High Idle Problem

[JStraw]

Hi all, I need some brain power to help me with an intermittent problem. At any given time at start-up or during driving (throttle let off), the idle will either stick increased and stay that way or decrease back to normal. Right now its idling at about 1500 rpm. I have changed out the fuel filter to no avail and tried to adjust the idle down with no help. I even untweaked everything- no help. I also disconnected all the linkages when it was idling high- no help. When it is idling normal I notice that the throttle linkage assy is farther forward by about 1/2 an inch. I didn't feel any binding in the cables either. The truck did set up for 2 years while I was contracted overseas. It was started occasionally during this period.



I don't know if it's coincidental but this didn't start until I had the transmission upgraded in December. I just can't see a correlation. I've just turned 86,500 mi. Any thoughts? Thanks.

 

[bmoeller]

May want to run some fuel treatment thru it first, double stength. I use Lucas fuel treatment myself. Really like it alot better than the Power Service I was using before. I get it at Flying J.

 

[nascar mark]

Try taking your TPS off your truck. It may have binded up over time and got set up after transmission re & re which made for a sticky spot. 1 min job to remove 2 small screws and go for a drive. If that don't do it check your kick down cable where it attaches at the transmission and look for electrical wires catching on the lever.

 

[JStraw]

Thanks Mark. I was wondering if the TPS needed to be connected to drive the truck. I'll try that tonight. Is there any adjustment on the TPS?



On another note, the transmission will not up-shift from 2nd to 3rd under heavy accelleration. Otherwise it shifts good. Could this be related?

 

[bmoeller]

Originally posted by JStraw

Is there any adjustment on the TPS?



On another note, the transmission will not up-shift from 2nd to 3rd under heavy accelleration. Otherwise it shifts good. Could this be related?

http://dodgeram.org/tech/transmission/automatic/TPS_adjust.htm



The TPS (throttle postion sensor) is for the transmisson only on your truck. Doesn't control the engine speed like the 24v. engine.

 

[hdm48]

JStraw, I agree with mark on the TPS issue. As far as the shifting goes, I would re-adjust your kick-down linkage to where it shifts just as it starts to de-fuel. This will take a little trial and error but will help it to pull better. Nothing worse than "wait a minute" shifting.

It sounds to me like the transmission shop put in the govenor weights for a gas engine instead of the ones for a diesel. Or the valve body is set up with the wrong springs for pressure control. You didn't have a shift kit put in did you?

Have the transmission shop do a line pressure test. That will tell you a lot. Too much line pressure can blow lip seals and snap band struts. This is a bad thing. So do this soon before you break something.

One thing you didn't say was how it shifts under light loads. Is it hard? How does it go into gear? Hard? will it shift into 2nd normally? Does it "buzz" in reverse? Does your shift lever indicate "d" when your in drive?



good luck

Dave

 

[JStraw]

Dave, it has to wind a little to shift into second but the shift is smooth and powerfull. When it does shift into 3rd it is very hard.

Now, if I lightly apply throttle it will smoothly shift through all gears. Shift indicater is pointed to 'D' and there is no buzz in reverse.



I haven't try'd a test drive with the TPS off yet but will this weekend. If that doesn't point to the culprit I'll use the link to check its adjust ment.



Does this adjustment apply to 1st gen's? After reading the proceedure it talks about TC lockup. 1st gen's don't have an unlocking TC, correct?



How do you check/set the shift cable. If I can get the info I'll have a lot of things I can check and hopefully find the fault.



Mouse, the codes are 12 and 55.

 

[cerberusiam]

You said the linkage is a half inch farther forward when idle is right, can you grab the linkage rod and push it forward to shut the idle down? This would indicate the linkage is jamming somewhere. You said the cables are free. Do they have slack when the idle is high or is one of them holding the linkage back? The throttle and kickdown cable can fray inside the housing where it is hard to find and keep the linkage from returning.



Another cause could be the spring on the bell crank assembly for the throttle linkage. It has a spring wound around a nylon bushing and wear will cuts groves in the nylon and cause a linkage jam. Pull the throttle assembly apart where the throttle cable hooks to it and verify the spring and bushing is in good shape.



If your truck has a lockup TC you will have four wires on the transmission connection. Non-lockup models have 3.



The error code 12 means the power has been lost to the PCM lately, such as disconnecting the battery. Code 55 means end of code list.



Here is a handy link to error code listings.

http://www.minimopar.net/



Good luck.

 

[hdm48]

Jeff, our 1st gens don't have lock-up converters. The way you describe the shifting it sounds like it may only be a K/D adjustment. I have seen this before and it has to do with the valvebody spring rates. No big deal. Just adjust the K/D cable one click or two clicks on the softer side.

If you follow the cable back you will see the adjust point. Look at the top of this and you will see a hindged plastic locking tab. while holding the cable on the back side ( there is a spring here trying to push it back. Don't let it move yet) release the lock and move it back about 1/16th of an inch. Do yourself a favor and measure the distance between the spring coller and bracket before you unlock it so you know where you were at the begining.

If it doesn't shift the way you like, move it another 1/16th. Do not go back anymore than what is needed to get the shifts right.

This help? More is available if needed.



Dave

 

[BushWakr - RIP]

I agree, you need to use caution on the throttle valve cable adjustment. The factory spacing is . 180" between the firewall inside end of the slot, and the post which is in the slot.

A misadjusted throttle valve cable can cause premature wear and problems.

Mark the current position as mentioned and use a 1/8" drill bit end/shank to estimate the correct spacing.



Next, look at the throttle linkage at the point were it is attached to the throttle shaft on the pump. If a part of the that linkage/ shaft/assembly is rubbing on the fuel line ahead of it, it may be sticking there.



This has been mentioned but the throttle return spring is a dual spring, if one is broken or fractured, it may not pull the throttle back fully.



Last one, under the truck, on the transmission, were the throttle valve cable attaches to the transmission lever you should have a spring there (or on the end of the slotted part under the hood, to pull the throttle valve arm fully forward.

On mine I have used a "universal throttle spring" to attach to the trans. rod and hooked the front facing end of the spring to the bracket nearby.

This assures the throttle valve cable fully returns to the forward position.



I hope that somewere in this thread you find your answer.



regards, Bob.

 

[JStraw]

I adjusted the kick down cable last night and it made a day to night difference. It still needs a little tweak but she's running the stripped ape she used to be. Thanks to all