JeepcoMJ Posted March 10, 2010 Share Posted March 10, 2010 I've got a friend with a 1987 mj, 4.0 auto. won't rev above 3400 rpm. have swapped ECU, TCU, ALL engine sensors including TPS, IAC, IAT, ICM, and distributor. the only thing I haven't done is swapped the CPS. haven't ohm'd it out or anything, either. the odd thing is that the CPS appears higher on the bellhousing than typical. there are two different positions (approx. 1/2" difference) where it can mount on this bellhousing. this jeep originally came from colorado and so I'd assume that's a high altitude thing, but don't quote me on that. anyways, I'm thinking I need to put the CPS in the lower of the two mounting positions, but wanted to get your guys opinions. and no, I don't have pics of the CPS locations...nor will I have any. Thanks, Pat Quote Link to comment Share on other sites More sharing options...
Geonovast Posted March 10, 2010 Share Posted March 10, 2010 I would like to see this bellhousing... But of there's nothing mechanically wrong with the motor.. I'd say that could definitely be it. I would think that if there was a valvetrain problem, the motor would complain quite a bit when you tried to rev it higher. Quote Link to comment Share on other sites More sharing options...
Justin_k Posted March 10, 2010 Share Posted March 10, 2010 Could the cat be plugged off bad enough it won't allow that much rpm? Or do those old ones have a cat? Quote Link to comment Share on other sites More sharing options...
JeepcoMJ Posted March 10, 2010 Author Share Posted March 10, 2010 no cat. no funny noises from the motor. Quote Link to comment Share on other sites More sharing options...
Eagle Posted March 10, 2010 Share Posted March 10, 2010 The high-altitude Renix models just used a different CPS -- it mounts in the same place. I'm running a high-altitude CPS in the '88 XJ. It allows more advance when the engine isn't under load, which in theory should help gas mileage. Quote Link to comment Share on other sites More sharing options...
asm4mcc Posted March 11, 2010 Share Posted March 11, 2010 I HAD THE SAME PROBLEM IT WAS MY CPS ON THE BELL HOUSING Quote Link to comment Share on other sites More sharing options...
kro10000 Posted March 11, 2010 Share Posted March 11, 2010 Please turn off the Capps lock :thumbsup: Quote Link to comment Share on other sites More sharing options...
Oizarod115 Posted March 12, 2010 Share Posted March 12, 2010 have you gone through and checked all the engine ground straps? Quote Link to comment Share on other sites More sharing options...
JeepcoMJ Posted March 12, 2010 Author Share Posted March 12, 2010 yep, they're brand new. Quote Link to comment Share on other sites More sharing options...
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