2010 v6 base idle problem

Iamsupernova

New Member
Jan 3, 2020
8
0
1
36
Houston
Having an idle problem. Normal idling the RPMs don't hold steady, they kinda bounce around between 700-750. Can't ever recall a car where they did that but it's not varying by much either. The real problem is while idling occasionally they'll bounce around between 200 to 1k plus and the car shudders really badly and half the time dies soon afterwards.

So far I've changed the spark plugs and wires, the fuel filter, cleaned the throttle body, the EGR valve, the PVC valve, used starter fluid on all the vacuum lines to check for leaks (none I can find).

I did have a p0402 engine code, but after cleaning the EGR it never came back. Been about 500 miles since that, no other codes.

Only happens at idle, if I give it a little throttle it idles just fine. No rough running.
 
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cbxer55

Active Member
Jan 25, 2020
293
60
38
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Oklahoma
Most often, the IAC is the culprit when idle problems occur. It is the device that actually maintains the idle, controlled by the computer. My 98 Ranger used to eat the damn things for lunch, El Cheapo parts from Auto Zone. Once I saw they had a premium part, made by Hitachi in Japan, it's become a non-issue. I put it on in 2015. My 04 Lightning has had three in the 10 years I've owned it. Like the Ranger, put the Hitachi part on it three years ago, no more problems.

Yes, when bad the idle fluctuates by a couple hundred rpms. Sometimes bad enough to cause the engine to stall. On the Lightning, due to it's intake dynamics, blower and huge plenum where the IAC is located, it makes a weird sound that is akin to a cow mooing. Totally freaks you out when you hear it. LMAO!!

I don't know where the IAC is located on the 4.0 V-6. I'd go out and look at mine, but is's pouring rain and cold. It's in a separate garage, so I just don't want to go out there today.
 

Iamsupernova

New Member
Jan 3, 2020
8
0
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36
Houston
Went to orielys to see about getting one, and they can't find one for my car. Someone on this other forum says these cars don't have one either: https://mustangforums.com/forum/2005-2014-mustangs/683004-idle-air-control-valve-help-locating.html

I know a little about cars, been doing basic repairs for about 15 years, but I don't know enough to look at an engine and identify an IAC. If you could find it on your car or show me a picture of one that definitely is to my car I can probably locate it. Otherwise it looks like I need to be looking at the TPS. Cuz I've done everything else I can think of aside from having my fuel injectors cleaned professionally.
 

cbxer55

Active Member
Jan 25, 2020
293
60
38
60
Oklahoma
Yeah, it may not have one. Since the car uses fly-by-wire throttle, the computer may be controlling the idle through the servo motor that opens and closes the throttle when you move your foot. I've looked at the throttle body on mine, and not even sure it has a TPS. If I get the chance, I'll go look at it this afternoon before I have to go to work. Maybe, possibly, the device that moves the throttle plate on yours is bad. Has to be some kind of servo motor that responds to your foot movement. I'm not too terribly familiar with this type of throttle control. Also don't like it a whole bunch. I don't know if it';s just mine, but it's hard to get a snail start. It's more like VRoom, here we go. If it was slick outside, it would be rough.
 

Iamsupernova

New Member
Jan 3, 2020
8
0
1
36
Houston
I don't have much of a problem with slow starts. I have an issue with it not going when I press the gas pedal. There's always like a 1-2 seconds delay, even if I floor it. I don't like that. I read someone's tutorial on how to remedy it but it involves modifying the gas pedal and I'm not gonna do it until I buy a second one just Incase I screw it up.

It has a TPS. I can find the part online for that. It's like 70 bucks which I don't have right now. That's why I've been doing all the cheap easy stuff. Hoping it was one of those things.
 

cbxer55

Active Member
Jan 25, 2020
293
60
38
60
Oklahoma
Yeah, mine has that delay too. It's odd when you're used to the quicker response from a good old fashioned cable throttle. Both my Ranger and Lightning have this, and a quicker response than stock only requires the use of a zip tie around the throttle linkage to take the slack out of the cable. Than VRoom, off to the races. With the Mustang, I have to wonder if those behind me are waiting for me to go, when trying to make a casual start, rather than a VRoom start. LOL!!
 

Iamsupernova

New Member
Jan 3, 2020
8
0
1
36
Houston
Bump with error codes..

P2196: O2 Sensor Signal Stuck Rich (Bank 1 Sensor 1)
P0616 Starter Relay Circuit Low

Today car died going 40 down the freeway in heavy traffic. I was coasting so RPMs were still low. It's also happening more frequently, and yesterday the wrench icon came in which is apparently "limp home mode".

Any ideas? Don't want to just haul off and replace the O2 sensors cuz I know it could still be other things.
 

cbxer55

Active Member
Jan 25, 2020
293
60
38
60
Oklahoma
Bump with error codes..

P2196: O2 Sensor Signal Stuck Rich (Bank 1 Sensor 1)
P0616 Starter Relay Circuit Low

Today car died going 40 down the freeway in heavy traffic. I was coasting so RPMs were still low. It's also happening more frequently, and yesterday the wrench icon came in which is apparently "limp home mode".

Any ideas? Don't want to just haul off and replace the O2 sensors cuz I know it could still be other things.

The wrench icon is just the newest and greatest version of the Check Engine Light. Pay it no mind and keep driving. Mine comes on occasionally for P0300, Random misfire. I replaced coils, plugs and wires, checked fuel pressure. All that's left I guess is plugged injectors. I'm running some cleaner in it now. But honestly, the old plugs looked fine, all identical, no indication anything is amiss. And it runs GREAT!

My 98 Ranger has been running with a piece of black tape over the CEL for years. Nothing amiss. I just gave up on the POS and I'll keep driving it til it goes BOOM! Then off to the scrapper yard with it. No smog or safety checks where I live, so no biggie.
 

Iamsupernova

New Member
Jan 3, 2020
8
0
1
36
Houston
I have a new symptom now. At under about 20 mph now it won't go. Even if I floor it, the acceleration is not there. It's like my car is powered by a go-kart engine or something. Once I get above 20 it will take off like a rocket like it's supposed to. Does any of this nature it down? Right now as far as I know it could be TPS, o2 sensors, fuel pressure, MAF sensor, throttle body, fuel injectors, and maybe a couple of other things. I really need ideas here. I know it was said when this is an issue it's usually IAC, but to the best of my research, this car doesn't have one.