Hey guys,
My 99 2500 5.9 has had a growing issue of suddenly very low idle/loss of gas power (combustion/forward movement, etc, NOT LOSS OF BATTERY POWER.) when there is moisture in the air. It runs great all day on nice days, then as soon as a strom front comes in and I stop at a stoplight it will idle to about 300 rpms, and then start to choke out, when I hit the gas I can hear the fuel pump trying to run but the truck stumbles along like it is a dying animal for about 1 minute before recovering. Sometimes keeping it in nuetral helps and then putting it in gear and going, turning the truck off and then back on works great, it starts up with no issues. It will slowly start to deteriorate at a stop. I have changed all the plugs, wires, cap, and rotor, battery and ecm recently, and fuel pump about three years ago. I tested the fuel pressure and it does become more volatile around these low idles swinging between 44 and 50 faster, but nothing to make me think it is a loss of pressure. I am thinking there must be some sort of sensor not working andchoking the engine. Sometimes when I start it up after a low idle it will rev up automatically to about 3000-4000 rpms for a second. Any ideas?
Thanks,
Kevin

 

How old are you spark plug wires? My brother had issues with a car of his dying on humid/rainy days, and it was due to worn plug wires.

 

I replaced the plugs, wires, cap and rotor about two months ago and the problem went away. One of the posts on the cap had popped up. During a few of the death crawls ill hear a metallic popping like a muffled hitting a pot with a wooden spoon.

 

Put a dab of dielectric grease on every contact point on the ignition system, cap posts, coil post, and spark plugs. Then see if that helps. If not, start putting dielectric grease on the contacts of your various sensors.

 

Thanks for the replys. I checked all the plugs again and put grease on all the points and still the problem. I have now begun to just put the truck in neutral and turn it off and on while cruising down the road. This may not be the safest, but for some reason this will stop the problem. If anyone has anymore suggestions let me know,
Thanks,
Kevin

 

I'd take the TB off and clean it and the IAC for the heck of it. While it's off don't forget to look and see if you have any oil pooling inside the intake.


Get a spray bottle with water. Go out some night and start the engine. Squirt the water around the wires,coil,cap,etc... See if anything comes up.

 

Hmm, I like that water bottle idea. I am going to take the truck to a buddy with a diagnostic handset, I'll let you guys know how that turns out.

 

Well before I took it to my buddy it broke down. It wouldn't start. Luckily I was near home and ran over to napa with other car and replaced the battery wires. It became clear to me that the negative connection was not able to be screwed around tight enough to create a secure connection. This (what I am guessing) lead to the positive wire becoming very badly corroded under the shielding. After replacing both which much better terminal clamps, it is running much better. It has had very slight hesitation, and has once had some low idle issues, but I am wondering if in the process of this crappy battery wires I didnt pop one of the distributor cap posts again, so I am going to inspect the cap, wires and plugs again when I get a chance.