Virginia Posted June 20, 2015 Share Posted June 20, 2015 I now have an 89 4.0 6 cyl 4wd automatic comanche that has begun chugging down and sort of softly backfiring almost when I give it gas. I have to floor it and it will eventually catch and accelerate normally. Usually within a few seconds. Doesn't do this all the time though. I've had a new muffler and catalytic converter put on it but don't think these two things are related. The vacuum diverter is toast. Melted and is not connected to the egr valve but had a mechanic tell me that this would not cause what I'm describing and in fact, should make the engine run better. He said it could be bad gas and to check my spark plugs. I've sprayed carb cleaner in the throttle body and cleaned that out as best I could. I've run some techtron through the gas line. The air intake is clear and the air filter is in decent shape. No blow by but some dust. I've also had someone tell me it could be a sticky choke. I don't know what else to check or do. Suggestions? Link to comment Share on other sites More sharing options...
Jeep Driver Posted June 20, 2015 Share Posted June 20, 2015 TPS would be my guess. Link to comment Share on other sites More sharing options...
Virginia Posted June 20, 2015 Author Share Posted June 20, 2015 That looks easy enough to replace. Link to comment Share on other sites More sharing options...
Eagle Posted June 20, 2015 Share Posted June 20, 2015 You don't have a choke -- they don't exist with electronic fuel injection. So we've eliminated one possibility, and now you know what mechanic NOT to go back to. It might be dirty injectors, or it might be the CPS showing the first signs of old age. Also possibly even the oxygen sensor. If it's old it may not be responding fast enough to changes in the exhaust flow. Typically, though, with the O2 sensor failing you get backfires when you let off the throttle. How old is the CPS? Link to comment Share on other sites More sharing options...
Virginia Posted June 20, 2015 Author Share Posted June 20, 2015 No idea. I'm going to assume original to the truck and it's an 89. I get no backfires when I let off the gas and the sounds I'm hearing may not be backfires at all. Maybe more like misfires. Link to comment Share on other sites More sharing options...
Virginia Posted June 21, 2015 Author Share Posted June 21, 2015 So, I put a new TPS and that seemed to do the trick. I drove it pretty hard and had no problems. My son got in it and says it died on him once and did the thing were we get no lights, no air blower and no radio, nothing electric but the engine runs. I have NO idea what that would be. Link to comment Share on other sites More sharing options...
cruiser54 Posted June 21, 2015 Share Posted June 21, 2015 So, I put a new TPS and that seemed to do the trick. I drove it pretty hard and had no problems. My son got in it and says it died on him once and did the thing were we get no lights, no air blower and no radio, nothing electric but the engine runs. I have NO idea what that would be. Click on the link in my signature below and be sure to perform Tips 1,3,4, and 5 thoroughly to make sure that's not part of the problem. Spark plugs, wires, cap and rotor are due to be replaced every 30,000 miles......Maintenance here.... Link to comment Share on other sites More sharing options...
Virginia Posted June 21, 2015 Author Share Posted June 21, 2015 Whew....ok. That's a project for next weekend. Link to comment Share on other sites More sharing options...
Virginia Posted July 3, 2015 Author Share Posted July 3, 2015 Does anybody know what these boxes are and would they have anything to do with why the air conditioner would still run when the motor is turned off? They're on the passenger side behind the battery. Link to comment Share on other sites More sharing options...
cruiser54 Posted July 4, 2015 Share Posted July 4, 2015 Link to comment Share on other sites More sharing options...
Virginia Posted July 6, 2015 Author Share Posted July 6, 2015 OK, so the fuel pump relay is the one that got hot enough to melt the negative cable to it. My guess is that wouldn't have anything to do with the airconditioner still running after the motor is turned off or the lights and air blower going off while the engine is running. Link to comment Share on other sites More sharing options...
Siopposition Posted July 6, 2015 Share Posted July 6, 2015 What exactly do you mean by the air conditioner is still running after the motor is off? The blower fan? Or the aux fan up front. Link to comment Share on other sites More sharing options...
Virginia Posted July 6, 2015 Author Share Posted July 6, 2015 The key is turned off and in my hand while the air conditioner is still running and blowing cold air. Link to comment Share on other sites More sharing options...
Virginia Posted September 1, 2015 Author Share Posted September 1, 2015 OK, so a new TPS, new O2 sensor, vacuum lines checked, new plugs and wires, new air filter has fixed a few of the problems but the random dying is still happening. It acts is if it's running out to gas then sometimes will catch and idle back up where it belongs or run like it should and sometimes it dies completely and there seems to be no pattern to it. Don't know what else to check. Link to comment Share on other sites More sharing options...
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