Weird idle, then engine suddenly stalled
- Thread starter vanion2
- Start date
jeremyc74
Banned
It's a strange problem. I'd be interested to know if it's the A/C compressor that's causing the issue, or if it's the electrical load.
If you can replicate the problem, try turning the A/C off, but running the fan on high (and headlights for good measure) and see if it does the same thing. I could see a very low voltage situation causing some strange issues, but you should be seeing a battery light if that's happening, telling you the alternator isn't charging.
It's possible the alternator has several bad diodes in it and is producing a lot of AC ripple that's screwing with the ECU, but I'd say that's a long shot. The other possibility is that your A/C compressor is starting to seize up, but that would typically make a considerable amount of noise when it happened, and you'd likely hear the belt slipping before it actually killed the engine.
It's an interesting problem. Let us know what it turns out to be.
op2:
If you can replicate the problem, try turning the A/C off, but running the fan on high (and headlights for good measure) and see if it does the same thing. I could see a very low voltage situation causing some strange issues, but you should be seeing a battery light if that's happening, telling you the alternator isn't charging.
It's possible the alternator has several bad diodes in it and is producing a lot of AC ripple that's screwing with the ECU, but I'd say that's a long shot. The other possibility is that your A/C compressor is starting to seize up, but that would typically make a considerable amount of noise when it happened, and you'd likely hear the belt slipping before it actually killed the engine.
It's an interesting problem. Let us know what it turns out to be.
op2:
LittleCaesar
New member
Make sure the ground bolt by the diagnostics box for the ABS under the hood is tight. Also check the battery connections. Definitely sounds electrical in nature.
The voltage is fine by the way, unless you feeling like throwing money at an alternator.
The voltage is fine by the way, unless you feeling like throwing money at an alternator.
It wasnt solved..
I know it isnt throwing a CEL light but have you ran the scan tool? Intermittent issues usually will flash and get logged.
vanion2
New member
Yes I ran the scan tool. Literally right after it stalled trying to catch a code without touching anything (well except the brakes after I coasted of to the side of the road).
4Reak Show
New member
Easy check and likely solution
The one thing this entire symptom has in common is the throttle body. Somebody mentioned "a/c idle up valve" and this isn't entirely inaccurate. The fly by wire systems sometimes use the throttle blade motor to change the idle. I know for a FACT the 4.7 V8's do. Also, it dying at a stop light Leads me to the throttle blade motor once again or the IAC (idle air control) depending on which one it has. (I see a lot of cars every day and it's hard to remember which one is equipped with which system)
At any rate I would do 2 super easy cheap quick things: 1) remove the air intake tube going to the throttle body and manually move the throttle blade and clean the entire thing. The best way is with a rag/towel soaked in brake parts cleaner and really get 2-3 fingers in there all around the blade. You want the blade and throttle body to be as close to pristine as you can make it. Both sides of the butterfly if possible, and get the build up off the ridge/lip of it. Seen carbon build up cause these trucks to die and also act funny with NO codes ever. 2) if it has a separate IAC valve, clean that as well. It requires removing some factory epoxy which seals 2 screws. (You see a beige colored item directly below the throttle body opening, that's the IAC). When you remove the 2 screws it allows you to remove the electric motor portion of the valve so you can manually rotate it and really get the cleaner into the ports. If you need a picture I can take some when I get home and show you what I mean. I've had a lot of success on Toyota products cleaning the IAC passages. Let us know what you find out.
The one thing this entire symptom has in common is the throttle body. Somebody mentioned "a/c idle up valve" and this isn't entirely inaccurate. The fly by wire systems sometimes use the throttle blade motor to change the idle. I know for a FACT the 4.7 V8's do. Also, it dying at a stop light Leads me to the throttle blade motor once again or the IAC (idle air control) depending on which one it has. (I see a lot of cars every day and it's hard to remember which one is equipped with which system)
At any rate I would do 2 super easy cheap quick things: 1) remove the air intake tube going to the throttle body and manually move the throttle blade and clean the entire thing. The best way is with a rag/towel soaked in brake parts cleaner and really get 2-3 fingers in there all around the blade. You want the blade and throttle body to be as close to pristine as you can make it. Both sides of the butterfly if possible, and get the build up off the ridge/lip of it. Seen carbon build up cause these trucks to die and also act funny with NO codes ever. 2) if it has a separate IAC valve, clean that as well. It requires removing some factory epoxy which seals 2 screws. (You see a beige colored item directly below the throttle body opening, that's the IAC). When you remove the 2 screws it allows you to remove the electric motor portion of the valve so you can manually rotate it and really get the cleaner into the ports. If you need a picture I can take some when I get home and show you what I mean. I've had a lot of success on Toyota products cleaning the IAC passages. Let us know what you find out.
vanion2
New member
I'll give it a shot and let you know. I have had to clean IAC's before on other vehicles and cleaning the TB blade shouldn't be too hard once I get the intake hose out of the way.
ajonesnv
New member
This was going to be my guess...the IACM needs cleaned or replaced.
Mine is doing the same and I have the problem isolated to when the truck is warm from a full commute of driving in the heat. AC has no bearing on its actions. I have been feathering the pedal at stop lights when it starts to happen.
It seems to first drop idle way low, like into the 500's, and then jumps up to 900-1000 to eventually stall. A Toyota mechanic directed me to the IACM as the most likely cause of the problem.
Mine is doing the same and I have the problem isolated to when the truck is warm from a full commute of driving in the heat. AC has no bearing on its actions. I have been feathering the pedal at stop lights when it starts to happen.
It seems to first drop idle way low, like into the 500's, and then jumps up to 900-1000 to eventually stall. A Toyota mechanic directed me to the IACM as the most likely cause of the problem.
He said he had hesitation at 55mph though which would be weird for a IACV. But the first symptom hesitation when ac turn on is a common with IAC. When under strain it tend to buck and possibly stall the car. With IACV you usaully get bouncing rpm at idle. OP hasnt mention that. You have no issues when cold it seems like this is when most IAC issues are.
You have a scan tool did you read where the IAC count was?
Curious were your odometer still moving when your rpm jump? Did you see lany other strange symptoms.
The problem is intermittent and when you ignore the a/c coincindence it can be a whole host of things.
ajonesnv
New member
Yea, your right...I thought he mentioned it happening at the idle as well.
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Out of curiosity OP when were your plugs checked last?
Odometer? No, its happens only at idle so Im not moving...the tachometer is moving with the corresponding RPM's. Or was this questioning for OP?
vanion2
New member
I did mention the rpm rapidly roams from 1k-2k rpm at idle or off throttle when it starts misbehaving. The problem occurs regardless of whether the engine is warmed up or not.
I just had new plugs and wires installed at the beginning of last month so I highly doubt that is the problem.
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vanion2
New member
From both posts stating the problem. I admit I didn't specify this happening in off throttle/idle situations though so I can see how it could be misinterpreted.
Did you ever get it figured out?
vanion2
New member
Not yet. Taking it to a mechanic in about 15 minutes. I promise to update once this gets resolved but I wouldn't expect an answer until next week because it has to act up at the shop and when I drove it this morning it was behaving again.
vanion2
New member
Well what?
Just kidding. I got it back from the mechanic this afternoon and here is what he did.
Cleaned the hot wire, the throttle blade, the battery terminals (at my request), checked the ECU for codes, and some other little things.
He said the hot wire and blade were pretty dirty. His biggest concern though was my ECU scanner. He said he has seen several of those Progressive insurance ones that were causing problems with the ECU's and there is a class action suit in progress. Mine is just a blue tooth scanner I use for my Torque app but he strongly suggested I leave it off until it acts up again to be sure. If that doesn't eliminate the problem he thinks it means the IAC might be bad. Here's the kicker. The 2001,2002 models have the IAC assembled as part of the throttle body which means the whole thing would have to be replaced. $1200 shop price.
I am hoping at this point it was just the dirty hot wire and blade. If it doesn't act up again in the next two weeks I will hook up the scanner again for a road trip I have planned and see what happens.
The good news is it only cost me $52 to get all that done so at least the shop is honest. After all, they could have just tried selling me a new throttle body.
Just kidding. I got it back from the mechanic this afternoon and here is what he did.
Cleaned the hot wire, the throttle blade, the battery terminals (at my request), checked the ECU for codes, and some other little things.
He said the hot wire and blade were pretty dirty. His biggest concern though was my ECU scanner. He said he has seen several of those Progressive insurance ones that were causing problems with the ECU's and there is a class action suit in progress. Mine is just a blue tooth scanner I use for my Torque app but he strongly suggested I leave it off until it acts up again to be sure. If that doesn't eliminate the problem he thinks it means the IAC might be bad. Here's the kicker. The 2001,2002 models have the IAC assembled as part of the throttle body which means the whole thing would have to be replaced. $1200 shop price.
I am hoping at this point it was just the dirty hot wire and blade. If it doesn't act up again in the next two weeks I will hook up the scanner again for a road trip I have planned and see what happens.
The good news is it only cost me $52 to get all that done so at least the shop is honest. After all, they could have just tried selling me a new throttle body.
Nice, hard to find honest shops now a days. If your maf was that dirty and blade I can see it causing those issues. Do you have a K&N filter? Those are fine just needs to be clean often. This is what I have and notice this get covered in dirt faster.
LittleCaesar
New member
I did not know Flo sold ECU scanners though at this point I wouldn't be surprised. I'd love to see a pic of one if you can find one. Leave yours plugged in, no harm no foul.
If it is the IAC, then find a junkyard at Car-Part.com--Used Auto Parts Market nearby.
vanion2
New member
Straight up stock filter. If I were to put in a higher flowing one it would be a dry filter by preference.
Progressive doesn't sell them. They use them as monitoring devices to track speed and such for people who want deeper discounts on their insurance. Not something I would be willing to do.
I will be driving the 4Runner a lot over the next two weeks to see if it does it again because I have a planned road trip and want to make sure this issue is locked down one way or another. Hopefully it's not the IAC but if it is then I will definitely use the link you posted since they are ranging from $200-$360 there.
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