing. Removed all the exhaust except the down pipe. Same thing.
Checked all the grounds, connections, vacuum lines, ect. No problems. checked for codes - none. Disconnected the battery & did the reset thing. Didnt help. Removed the connector at the ecm while the battery was disconnected. All the pins looked good. reconnected everything. Same thing.
As you can see, I know how to work on vehicles, & what to check when there is a problem, but this one has me stumped.
One thing I did notice that is strange is the distributor cannot be moved to adjust the timing because it is controlled by the ecm. However, when I put a timing light on the timing tab with the engine idling (before it dies LOL) the timing is running at 40-50 degrees BTDC, which seems extremly high to me at idle & may be the cause of my problem, (especially the red hot exhaust) but I dont know & dont want to waste $400 on an ECU to find out without knowing for sure.
Sorry to be so long winded. Just trying to avoid all the "did u do this or that" questions. ANY ideas would be awesome. I am down to ECM or jumped timing, but I dont believe it is timing because the distributor goes in normally when I set the mark at zero. I dont know what to do next! HELP!
I bought this jeep about 4 weeks ago for only $300. It has 180,000 miles on it. It had been sitting for about 2 years. I aired up the tires, put in a new battery, & drove it home. It is in very good condition & even has Mickey Thompson wheels & BFG All Terrian T/As on it!
Since I am a mechanic, the first thing I did was clean it up & go over it to see what it would need to be reliable. I did a full tune up (plugs, cap, rotor, wires), changed the oil, changed the trans filter & fluid, changed the fuel filter, & put in a new air filter. I also cut the old battery connectors of & put new ones on so it would get a good connection.
I fixed a few other issues with the lights, put new fog light on, & checked the brakes. They were all new, so I didnt have to do them. The front end has been rebuilt at some time, so I greased all the zerts & checked the front end. It was tight.
I have been driving it ever since then & it has ran great! A few days ago I noticed it was dripping oil, so I checked it out & found out the distributor was leaking. I pulled out the distributor to replace the gasket underneath, & found oil inside of it. I decided to purchased a reman distributor & put it in.
I put it in & cranked it, but it did not start, so I got out to look to see if I had done something wrong. I could smell fuel, so I knew it was getting fuel. Then I saw I had forgotten to put in the rotor
! so I removed the cap & put it in. When I turned the key again, it went BOOM! & backfired through the exhaust! It was so loud & thought I blew up the muffler, but when I looked, it was ok, so I cranked it again. It sounded like it wanted to start, but wouldnt, so I removed the cap & realized I had put the distributor in 180 degrees off. I re-installed the distributor correctly & WAH-LA it started right up! I was happy because I thought I had hurt something when it backfired. It idled normally, so I was going to let it run for a few minutes to be sure everything was ok.After about 30 seconds, it died like someone had shut off the key. I started it & it started right back up, & idled normally. After about 30 seconds it died again.
I got in it this time & started it & gave it some gas. It started right up & would stay running if I gave it gas, but didnt sound right. I revved it up & let it run for a couple of minutes, then got out to look at it. The first thing I noticed was the exhaust manifold was glowing red hot. Then it died again. I thought that maybe the distributor was off a tooth, so I removed the distributor & re-timed it. same thing. Removed & retimed again. Same thing. Again. Same thing.I thought that maybe the distibutor was wrong or bad, so I went & compaired it to another new one. They were alike. I compaired it to my old one. They were the same. I installed my old one back in the engine to see what would happen. Same result. I removed it & installed the new one again. Same result.
Then I got on the internet to try to find out what was causing this. I read that the cam sensor is in the distributor, so mine was new, plus it still did it with the old distributor. I aslo read that maybe the crank sensor could be the cause or the exhaust was plugged up. Put in a new crank sensor. Same thing. Removed all the exhaust except the down pipe. Same thing.
Checked all the grounds, connections, vacuum lines, ect. No problems. checked for codes - none. Disconnected the battery & did the reset thing. Didnt help. Removed the connector at the ecm while the battery was disconnected. All the pins looked good. reconnected everything. Same thing.
As you can see, I know how to work on vehicles, & what to check when there is a problem, but this one has me stumped.
One thing I did notice that is strange is the distributor cannot be moved to adjust the timing because it is controlled by the ecm. However, when I put a timing light on the timing tab with the engine idling (before it dies LOL) the timing is running at 40-50 degrees BTDC, which seems extremly high to me at idle & may be the cause of my problem, (especially the red hot exhaust) but I dont know & dont want to waste $400 on an ECU to find out without knowing for sure.
Sorry to be so long winded. Just trying to avoid all the "did u do this or that" questions. ANY ideas would be awesome. I am down to ECM or jumped timing, but I dont believe it is timing because the distributor goes in normally when I set the mark at zero. I dont know what to do next! HELP!
06-05-2011, 11:07 AM
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Year: 2001
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First, let me say that I am NOT a Jeep guru, but...
I would try re-indexing the distributor as described here:
https://www.cherokeeforum.com/f2/bac...38/#post336432
I would try re-indexing the distributor as described here:
https://www.cherokeeforum.com/f2/bac...38/#post336432
06-05-2011, 12:28 PM
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I have done that every time I had the distributor out. I made sure it was on the the compression stroke on #1, then rotated the crank until the mark on the balancer was sitting at zero on the timing tab. Then I indexed the oil pump to 11 o'clock. I had marked the distributor where the #1 wire sits. When I installed the distributor, it dropped right in & the rotor was dead center in the middle of the mark on the distributor. Thats how I have done it every time, with the same result.
Question for anyone: Would I have better luck if I ignored the timing marks & instead set the #1 piston at TDC & installed the distributor that way? Also, with 180,000 on it, could timing chain stretch cause the distributor to not be correct, even though it appears it is?
Question for anyone: Would I have better luck if I ignored the timing marks & instead set the #1 piston at TDC & installed the distributor that way? Also, with 180,000 on it, could timing chain stretch cause the distributor to not be correct, even though it appears it is?
06-05-2011, 01:40 PM
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Year: 1990
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Engine: The venerable 4.0
Shot in the dark..... You check out the cam position sensor? If it isn't functioning properly the ecu will get screwy causing lots of problems with ignition. I would think with that much timing at idle the thing wouldn't even run....wouldn't 50 degrees at that low of rpm fire at or close to the very beginning of the intake stroke?
Last edited by Slick761; 06-05-2011 at 01:45 PM.
06-05-2011, 02:24 PM
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On a 94 the cam positon sensor is the pickup inside the distributor. I put a new distributor in so it is new. When I set the rotor at #1 then I positioned the cam sensor. It is not it.
It ran very well for over 500 miles until I removed the distributor. Thats when the issue began, so I think it has something to do with the way the distributor is going in & what it is telling the ecu. I just have to figure out how to get it right. Having a vehicle with a distributor that you cannot manually ajust the timing on is a bad idea. I have read where there are a lot of issues on here with jeeps backfiring, & not running right. That is why they should have never allowed an ecu to decide where the timing should be.
It ran very well for over 500 miles until I removed the distributor. Thats when the issue began, so I think it has something to do with the way the distributor is going in & what it is telling the ecu. I just have to figure out how to get it right. Having a vehicle with a distributor that you cannot manually ajust the timing on is a bad idea. I have read where there are a lot of issues on here with jeeps backfiring, & not running right. That is why they should have never allowed an ecu to decide where the timing should be.
06-05-2011, 02:36 PM
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That's kinda what I was saying. Due to the fact that it is in the distributor and you took the distributor out and "upset" the sensor.... Do you think it's possible it was on it's way out and now it's dead? Check this http://www.lunghd.com/Tech_Articles/...lse_Stator.htm I know it's for renix but I'm sure about the same procedure applies to diagnosing. I couldn't see how you could be a tooth off after reinstalling the distributor that many times.
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06-05-2011, 04:54 PM
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Ok well I guess I am now offically a jeep guru! This is a new twist & Im sure if anyone that has replaced thier distributor & has had running issues reads this, they will be shocked.
I went out today to mess with it some more. First I stuck a long screwdriver in the #1 plug hole & slowly rotated the crank to see when it stopped moving up & started moving down, so I could see the relationship to the piston movment & the timing mark. The piston stopped moving at about 8* BTDC & started going down at about 2* BTDC. I figured this was close enough to ensure that the balancer had not slipped, & also I checked the rotor location & it was pointing straight at the #1 mark I had made on the distributor housing. I then knew that the timing chain had not skipped a tooth either, because everything was lining up.
I then decided I would remove the distributor & index it forward & backward one tooth on the camshaft & see if it would even start.
First I removed it & indexed it back one tooth. I rotated the crank through 2 revolutions & re-aligned the balancer mark to zero. The rotor was before my mark on the distributor, but the leading tip of the rotor was almost in line with the mark. I put the cap & wires back on & tried to start it. It sputtered & coughed & backfired through the downpipe, & would not start. I tried several times just to be sure & it would not start.
Next, I removed the distributor & indexed it ahead 1 tooth. Again, I rotated the crankshaft through 2 revolutions, & realigned the balancer mark to zero. Now the rotor was ahead of my mark by quite a bit. The trailing tip of the rotor was still slightly in front of the mark. I thought "the rotor is so far ahead of my mark now, there is no way this thing is gonna start". But what the heck, so I went ahead & reinstalled the cap & wires. When I turned the key to the start postion, it fired up instontaniously! I was shocked it would even start! I sat there waiting for it to shut off. 30 seconds go by, still running. A minute goes by, still running. 2 minutes go by, still running. WOW! Could it be that my computer required the distributor to be installed 1 tooth ahead of where it should be in order to run correctly? One way to find out. I got my timing light out & hooked it up. Pointed it at the timing tab - running between 12-14 degrees BTDC. Right where it should be. AMAZING!
So my advice to you is this. If you replace a distributor on a high mileage truck, & align the rotor to #1 & it backfires, stalls, runs like crap, or the exhaust glows red hot, MOVE THE DISTRIBUTOR AHEAD ONE TOOTH, AGAINST YOUR BETTER JUDGMENT. IT JUST MAY SLOVE YOUR PROBLEM!
I DONT KNOW FOR SURE, BUT I WOULD BE WILLING TO BET THAT ALOT OF THE GUYS THAT ARE EXPIRIENCING BACKFIRING & POOR RUNNING CONDITIONS IN THIER JEEPS COULD REMOVE THE DISTRIBUTOR & INDEX IT AHEAD 1 TOOTH & IT WOULD SOLVE THIER PROBLEM. I HOPE SOMEONE TRIES IT. IT MALKES SENSE ON A HIGH MILEAGE MOTOR BECAUSE THE TIMING CHAIN IS LOOSE & WOULD CAUSE THE DISTRIBUTOR TO RUN RETARDED. MOVING IT AHEAD 1 TOOTH WOULD ALLOW THE ECU TO ADJUST THE TIMING BACK TO WHERE IT SHOULD BE. BEATS WASTING MONEY ON PARTS YOU DONT NEED LOL!
If I can figure out how to do it, Im gonna take some pix & post them here to show I am telling the truth.
I went out today to mess with it some more. First I stuck a long screwdriver in the #1 plug hole & slowly rotated the crank to see when it stopped moving up & started moving down, so I could see the relationship to the piston movment & the timing mark. The piston stopped moving at about 8* BTDC & started going down at about 2* BTDC. I figured this was close enough to ensure that the balancer had not slipped, & also I checked the rotor location & it was pointing straight at the #1 mark I had made on the distributor housing. I then knew that the timing chain had not skipped a tooth either, because everything was lining up.
I then decided I would remove the distributor & index it forward & backward one tooth on the camshaft & see if it would even start.
First I removed it & indexed it back one tooth. I rotated the crank through 2 revolutions & re-aligned the balancer mark to zero. The rotor was before my mark on the distributor, but the leading tip of the rotor was almost in line with the mark. I put the cap & wires back on & tried to start it. It sputtered & coughed & backfired through the downpipe, & would not start. I tried several times just to be sure & it would not start.
Next, I removed the distributor & indexed it ahead 1 tooth. Again, I rotated the crankshaft through 2 revolutions, & realigned the balancer mark to zero. Now the rotor was ahead of my mark by quite a bit. The trailing tip of the rotor was still slightly in front of the mark. I thought "the rotor is so far ahead of my mark now, there is no way this thing is gonna start". But what the heck, so I went ahead & reinstalled the cap & wires. When I turned the key to the start postion, it fired up instontaniously! I was shocked it would even start! I sat there waiting for it to shut off. 30 seconds go by, still running. A minute goes by, still running. 2 minutes go by, still running. WOW! Could it be that my computer required the distributor to be installed 1 tooth ahead of where it should be in order to run correctly? One way to find out. I got my timing light out & hooked it up. Pointed it at the timing tab - running between 12-14 degrees BTDC. Right where it should be. AMAZING!
So my advice to you is this. If you replace a distributor on a high mileage truck, & align the rotor to #1 & it backfires, stalls, runs like crap, or the exhaust glows red hot, MOVE THE DISTRIBUTOR AHEAD ONE TOOTH, AGAINST YOUR BETTER JUDGMENT. IT JUST MAY SLOVE YOUR PROBLEM!
I DONT KNOW FOR SURE, BUT I WOULD BE WILLING TO BET THAT ALOT OF THE GUYS THAT ARE EXPIRIENCING BACKFIRING & POOR RUNNING CONDITIONS IN THIER JEEPS COULD REMOVE THE DISTRIBUTOR & INDEX IT AHEAD 1 TOOTH & IT WOULD SOLVE THIER PROBLEM. I HOPE SOMEONE TRIES IT. IT MALKES SENSE ON A HIGH MILEAGE MOTOR BECAUSE THE TIMING CHAIN IS LOOSE & WOULD CAUSE THE DISTRIBUTOR TO RUN RETARDED. MOVING IT AHEAD 1 TOOTH WOULD ALLOW THE ECU TO ADJUST THE TIMING BACK TO WHERE IT SHOULD BE. BEATS WASTING MONEY ON PARTS YOU DONT NEED LOL!
If I can figure out how to do it, Im gonna take some pix & post them here to show I am telling the truth.
06-08-2011, 08:13 AM
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Well, I be damned, I had the timing chain jump a tooth on my '93 XJ last weekend. Replaced the chain and gears yesterday, I had the same issue. Heading out now to index that sucker a tooth ahead. LOL, if it works for me, than you are definitely a jeep guru! I spent quite a while trying to figure it out yesterday without success. Damn computer controls. I really miss condensers and points. sigh.
Last edited by fishfast41; 06-08-2011 at 10:37 PM.
06-08-2011, 09:42 AM
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wags it sounds like all your messing around caused the the ecu to adjust the timing backwards too far, so when you installed the distributor correctly, the ecu was now way off, and couldn't adjust itself back to where it should have been in time. Very weird.
I think that in order you you to get it back to working where the indexing should be, you need to reset the PCM completely back to factory settings (search for the procedure). I don't know if you're up for testing this theory out after everything you've gone through already but it's worth mentioning at least for future references to this topic by others.
I think that in order you you to get it back to working where the indexing should be, you need to reset the PCM completely back to factory settings (search for the procedure). I don't know if you're up for testing this theory out after everything you've gone through already but it's worth mentioning at least for future references to this topic by others.