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Discussion Starter #1
Having trouble when at low RPMs. After I leave a redlight or when I am coming up my gravel drive way at a low RPM my truck is cutting out almost to the point of stalling but never stalls. First thought was a TPS sensor...bought and installed and nothing changed...does anyone has any idea or have ever had this problem...my logic is it may be in the TBI but not sure...any help is great thank you and have a Happy New Year!
 

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I'd suggest also checking the throttle kicker (what our throttle bodies use for an Idle Air Controller). After that - how old is the tuneup? Check timing? Plugs? Wires? Cap? Rotor?

Do the on/off/on/off/on dance (never starting the motor!) and see what codes flash on the "POWER LOSS" or "CHECK ENG" light. There's links all over on how to do that and what the codes mean.

Also, be worth checking fuel pressure - don't think that's the problem since it recovers, but eh.

OH! Don't forget to run your vacuum lines and make sure none are broken / leaking.

RwP
 

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Discussion Starter #3
What exactly is a throttle kicker? What does it do? And how do I get the light to blink? Just flip the switch twice?
 

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The "throttle kicker" is that solenoid at the front of the throttle body that kicks the idle up when needed.

And the cycle is - pull into a parking spot, run through the gears, turn the motor off, take a deep breath, and inside of a few seconds (5 IIRC), turn it on/off/on/off/on (without starting it! You want to go JUST to where it would be while it was running, but not far enough to crank the starter), then watch the "POWER LOSS" or "CHECK ENG" light. It will be on, go off, then start to blink.

The pattern will be like
BLINK
BLINK


BLINK BLINK BLINK BLINK BLINK
BLINK BLINK BLINK BLINK BLINK



That would be an 11, and a 55.

55 is "End of codes". If that's all you get, there's no codes stored in the ECU.

RwP
 

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So it's not tossing a code. That doesn't help much.

I'd still look at that throttle kicker.

One more thing - how old is the O2 sensor?

And lastly, have you connected a tachometer to it (I have an old dwell tachometer designed to set points on old points style cars, works a treat for the tach!) and seen how fast it's idling?

Adjustment (from the Factory Service Manual, page 14-59 and 14-60, but abbreviated a bit)

Run motor at least 2 minutes, turn it off for at least 60 seconds to allow the throttle kicker to fully engage.

Remove the wiring connector.

Connect a tachometer that can do at least 2500 RPM on a six cylinder motor.

Start the motor and let it warm up.

After it's warmed up (at 2500 RPM or so!), adjust the extension screw to between 2500 and 2600 RPM.

Shut motor off, disconnect tachometer, reconnect wiring adapter.

That's SUPPOSED to set it to the right idle speed.

Which means I probably need to do that this weekend, if it doesn't rain any, along with wires and plugs (for JustInCase, since the wires are crap on my truck.)

RwP
 

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The connector with the wiring in it.

The plug on the back of the throttle kicker, in other words.

If you look over the driver's fender to the throttle linkage, that thing hung off the front of the TBI body that has that threaded thing that the linkage is resting against is the throttle kicker - its purpose is to adjust the throttle speed as needed for cold idle or for situations like the A/C compressor kicking on.

RwP
 

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Discussion Starter #9
I know what you're talking about I call a throttle kicker I throw the position sensor I know exactly what it is now thank you I do believe the TPS sensor has gone bad I played with it earlier and it cleared it up so I'm just going to replace the whole sensor
 

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Blaketippett - Could you repost and pay attention to what you're typing? If I understand correctly, what Chrysler called the "throttle kicker" is what you call the TPS?

If so - no, the TPS is on the passenger side of the throttle body, and is different.

(And if that's not what you mean, sorry - I could not parse the phrase "I throw the position sensor" any other way.)

RwP
 

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I've seen it called that, but that's not what it is. An idle air control valve will vent air around the throttle body under ECU control.

THIS tool "kicks" the throttle.

Hence the name, "throttle kicker".

Olde skool tek it is *grins*

RwP
 

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Discussion Starter #13
i meant to type idle air control valve tps must have been on my mind...i have changed the idle and no change. i take my finger on the tab that touches the idle air control valve nut and barely push back and it starts cutting out to a near stall. i took of the idle air control valve this morning and took it apart everything inside is in great shape. i installed it back and tried again, same stuff happened. i even unplugged it and no change again...im going to do a tune up asap its raining today so no reason to tune up in the rain. i got cap, rotor, plugs and wires so as soon as it clears up i will do that and see if i have any change at all. i wonder if it has dropped a valve...i have an odd noise coming from under the hood when i let off the gas peddle sounds like metal rattling i have checked exhaust shields thats not it so i have no clue its odd for sure...im to the point i wasnt to blow this motor up and start again but at the same time it is an all original truck with 89500 miles total its flawless just making me pull my hair out and driving me insane...
 

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Either my description isn't very good, or you don't have a 1988 motor/throttle body in that truck.

Here's a pic off the Internet showing the throttle body that the 3.9 got that year:



At the right, that solenoid thing, with the wiring harness running across to the left in front of the throttle body? That's the throttle kicker.

Here's another image, the throttle kicker is right over the front spring, with what looks like a hex bolt sticking into it:



Now, if yours doesn't look like that, then yes, it's probably an IAC, and we'll have to find out what motor you've gotten grafted into the truck.

If, however, that's what you're seeing - that's the throttle kicker, there IS no IAC on the throttle body (it does the air bleed by kicking the throttle open a bit), and I have NO idea what you were cleaning and looking at!

But to get back - unplugging the IAC should cause a motor to stumble and almost, or possibly, die.

Unplugging the throttle kicker should kick RPMs up to about 2500 according to the service manual.

If unplugging whatever you have didn't make any difference, I think we've found where your problem is.

RwP
 

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Discussion Starter #16
that is the idle air control valve lookup in idler control valve for 3.9 and you'll see that same pic. I think it has gone bad I will replace it as soon as possible
 

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Well, whatever they call it, it's a throttle kicker to Chrysler. And it doesn't bleed air.

I typed how to adjust it earlier - have you tried to set it?

RwP
 

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Discussion Starter #19
When I looked it up at work (O'Reilly auto parts ) that part comes up under and idle air control valve. Indeed it does not make any difference plugged or unplugged and whoever had the truck before me broke the clup on the plug but it still makes a solid connection and I can order a new plug from work.
 

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Yes, and if you look up the front shocks on my 1991 Cougar it says "strut". Doesn't make it right. Calling the tail of a dog a leg doesn't make it a leg either. But eh. There's no air bleed, but it does kick the throttle to perform the idle speed adjustment.

Did you adjust it to 2500 RPM with it disconnected as per the factory service manual? It may just be that far out of adjustment.

RwP
 
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