jeff Posted April 25, 2013 Share Posted April 25, 2013 So my comanche started missfiring really bad all over the board and running really rich. It has no power and going through gas like no other. All the grounds are cleaned and TPS are working as they should. So far the knock sensor has been replaced, the o2 sensor and the coolant temp sensor. Looked and found no vacumm leaks. Replaced the intake manifold gasket and still the same thing. Found a connecter to the CPS that was melted and just spliced in another and the o2 sensor wiring was all jacked up. Also the check engine light never came on through all this. Starting to think there might be a problem with the computer itself. Its a 1988 4.0 auto 4x4. Link to comment Share on other sites More sharing options...
Lee21490 Posted April 25, 2013 Share Posted April 25, 2013 So my comanche started missfiring really bad all over the board and running really rich. It has no power and going through gas like no other. All the grounds are cleaned and TPS are working as they should. So far the knock sensor has been replaced, the o2 sensor and the coolant temp sensor. Looked and found no vacumm leaks. Replaced the intake manifold gasket and still the same thing. Found a connecter to the CPS that was melted and just spliced in another and the o2 sensor wiring was all jacked up. Also the check engine light never came on through all this. Starting to think there might be a problem with the computer itself. Its a 1988 4.0 auto 4x4. Check out your MAP sensor. Would cause it to run like $#!& / lose all power. Link to comment Share on other sites More sharing options...
jeff Posted April 25, 2013 Author Share Posted April 25, 2013 The map sensor is working and the vacumm line is fine. :???: Link to comment Share on other sites More sharing options...
ComancheKid45 Posted April 25, 2013 Share Posted April 25, 2013 Condition of plugs/wires? Possible EGR issue? The Renix era trucks do not have a CEL. So that would explain why 1 hasnt appeared for ya. Link to comment Share on other sites More sharing options...
jeff Posted April 26, 2013 Author Share Posted April 26, 2013 Plugs and wires are relatively new and in good shape. i will have to check into the EGR. Link to comment Share on other sites More sharing options...
JeffN Posted April 26, 2013 Share Posted April 26, 2013 make sure you have vacuum to the fuel pressure regulator, and make sure it isn't leaking fuel through the vacuum port on the regulator (a sure sign of a bad regulator) Link to comment Share on other sites More sharing options...
cruiser54 Posted April 26, 2013 Share Posted April 26, 2013 The map sensor is working and the vacumm line is fine. :???: How was it determined that the MAP is fine? Link to comment Share on other sites More sharing options...
jeff Posted April 26, 2013 Author Share Posted April 26, 2013 bypassed the egr and still nothing. also replaced the coil and control module from ones out of the junk yard but still nothing. Link to comment Share on other sites More sharing options...
jeff Posted April 27, 2013 Author Share Posted April 27, 2013 A connecter for the cps to the harness was all melted and the o2 sensor wiring was messed up. I'm curious if some wires could have crossed and shorted out the ecu? Link to comment Share on other sites More sharing options...
cruiser54 Posted April 27, 2013 Share Posted April 27, 2013 Doubtful. Shorted CPS doesn't fry the ECU. Nor does bad O2 sensor wiring. Check the sensor ground circuit with a meter. It's responsible for proper grounding of the IAT, CTS, TPS, and MAP. Spray along the MAP hose, especially near the throttle body, to see if it's leaking. Again, how was it determined the MAP is "fine"? Link to comment Share on other sites More sharing options...
jeff Posted April 27, 2013 Author Share Posted April 27, 2013 well thanks for the help guys! i found the problem! no compression on cylinder 6! I'm pulling the engine tonight. Link to comment Share on other sites More sharing options...
jeff Posted April 29, 2013 Author Share Posted April 29, 2013 Well the cause to no compression was the lack of a camshaft lobe. The lifter collapsed and wore out the cam shaft and push rod. Probably gunna end up getting a mild cam and maybe springs. Link to comment Share on other sites More sharing options...
jeff Posted April 29, 2013 Author Share Posted April 29, 2013 http://m.summitracing.com/parts/cca-cl68-232-4 I'm thinking this is the cam I want. What do you guys think? Link to comment Share on other sites More sharing options...
MJ_Milam Posted April 30, 2013 Share Posted April 30, 2013 http://m.summitracing.com/parts/cca-cl68-232-4 I'm thinking this is the cam I want. What do you guys think? numbers look good. personally I'd look for something for a little shorter duration. I like a cam with a low lobe center I.E. 106 with a short duration and high lift. makes great torque but still leaves you with good idle quality but that's just my two cents. If that's the cam you go with I would like to see a write up about it and how well you liked it :cheers: Link to comment Share on other sites More sharing options...
jeff Posted April 30, 2013 Author Share Posted April 30, 2013 i will do. i ordered it yesterday. I'm hoping it will be in before the weekend so i can get it put together before the blessing of the jeeps this weekend. summit has been quick with past orders. Link to comment Share on other sites More sharing options...
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