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Unread 11-20-2009, 09:15 AM   #31
RebuildRookie
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1988 YJ Wrangler 
 
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Alright, last night I swapped the air box hose to exhaust manifold around. Bad end on air box and better end on exhaust manifold.

2 days ago I did the "Seafoam" treatment, and runs better than ever. Got to work this morning and no "Poof". dont know if it was a fluke or not.

I ran the seafoam, because I got to thinking: Backfiring is caused by gas vapors that make it to the exhaust and ignite, what if the super rich running problem I had before I started working on it, created alot of buildup in the cylinders and it wasnt burning the fuel properly or fully.

Gonna keep monitoring it.

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Unread 11-20-2009, 10:51 AM   #32
5.7YJ
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Good to hear you didn't get a POOF today! Hope it stays that way for you!
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Unread 11-20-2009, 11:22 AM   #33
Que89YJ
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oh come on RR. tell the truth. You just went light on the Chilli and Beer last night. No more Poofing...
Glad to hear things are riding well on the heep. Did you ever take a look for leaking around the intake egr?
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Unread 11-20-2009, 11:25 AM   #34
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Chili maybe, but beer no way.


I did look and realized that the intake side was good, but where the tube goes into the exhaust manifold right above the O2 sensor, there is no gasket, must have forgotten to put it in for some reason. Thinking about putting som RTV on it.

Wondering where you've been lately, didnt know if you where sick or something. I realize why you go to that part of TN. We had a blast and it was beautiful. My buddy took his 92 YJ and went riding a little. We stayed at the Natchez Trace State Park in Wildersville/Lexington TN.
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Unread 11-20-2009, 01:04 PM   #35
Que89YJ
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Honey do's and honey don'ts if you know what I mean. Work is begining to pick up too, so I actually have to do some real tech work during the day. I have relatives and friends al over the place in Tennesse. I mainly stay on the east side Pidgeon Forge area. I love it in Tenn. there are so many beautiful places to play. With no gasket your going to have a difficult time sealing it. I hate to say it because I know what a pain it is dealing with those 2 bolts for the egr tube but you might be better off pulling them and getting a gasket in there. That tube gets so hot that I think any rtv will not hold even the high temp stuff.
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Unread 11-20-2009, 01:19 PM   #36
RebuildRookie
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I was thinking the same thing with the RTV. Taking the bottom of the tube isnt so bad now, I have a 12" extension and there are 2 spots by the powersteering pump that I can get to it real easy. But still no fun.

Just got back from meeting the wife for lunch. On the way I putted along at around 55 and when I got there no "Poof". On the way back to work got it up to 70 and was on it hard, parked it and got a "Poof". Seems like for some reason when i'm on it hard it does it.
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Unread 02-08-2010, 11:04 PM   #37
SDGBASSE
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Any new input on this? I'm getting the same thing on mine. How's your idle, mine's horrible, it goes to 1800 RPMs at operating temp. And how were your spark plugs, I think it's backfiring on mine because my #4 plug is lead-fouled, and when I shut the engine off the deposits are hot enough to ignite what may be left of vapors in the cylinder. And I'm running a bit lean, since my plugs are whiteish.
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Unread 02-19-2010, 07:40 PM   #38
SamzJeep
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Hey SDGBASSE.....mine was doing pretty much the same thing too. I did find that pretty much most of my vacuum lines were bad (even those four little ones on the side of the throttlebody). Afer I replaced all of my vacuum lines, my idle went down to about 1200 rpms and she runs really well. I am still getting a slight backfire after I've driven it home from work (30 minutes on the freeway). I've replace my cat, muffler, fuel injector (inside the throttlebody), exhaust manifold (it was cracked and leaking bad), spark plugs, plug wires, 02 sensor, and that's pretty much it. I thought the cat was bad, but that didn't do anything. I recently failed my emissions test (Maricopa County, Arizona) because they said it was running rich. I'm going to see if I can pass tomorrow morning because I just fixed the vacuum leaks this week. If it doesn't pass/runs rich, I'm going to see about changing that CTS (whatever that is). But, I'd say yours may be a vacuum leak, because that's what was causing mine to idle so high. Hope this helps....
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Unread 04-08-2010, 08:59 AM   #39
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Alright its been a while, but I finally got it to quite backfiring. Vacuum leaks, vacuum leaks, vacuum leaks, I kept tracking them down and finally got all of them fixed. Hasnt back fired in a couple weeks or poofed in a couple of weeks.
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You plant the crops before you starve.
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Unread 04-08-2010, 09:37 AM   #40
Que89YJ
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No beer???? Come on RR. LOL Did you put the gasket in the EGR tube or did you just cap it off?
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Unread 04-08-2010, 11:20 AM   #41
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Plenty of Beer to tell the truth. Sometimes a 6 pack or 2 just looking at the engine with the hood proped, thinking about what could be wrong, without actually touching anything. haha

RTV'd the EGR Tube.
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Unread 04-08-2010, 11:34 AM   #42
bharris68
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I think that the key here is that the 2.5L in 89 & presumably 88 were TBI and controlled by a pretty accurate computer.

Mine runs like a Swiss Watch even after 21 years. If you start testing your voltages via the underhood ports: Passenger side, just under the hinge and above the battery, you'll likely find your culprit. My vote is 02 sensor will be off, causing you to run rich. It may also be that you've got a clogged Vacuum line, in which case, blowing them out or siphoning seafoam into the system will clean them out.

The tube that comes off the exhaust manifold to the air cleaner box tells the PCM that the engine is warm. Check to make sure that vacuum line is cleaned out. Again - my vote is 02 sensor - unless you put a new Bosch sensor on there AND there is voltage getting to the PCM, you're probably going to run rich.
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