702_MJ Posted February 25, 2013 Posted February 25, 2013 So I was trying to help my cousin with his MJ, its an 87' 4.0L. It was running before, then we put the TNT y link kit on(completely irrelevant), put everything back together and the truck has a really low, like 1-200rpm and its extremely rough and stumbles and will eventually die, every now and then itll sound like a cylinder will fire with the intake valve open. Checked timing again and again everything is fine, we have the right amount of psi for fuel, have enough flow for fuel, its getting air, and its getting spark. So to me a sensor must have decided to go out. Anyone have ever dealt with a similar problem on an 87-90 4.0L MJ? Any help would be great, thanks in advance!
Lee21490 Posted February 25, 2013 Posted February 25, 2013 So I was trying to help my cousin with his MJ, its an 87' 4.0L. It was running before, then we put the TNT y link kit on(completely irrelevant), put everything back together and the truck has a really low, like 1-200rpm and its extremely rough and stumbles and will eventually die, every now and then itll sound like a cylinder will fire with the intake valve open. Checked timing again and again everything is fine, we have the right amount of psi for fuel, have enough flow for fuel, its getting air, and its getting spark. So to me a sensor must have decided to go out. Anyone have ever dealt with a similar problem on an 87-90 4.0L MJ? Any help would be great, thanks in advance! Check around the Y-link Sounds like you unplugged a sensor or vacuum or something.
Naterenfo1 Posted February 25, 2013 Posted February 25, 2013 Check around the Y-link Sounds like you unplugged a sensor or vacuum or something. X2 theres a vacuum plug on the passenger side near the stock upper control arm mount. With 6" of lift, the vacuum lines on mine were not long enough to leave the connector plugged in, so had to re-route the hoses a bit to get it to fit correctly
702_MJ Posted February 25, 2013 Author Posted February 25, 2013 ok, the truck has 8.5" of lift. And maybe we knocked something loose down there. I was thinking CPS cuz thats like the only thing that we kinda unplugged but maybe not. Ill have him go check.
cruiser54 Posted February 25, 2013 Posted February 25, 2013 Did the vacuum hose from the MAP sensor get tugged on, cracked, disconnected?
702_MJ Posted February 25, 2013 Author Posted February 25, 2013 Did the vacuum hose from the MAP sensor get tugged on, cracked, disconnected? Negative, checked that, even swapped the MAP from my MJ to make sure it wasnt that.
702_MJ Posted February 27, 2013 Author Posted February 27, 2013 It was the CPS....my cousin told me he tested it. But he threw one at it anyway and that's what it was. Problem solved, disregard problem. Thanks
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