Help, truck wont idle

[Mikecollins]

Hey guys i have been chasing this gremlin for months, thought i solved it yesterday was idling rough but was idling, yesterday I took the PCM of and used electric cleaner to clean all the contacts o it and the harness checked each connector for broken or burnt wires all looked good did the same on the ECM hooked it all back up and for the first time in months the damn thing would crank and run without me giving it any throttle. Before the only way it would crank was to hold it full throttle and then it would not idle. I have a wire that was either sheared off or cut the angle suggest sheared to me it is either blue or purple (red green colorblind here,) i am going to add pics of it if i can . It is located on the driver side just behind wheel well and runs to the back of the truck and splits right there the other wore runs up towards the brake controller box. Would this little ******* be the cause of my hell. I have done all the fixes to get it running again from this problem.

 

[Mikecollins]

Pictures are to large will try to shrink file and then load

 

[Mikecollins]

Ok so im off today and retesting stuff and the iac is hot to touch ordered replacement will be here in days, i have prime account.

If i just yank it out shouldnt i get an idle very lean idle but it should at least start with no throttle right, still chasing the blue or peurple wire out cannot find where it goes but it is hot so i know its important

 

[Mikecollins]

Another piece of the puzzle yesterday i got a high fuel pressure code just for few minutes but if its over pressurized it may be shooting way too much fuel in with each injector pulse, since mystery wore runs to the back i wounder if it comes from pump to a psi sensor up front.


Starting to feel alone here at least I am chronicling it for others with this issue

 

[Mikecollins]

Ok simce last post i have changed iac, pcm, and still chasing down this mystery wire. Just noticed oil in the tailpipe thinking its a blown intake gasket. Could be part of the problem but thinking it should still run just like **** and blue smoke. Gonna switch out the ignition switch next and start testing wires to the pcm.

 

[chrisp2493]

Do you have any check engine lights? Any codes? I've had idle issues with intake sensors

 

[Mikecollins]

Do you have any check engine lights? Any codes? I've had idle issues with intake sensors

Yes to the light no to the codes only code i have gotten recently was the high fuel psi code dont remember the number just what it was, i do have quite a few c codes but will have to pull them again most doing with no communications from the different computers could be a bad ground but i dont where the grounding points are, every thread i read about them people will post the diagram which really does no good it doesnt actully tell or show you exactly where the grounds are on the frame or where they originate and when you colorblind colors bleed together so makes it extremeley difficult to trace them out

 

[chrisp2493]

Man that's a rough situation, pretty hard to try to diagnose.

 

[Mikecollins]

Yep after swapping pcm im pretty sure its a wiring issue and i believe its on the asd circuit since radio doesnt have power either

 

[SYKRAMMAN]

Yes to the light no to the codes only code i have gotten recently was the high fuel psi code dont remember the number just what it was, i do have quite a few c codes but will have to pull them again most doing with no communications from the different computers could be a bad ground but i dont where the grounding points are, every thread i read about them people will post the diagram which really does no good it doesnt actully tell or show you exactly where the grounds are on the frame or where they originate and when you colorblind colors bleed together so makes it extremeley difficult to trace them out

grounds are usually on the frame, engine and chassis, you don't need to see color, just look for wire's that bolt to the body,frame,under hood on fender rails, and on engine, that's where they all are and there's really not many, maybe 7 or 8 all together. It's time consuming but you can do it, disconnect battery first then take them off and wire brush and sand down to bare metal, bolt back on and spray with electro protection.

 

[SYKRAMMAN]

Yep after swapping pcm im pretty sure its a wiring issue and i believe its on the asd circuit since radio doesnt have power either

I had similar issues, high fule pressure code,asd relay had a jumper in it. My truck ran and idled all over the tach. My tipm was shot and in turn ruined my pcm so a pcm,tipm,and harness and now it's a new running truck, lovin it.

 

[Mikecollins]

Just saw last reply and yea im thinking wiring harness just think there should be a picture of the damn plugs with each pin labeled

 

[Mikecollins]

Ok so map changed cps cks changed all leaking injectors, iac tps instrument cluster and no change still wont start without wot does run a smoother now but still wont idle, is it possible to put the pcm and tipm connectors in the wrong place

 

[Mikecollins]

Does anybody have the wiring diagram for the fuel system i am still thinking the mystery wire is fuel related

 

[Mikecollins]

Ok I bought a fuel psi test kit yesterday, the gauge was busted but I had a 3000# gauge that has 50# increments it didn't budge so I think my injectors are hanging open. Next good weather day I get I'm going to try disconnect one a t time and see if it makes a difference. I believe the problem is in 8, 6, and 7 cylinders

 

[Mikecollins]

Finally I got a code it is the dreaded 1391, I swapped tipm again this one came out of truck that was wrecked. I'm pretty sure it's good most of these style dodges that I see in the parts salvage yard are in perfect condition body wise which makes me believe that they are having this issue which so far seems impossible to track down. I did a lot of searching last night and it points to the cmps and ckps being out of sync with each other and know a way to resync them without a star scan or drb3. I also replaced 4 burnt around the bottom coils and it is not missing near as bad, radio will not work some I'm thinking I still have ground issues somewhere also, mystery wire is starting to look like a wire for a trailer brake booster that was removed by the seller. Also the rpms are way off on the cluster 500 seems to be closer to 1200 and it doesn't move until you are way above idle speed on the rpms. When I did my front end work I noticed the grounding strap that comes from the heads to the heat shield wasn't connected. At the time I didn't know where it when and the upper control arm on that side off so I connected it there, is this strap the main ground for the cab and that what's giving me so much hell. That grounding point on the heat sheild isnt far from the pcm.

 

[Mikecollins]

Oh and fuel psi is strong and holds for a long time after key off 46 psi sitting 50-60 while cranking it bounces a little

 

[SYKRAMMAN]

Did you say that you grounded the heads to the uca? If you did, it won’t ground. The ground straps from the back of the heads go to the passenger side fire wall, there should be a stud there but if not then use a self tapper in the same area. Gl.

 

[Mikecollins]

Yea I have a feeling this is part of the problem it should still get a ground from the bolt to the metal bracket made sure there was bare metal to contact with but I'm thinking its more important as a cab to motor ground not motor to cab and could explain why I don't have a working radio, that's an issue for another day, getting her running is primary.

 

[Mikecollins]

Another thing I have recently learned is apparently when you change the cmp and ckp you have to use a scan tool to reset the fuel sync, anybody know of a obd tool that will do it without costing an arm and a leg