Hello,

I have a 2001 Taurus 3.0 that has developed a rolling idle. :banghead: The idle speed goes from around 500 then up to 1000 down to 300 and all over. Followed shortly by a stall. I took it for a test drive tonight and it stalls when sitting at a light, but only after the the idle surges. If I do the two foot brake / gas pedal juggle, it stays running but rough! Seems OK at highway speeds. When I came home, I put in park and it was still there. Revved to 3500 rpms and it started cutting out and popping.

My guess would be fuel supply, but I don't like to shotgun parts. Took to autozone and they found 4 codes~

P-1151
P-1131
P-0171
P-0174

The guy at the counter said " 95% of the time its the MAF sensor" and showed me some book that they gave him after his training process!!! Any suggestions out there? Fuel pump quoted at 459.00, MAF 239.00, OUCH!!!!!

Thanks

Al

Do you hear a "sucking sound." If so, check all the egr, pcv and vacuum hoses for leaks. I found a rotted hose under the throttlebody (pcv hose), was free from Autozone cause the piece was under a foot long and he had previously led me on a goose chase with the codes. Only had the p0171 and p0174. Check for the noise. If you do need an MAF they can be bought for much less. Try rockauto.com or ebay. Never priced a fuel pump. Won't it throw a seperate code for low fuel pressure?

This does sound like a vacuum-related problem.

Do you happen to have a K&N or similar oiled air filter? If so, the MAF sensor elements may just be coated with contaminants due to the oil from the filter. You can carefully remove the MAF sensor and very carefully clean the reference element and sensor element. In the process, make sure that all the air intake hoses are tight and in good condition. If there is unmetered air entering the engine due to a loose hose connection, etc, it could cause symptoms similar to what you describe.

Also, if your EGR valve is not closing completely at idle, it could cause the stalling. If you have access to a vacuum pump, pull a vacuum on the EGR valve with the engine running at idle and see what happens. If the car acts differently, then this may not be the problem. If the engine continues to run the way you describe, then I'd suggest starting by removing the EGR valve and cleaning it and the passages for it. With it off the car, use the vacuum pump again and make sure the valve moves and that the diaphragm holds a vacuum.

Before condemning the MAF sensor, since you don't want to shotgun parts, find a scan tool with the datastream function and monitor the MAF sensor flow readings while driving the car to see if they are within specification. I would certainly try cleaning it before replacing it though.

-Rod

I am guess ohc?
Will it die if the over drive is off?

If not then I would be looking into a vaccum problem such as EGR, PVC or routing manifold problem and even it does die with overdrive off I would still look into it being a vaccum problem. Also take a piece of tubing after you hear the popping sound and listen for hissing towards the back of engine under the throttle body area.

Also don't go to AutoZone/ABC Auto they charge markups that often time exceed the dealership. I prefer O'Reilly or Napa.

Fuel Pump $215.

DOHC MAF: $125.50 + $75 core.
OHV MAF: $195.00 + $75 core.

I missed your comment in the original post that revving to 3500 in park the engine starts to cut out an pop. This is normal. The PCM incorporates a rev limiter in Park and Neutral to prevent one from over-revving the engine.

-Rod

Following are the diagnostic steps for the P1131 and P1151 codes from the factory service manual:

Electrical:
Short to VPWR in harness or HO2S
Water in harness connector
Open/Shorted HO2S circuit
Corrosion or poor mating terminals and wiring
Damaged HO2S
Damaged PCM
Fuel System:
Excessive fuel pressure
Leaking/contaminated fuel injectors
Leaking fuel pressure regulator
Low fuel pressure or running out of fuel
Vapor recovery system
Induction System:
Air leaks after the MAF
Vacuum Leaks
PCV system
Improperly seated engine oil dipstick
EGR System:
Leaking gasket
Stuck EGR valve
Leaking diaphragm or EVR
Base Engine:
Oil overfill
Cam timing
Cylinder compression
Exhaust leaks before or near the HO2S(s) For the P0171 and P0174, look into:
For lean and rich DTCs:
Fuel system
Excessive fuel pressure.
Leaking/contaminated fuel injectors.
Leaking fuel pressure regulator.
Low fuel pressure or running out of fuel.
Vapor recovery system.
Induction system:
Air leaks after the MAF.
Vacuum Leaks.
PCV system.
Improperly seated engine oil dipstick.
EGR system:
Leaking gasket.
Stuck EGR valve.
Leaking diaphragm or EVR.
Base Engine:
Oil overfill.
Cam timing.
Cylinder compression.
Exhaust leaks before or near the HO2Ss Since you're getting matching codes for both cylinder banks, the problem is likely common to both, such as a vacuum leak, problem with the air intake hose, MAF sensor, PCV, EGR, etc. Compare the two lists, see what's common between them, and go from there.

-Rod

The same thing happened to my Ford. It was the crank sensor

Also had a taurus with the same problem. I pretty sure it's the idle air control valve you need. This part controls the speed of idle and when it goes bad it will cause your rpm to go up and down. And the reason why your car is normal at highway speeds is because this valve does not effect anything other than idle speed. What I'm tryin to say is it's definetely your idle air control valve, because if it was your mass air flow sensor (MAF) than you would have problems at all speeds not just idle speeds. Hope this helps.:licka:

Also had a taurus with the same problem. I pretty sure it's the idle air control valve you need. This part controls the speed of idle and when it goes bad it will cause your rpm to go up and down. And the reason why your car is normal at highway speeds is because this valve does not effect anything other than idle speed. What I'm tryin to say is it's definetely your idle air control valve, because if it was your mass air flow sensor (MAF) than you would have problems at all speeds not just idle speeds. Hope this helps.:licka:

Well, not necessarily. The codes P1131 and P1151 indicate that both cylinder banks are lean (ie: too little fuel for the amount of air). The Idle Air Control (IAC) valve increases and decreases the amount of air that bypasses the throttle plate. To cause a lean condition, the IAC would need to fail in an open condition. Also, there are codes, such as a P0505, to indicate problems with the IAC system.

Does the idle speed change when the air conditioning is turned on? How about when you turn the steering wheel to one of the locks? If is does, the IAC is likely working. This may be hard to determine since idle fluctuates, but if it doesn't kill the engine immediately due to the increased load, I'd suspect that the IAC is still functioning.

Since you don't want to shotgun parts, start with the inexpensive, simple things such as vacuum. If you can find a scan tool with datastream mode, you will be able to monitor desired idle speed, current idle speed, HO2S response, and crankshaft position sensor. All 4 of the diagnostic codes your car is reporting are related (lean conditions on each bank) so I would certainly focus on the items outlined for them.

-Rod