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Unread 03-23-2011, 08:18 AM   #16
Tonks
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1997 ZJ 
 
Join Date: Nov 2010
Location: Newburgh, IN
Posts: 14
Thank you for this info csouers!!!!

98mopar Yes the exhaust sounds lobey at idle. Yes I can feel it missing at times when at a stop light up till yesterday when I reposistoned spark plug wire 1 which I think might have been too close to the valve cover after the spark plug wire rerouting TSB I have not checked my injectors but I am also not sure how to do that.. any advice?

Zombie I have not noticed any knocking or pinging it actualy runs best when out on the road at high way speed. I notice the most troubles when at idle

I really appreciate everyones assistance with this problem.


As of yesterday after the spark plug rerouting I have had the longest run with out a check engine light. It is still pulling but not as bad and I am going to start looking for vacuum leaks


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Unread 03-31-2011, 05:22 PM   #17
bigbossd1030
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1995 YJ Wrangler 
 
Join Date: Feb 2010
Location: Edmonton, AB, Alberta
Posts: 2,515
My rpms were around 850 or so.
Any vaccuum leaks so far?
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Unread 04-01-2011, 02:16 AM   #18
HeavyArms
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2004 WJ 
 
Join Date: May 2010
Location: Cadillac, Michigan
Posts: 1,940
is it wrong that im a little revealed that im not the only one that has this problem?

i also have a 97 that dose this but not as bad. it maintains speed when i let off.

so please hurry and figure out how ta fix it so i can copy you! lol
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Unread 04-01-2011, 07:13 AM   #19
Tonks
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1997 ZJ 
 
Join Date: Nov 2010
Location: Newburgh, IN
Posts: 14
So far the Throttle Position sensor has given the biggest improvement. I did find a vacume line that I thought might be leaking and put a zip tie on the connection to tighen it up. Still same problems.


Then Yesterday it was warmer 65 or so outside and when I was going down a small hill I let off and I was stunned when the jeep started slowing and it dropped back to idle just like it is supposed to.

So I put a vacume gauge on the jeep to see if I can tie a certin vacume reading to it kicking out and coasting. I have not been able to get the conditions correct yet to cause it to work properly.

MY guess at this time is that I have a intake pleum gasket that is leaking. As that would be a big vacume leak or the PCM needs some soldering done to it as in some of the other posts.

If anyone has any known symptoms of a bad plenum gasket please let me know if the problem we are having is a known symptom.
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Unread 04-01-2011, 07:58 AM   #20
BlueDevil
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1995 ZJ 
 
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Location: Croatia
Posts: 680
Bad plenum gasket = excessive engine oil consumption (also: black exhaust fumes) and rough idling. Also there would be some (not so little) oil in the intake manifold, as I gathered, and even some on the air filter (NOT to be confused with oil in air filter made by bad PCV valve). But however it turns, the excessive oil consumption is the most obvious sign.
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Unread 04-01-2011, 04:32 PM   #21
bigbossd1030
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1995 YJ Wrangler 
 
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So it seems to get better when it warms up outside... Hmmmm.
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Unread 04-02-2011, 09:20 AM   #22
ZombieJeep93
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1993 ZJ 
 
Join Date: Sep 2010
Location: westminster, co
Posts: 125
Intake pan leak can give you spark knock on acceleration, oil consumption. Here's how to check it:

If the intake manifold plenum pan gasket is leaking, an additional vacuum source will be created inside of the engine at the location of the pan gasket leakage. Engine combustion blow-by gases, oil vapor, and air from the crankcase filter/breather may be drawn past the leaking pan gasket and into the intake manifold. In most cases when this condition occurs, an engine at idle will create the highest vacuum and lowest amount of engine blow-by.

1. Allow the engine to reach normal operating temperature.

2. Stop the engine.

3. Disconnect the breather hose from the air cleaner.








4. Attach a vacuum/pressure gauge to the end of the breather hose (Figure 1).

5. Disconnect the PCV valve hose from the intake manifold.

6. Seal off the intake manifold PCV valve hose port opening.








7. Seal off the open end of the PCV valve hose (Figure 2).

NOTE: DURING THIS DIAGNOSIS, IT WOULD BE NORMAL FOR THE ENGINE TO DEVELOP PRESSURE WITHIN THE ENGINE CRANKCASE. THIS IS DUE TO THE NORMAL PROCESS OF EXHAUST BLOW-BY GASES LEAKING PAST THE ENGINE PISTON RINGS AND ACCUMULATING IN THE ENGINE CRANKCASE. DO NOT ALLOW MORE THAN 3 PSI (20.7 kpa) OF PRESSURE TO BUILD WITHIN THE ENGINE WHEN PERFORMING THE FOLLOWING DIAGNOSTIC PROCEDURE.

8. Start the warmed engine and observe the vacuum gauge.

9. Allow the engine to idle for approximately 30 seconds. Do not allow more than 3 psi (20.7 kPa) of pressure to develop in the engine crankcase.

10. If the attached vacuum / pressure gauge does not indicate that a vacuum is present in the engine crankcase, then the intake manifold plenum pan gasket is good and no further internal engine vacuum leak diagnosis is required.

11. If an internal vacuum leak is present then perform the Repair Procedure.


The repair being, remove intake, replace pan gasket. Mopar revised this gasket years ago and has not been an issue with new gasket blowing out.
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Unread 04-14-2011, 07:05 AM   #23
Tonks
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1997 ZJ 
 
Join Date: Nov 2010
Location: Newburgh, IN
Posts: 14
Problem might be resolved!!!

Dad and I replaced the intake gaskets. They appeared to be leaking and were very very brittle and dried out. 289,000 miles. This absolutely gave more vacuum on the gauge we had hooked up we were at a steady 20 in/Hg no matter how you rev'd or drove the jeep. Now we are getting 22 in/Hg all the time with spikes above that at times depending on how its being driven. Test drive resulted in the jeep no longer pulling its self down the road like it had been doing. It was still reving up on its own in neutral and now was searching between idle and 2500 rpm.

A few days later I started getting Service engine soon light for code P301 which was cyl. #1 misfire. So since I had gotten rid of this code before by rerouting spark plug wires... I started that process again.. Its funny how many people will look at you in a parking lot when you are under the hood but no one will even say hello!!! LOL.

After some rerouting of the spark plug wires (about 10 different tries) the service eng. soon light went out on its own and it appears to no longer misfireing..

SO with that long post... intake vacuume leak fixed marked improvement. Misfire code back and patched. I dont know if i would call it a fix. Jeep now slows on its own when you let off the gas..

Now for the fun part.. I am wondering if my new parts store spark plug wires are causing me problems with my misfire .. Does anyone have any experience with new non oem plug wires producing too much EMI and messing with the injectors and computer?????

Thanks for all your help.
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