why are my RPM’s so low even under load?

[Chris]

So I have this 1994 Dakota 3.9L. You may have seen a recent post by me asking for help with the intake plenum and timing chain replacement. It is much better but I still don’t have the power at the peddle which I feel coming from the motor.
I have been reading posts by other owner’s and some talk about it running at ranges over what I think is right and mine does. At 65 it basically sits at 18-1900rpm which I think is right for any vehicle in the right gear. But it got me paying attention and I have noticed my rpm’s do not go above 2000 much and I can’t remember ever seeing them go past 2500. Even when it kicks down it only momentarily spikes up near 2500 and then drops to a place above where it was prior but not by much.
So 18-1900 is pretty much the max this thing runs at normally in town it is around 14-1500rpm or less. It had horrible MPG’s 9-11 (MPG is my guess for why the factory might do this) which have improved some since I added the new tune up parts and sensors; TPS, IAC, MAP, PCV switch plate, plugs wires, cap, rotor, coil, oil sensor, EGR, Timing Chain/tensioner, new intake plenum. I think the MPG’s are about 19 I can;’t really tell because the gas gauge doesn’t work. Yes I put a new pump with sending unit in. I think I need to do the TSB on the sending unit wire but I don’t have the energy to remove the bed again.

I’m convinced the rpm’s are being retarded by something. Either mechanical part that is malfunctioning or possibly the PCM is supposed to do this. I know this is the year they restricted the exhaust from the manifold back. This thing has scads of power in it based on how the motor sounds and feels when it is running but I’m estimating barely 60% of it is getting to the wheels. Maybe I am being fooled by the sexy sound of the Magnum exhaust?

Anyone, hopefully with experience on 1st Gen Dakota’s have input?

Topic

[college man]

The pcm controls timing. check that your distributor rotor lines up.
here is a procedure.Does the truck idle correctly? any check engine light?

http://www.justanswer.com/dodge/2pinq-timing-spec-1994-dodge-dakota-3-9l.html

http://www.justanswer.com/dodge/26faw-1994-dodge-dakota-3-9-v6-timing-chain-gear-set-up.html

[Chris]

[quote=”college man” post=105212]The pcm controls timing. check that your distributor rotor lines up.
here is a procedure.Does the truck idle correctly? any check engine light?

http://www.justanswer.com/dodge/2pinq-timing-spec-1994-dodge-dakota-3-9l.html

http://www.justanswer.com/dodge/26faw-1994-dodge-dakota-3-9-v6-timing-chain-gear-set-up.html%5B/quote%5D

Thanks for that. I’ve seen those before. I have just done the timing chain and the rotor was lined up dead on with the mark on the switch plate when I looked down on it. This issue preceded the work I have done. I expect it is intentional part of PCM operation or may be one of the things fixed by the Flash updates I saw mentioned on some site listing all the TSB’s and recalls on this vehicle. I suppose I’ll have to find a dealer to do it or check if they have been done. My local acts stupid when I call with TSB numbers claims there aren’t enough of them in the number I give. Even told me they could not find a TSB for my truck when I gave the date the of the TSB and described the problem/fix to him. I’m getting the numbers here. http://dodgeram.info/tsb/index.html This guy seems legit to me.

[Chris]

I found a dealer nearby who will check for codes and flash updates for $49-$98. Made an appointment. With luck this will fix the RPM issue. He did not offer any possible reasons for it.

In spite of the fact of the TSB on the sending unit wire, he seemed convinced it is the instrument cluster that is the problem with the gas gauge. Not sure I want to trust that since the TSB explicitly describes replacing a wire in the bundle that carries the sending unit signal.

[EricTheCarGuy]

That’s a lot of work you’ve done. Was the same issue there before you did that work? If not, you might want to recheck it. That said, let us know what you find out at the dealer.

[Chris]

They had to find an old code reader. There were no updates that apply and no indications of misfire and no codes. No Charge! He gets my business at least once more.
The RPM issue existed before all that work. Even though someone had increased the idle with the set screw and it was pretty high, it didn’t like to rev up while driving.

Lets correct things. It spikes to 3K when I punch it and drops off fast. Today it lasted longest and it stayed over 2K for about 30 seconds when I was merging.
It goes to 2400 on a hill if I punch it or hit the OD button then it drops down to below 2k pretty quickly.
I got on the Hwy coming home from the dealer and it hit 55 and dropped down to 1400! I had to punch it to get up to 65. It cruises at 55 with 1400rpm, but I have no power and if i have to punch it there is a delay. It doesn’t feel right.

Edit 7-24-14 1pm
Today I had to make a trip to the same two block radius about 7 miles away 4 times to rent a tool that did not work. Heck the one I have now barely works. Anyway I was being heavy on the peddle and it hit 4K once when I was passing some slow poke. Yet it still wants to go as low as possible as soon as possible. I’m theorising the PCM is failing or the OE settings just do not suit me. It feels dangerous not knowing exactly how it is going to react when I need it. It has also started jumping from the start, it did this before I got heavy on the peddle.
I have a JET performance PCM on my wish list I am going to talk to them about what the programmer it comes with is all about as PCM engine management is new to me.

[Chris]

I’m resurrecting this just to keep the continuity of the storyline.

After a process that lead me to think I needed a manual transmission I called a place who ended up talking to me about what it was doing because he felt it was too old to spend that much money/effort on switching the transmission to manual “unless you really love this truck”. He referred me to someone he said was a Chrysler Line Mechanic for years. I called. He says after describing what I have in this thread that it is not my transmission and that he will hook up his diagnostic machine and tell me ‘exactly’ what’s wrong. Exactly underlined with emphasis, he was very certain.
I’m suspicious.
If such specificity were possible I think I might have heard about it. Also I would have thought the dealer’s scanner would have picked up any problems.

Does this sound honest? Or is it a case of hyping ones business and talent?

[Author]

Replies