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Random Startup Issue, Rough Idle, and Stalling


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Ok. It’s a long story…..

 

Well. Went to head out last night in the truck and got a new issue :crazy:  It cranked up faster than normal but only went up to 1500 RPM and then stayed at ~1k ish idle. It was running rich and sputtering etc bad. It’s fine this once before when I had the interior out so I never bothered digging into it. I went ahead and drove it down the street where it lost all power and wouldn’t rev at all until it stalled. So now I’m in the middle of a poorly lite street with a dead truck :banana:  I had to push it off to the side. Popped the hood to check it all out and everything looked good. No matter how many times I cranked it over I got no start. Finally I let it sit for 30 minutes or and as I decided to just walk back to grab my tools and my JK to whim he it safely to a traveled parking spot I tried it one more time. It tried to start. Hit the ignition again and boom. It fired up. Turned around and limped it home real quick so I could diagnose it tomorrow. Tried to crank it this morning before heading out for the day and it did the same thing. Here is what it does. 
 

I am digging into the CPS tomorrow. My experience with them is either good or bad and not intermittent but from what I read it can cause a random stalling issue. It a sensor I have meant to at least check and clean since I bought the truck but just haven’t got to it. The fuel pump is good and pressure is good. Ignition, fuel lines etc, TPS, IAC, and MAP are all new and verified to be good. At least they were a couple days ago lol. I have tested sensor grounds as Cruiser lays out and everything checks out good. I will mention it was damp and wet yesterday and today when I took the video. 

 

any other ideas or helpful suggestions?

 

TIA. 

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Are you certain it's rich? Sounds like lack of fuel to me. Air is easier to compress than fuel so lack of fuel would cause it to start easier than normal. A lean mixture also causes a hanging or high idle. A "surging" or empty gas tank feeling while driving would confirm. A vacuum gauge or some alcohol based spray could rule out any intake/vacuum leaks. Having an extra spark plug on hand would allow you to check for spark when it does stall.

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8 hours ago, Billabob said:

Are you certain it's rich? Sounds like lack of fuel to me. Air is easier to compress than fuel so lack of fuel would cause it to start easier than normal. A lean mixture also causes a hanging or high idle. A "surging" or empty gas tank feeling while driving would confirm. A vacuum gauge or some alcohol based spray could rule out any intake/vacuum leaks. Having an extra spark plug on hand would allow you to check for spark when it does stall.

Yeah I’m sure. Everything else has been verified except the CPS which I did today. Definitely the issue.  .2 VAC while cranking. Replaced with a new sensor and check output again. All is good with the idle and how it runs. 

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4 hours ago, cruiser54 said:

Make sure the wiring harness is routed properly and secured. 

CPS location.gif

Thank you sir, I put it back just like factory.  It was super easy to do after I studied how to unbolt / bolt it in.  If you jack up the front driver tire, remove the front driveshaft from the pinion and slide it out of the way, you can get to it by going in by the front lower control arm.  Literally a 10 minute job after I learned that little trick haha.  

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17 hours ago, oleskool said:

Thank you sir, I put it back just like factory.  It was super easy to do after I studied how to unbolt / bolt it in.  If you jack up the front driver tire, remove the front driveshaft from the pinion and slide it out of the way, you can get to it by going in by the front lower control arm.  Literally a 10 minute job after I learned that little trick haha.  

Yes. Those of us with real arms do benefit from the driveshaft drop. 

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