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  #16  
Old March 17th, 2013, 18:40
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Ecomike Ecomike is offline
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Re: diagnosing engine vibration

Plug wire check to make sure two distributor wires are not criss crossed, and check that the rotor is in fact pointing at #1 on the cap when cyl #1 is at TDC is next.
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  #17  
Old March 19th, 2013, 14:10
wheelinscott wheelinscott is offline
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Re: diagnosing engine vibration

Did you find out anything? I'm having the exact same issue right now(though I haven't replaced the engine).

I put a new IAC in, which ended up being bad (would idle at 2000 rpm) and I noticed that it was still vibrating bad. My next step is putting an O2 sensor in (just awaiting for the exhaust to cool).
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  #18  
Old March 30th, 2013, 23:20
wheelinscott wheelinscott is offline
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Re: diagnosing engine vibration

hmm I haven't driven my jeep in a while, but it is still having the vibration problem (I did replace the O2 sensor). Am I down to the MAP sensor then?
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  #19  
Old March 31st, 2013, 01:14
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Re: diagnosing engine vibration

You may be on the wrong track, if it isn't ignition, it may be fuel. I've had partially plugged injectors that made the motor vibrate.

Swapping out sensors and components hoping to get lucky IMO is a poor way to troubleshoot. You can change out every sensor in the motor and still have a dirty connector or a bad wire. The 5 volts or so in most sensors isn't going to make it through an oil covered contact inside a dirty connector.

The pins sometimes bend or are forced partiaqlly out of the back of a connector.

If they swapped the motor out, chances are they had many of the connectors apart and they may have been damaged or got covered in oil.

Listen to Mike maybe your original setup is wrong. Especially with a new cam, it is possible the cam timing is off and/or the initial setup for the distributor is off, the cam drives the distributor.

Last edited by 8Mud; March 31st, 2013 at 01:25.
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  #20  
Old March 31st, 2013, 01:22
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Re: diagnosing engine vibration

Quote:
Originally Posted by wheelinscott View Post
Did you find out anything? I'm having the exact same issue right now(though I haven't replaced the engine).

I put a new IAC in, which ended up being bad (would idle at 2000 rpm) and I noticed that it was still vibrating bad. My next step is putting an O2 sensor in (just awaiting for the exhaust to cool).
Idling at 2000 RPM isn't likely to be a sensor problem, but may be a TPS. More likely to be a vacuum leak.

Swapping out sensors hoping to get lucky is a poor way to troubleshoot and expensive.

Between you two guys, you have swapped out more sensors than I have in 25 year and four XJ's. Just saying.
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  #21  
Old April 9th, 2013, 12:41
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Re: diagnosing engine vibration

8mud, the reason I swapped most of the sensors is because there had been an engine fire before the rebuild. Many of the sensors still worked fine, but it had been my intention all along to to put new sensors in a new engine.

If I were just swapping to check things, I would just have a friend with a similar year drive his Jeep over and start swapping out his parts. If one fixed it, bingo, if not, new approach. =)

I just list all the sensor swaps ahead of time so that people don't start suggesting sensors.

But, to get back on topic, so it's been a while since the Jeep ran. I went out and started it up, and it was running a little rough at idle too. In fact, it kind of seemed to have the harmonic. I haven't had a chance to get out, and check the number one cylinder against tdc yet. I did verify that no wires were crossed when I pulled the plugs.

As soon as I can check the distributor, I'll chime back in. My other fear, as I'm pretty sure we double checked the distributor already at the shop, is that maybe the timing chain is off by just a hair.

As for the injectors, the jeep has new rebuilt Ford Mustang injectors and they were pulled and cleaned as one of the first diagnostic steps after the rebuild...did that just after checking fuel pressure.
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  #22  
Old April 9th, 2013, 13:50
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Re: diagnosing engine vibration

Fuel pump. Delivers enough at idle, but engine stumbles due to lack of power under load/ raised RPM.

Replace your Fuel filter with a unit from NAPA.
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  #23  
Old April 10th, 2013, 09:00
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notamos notamos is offline
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Re: diagnosing engine vibration

Quote:
Originally Posted by Spearfisher XJ View Post
Fuel pump. Delivers enough at idle, but engine stumbles due to lack of power under load/ raised RPM.

Replace your Fuel filter with a unit from NAPA.
+1
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  #24  
Old April 11th, 2013, 21:00
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Jonner Jonner is offline
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Re: diagnosing engine vibration

You mentioned motor mounts... I may be way off, but hear me out.

I just replaced my motor mounts with Brown Dogs. In the instructions they state to loosen the transmission mount until the motor mounts are are settled into place and fasteners torqued. Then tighten the transmission mount. If the driveline is a little twisted, but locked into place I'd imagine that could cause a little vibration.
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  #25  
Old June 17th, 2013, 08:12
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SanDiegoXJ SanDiegoXJ is offline
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Re: diagnosing engine vibration

OK, been a while since I chimed in on this because I had no place to do any work.

Just got into a new place with a garage and popped off the distributor. Following the directions in the FSM, the distributor appeared to be pointing closer to 6 'o clock than 5 'o clock. I pulled it out, moved it one tooth back and reinstalled it. This time it looked more like 4:30 than 5 'o clock. Also, I scribed the outside of the post the distributor, and when I lined up the rotor, the trailing edge had not quite completely passed the scribe mark. The trailing tip of the rotor was still slightly behind it. I fired it up, revved it, backfired a couple times, and then the idle settled down. But the vibration was almost gone!

So I take it out for a test drive and theengine vibration is significanty reduced, but I also can't get it above 60mph without it coughing and bucking. =(

This does make me think it is more ignition related than fuel pump related though. I would believe it was the fuel pump more if the stumbling didn't die out. The vibration really strikes me as a harmonic vibration in that it appears and disappears at rpm and load, but it always does it under the same conditions...i.e., same speed on different roads. (but no, it's not the road because it will do it in park too).

On a side note, it went to smog about a year ago, right after the rebuild, and it still had a tough time passing because of NOx. The guy said the temp would look good until the second test, then it would just slowly keep climbing out of range.

I'm wondering if it's just a little too advanced. Since I can't adjust my distributor, would that mean an error in the timing chain installation?
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  #26  
Old June 17th, 2013, 19:39
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Ecomike Ecomike is offline
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Re: diagnosing engine vibration

I was thinking timing chain 15 lines before I got to the end of your last post!!!
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  #27  
Old June 18th, 2013, 22:40
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Re: diagnosing engine vibration

Ok, so started to pull stuff off today. since I can't get the engine out, I'm planning on removing the whole front grill assembly, the radiator, etc. so I can just pull up a chair and work directly on the motor...I know, it's a lot of work, but I don't want to mess around with trying to reset the timing. So it's gonna be another bit of time before I get back with any results.

But on a side note, as I began removing stuff from the engine bay to get started, I decided to yank and toss the whole cruise control system. At which point, a gave the old A/C compressor a spin and it sounded like it was missing a bearing. So, since it doesn't work, it's noisy, and the tubes get in the way of everything, figured I'd toss it in the trash heap as well, but how do I clear the system of the R12 responsibly?

Last edited by SanDiegoXJ; June 18th, 2013 at 23:03.
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  #28  
Old June 23rd, 2013, 15:42
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Re: diagnosing engine vibration

Ok, got the whole front of the Jeep pulled off, removed all of the A/C crap, and got started on the timing chain.

I made sure I was at TDC on the compression stroke, I pulled the harmonic balancer (but when I did, it started to turn a bit, so I moved it counter clockwise back to the TDC position, however, it left some slack in the chain. =(



But this is what I can see now.

Should those two indents be 180 off from each other? Or should they be pointing at each other?

I'm thinking that's the problem, just not sure. Any suggestions?
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  #29  
Old June 23rd, 2013, 17:47
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Re: diagnosing engine vibration

I guess I should note that I was following a write up on from Jeff in VA.

His instructions said to line up the TDC with the rotor...which I did, and which came after the compression, so it made sense. but if the cogs will only go on one way, did I just have the distributor 180 degrees off? Because the next TDC they match up perfectly.

So maybe I misunderstood, but when they say, "TDC on the compression stroke", do they mean at the beginning of the compression, or at the end of the compression? I always figured end because that's where you'd want the spark to fire, once the gas had been compressed. But from what I understand, the gears only go on one way, so how can it be 180 degrees off?

Last edited by SanDiegoXJ; June 23rd, 2013 at 17:54.
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  #30  
Old June 23rd, 2013, 19:42
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Re: diagnosing engine vibration

OK, so while I'm waiting...(I can't believe you people don't sit by your computer waiting for me to have a problem)...I tried desperately to find anywhere in the FSM that it said the distributor should be pointing at the #1 cylinder while these two marks met. But I just couldn't find it anywhere but the walkthrough I was following. However, if we assume there is only one way to put these gears on, which is what I'm reading over and over, then by the FSM, everything checks out. At TDC on the exhaust stroke, the two dots line up. If I rotate until the dot on the large gear is at 2:00, then count the pins, as it says in the FSM, I get 15 pins between the two which is what it says it should be. All the videos then show that I was correct in that I should wait for air to blow, then set the engine to top dead center, and then point the dizzy at position #1.

Now the new news...before I totally disassembled it, I had drained the tranny fluid. I tried starting it up to make sure that everything was back to the way it was before I started diddling with it. The Jeep still ran like crap, but when I pulled the plugs, the #2 plug was wet with gas...I'm wondering if the rotor/cap/plugs/coil have something to do with it. It tend to think it isn't the coil, but the wires may have too much resistence, or the steel rotor and cap may not be conducting enough electricity. However, I also heard several bangs come from the tranny area whenever I'd rev it a little, so I'm back to thinking it might just be tranny related issues.

Anywho, unless someone can tell me that I'm wrong and the cog on the camshaft needs to be spun 180 degrees, I'll just have to wait until the new cap and rotor with brass fittings from summit, the accel spiral core wires, and the new pulley to replace the A/C show up and see how it runs.

Should of just ran the old engine till it died. =(
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