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Professional Lackey
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428 Posts
Discussion Starter #1
I've had this problem on my 02 L now for over a year and a half and i'm finally to the point where I am willing to ask for help to figure out why it's happening and fix it. The truck is my 2002 Lightning and the engine mods are a 6lb lower, ported Eaton, Accufab SBTB, REM air intake, JBA shorties, Magnaflow cats, full 2.5" magnaflow exhaust, LFP valve body in my trans, and tuned with an Xcal2.

The problem is when my truck is WARM and I start it up the RPMs will drop down, sometimes it'll pick back up and idle properly and other times it'll just die. When it dies I restart it and hold the RPMs up for like 30 seconds or so and it idles just fine after that. Now the weird part is when the engine is ice cold or when it's still hot and at operating temp it will start normally and it doesn't try to die. It only tries to die from a WARM start.

Now i've already gone through and tried to fix this on my own with no luck. I've tried to tackle this a few times with everything i've done being in vein. First thing I did was to try some simple routine maintenance, I cleaned my MAF sensor with contact cleaner, pulled the IAC off and vigorously cleaned it with brake cleaner, and I checked the TPS voltage which was already at .99v. None of that worked but since it was an idle problem I went ahead and replaced the IAC anyway, again no change. Second, another round of routine maintenance, the supercharger was pulled and the IC was cleaned, new set of NGK TR6 plugs gaped at .34, and new Motorcraft O2 sensors, again to my disappointment the warm start problem persisted.

After failing at fixing this over 2 rounds of attempts I came to the site and began searching the forums and I came upon a few members that seemed to have had a similar problem to what I was experiencing. Turns out the symptoms my truck was experiencing pointed to a bad or failing Fuel Pump Resistor. I even found a video on YouTube that seemed to cement my latest diagnosis. Not an easy part to find but again the search function of the forums came through for me and I was able to order one. I got around to installing it this past Sunday. After the install I drove around a bit and parked my truck in the driveway. I went back out after a couple of hours when the engine was still warm and started it up. It started and the idle dropped down and it stalled :smt013

After all that, the routine maintenance and the pump resistor, none of it has worked. I'm at my wits end here, and i'm totally out of ideas of what could be wrong. Please help, this is getting to be an annoying problem.
 

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Professional Lackey
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428 Posts
Discussion Starter #3
It's not a canned tune, it's tuned by a local performance shop, GearHead's Performance. I know there's some that will tell me that's my problem but the initial custom tune they did for me was done in 07 and this problem started happening well after the tune. It was retuned from the DD tune to a more performance oriented tune about a year ago after the new plugs, IC cleaning, and O2s were done.
 

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Professional Lackey
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428 Posts
Discussion Starter #5
No, the problem started a little over a year and a half ago, the retune was a year ago, after the problem showed up. Maybe you should reread the first post.
 

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i have a similar problem. if i drive s to store. shut off truck. come out start truck. reverse out of parking stall. then truck will die when i apply brake to go forward. put in neutral and it starts right up again. also if im idleing around barely on the throttle at all and let off fast (like reverse stab of throttle) the rpms will dip low like 550 and i think if i wasnt already rolling that it would die.
 

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Stock Block [email protected]
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3,239 Posts
Hers a couple things mite help...

Any cel's?

Vacuum leak's? -turkey pan fitting cracked....

Have u checked fuel pressure? Possible cracked Y fitting in tank.....
 
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I woild check vacuum leaks and fuel filter 1st......if no luck...then ill replace the coil packs and cam positioning sensor
 

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Open the the throttle body blade up a little bit with the set screw and then re-adjust your tps, betcha that'll help...proper way of setting the adjustment screw for the throttle body is to get it to just barely idle with the iac disconnected and then reconnect it and set tps...
 

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Professional Lackey
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428 Posts
Discussion Starter #12
Hers a couple things mite help...

Any cel's?

Vacuum leak's? -turkey pan fitting cracked....

Have u checked fuel pressure? Possible cracked Y fitting in tank.....
CEL isn't on and there are no codes stored in the PCM's memory. I also do not believe there is a vacuum leak, if there were I would think it would set a lean code and the engine would have a rough idle, which neither are present and have not been since this problem arose. Although after reading several members talk about the turkey pan vacuum leaking I do want to delete it at some point.

As for fuel pressure I have not checked it, and at the moment I don't have the means to check it. I would like to see what the fuel pressure is doing when the idle drops and it tries to die. If the Y fitting in the tank were cracked though wouldn't that affect the startup every time and not just on a warm start?

I woild check vacuum leaks and fuel filter 1st......if no luck...then ill replace the coil packs and cam positioning sensor
As I said already i'm not too sure on the theory of a vacuum leak, but the cam sensor idea has me wondering, looking it up it's a relativity cheap part. The COPs though, due to cost that would be something i'd look at once i've exhausted other options, but it's hard for me to see how all 8 coils could cause a warm start problem like this one. Although I am inclined to think it's more like an electrical/sensor problem like that.

Open the the throttle body blade up a little bit with the set screw and then re-adjust your tps, betcha that'll help...proper way of setting the adjustment screw for the throttle body is to get it to just barely idle with the iac disconnected and then reconnect it and set tps...Common issue with the accufab throttle body from what I've read and experienced myself.
My Accufab SBTB is one of my oldest mods, I put it on way back in 03 before I moved to where i'm living now. I would think if it were the SBTB that the problem would have shown up way before it did, but the procedure you describe sounds fairly easy to do. When I get some extra time this weekend i'll reset the blade and TPS and see if that makes any difference.
 

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its not the tb...its not pumps since he said happens when warm...could be vapor lock but i havnt seen that happen to these trucks...

coil arent that bad in price ...i forgot the brand but their cheap on amazon.com and it from the same people who make ford motorcaft coils...brand name starts with a v
 

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I would say vacuum leak, I had what sounds like the same issue as u. My PVC valve popped out if the valve cover. It was right there and looked like it was in. I went through everything u did changed the iac. Etc. and nothing. Finally was changing my oil and went to drain my oil separator and realized it was not plugged in. Popped it in and she was all better.
 

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Professional Lackey
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428 Posts
Discussion Starter #18
Any resolution to this? I believe I am having a similar issue.
It's been a while obviously(7 years), but as I recall it turned out to be my O2 sensors. Upon start up one of the two upstream sensors would intermittently stop reading. At least when I finally got fed up and asked my tuner to look into it that's what he said it was.
 
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