Dando Posted July 17, 2014 Share Posted July 17, 2014 So on my 90 4.0 aw4, I am experiencing a problem that only happens after the truck has been driven for about an hour on and off in the evenings. Seems to be only when the truck is really warmed up. But I can also drive for the same amount of time in the morning or after sunset and it seems fine. Well anyway the problem seems to be that it is running rich and when I go to put more throttle the truck sputters and if I am coming out of a full stop the truck will stall out. It starts right back up easily after this and then will take off fine, if I feather the throttle it will stutter down to low Rpms and then surge back and then jerk to take off. When on the highway it will almost feel like a lag when you hit the throttle. But as I said in the last section this is totally intermittent, it happened last night around 8pm while I was making a 40min drive, but then a few hours later on the drive home it ran just fine. So what do you think may be causing this? I have been fighting a running rich condition since buying the truck. The only sensors that haven't been changed out yet that I can think of are my coolant temperature sender and my o2 sensor. Do you think either of these could cause this problem or do I have another issue of sorts? Thanks Link to comment Share on other sites More sharing options...
Jeep Driver Posted July 17, 2014 Share Posted July 17, 2014 O2 sensor. Link to comment Share on other sites More sharing options...
Dando Posted July 17, 2014 Author Share Posted July 17, 2014 Just changed the o2 sensor so hopefully that will help Link to comment Share on other sites More sharing options...
cruiser54 Posted July 17, 2014 Share Posted July 17, 2014 Click on the link in my signature and do posts 1,3,4, and 5 before wasting any more time and money replacing parts. Link to comment Share on other sites More sharing options...
Dando Posted July 17, 2014 Author Share Posted July 17, 2014 #1 I have already refreshed the grounds and added the additional 4ga cables #3 I have cleaned with electronics spray cleaner all under good connectors then I applied dielectric grease to them #4 coil is new and connections were sanded, cleaned, and dielectric greased #5 when doing as the instructional states I probed at the tps and when hooked to the negative my ohm reading is 00.3, this number doesn't change even slightly no matter where I grab and shake on harnesses. Link to comment Share on other sites More sharing options...
cruiser54 Posted July 17, 2014 Share Posted July 17, 2014 Have you tested the fuel pressure? What kind of shape is the line from the throttle body to MAP sensor? Must be perfect. Link to comment Share on other sites More sharing options...
Dando Posted July 17, 2014 Author Share Posted July 17, 2014 I have not tested the fuel pressure, and the vacuum line going from the map to the throttle body is somewhat questionable but I am having trouble getting one specifically made for it and the parts from store are not quite right. Link to comment Share on other sites More sharing options...
cruiser54 Posted July 17, 2014 Share Posted July 17, 2014 That line could be the whole problem. They're not availalble new any more. How's the rubber end at the throttle body? Intact? Link to comment Share on other sites More sharing options...
Dando Posted July 18, 2014 Author Share Posted July 18, 2014 Ok so I replaced the line last night, it ran well this morning. We will see this evening as it usually only does it in the evening after work. Out of curiosity, how could that line cause so much trouble for me? Link to comment Share on other sites More sharing options...
88ComancheMitch Posted July 18, 2014 Share Posted July 18, 2014 That sensor controls some of, if not most, of your a/f ratio to my understanding. Improper vacuum readings wild neb is not getting the proper air/gas mixture. Link to comment Share on other sites More sharing options...
cruiser54 Posted July 18, 2014 Share Posted July 18, 2014 MAP is a major player in the grand scheme of things, and it relies on a proper vacuum signal to do it's job. Link to comment Share on other sites More sharing options...
Dando Posted July 19, 2014 Author Share Posted July 19, 2014 Fixing the vacuum line has appeared to have fixed the problem. Hasn't happened since replacing the hose with one that better sealed on the throttle body side. Link to comment Share on other sites More sharing options...
cruiser54 Posted July 19, 2014 Share Posted July 19, 2014 Fixing the vacuum line has appeared to have fixed the problem. Hasn't happened since replacing the hose with one that better sealed on the throttle body side. Well I'll be dipped. Whooda thunk it? Link to comment Share on other sites More sharing options...
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