Throttle Problem

New member here with a problem. Have a 2001 Ram 2500 4X4 with a 5.9L Gas V-8. I have owned the truck since it was new and it just turned 100K miles. The truck has been meticulously maintained and looks (and until recently) ran perfectly. It is bone stock. Here is a summary of the problem.

Took the truck in to the dealer in July 2014 and had the full fuel system service done (induction and injection) and a major tune up (plugs, distributor cap, rotor, and plug wires). Dealer also re-indexed the distributor.

Truck ran perfectly for about 2 months. Then I noticed the truck would accelerate moderately on its own without stepping on the gas. Usually did it when warm at highway speeds. Also, at times, when I took my foot off the throttle, the truck would continue on as if I had maintained pressure on the throttle.

I took the truck back to the dealer in Sep 2014 and they replaced the throttle position sensor (TPS). Problem still existed and in fact the at one point, the truck tried to run away with me in a parking lot as if I had stepped hard on the throttle even though I barely touched it. I took the truck back to the dealer again and they replaced the Idle Air Control Motor (IAC). Could not find anything else wrong. No codes thrown at any time.

Well as of now, the problem still exists. Not sure what to do at this point but the truck is potentially dangerous to drive. Does anyone have any idea what might be causing the problem??

Dave

Welcome to RF

Ok well the fact that the dealer moved the dizzy tells me the timing chain has lot's of slack in it, too much. On these motors turning the dizzy does not control the timing it only controls the fuel sync, so they adjusted the fuel sync.

They replaced the IAC but did they clean out the TB and the port the IAC it fits into? If they did not it should be done. It might be fine but you have to check it. Other than that Vacuum leak, stuck throttle cable or cruise control cable. You can disconnect the cruise control cable up at the TB and see if that helps. There is also a transmission TV cable that goes to the TB make sure it moves freely and that the end on the tranny has a spring on it.

I like to tell people to do a compression test before any work is done so please do one if possible. Make sure the motor is worth fixing as it is getting old.

Also see the thread about the intake plenum gasket.

Merc225hp. Thanks for the input. Hard to believe the timing chain has much slack. Should not be a lot of wear on the motor. Have changed the oil every 3K miles since new with Mobil 1. The throttle bottle was supposedly cleaned during he induction and injection service and the dealer said they checked for any debris when they changed the IAC and the TPS. Check turned up no vacuum leaks. Throttle cable also checked. I asked them about the cruise control and they said that would not cause this problem. No one mentioned the transmission TV cable so I will ask them about that. Other than the problem I described, the engine actually runs as strong as it ever has (starts instantly, idles smoothly, great acceleration, uses no oil, no smoke).

Since my original post, I tried another dealer and they had the whole shop trying to figure this out. They replaced the TPS again and said the problem was the previous dealership forgot the put the gasket on the TPS and that was causing the throttle shaft in the throttle body to bind. Well it worked great for about a day and then started doing the same thing again. Very frustrating. I am taking the truck back to dealer 2 next week for another try. I will discuss your points with them.

Thanks again. Dave

No problem Dave

I suggest to most that have over 80k to expect slack in the timing chain and to replace it. For your year truck the motor may or may not have the T chain slack tensioner from the factory, the shop can do a test to check the slack in the T chain.

The cruise control cable can cause this if it is keeping the throttle plates open, this is a easy thing to test just unclip the cable from the TB. You can operate the truck without it hooked up. The other thing to check is that all the cables are clipped on right they must click when they go on the stud, they only go on/come off one way, be careful don't break the plastic ends.

Side note; When the shop is replacing the IAC and TPS or any other sensor its best to have the neg cable off the batt, this will reset the pcm so it learns the parameters of the new part and not going off the old parts readings. So make sure they are resetting the pcm.

The Factory Service Manual can be downloaded here on RF for free see the link. Its dry reading but very helpful.

Link to FSM; http://www.ramforum.com/f77/2nd_gen_service_manual-986/

Link to the plenum gasket thread; http://www.ramforum.com/f61/plenum_gasket_what_where_what_should_i_do_about_*info*-37635/


Photo of the cable orientation on the TB.

Merc225hp: More good thoughts. You obviously know what you are doing. Thanks. I will check the cables. Shops both said they reset the PCM but I will disconnect the battery myself to be sure. I have a good old paper copy of the 2001 factory service manual in my garage. I actually read it a lot (a cold beer makes it less "dry"). There is no trouble shooting section that relates to this problem. Thanks for the link on the plenum thread and the photo of the cable orientation.

Dave

If the shop just used there DRB scanner tool to reset the pcm thats not the same as what I would call a hard reset (disconnecting the batt). There are only so many things that can cause this, keep it KISS and that might help. You might head to a auto wrecker and find a used TB and give that a try after you go though the above stuff and nothing helps.

Edit; It would not be the first time I have seen a new part fail have them try a another IAC.

Edit 2; I am sure you have read this but I thought it should be posted.

From the 2001 FSM

IAC Stepper Motor Program: The PCM is also
equipped with a memory program that records the
number of steps the IAC stepper motor most recently
advanced to during a certain set of parameters. For
example: The PCM was attempting to maintain a
1000 rpm target during a cold start-up cycle. The last
recorded number of steps for that may have been
125. That value would be recorded in the memory
cell so that the next time the PCM recognizes the
identical conditions, the PCM recalls that 125 steps
were required to maintain the target. This program
allows for greater customer satisfaction due to
greater control of engine idle.

Another function of the memory program, which
occurs when the power steering switch (if equipped),
or the A/C request circuit, requires that the IAC stepper
motor control engine rpm, is the recording of the
last targeted steps into the memory cell. The PCM
can anticipate A/C compressor loads. This is accomplished
by delaying compressor operation for approximately
0.5 seconds until the PCM moves the IAC
stepper motor to the recorded steps that were loaded
into the memory cell. Using this program helps eliminate
idle-quality changes as loads change. Finally,
the PCM incorporates a 9No-Load9 engine speed limiter
of approximately 1800 - 2000 rpm, when it recognizes
that the TPS is indicating an idle signal and
IAC motor cannot maintain engine idle.

A (factory adjusted) set screw is used to mechanically
limit the position of the throttle body throttle
plate. Never attempt to adjust the engine idle
speed using this screw. All idle speed functions are
controlled by the IAC motor through the PCM.

Good luck and keep the forum updated please.

Merc225hp: Thanks for the additional information. I just finished disconnecting the battery and will give the truck a try tomorrow to see if that worked. If all else fails, a new TB is a definite possibility (either that or a new RAM). I love my truck and do not want to give it up. After almost 14 years of trouble free service it has become part of me. I will keep you posted.

Dave

01Ram2500 said:

Merc225hp: Thanks for the additional information. I just finished disconnecting the battery and will give the truck a try tomorrow to see if that worked. If all else fails, a new TB is a definite possibility (either that or a new RAM). I love my truck and do not want to give it up. After almost 14 years of trouble free service it has become part of me. I will keep you posted.

Dave

Click to expand...

Yes definitely get a new Ram and sell me the old. I'm on the hunt for a '00-'02 V8 2500.

BBartow said:

Yes definitely get a new Ram and sell me the old. I'm on the hunt for a '00-'02 V8 2500.

Click to expand...

Well you would be getting a good one. Has 75 coats of Liquid Glass on the finish which looks better than new (See attached photo - look carefully and you can see a Shelby GT500 in the finish reflection). Not even one parking lot ding in nearly 14 years. Except for the problem I have described here it is mechanically perfect. It would be hard for me to give up.

Dave

So did the problem start when the GT500 started to use the Rams shop space........



I had to.

Looks great!

Merc225hp said:

So did the problem start when the GT500 started to use the Rams shop space........



I had to.

Looks great!

Click to expand...

Actually, you might be right. The old girl now has to share space with all the toys and may be getting jealous.

Mine has a serious jealousy problem...always has, she loves to throw small temper tantrums if I don't pay attention to it or spend money on it once a month.

Don't sell the truck keep it.

Back on topic; How did it run up this am?

Definitely plan to keep the truck unless it costs more to repair than it is worth. Did not have a chance to drive the truck today. Spent the AM giving money to the Indians at the Seminole Hard Rock Casino in Tampa. Spent the PM playing with the HD and Shelby. Will drive the truck tomorrow and give you a report.

Dave

Well I drove the truck today after disconnecting the battery. The hard reboot made the problem far worse than it was before. Now the truck tries to run away from me constantly, idle is rough (first time for this issue) and it is surging while in gear and running (not while idling in neutral or park). Could that mean a PCM problem? I plan to drop it off at the dealer tomorrow in the AM. Told them to keep it until the problem is fixed.

Dave

Have you pulled the air box off yourself to make sure the throttle linkage is on the idle stop?

dodge dude94 said:

Have you pulled the air box off yourself to make sure the throttle linkage is on the idle stop?

Click to expand...

Yes, had it off many times. All looks normal. Just dropped in off at the dealer. They have it until fixed. Will let you know the final solution.

01Ram2500 said:

Well I drove the truck today after disconnecting the battery. The hard reboot made the problem far worse than it was before. Now the truck tries to run away from me constantly, idle is rough (first time for this issue) and it is surging while in gear and running (not while idling in neutral or park). Could that mean a PCM problem? I plan to drop it off at the dealer tomorrow in the AM. Told them to keep it until the problem is fixed.

Dave

Click to expand...

I am thinking CKPS. Sorry the hard reboot has made it worse but it might help them find the problem faster and easier. Did it flip a CEL after the reboot?

Merc225hp said:

I am thinking CKPS. Sorry the hard reboot has made it worse but it might help them find the problem faster and easier. Did it flip a CEL after the reboot?

Click to expand...

I passed your CKPS idea on to the Service Advisor (along with some other thoughts) by e-mail this PM. Truck did not show a CEL after reboot. We will see what happens.

I wonder if the TB or intake is slightly warped, or a gasket is failing, and the PCM had been correcting for that all this time until you reset it and are forcing it to re-learn that behavior? Just a thought...

WarrenRam said:

I wonder if the TB or intake is slightly warped, or a gasket is failing, and the PCM had been correcting for that all this time until you reset it and are forcing it to re-learn that behavior? Just a thought...

Click to expand...

Entirely possible. I just picked up the truck today and, although the problem is not as bad, it is still there. The second dealer basically gave up after 2 attempts to fix. I even told them to do whatever they thought might fix the problem. They elected not to do anything. Can't believe nobody can fix this problem. The good news is that they did not charge me a dime for their efforts. Got to applaud them for that.

Does anyone know of a non-dealer shop that does outstanding work on these Gen 2 motors in the Tampa Bay Region????