Hey guys, Im having trouble with my truck and don't really know what is going on and Im looking for a bit of insight. First off, my truck is a '99 Dakota Sport 5.2L.
Just a couple weeks ago, I replaced the IAC and TPS because I was having a problem in which the rpms would stay up high when I pushed in the clutch. It turned out to be the TPS as far as I could tell. Regardless, after replacing those two things and resetting the PCM, the problem went away. For a day.
On cold starts, the it seems to struggle idling. When driving or giving it gas, it is perfectly fine, but as you let off the gas, it struggles to idle. But it will only do this for about 2 miles of driving. Which makes me think that it is only an issue while in Open Loop operation. But maybe that has nothing to do with that.. I don't know. Anyways, after about 2 miles, all is well and there is no problems. However.... Once I am within a couple of miles of work/home (after about 15-20 mins of driving) I will go to shift and as I take my foot off the gas and push in the clutch, the rpm's jump up to 3000 like my foot is still on the gas for 2-3 seconds, then falls back down to normal. Since it seems to start to do this consistently near the same spot every day, I have kind of played with it to get a better idea of what is happening. Once it starts to do it, I will tap the gas while in gear and I can feel and hear the engine revving like my foot is holding the gas for 2-3 seconds. Similarly, while holding the clutch in, I will tap the gas and the rpm's jump up to 3000 for 2-3, again, like I'm stepping on the gas. I am quite sure the throttle is not sticking, because it snaps right back. And it only does this after 15-20 mins of driving.
I don't know if these issues are related, but they both started right after replacing the IAC and TPS and resetting the PCM. Any Ideas?? Any help is greatly appreciated. Thanks guys.
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I will have to check the book for the Pintle length, but before installation the manual state to adjust the pintle length (the distance from the pintle(plunger on the end of the IAC)) to a preset distance from the plastic part. Usually you can just push it in or pull it out to the needed distance.
Ok, so i cleaned out the TB. Now ot seems to start up and idle just fine for a little bit, then it starts to idle really rough.. To the point that I can feel the whole truck shake. PLUS, now its back to the rpms staying up high until I come to a complete stop (the reason I replaced the iac and tps im the first place). So I will be driving down the road and when I push the cluch, the rpms fall to only about 1500 until I come to a COMPLETE stop, then they fall to 800ish (normal)..
You could also try cleaning the map sensor. That's a 50/50 on whether it will help or not. Sometimes it does sometimes it doesn't.
Also have you tried using an ohm meter to check the IAC and TPS? You can also check the map sensor with one too.
Also, and I am not sure if the 99 has one or not(I have a 4.7 03 and haven't worked on a 99 5.2). But see if it has an IAT sensor located in the intake air tube. Usually between the filter and TB. Also there may be a CTS(coolant temp sensor) that tells the ECM when the engine is cold and adjusts for it. All of these can be checked with an OHM meter.
It's possible it could be the EGR also.
I know it's a lot of stuff to check but you don't want to just throw parts at it. That can get VERY expensive.
To be honest what you are describing sounds more like a vac leak than a sensor problem.
Just to illustrate: I had a 95 S10. I replaced every sensor on it (IAT,CTS,TPS,IAT,o2,EGR,EGR solenoid,MAF,) and it still ran terrible. It would start and run great for about 20 minutes. So after a year of throwing parts at it I checked the injectors with a meter. Bingo! One was reading 1/4 of what the others were. Replaced it and all was good. That was an expensive lesson.
Ok. So I just determined that the MAP sensor is ok. So that's not it.
I guess I will check for vac leaks. Is there any other effective way to search than carb cleaner?
Also, I noticed the one of the TB bolts are missing... possible culprit; leak under the TB? (just bought this truck 8 months ago, so the A-hole that traded it into the dealership I bought it from must have lost it.. I'll have to get another)
Its weird how when you take a vehicle for a test drive, all is perfect, then a couple months later, things just start.... happening. Like just a month ago, either the ABS pump went out, or one of the speed sensors, because suddenly the pump would run constantly, even with the key off and out! So I just pulled the fuse and called it good for now. It never fails that something goes wrong shortly after you buy a vehicle. Strange that I started having this idle and surging issue almost immediately after the ABS problem.