Engine cuts out while driving
Thread Starter
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Fleet Mechanic
Joined: Dec 2013
Posts: 1,268
Likes: 35
From: Utica, Nebraska
Engine cuts out while driving
Was just out and about today with my girlfriend and while driving back home, the engine just randomly cutout. I pulled over to the side of the road and popped the hood just to see if something came undone. Everything is kosher. Started it back up and carried on, but while driving the rpms kept dropping low and when stopped it would drop to about 450-500rpm. So I put it in neutral and kept my foot on the gas to keep the engine up to about 1000-1500 RPM just so it wouldn't cutout. Drove part of the way home with overdrive off, even though speed limits in some areas won't let me even get into over drive.
No check engine light, no messages on the message center, nothing. Looked into it and it seems to be one of several things,
Mass Air Flow sensor
Fuel Filter
Fuel Pump
Throttle Position Sensor
Yesterday I did fill up with gas, so maybe I got a there after they filled up the tanks, no idea.
2003 Merc. Mountaineer 4.6L.
No check engine light, no messages on the message center, nothing. Looked into it and it seems to be one of several things,
Mass Air Flow sensor
Fuel Filter
Fuel Pump
Throttle Position Sensor
Yesterday I did fill up with gas, so maybe I got a there after they filled up the tanks, no idea.
2003 Merc. Mountaineer 4.6L.
Logistics Pro
Joined: Jun 2009
Posts: 4,817
Likes: 83
From: Cedar Rapids, IA
Do you have access to a scan tool with datastream mode? Is so, and assuming you can duplicate the issue, I'd suggest datalogging to see if there are any sensors that are giving an atypical response.
The low RPM could be something as simple as a misfire or vacuum leak. You might also want to perform a tune up and make sure there are vacuum lines that are cracked, split, or disconnected.
-Rod
The low RPM could be something as simple as a misfire or vacuum leak. You might also want to perform a tune up and make sure there are vacuum lines that are cracked, split, or disconnected.
-Rod
Thread Starter
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Fleet Mechanic
Joined: Dec 2013
Posts: 1,268
Likes: 35
From: Utica, Nebraska
Outside of going to an auto store, I do not have access to a scanner. Would take it to a shop, but the ones I know of have screwed us over in the past. It's possible it could still go low rpm while idling in a parking lot, so I may try a parts store one. Worth a shot.
Thread Starter
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Fleet Mechanic
Joined: Dec 2013
Posts: 1,268
Likes: 35
From: Utica, Nebraska
Borrowed Oriley's scanner and it pulled zero codes. So far talking with them it's either IAC or one of a few vacuum lines. I told them that a while back over a month ago, it would rev up to 2000rpm while in drive or in park, so they are thinking that it is the IAC. The bogging down to 500rpm then cutting out just started yesterday. It hasn't randomly revved up in a while either, just drops down.
Another thing I have to add is, while coasting, instead of slowly dropping rpm, it goes from whatever RPM I'm at while in cruise control then just drops down to about 450-500rpm.
Another thing I have to add is, while coasting, instead of slowly dropping rpm, it goes from whatever RPM I'm at while in cruise control then just drops down to about 450-500rpm.
Thread Starter
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Fleet Mechanic
Joined: Dec 2013
Posts: 1,268
Likes: 35
From: Utica, Nebraska
Well just cleaned the IAC valve and the MAF sensor and it did nothing. Got it started and it would only idle to 500 rpm after sitting for an hour and a half. It started normally like it would as a cold start, then as it ran it dropped to 450-500rpm again.
Still no codes coming up. So either that idle control valve is shot, fuel filter needs to be changed or the fuel pump is going out.
Edit: Before I wasn't sure how the actual idle was but when I did turn it back on and it was running low rpm, it was misfiring a bit. Couldn't feel it but you could hear it. Before would tell because it's a very quiet engine, but with the hood up yeah it's miss firing a bit.
Still no codes coming up. So either that idle control valve is shot, fuel filter needs to be changed or the fuel pump is going out.
Edit: Before I wasn't sure how the actual idle was but when I did turn it back on and it was running low rpm, it was misfiring a bit. Couldn't feel it but you could hear it. Before would tell because it's a very quiet engine, but with the hood up yeah it's miss firing a bit.
Thread Starter
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Fleet Mechanic
Joined: Dec 2013
Posts: 1,268
Likes: 35
From: Utica, Nebraska
I'm at a complete loss here on what could be causing this. There is no signs of it being the fuel pump and there are no codes coming up. I pulled a spark plug and the wire was kind of a bright white.
Thread Starter
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Fleet Mechanic
Joined: Dec 2013
Posts: 1,268
Likes: 35
From: Utica, Nebraska
For future reference, it was the IAC (Idle Air Control) valve that was causing the issue. $80 at O'Riley's. Runs much better, just on start up it idles at 2,000 then drops to where it needs too. Doesn't fall on its face while coasting, just drops gradually and doesn't cutout while stopped either.
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Fleet Mechanic
Joined: Dec 2013
Posts: 1,268
Likes: 35
From: Utica, Nebraska
So it's been a bit, but after I replaced the idle air control valve it has started to rev at 1600rpm and it takes quite a bit longer to drop to its normal range. Then while driving, whenever I come to a complete stop then engine is still running over 1200rpm and then abruptly drops to normal load rpm. After I park and shut it off for about a half hour to an hour even, when I start it up, the engine idles at 2500rpm. Gas pedal isn't sticking...just happened after I replaced the valve. Vacuum lines are not cracked in anyway nor feel spongy.
This has really cut the fuel economy significantly...use to get 16.9mpg with my mix driving, now I'm lucky to get 16.2mpg. Did it mess up the tuning of the engine and needs to be retuned?
This has really cut the fuel economy significantly...use to get 16.9mpg with my mix driving, now I'm lucky to get 16.2mpg. Did it mess up the tuning of the engine and needs to be retuned?
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Logistics Pro
Joined: Jun 2009
Posts: 4,817
Likes: 83
From: Cedar Rapids, IA
Have you cleaned the throttle body, paying particular attention to the back side of the throttle plate? If not, I'd suggest that you remove the throttle body and clean it real well. It's possible there is a build up of carbon preventing the throttle plate from closing fully. Also, if you bought the truck used, it's possible that a previous owner adjusted the throttle plate a bit to compensate for a faulty IAC servo.
Other things to try include resetting the Keep Alive Memory (KAM), replacing the spark plugs, and performing a cylinder decarb using SeaFoam through a vacuum line.
-Rod
Other things to try include resetting the Keep Alive Memory (KAM), replacing the spark plugs, and performing a cylinder decarb using SeaFoam through a vacuum line.
-Rod
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Fleet Mechanic
Joined: Dec 2013
Posts: 1,268
Likes: 35
From: Utica, Nebraska
When I changed the IAC, I did spray a full can of throttle cleaner, changed all 8 plugs with proper gapping, added a can of SeaFoam through the gas tank (haven't tried the vacuum line type yet). Before I changed it and before it started acting up, everything was fine. Except for the couple times where it would rev over 1500rpm while stopped and in drive...did it in the drive-thru lane and scared the crap out of me.
The PO only brought the vehicle in for basic maintenance and one month after they bought it, hit a deer with it, so the panels on the passenger side in the front were replaced. When I took the old IAC off, I looked up the part number and its a Delphi part number...not sure if that's OEM but here's the original part number from the one I pulled; ABV509-T1 LA. The only thing I could think of is that it not being a Ford OEM (the new one) that its screwing with the control module tuning, but I have my doubts.
Like before, this is not bringing up any codes, so a scanner will be worthless. Never heard of doing a KAM reset (hardly anything that is brought up on here or any other forum), I did find this from FordTech
The PO only brought the vehicle in for basic maintenance and one month after they bought it, hit a deer with it, so the panels on the passenger side in the front were replaced. When I took the old IAC off, I looked up the part number and its a Delphi part number...not sure if that's OEM but here's the original part number from the one I pulled; ABV509-T1 LA. The only thing I could think of is that it not being a Ford OEM (the new one) that its screwing with the control module tuning, but I have my doubts.
Like before, this is not bringing up any codes, so a scanner will be worthless. Never heard of doing a KAM reset (hardly anything that is brought up on here or any other forum), I did find this from FordTech
Logistics Pro
Joined: Jun 2009
Posts: 4,817
Likes: 83
From: Cedar Rapids, IA
Hmmm, FordTech puts out some pretty good information, so this may do the same as clearing the KAM from a scan tool. Worth a try anyway.
Also, if you have a scan tool versus just a code reader, you can monitor various parameters like fuel trims, MAF flow rate, engine coolant temperature, etc. to attempt to catch a sensor that is reporting something other than what's expected, even though no diagnostic codes are being reported. You can also check for pending diagnostic codes that have not occurred enough yet for them to be set as hard codes.
When you replaced the IAC did you check to make sure there was no gasket residue left on the sealing surfaces? The symptoms you describe seem like they could be from an intermittent vacuum leak, but I'm struggling to understand why they never cause a rough or low idle.
-Rod
Also, if you have a scan tool versus just a code reader, you can monitor various parameters like fuel trims, MAF flow rate, engine coolant temperature, etc. to attempt to catch a sensor that is reporting something other than what's expected, even though no diagnostic codes are being reported. You can also check for pending diagnostic codes that have not occurred enough yet for them to be set as hard codes.
When you replaced the IAC did you check to make sure there was no gasket residue left on the sealing surfaces? The symptoms you describe seem like they could be from an intermittent vacuum leak, but I'm struggling to understand why they never cause a rough or low idle.
-Rod
Thread Starter
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Fleet Mechanic
Joined: Dec 2013
Posts: 1,268
Likes: 35
From: Utica, Nebraska
The mating surfaces for the gasket did look clean, but I never did spray anything and wiped it down. Unfortunately I do not have access to any kind of tuner, let alone a scanner either. Only ones I know that could have one, are into carburetor and OBD-I generation vehicles, so they would not have one.
I'll give the trick a try, can't hurt to try.
I'll give the trick a try, can't hurt to try.
Freshman User
Joined: Jul 2012
Posts: 40
Likes: 0
From: Black River Falls,Wi.
93 ford Exployer 4.0
I have the same thing going on with my 4.0 5 speed.Under full throttle runs good.Normal driving runs rough,miss fires,and poor gas mileage.I am putting a set of new plugs and wires on today.I am leaning toward a fuel issue as the last owner put an in line fuel pump on that is not hooked up now.Trying to figure out if it is electrical?
Freshman User
Joined: Jul 2012
Posts: 40
Likes: 0
From: Black River Falls,Wi.
93 ford Exployer 4.0
I have the same thing going on with my 4.0 5 speed.Under full throttle runs good.Normal driving runs rough,miss fires,and poor gas mileage.I am putting a set of new plugs and wires on today.I am leaning toward a fuel issue as the last owner put an in line fuel pump on that is not hooked up now.Trying to figure out if it is electrical?
Freshman User
Joined: Jul 2012
Posts: 40
Likes: 0
From: Black River Falls,Wi.
I have the same thing going on with my 4.0 5 speed.Under full throttle runs good.Normal driving runs rough,miss fires,and poor gas mileage.I am putting a set of new plugs and wires on today.I am leaning toward a fuel issue as the last owner put an in line fuel pump on that is not hooked up now.Trying to figure out if it is electrical?