'93 Dakota won't run below 1200RPM? UPDATE!!

Pulled my Dakota out of storage today and left it idling while I locked the place up again. Was idling fine when suddenly there was a VERY loud 'POP' and the idle dropped, shot way up then dropped again and stalled.

Checked for obvious signs, didn't see anything out of place.

Truck starts right back up as long as your foot is on the gas. Take your foot off or just let the RPMS drop a little, and it cuts off. Not spit/sputter die, just OFF.

Didn't have tools with me at that moment, so I'm going back tomorrow to take a closer look.

Any suggestions on what to check?

On a side note, truck sees limited use lately, and it hadn't been run in about a week. At that time, there were no issues.

Thanks.

I don't know anything about the first part of your post, but this part sounds a bit like IAC motor troubles.

Had a '90 Dakota v6 did something similar; was IAC.

Sounds like a big vacuum leak. Could be the IAC but could also be some other sort of vacuum leak. PCV, PCV hose, brake booster hose, rubber caps or plugs on the intake, etc.

That has a barrel intake like the 5.2 right? Those have a metal plate bolted to the bottom of the intake.(at least the v8 intakes do) That gasket can blow out causing a big vacuum leak. Usually the tell tale sign is a really high idle and a lot of pinging on the road.

Another IAC vote. this happened to me as well. If I remember correctly, I did shoot some carb/FI cleaner in it. Settled it down some

I'm thinking IAC as well. What threw me was the POP it made. Backfire? I don't know where it came from as my back was turned when it happened.. I wasn't able to get back to the truck tonite, but I have a spare IAC that I can try tomorrow.

I checked all the vacuum lines and capped ports and didn't find anything. I did the plenum upgrade shortly after I bought the truck, hopefully that didn't go bad again.

I'll report my findings tomorrow.

I would drive it and get it fully warmed up before doing anything. Its possible that you had a low voltage spike when starting and the computers memory is erased. Once it relearns it may be ok.

Hold the throttle at a high enough speed to stay running the next very slowly lower engine speed so the PCM can learn the IAC steps to regain control.

x4 for idle air control.

You can take it out and clean it with oven cleaner first. That always works for Me along with O2 sensors. I just did one and took the whole throttle body off, brushed it good with gas and compressed air to blast the crud out.

Runs like new.

A majority of the problem was the IAC......

However, I found two other issues?

1) The throttle body baseplate gasket was in two pieces. And based on witness marks on the manifold, it had been that way for some time. I replaced that gasket when I did the intake manifold, throttle body hasn't been off since then until today. Source of a vacuum leak?

2) the port that the MAP (?) plugs into was almost completely blocked. No amount of spray or compressed air was clearing it, I had to get after it with a metal pick. Carbon? Dirt? I could have missed this the first go around.

I didn't replace the IAC, I just gave it a good cleaning and polish. Turned out my extra IAC was different, so I couldn't use it.

Truck idles MUCH smoother now and smells different now too, leaner? If that makes sense. Gave it a 5 mile run, she does pull harder when matted now (cup holder on dash slid open..... )

I spent so much time tinkering on it, I never did get to work on the roof. Oh well. I actually enjoyed doing this today. The weather was good, no interruptions, just got lost in it for a few hours. It felt good.

Thanks everyone!

All was great for a few days, then the problem came back, but with a twist? Between work and nursing a bum ankle, haven't really looked into again until this past week.

I went ahead and changed the IAC and the fuel filter. Truck runs buttery smooth now!

BUT...as the truck warms up, the idle gets lower and lower until it reaches full temp where it won't idle at all. Doesn't matter if you're just sitting idling or driving, take your foot off the gas and it just dies.

I switched the IAC because it wouldn't idle cold or hot, now with the new one, it idles only when cold.

It doesn't run rough at any point, it stays smooth at all times, even just before stalling.

Bad IAC?

Any vehicle I've owned with a vacuum leak, the idle went higher, not lower, but I checked everything visible that I could and didn't find anything.

Suggestions? I REALLY need this truck right now, but its basically undrivable.

If you know someone with a snap on or simular scanner have all the settings reset to default.

Is that even possible with OBD1?

Along those lines, I did disconnect the battery while I made the change, thinking it would 'learn' the new IAC?

For a temp fix, you can unplug the speed plunger and turn it to an rpm range that works for you, then leave it unplugged. Its a compromise between a too low rpm cold idle and a too fast warm idle. I choose the correct warm idle and do a slight power break when its cold, until it will idle on its own.

My temp fix is about 3 years old now, my truck is a rusty pile. Its probably the best its ever going to get because it only see about 3,000 miles a year. I've been hoping I only have to drive it 1 more winter for 3 years now. I almost have its replacement finished. Gene

I looked at my old IAC, it didn't seem adjustable, but I didn't force it either.

Watched a few videos on the subject matter tonight. While I understood the function of the IAC, seeing the videos made it even more understandable. Based on what I saw, it seems like the IAC is stuck 'in' or simply not functioning.

The new one is under warranty, so I may just swap it out after checking a few things.

Silly question? Any chance the temp sensor is bad and possibly going open or giving the wrong value to the ECM. Just a thought

That's a good move, my experience with aftermarket sensors or anything electrical is terrible. If the part is NS1 at the dealer, go to Pick and Pull and grab a few.

i have seen temperature sensors act like that when they have a "coating" of sorts on the bulb that sees the coolant.
when shined up to "new" brass, sometimes they come back to life.
would be an easy thing to try.

I read somewhere that aftermarket replacement parts like this don't play well with the computer? I priced a 'genuine' Mopar one and the price was $70-$100. I bought a Standard Brand one from ORileys for $42.

With my bum ankle, I haven't had the ability to go wander a PNP for parts.

Is there more than one? Temp gauge seems to work correctly.

Before I scampered off to ORileys, I took a look the new IAC I had installed. Unlike the old one, it IS adjustable. Hmmmm. Went to Standards website, and found instructions on how to adjust it. My part came with no instructions, and I didn't know I HAD to adjust it.

Well, I made an adjustment and have it running now. I'll see how it is once it gets up to temp.

PART LINKY with link to instructions.

There are actually two temp sensors on the Magnums. One is for the gauge, the other is for the computer.

They are close to each other, but one kinda hides back in there.

I think it needs a little more adjusting, but for now, she's a runner again! Thanks everyone!

Well, still not 100%. (haven't made more adjustments since video) It's in the upper 50's here now and I used the truck tonite to run a few errands after work.

Cold start, started fine, idle was a little low, but it did idle. Full temp, idled as in video.

However, that gray area between not quite cold and not quite hot caused issues. I had to two foot it a few times until the temp came back up.

Well, got tired of jackin' with the aftermarket part and bought a genuine MOPAR one instead........



Initial driving impressions are that the truck has NEVER run this smooth or has been as responsive.

Stop and go traffic, blasting down the freeway, cold start, hot start, lukewarm start, it never missed a beat.

Dare I say I have my truck back?

Did you buy the Mopar one from a dealer, or someplace else? Mind telling us how much it cost? Gene

[quote=Satilite73]
Well, got tired of jackin' with the aftermarket part and bought a genuine MOPAR one instead........

What OE part,temp sensor? or??

The only place I could find an IAC was on ebay.

Here's the listing: Mopar 53030657AB Idle Air Control

Supposedly the last one they had in stock.

Got here sooner than estimated.

Local dealer didn't have one and couldn't get one. Knowing one was on ebay, I didn't argue with the dealer about it.

because I don't know if the people who asked questions got their answer......

Its always sounds ignorant and bad to say "I saw on the internet...." But via the internet watching legit techs/shop owners on Youtube- and repair podcasts I learned about 5 years ago when it comes to certain models - replacement sensors and computers must be an OEM unit and is the the only choice- no matter how much $$$. The trusted aftermarket name brands of yesteryear have thrown in the towel and went extra cheapie cheap.

The trusted aftermarket name brands of yesteryear have thrown in the towel and went extra cheapie cheap.

100% The first one that popped into my mind when reading that statement was MOOG, but it seems prevalent with all aftermarket companies now. Unless I do something to eliminate the factory electronics in my truck, I'm pretty sure they're gonna be its downfall above anything else.

A repair shop in Louisiana that has a Q&A show calls OEM parts "The Best of the Worst."

I was going to suggest Microsquirt, which is what I am using on my 51 Plymouth's EFI swap. However, you are still stuck with poor aftermarket parts for sensors and such. Junkyard here we come.