Dodge Ram intermittent high idle and stall issues.

[Alex]

Hello all! I’m new to the forums. I’m having some issues with my truck and I’m hoping for some advice/help?

I have a 1997 Dodge Ram 1500 w/ 131K miles, 5.2L, V8, auto., 2wd.

Upon initial start-up (when the engine is cold) the engine will rev’ to 1600 rpms and down to 1200 rpms for about 20 to 30 seconds, this is when it’s 60 F or below. When it’s warmer the engine will idle at a constant 1000 rpm’s. When you lightly hit the accelerator the rpms will jump to 1600 down to 1200 up to 1400 and down to 1000 and steady- this will happen until the engine warms-up and the idle is about 700. When you go to shift through the gears – the idle will jump to about 1400 when going into neutral or park (again until it warms-up). When going from reverse (as I back out of the drive-way) into drive the engine will die. Upon start-up it will run just fine and continue running fine all day. I do not get any CEL’s. This routine happens every start-up.

I’ve checked the TPS and the MAP sensor recently, they both came up OUT of specs according the the repair manual. When I checked the 2 sensors listed above I got a code for the TPS (24) and O2 sensor (21). I think that had to do with me disconnecting and checking the sensors as I’ve since cleared the codes and they have not been back. I’ve checked for vacuum leaks with carb. cleaner and a hose to my ear – no luck.

Should I replace the 2 sensors or at least the TPS. Or is there another issue as the truck seems to run fine after it warms up.

Sorry for the long winded question. Just wanted to be thorough. Can anyone help? Thank you.

Topic

[exceptionalchris]

I recommend you give your throttle body a good cleaning as well as the IAC valve. Do this before replacing the TPS or MAP sensor. Does this trunk have an electric TB? if it does don’t remove it clean it on the vehicle. Did cleaning the MAF show improvement?

[Alex]

Thanks for the recommendation.

Yes, I did clean the TB when I first bought the truck (it was in bad shape), also cleaned the IAC.

I don’t think the truck has an electric TB, as all I can see are cables attached. Is that how you would tell if it’s electric or not?

I didn’t clean the MAP. Is it a matter of taking the sensor off the TB and removing any build-up (if it’s not electric)?

[exceptionalchris]

Correction: when you cleaned the MAF sensor did you see an improvement? Also does the idle change from drive to park?

[Alex]

Thanks for your help.

I don’t believe this vehicle has a MAF sensor. I’ve looked through the book and there is no reference to it, unless it’s called something else. I’m assuming the MAF sensor would be before the TB and I don’t see any kind of sensor or electrical connection inline. From what I see, my TB has the TPS, IAC and MAP attached.

As far as the neutral and park:

If you go from park to drive there is no change in idle, if you further go down to neutral it will idle up to 1600 rpms momentarily and return to 1000 rpms, same if you go from N to D to P. Only N and P gears will jump to 1600 rpms when the engine is cold.

There is no difference in idle speed between N and P, they’re both around 1600 rpms when this issue occurs.

[exceptionalchris]

No DTC codes? If you a sure you don’t have a vacuum leak.I vote IAC. Found a link for you. http://www.autoserviceprofessional.com/article/92420/The-dreaded-engine-surge?Page=2

[Bill]

Does this truck have an internal IAC or is it external? (stepper motor that moves the linkcage).

[Alex]

The CEL is off – so there are no codes presently, unless there are some that are stored. I do not have a scanner, last time I checked for codes was when I purchased the vehicle about 6 months ago and there were none present and none stored.

I’m NOT sure that there’s NO vacuum leak. I did take some carb. cleaner and sprayed it everywhere I saw a vacuum line and around the intake – no change in engine performance. I also took a hose, one side to my ear and one side all around the engine and vac. lines – I heard no leaks, but I might just not have the ear for it as an auto. mechanic would. So, yes there certainly could be a leak.

I can see the IAC being the problem. I have not checked it yet – according to the repair manual specs. I guess I’m hoping it’s the TPS or MAP to be the fix. They’re the first ones I checked and they both came in out of spec.

Thanks for the link.. I’ll check it out.

[Alex]

I’m not sure if it has an internal or external IAC. I looked online and have not found any explanation or graphics for me to distinguish between an internal or external IAC.

I’ll describe it – It’s located on the side of the TB. It has an electrical connector. When I cleaned the TB, I took it off to clean it as well. It has a plunger and w/ spring around it’s shaft. I don’t see any other parts or hardware associated with it. I would assume it’s a stepper motor controlling the plunger.

[Bill]

Really…I should have asked if it was throttle body injection (2 injectors in throttle body) or port injection (8 injectors in manifold).

[Alex]

No TB injectors. Has 8 injectors for each port.

Is that how to distinguish the IAC from internal and external?

TB injectors = internal IAC?

Individual injectors = external IAC?

Or is it a visual inspection?

[Bill]

Yeah…That’s how i distinguish the 2 types. Older cars in the USA especially California cars were a little ahead of Canadian cars in regards to emissions and other technology so i need to be careful with my advice sometimes. You might have a port injected vehicle in the US while Canadians are still getting Throttle body injected vehicles.

These days Canadian cars are usually the same as federal emission cars in the USA.

Anyhow…Throttle body injected trucks like yours use an external stepper motor and it was a pain in the Butt. Idle speeds were always all over the map cuz it was mechanical with different gears and motors inside to allow it operate.

Port injected engines like your truck used internal IACs. Other than being susceptible to sticking have only one moving part so are more accurate. They allow more or less air past it to adjust the idle speed.

That crap said…It is possible that the TPS is at least part of your problem.

Some vehicles may require a computer reprogram to address temp related issues. The best way is to go to the dealer with your VIN# in hand and they can check for you.

[Alex]

I appreciate all the info and advice.

I think I’m going to start with the TPS since voltage test didn’t come up to specs. according to the book.

If I may run the following by you?

Transmission Issue (related or unrelated?):

When the engine is cold the trans. will sometimes not engage on the initial acceleration or is very slow to do so. Also, when cold the trans. rpms will run from 2500 to 3000 ( for 2-5 sec.) before it engages 4th gear. This only happens once or twice then it’s fine all day. If you sit in the driveway and go through the gears the engine bogs down when you go into #1 gear ( down to 300 rpms, likes it’s going to die ). I don’t think this issue is related with the idle problem because the truck does not jerk before dying when going from R to D as I mentioned in my initial post, so I assumed it wasn’t the converter. I thought I throw that out there considering the great advice I’m getting and the knowledge factor seems to be pretty high here.

Thank you.

[Bill]

I don’t think it’s related either. It sounds to me like the trans is getting tired. The clutch pack piston seals are likely getting hard and worn and don’t seal like they used to when it’s cold.

I would have the fluid and filter changed with the correct fluid. I don’t think it will help but it can’t hurt.

Just be patient with it and it could last a long time like that.

[Alex]

Thanks for all the info and suggestions.

[Author]

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