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4.0 Litre Running Rough


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I bought my 87 comanche about six months ago at 165k and within the first month i had to replace the slave cylinder which was a lot more work than it shouldve been on account its internal. It ran decent over the summer but now first when I start her up it gets to some high RPMs. while driving there is a big loss of power and whats seems to be a horrible vaccum leak.It sounds like a lot of air is being blown and also whenever the engine is under heavy load air will come out of the defrost wheather the switch is on or off (the other vents don't work). ive checked all the hoses and replaced attachments, checked the resovior in the bumper but can't find anything that screams at me. I recently had to take the truck to a shop in to a shop to fix some wiring for my tailights that I didnt have time for and I asked them to see if they could find a vacuum leak. They fixed the lights and just told me my 02 sensor shorted out. I had my doubts this was the problem but replaced it anyway. Didnt make any difference it still runs like crap. If anyone has had this problem or has any ideas how to pinpoint this issue I would graetly appreaciate it.

-jake

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With the engine ICE COLD start it, let it idle and take a can of Carb cleaner and spray around the manifold and all vacuum hoses. If there is a vacuum leak it will pull in the cleaner and you will hear your idle change. Most likely sputter and or die if bad enough.

 

 

If you use this method keep a fire extingusiher handy, cause this stuff can ignite if the engine is/becomes hot.

 

 

As for the High RPMs you could have a faulty TPS sensor.

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alright sorry for taking so long to reply working full time and college doesnt leave me much time. I bought some carb cleaner and sprayed around every connection, hose, and all around the manifold and nevr had a change in idle. I have also followed all the lines countless times.

I also read threw that link and I had actually already come across it before and had cleaned the ground by the oil dip stick but didnt seem to be my problem. I have noticed that whenever there is a hill (even a smaller one) i almost always have to downshift, the thing used to have a bunch a power. I'm pretty sure though whatever is causing the vents to be acting up is the cause of everthing else because when my vents stopped working properly is when i noticed my truck started runnig weird.

I think I'm just going to try changing my vac resovoir that inside the bumper and see what happens.

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