bigburly Posted September 16, 2007 Share Posted September 16, 2007 I have an 87 comanche, 4.0 5spd. Lately it has started to miss or sputter when I push the accelerator DOWN like in 3 and 4 when I want to run the speed up. It will just do nothing and start to act like I'm running out of fuel. I've owned it for just over a year. Over the last winter when it was about -10F I started it and it revved HIGH and I couldn't get the engine to settle down until I GUESSED which TB harness to unplug. It was the one on the right, TPS? I hadn't had any problems since then, (I plugged it back in again). This problem started off as, I would be pulling a hill and all of the sudden I would get a power surge. Not so much of a Miss, just like, "here's some extra horsey's for ya." Now it just about dies. I replaced the plugs, wires, and distributor cap last fall. Now I removed the catalytic converter and installed a 2.5" muffler instead. I just changed the fuel and air filter too. It seems to start as well as any other Jeep. It takes a while to crank, but if I tap the accel once it starts quicker. I've read on here that the CPS may cause this, but I wonder if the TPS could be at fault too. Any suggestions would be appreciated. Thank you. Link to comment Share on other sites More sharing options...
fiatslug87 Posted September 16, 2007 Share Posted September 16, 2007 Check the EGR valve and transducer operation. Link to comment Share on other sites More sharing options...
CWLONGSHOT Posted September 16, 2007 Share Posted September 16, 2007 Check the EGR valve and transducer operation. I agree, look at your EGR. CW Link to comment Share on other sites More sharing options...
Rob S Posted September 17, 2007 Share Posted September 17, 2007 Well also the cps will be an issue if you have long crank times. Sensors are a bear to pinpoint. They are expensive and hard to track down. Search Naxja and Jeepsunlimited for info too, lots of XJ's on there with the same running gear, may find some insight as to the problem. Link to comment Share on other sites More sharing options...
FxRacing282 Posted September 17, 2007 Share Posted September 17, 2007 well... hows the idle? what are you running for gas? clean your airfilter? make sure to check all fluids and put some engine stop leak (marvel mystery oil works great) and injector cleaner. should take care of the problem. plus if it don't you still get all the benefits of what you put in and if you put in a new cps and it don't take care of the problem your outta some sweet cash Link to comment Share on other sites More sharing options...
bigburly Posted September 17, 2007 Author Share Posted September 17, 2007 Check the EGR valve and transducer operation. I agree, look at your EGR. CW I picked up a transducer, nothing like the Chilton manual shows. IS the transducer what threads into the intake manifold? This looks similar, but not identical. OR is the transducer on the fender wall with a wiring harness attached? According to the manual a vacuum line runs DIRECTLY from the EGR to the Transducer. Mine goes to a little block of vacuum lines. Link to comment Share on other sites More sharing options...
bigburly Posted September 18, 2007 Author Share Posted September 18, 2007 I took it out for another spin tonight. It seems to be definitely related to Exhaust Gas Temperature or Mixture. While going up a hill at lower speeds and gently pushing on the throttle to maintain speed, it started to work it's magic again. Link to comment Share on other sites More sharing options...
FxRacing282 Posted September 18, 2007 Share Posted September 18, 2007 hmmh weird... i would go to the closest vocational school and have them use a scan tool to see what the comp. says Link to comment Share on other sites More sharing options...
fiatslug87 Posted September 18, 2007 Share Posted September 18, 2007 The thing on the fender is the EGR solenoid the transducer attaches to the EGR with a vacuum hose. Here's how to check operation of the EGR. It's from the '88 FSM. Link to comment Share on other sites More sharing options...
bigburly Posted September 18, 2007 Author Share Posted September 18, 2007 Thank you very much fiatslug. My EGR diaphragm is kaput. I went through the tests and when it came to directly hooking the vacuum line to the EGR, it did nothing to the idle. I can push it in with my finger and affect the idle. Are these things really $166 ? NOTE: I have NO transducer. I only have the solenoid. was there an update? The solenoid has the vac line and the output line, the rubber fitting could accomadate 2 outputs, but the end one has been blocked off. Link to comment Share on other sites More sharing options...
fiatslug87 Posted September 20, 2007 Share Posted September 20, 2007 btt NOTE: I have NO transducer. I only have the solenoid. was there an update? The solenoid has the vac line and the output line, the rubber fitting could accomadate 2 outputs, but the end one has been blocked off. Anyone out there with an '87 4.0L that can help? The above was from the '89 FSM (correction to original post). I know '88, '89, and '90s had a transducer on the EGR and all vacuum lines are as shown in the diagrams, only two lines to the solenoid. Is the rest of the vacuum harness as above or did a previous owner modify it? Link to comment Share on other sites More sharing options...
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