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Unread 04-14-2013, 05:31 AM   #16
AVR2
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1993 ZJ 
 
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When I first turned the key after doing some work around the AC compressor side of my 4.0L, the engine was suddenly misfiring and I was getting a CEL. I got my stethoscope onto the injectors and two of them weren't firing. The fix was very simple - I just needed to pull the connectors and clean off the green corrosion.

The weird part was why those two injectors suddenly stopped working simultaneously, given that I hadn't touched that side of the engine. I could kind of understand it if I'd disturbed the injector wires in some way, but I hadn't gone near them. I guess it's a Jeep thing...

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Unread 04-14-2013, 11:17 AM   #17
KranMan
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when i changed the clutch on my 94 cherokee the engine tilted back alittle it didnt seen like a big deal to me at the time. when it was time to start it up it wouldnt then it would but would run like crap it kinda sounded like yours in the video after the little wiggle test with the wires i started to pinpoint where it was. where the wires running to the fuel rail coming out of the main harness at the back of the engine it made a very tight bend and from playing around working on it snapped the wire. you might have a differant problem im not sure but take your time and check it out. good luck with it
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Unread 04-15-2013, 06:41 PM   #18
gunner608
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Got a couple more bits of info, i did fuel pressure test and was 31 at idle and 40 with unplugging the fuel regulator, I also did a compression test. #1 115 PSI, #2 130, #3 130, #4 130 PSI, #5 125 PSI #5 130 PSI. Not really sure what that really tells me but I did it as the guy at the parts store said i should, told me i would want to above 90 and all should be pretty simuliar. I again double check the wires on the cap and cylinders and are definitly hooked up correctly. Talked with one mechanic and he talking about jumping timing chain and messing my timeing up not really sure what he ment by that either. Again I checked for vacuum leaks with propane including the brake booseter as suggested but didn't here any change in idle. I can kinda here a little whislte when you just start to open the throtle but im like 95% sure it's from IAC which would it run any different if the IAC was unplugged because when i unplug my IAC it does not change at all with it plugged in or not. I already cleaned it ealier, would it be worth replacing it. I checked around the gasket no pinched wires, wire harness intact, no corrosion at the injector clips. Im thinking i might just go to a junk yard and rip off a map sensor, TPS, IAC and just see if that would make a difference, i hate to go buy all new and see it still running like crap. Getting pretty frustrating. Would taking it to a shop be any good. Only code it shows is 12 for battery disconnect, is a shop going to be able to any more with computer they have to check for correct timing or sensors or anything. Im really getting sick of looking at this thing and coming up with nothing. Do i take all apart and start over again, im pretty postive i do not have a leak at the gasket but I feel pretty clueless. I was really hoping fuel pressure or compression test would tell me somthing that it is missing so bad. What should i do next?
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Unread 04-15-2013, 09:10 PM   #19
zjosh93
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How long did you power the injectors when you where cleaning them? Applying constant power is basically like running the injector at 100% duty cycle and can cause them to overheat. With no fuel flow through the injector there isn't much to cool them. They might be damaged. I can replicate your chugging by unplugging three of mine. You can check the injectors on the jeep by unbolting the rail and lifting it just enough to see the end of the injector. As long as you still have all your injector clips intact and the injectors have grooves for the clips the injectors shouldn't pop out under pressure. Shouldn't. It never happened to me but use at your own risk. If you are concerned there should be enough residual pressure to check each injector once at least. Just use your switch setup to trigger the injectors and see if they spray.
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Unread 04-16-2013, 02:34 PM   #20
ratmonkey
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your compression is low across the board. 90psi is the minimum for a cylinder to actually fire. any one cylinder at 130 or below is cause for a full motor rebuild. as would a spread of 15psi between high and low cylinders.
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Unread 04-16-2013, 08:20 PM   #21
gunner608
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I pulled the fuel rail while is was running and all injector were shooting gas and of course the idle went up with the vacuum leak. The thing only idles around 4-500 rmps like it's barley keeping its self going but has never actually stalled out. I again was spraying carb cleaner all over the place and on the gasket and didn't notice an idle change. I bought it 8 years ago and it's never had a cat on it. Could it have anything to do with the exhaust or back pressures of any sort. I was thinking about unhooking it at the collection just to see how it would run im sure it would be loud as hell but im just thinking out loud. Just really trying to focus on what I did as I find it hard to believe that my motor just took a sh*t on me after putting a new exhaust manifold in. So my pressure are a little low but she still had a good amount of power before I did the exhaust manifold. Could any these symptoms be from leaking exhaust or air intake and how do you check for either of those. I've done propane and carb cleaner around the gasket and no changes, super low idle like it's barely running but if I unplug a vacuum line it will speed up. Wouldn't a intake leak sort of do the same thing. Im almost to the point of ripping it all apart and putting a new gasket on there again even though I feel pretty positive it's not leaking but is there any better for sure test other than propane and carb spray. Does anyone else have any experience with this sort of compression test. How bad is 130?
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Unread 04-16-2013, 10:12 PM   #22
jeepkid945
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All your comp readings are close , im pretty sure thats not your problem. Are all your plug wires in the right spot? I know you checked but they could all be moved over one post on the dist.cap. previous owner did it to mine and acted similar.
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Unread 04-16-2013, 11:11 PM   #23
Uniblurb
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Quote:
Originally Posted by gunner608 View Post
I pulled the fuel rail while is was running and all injector were shooting gas and of course the idle went up with the vacuum leak. The thing only idles around 4-500 rmps like it's barley keeping its self going but has never actually stalled out. I again was spraying carb cleaner all over the place and on the gasket and didn't notice an idle change. I bought it 8 years ago and it's never had a cat on it. Could it have anything to do with the exhaust or back pressures of any sort. I was thinking about unhooking it at the collection just to see how it would run im sure it would be loud as hell but im just thinking out loud. Just really trying to focus on what I did as I find it hard to believe that my motor just took a sh*t on me after putting a new exhaust manifold in. So my pressure are a little low but she still had a good amount of power before I did the exhaust manifold. Could any these symptoms be from leaking exhaust or air intake and how do you check for either of those. I've done propane and carb cleaner around the gasket and no changes, super low idle like it's barely running but if I unplug a vacuum line it will speed up. Wouldn't a intake leak sort of do the same thing. Im almost to the point of ripping it all apart and putting a new gasket on there again even though I feel pretty positive it's not leaking but is there any better for sure test other than propane and carb spray. Does anyone else have any experience with this sort of compression test. How bad is 130?
I used carb spray and propane on everything while the engine never revved. But as mentioned before it had a large vacuum leak on the rubber grommet on the brake booster and once sealed with gasket sealer it quit coughing & sputtering. I've even tried starting fluid to check for vaccum leaks but do at your own risk, only use on a cold engine, and you best not have any sparks/arcs around. Which brings up another point; why don't you do the old test by looking at your engine running in the complete darkness while looking for sparks arcing. You never know...

You can also have your intake smoked to check for leaks. Lots of shops do this but there's some DIY techniques you may want to do a search for but believe some type of specialized equipment is needed. Like a party smoke machine! LOL.

Believe before tearing it apart and installing another new gasket I'd try re-torquing the manifold/intake. While I thought I had them exactly correct I found 2-3 bolts/nuts which took a little more torque. Like the far back bolt by the firewall which is so hard to get to and the ones on the bottom/middle behind where the intake juts down where the throttle body is overhead. At least that's the way the 96 4.0 intake is shaped. Good luck.
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Unread 04-17-2013, 09:58 PM   #24
gunner608
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Gasket is only 12 bucks, so I have everything apart now back to square one. Figure it was cheaper to redo my work with a new gasket vs throwing parts I don't even know will fix it into it. What would be the best way to do this. Last time I used a gasket shellac that indian stuff in a brown bottle, was telling one guy had he said you should never use anything with gasket if you have 2 clean surface you shouldn't need any type of that stuff but the guy that sold me the gasket shellac swore by it and stated he's never had a leak using this stuff. Just wondering what you guys thinks best. I have it all cleaned up very well. Should I use any type of gasket sealant/RTV or just the gasket?
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Unread 04-18-2013, 05:53 AM   #25
ratmonkey
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Gasket only. Never use anything extra unless the factory manual calls for it.
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Unread 04-18-2013, 08:15 AM   #26
gunner608
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okay thanks, im going to be putting it back together tonight, so ill let you guys know if it improves my issues
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Unread 04-22-2013, 10:05 AM   #27
zjosh93
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Any update?
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Unread 04-22-2013, 12:04 PM   #28
Oldfrog
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Gasket only. Never use anything extra unless the factory manual calls for it.

I second this, for what it's worth.
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Unread 04-22-2013, 06:39 PM   #29
MrRoundel
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Bad plug wires?

My 4.0 Jeep was missing pretty badly a few months ago. I barely made it home from a 100 mile plus trip, and was a pucker-factor-fifteen the whole way back. It had driven that way since about 1/2 of the way down to my destination and no CEL light came on. When I got out from dropping off my passenger and restarted the car, the CEL finally came on. I limped home and immediately hooked up my OBDII reader. I believe that it read that there was a misfire on the #4 cylinder. I checked the wire and it was open, with no spark getting to the plug. I put on a new set of wires and, voila!, problem solved. I'd suggest checking the ignition wires for continuity.
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Unread 04-24-2013, 06:28 PM   #30
gunner608
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I broke down and took it to a local shop today to mainly get it smoke tested for any vacuum or intake leak and just to get a mechanic to look at it as i am no mechanic. They smoke it out and came up with no leaks, sounds like they started unplugging sensors and find that it drives significanly better almost night day and does still kinda chug and miss a little at idle or if i really hammer on it by having both the coolant temp sensor unplugged and the intake air sensor. Figure i will replace them both. Got new coolant temp sensor but waiting for intake air sensor to come in. Hopefully when i put both new sensors in it will fix my problems. I will have both new sensors into tomorrow and will post if it fixes my issues.
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