2000 ram van 3500 cold engine idle surging!

[sasquatchmystery]

My 2000 Dodge Ram Van with a 318 is idling up and down when I first start it up. The van has 66k on it it was previously owned by the Army so it has low miles. I traded in my 2001 Dodge Truck with a 360 engine 130k miles and it was doing the same thing at startup. I thought it might have had a vacuum leak at one of the injectors, but I could not find it on the truck. I have not checked the van yet.

Has anyone else had this happen? Email me!
[email protected]

Happy Holidays

[alloro]

A bad coolant temperature sensor will cause this. There are two, one has one wire and is for the dash gauge. The second one has 2 wires and is for the PCM. This second 2-wire one is the one to replace.

[sasquatchmystery]

I thought there might be a vacuum leak, but I never thought a coolant temp sensor could do that. I will have to look into that. I will have to try changing it and then see if it stops. I suppose the PCM controls the idle circut until the vehicle gets to normal operating temperature. Makes sense. Thanks for the tip.

Happy Motoring!

[alloro]

You got it...if the PCM thinks the engine is already warm it doesn't richen the fuel mixture. A cold engine running at a normal mixture acts just like a warm engine running lean, just like when there is a vacuum leak.

[sasquatchmystery]

I will be checking into that to see if that is the culprit causing the surging. A sensor is one component that is a high failed part of an electronic system so I am sure that is what is causing it. If not I will re-post my results.
Happy New Year

[papiichuulo]

crank sensor huh? I have a '91 B250 with a 3.9L. Parked one night and never started again. Owner said they changed the fuel pump because it wasnt getting fuel to the throttle body. When I got to it, it wasnt getting fuel. Checked the ASD relay, getting power in, but not out. Replaced the relay. Now, I am getting power in and out, only now I am not getting any spark. Test light shows me an intermittent signal to the coil. When the coil does get something, she sounds like she wants to start. After pulling half of the hair on my head out, I checked the ignition switch. "Looks good". Wiggle the switch and it seems to affect the starting, it sounds like it wants to start now, heck, it even started a couple of times and stayed running until I "wiggled" the connectors on the ignition switch or the key itself. Hmmm, maybe its the ignition switch's internal contacts corroding or something, makes sense to me so I changed the switch. Now, I am not getting either. No fuel to the throttle body and no spark or signal to the coil. I am thinking either the crank sensor or maybe even the computer now...

any replies would greatly be appreciated.

[alloro]

Was the battery disconnected when you changed the ignition switch or did you do it live? If you did it live there's a chance you fried a fusible link. Are you getting 12 volts at the ignition switch connector?

And don't forget about the pickup coil inside the distributor. If that's bad...no spark.

[sasquatchmystery]

It sounds to me like a typical electrical failure either with the wiring or another component. Be sure to check your grounds, that is almost always overlooked when troubleshooting electrical. There should be a ground from the engine to the body, if that is broke it could cause all kinds of different issues. Also sometimes wiring will break inside the insulator, from time,heat or physical seperation.

Good luck

[papiichuulo]

Originally Posted by alloro

Was the battery disconnected when you changed the ignition switch or did you do it live? If you did it live there's a chance you fried a fusible link. Are you getting 12 volts at the ignition switch connector?

And don't forget about the pickup coil inside the distributor. If that's bad...no spark.

no pickup coil here, on this particular one, I believe it has a "hall effect sensor", correct me if I'm wrong... a little crown on the base of the dist. that has tabs that rotate thru a magnetic sensor.

and yes, i did it live. but the van did run that one night, after I put that switch in.

[alloro]

The thread was about a 2000 I didn't realize that you changed it to an earlier year. Earlier years did use a hall-effects, but the same applies to it. If it has a break in it's coil wire...no spark. For your current problem though, you might want to check out the ASD relay again. I know that you already changed it, but maybe it's connector is the problem and not the relay itself.

[papiichuulo]

for some reason, I don't think my post/reply posted in the correct thread. Needless to say, I still appreciate the replies. The thread I was replying to was talking about a crank sensor... hence the first few words of my first post.