Could use some help from the Lightning gurus

Just in the past week or so my truck has been acting up. When I start the truck, after the initial rev, the rpms drop very low almost to the point where the engine dies. Also, if I rev the engine while in park or neutral to 3-3500rpm and let it fall back to idle it will die every time. I've pulled the chip and that wasn't it. I can't find any vaccum leaks. Could it be plugs or the O2 sensor? I'm stumped and plan on taking it to Tommy Vaughn Ford by the end of the week, but wanted to bounce it off you guys first.

Thanks

Oh and I tried a search but didn't see any symptoms like this...

 

Prob. not the same, but this happened to me and the vacuum line was melted coming from the EGR on top of the supercharger. Stupid sleeve to protect it had slid down. Pulled the vacuum line from the EGR and perfect idle.

 

Since it's a 99, I suspect the fuel pump line loose in the tank. Seems some 99 Ls have bad clamps and one or more lines can come off. Your fuel pessure would be too low. PSP has better replacement pumps and clamps that will fix that if it's the problem.

I always think of the IAC with an idle problem. They can get dirty/worn over time. How many miles on your L? You can take it off and flush out the insides(vane that rotates) with a solvent and see if the vane frees up if it was sticky/sluggish, otherwise, replace it.

Dan

 

If you are running a chip, pull it and see if it still does this. If it stops, try cleaning the contacts. Carbon will build up over time, due to the constant flow of electricty.

Kind of like an electric train set. The track gets really dirty after a while. That is the carbon buildup.

 

The fuel pick up line sounds reasonable, being a 99' w/ almost 50K. Dumb question, whats "IAC"?

Another investigation under the hood turned up a parted vaccum line. It appears as if it was melted, but I can't find the other end of it Any ideas about this?



The close up shows the end is kinda melted



Anyone know what this hose is for and if it could be the problem?

 

That looks like the hose that goes to the egr valve, mine melted in the same place.........

 

IAC = Idle Air Control

 

For what it is worth, I experienced a couple of the above mentioned problems over three years with a 99.

Running a chip, they can/will get loose and back out of the PCM from time to time. Usually, you will get a complete failure to continue and will have to reseat the chip.

On mine, the IAC valve "stuck" several times in colder weather and could be gotten back on line by tapping on it or just playing with the throttle until it unstuck itself. Recently traded mine for a Blackwood and the board member that it buying it from the dealer got them to replace it as part of the deal.

Personally never experienced any melted lines as mentioned above.

Bill

 

Speedfreak, that hose hooks to that solenoid on the right side of your photo with the green and white caps on it. Look on the bottom center of it for the connection point. A vacuum leak should be the cause of your problem.

 

Wow, this is interesting. My EGR tube melted last weekend as well. The truck wouldn't idle, and I had to nurse it to the dealer. The ordered the complete harness - for that section and used just the EGR tube from that to replace what was melted. So, if I have other melted tubes, I can go back and get them there.

I have looked at many other Lightning engines, and it seems that the heat shield has always slid down that EGR tube. Currently, I have all of my lines wire tied away from that tube, as it does get quite hot.

 

Well?

 

4D THNDR

Your absolutely right! I can see that there is a nipple pointing downwards where the line should be plugged in. I'm heading to Autozone to see if I can get a splice and some tubing. Man I hope thats it. I appreciate everyones help so far and I'll post the results in an hour or so.

 

Now I'm begining to worry. I replaced the entire hose that had melted and the truck still showed the same symptoms, so I disconnected the neg battery cable and let it sit. Approx 20 mins later I started her up and found that nothing had changed. D@mn! What's that thing with the green and white caps that the hose plugs into? Could that be it? I tried to remove it from the firewall to check it out but the two bolts that hold it in place would just spin.

 

Keep us updated on the results

 

We fix worse problems in the parking lot at our Burger N Fries every month. You should have attended last night, your worries would have been gone by now.