99 Taurus SE dohc 24v engine stutter

Taurusguy87 · 09-21-2007, 01:48 PM

Hey new here

, over the summer i picked up the Taurus with just over 100k miles, everything is stock as far as i know. For a while there were no detectable problems, but recently at idle the engine will stutter and the rpms drop below the normal idle. It is not right at start up though, because the idle runs higher at the time which i assume is normal. The problem occurs every time at idle after that though, and it seems to be increasing becuase low rpm acceleration is starting to feel a little unstable as well. There is no other indicators though, like the check engine light does not come on at any time.

help/suggestions

thanks

jfjohn · 09-22-2007, 09:23 AM

check all your vacuum hoses for cracks

Alastar Dragonfly · 09-24-2007, 03:29 PM

As an owner of said vehicle that had the same problem. Check this specific vaccuum hose. Look on the left(drivers) side of the engine, where the air intake tube connects the intake to the filter box. Remove the tube and look directly under the inlet and there is a "U" shaped piece of hard moulded rubber tubing. Where it is gets hot and the hard rubber tends to get brittle and crack open. I've seen them split lengthwise on the inside of the "U" and you can not see it. You have to phyusically remove the piece in order to see it most of the time. I have replaced 2 of them in the little over 6 years of owning the car.

Taurusguy87 · 10-05-2007, 10:41 AM

I had checked the vacuum lines and found nothing, but i will go over that specific one again as well thanks for pointing it out. Ive noticed another thing, the problem seems to fluctuate now. On days that are not to hot and humid the problem is less noticable. But on one hot day i was stuck on the freeway for an hour or so and it got really bad, to the point it would stumble while accelerating all the way up to 3gs on the tach. But, the next day it wasnt as bad. So, are there any electronics issues that would cause this problem?

jonmark1985 · 10-05-2007, 10:51 AM

Plug wires

jfjohn · 10-07-2007, 06:16 PM

what about fuel pressure? fuel filter?

jahtherock · 11-09-2007, 10:58 AM

Had the same issue with my '01 taurus, ended up being the IAC (idle air control) valve. Located on top on the intakemanifold about 12'' up from the Mass airflow sensor.

T_digger · 11-10-2007, 06:18 PM

Problem still a mystery. To summarize. The engine always starts fine. It idles rough hot or cold (like random misfiring). Brake torque slightly and the roughness goes away. Light acceleration is usually OK. Medium acceleration is usually (not always) awful (hesitation and rough running). WOT is solid after initial hesitation. Cruise is fine. However, shift into neutral while cruising and the RPMs go up slightly. Is that right ?
Checks done:

Plugs - look great.
Vacuum leaks - unable to find any.
Tested MAF, IAC, IAT sensors. All OK. Swap with known good.
Check MAF voltages - do not match A.Z. specs.
(14, 4.5, and .34 - 1.96) mine are (14, 1, and almost 0)
don't know which wire is SIG or SIG RTN (tan or lt blue)
unable to confirm specs. Seems bad specs should produce codes anyway.

Did not suspect fuel filter because WOT was solid. Will do that next anyway.
If problem is not solved - will replace PCV valve.
I believe the fuel system and plug wires should also be suspected.
Sure would like to figure out the problem before replacing parts. $$$ are tight.
That's the latest in this saga.
Anyone?

T_digger · 11-13-2007, 03:36 PM

Changed fuel filter. NO change to running problems.

Slightly discolored fuel (very light brown/red) drained from the OUT side of the old filter. Don't know what that means.

Components changed or ruled out by testing:

* Fuel filter
* MAF sensor
* TPS
* IAC
* Air temp sensor

Aggravation. I'm just guessing with guidance from AZone trouble shooting guidelines.

I guess plugwires, PCV valve, or EGR valve could be next.

T_digger · 11-13-2007, 03:44 PM

Possible MAF sensor issue?

I had a voltmeter, so I performed the checks outlined in the AZone trouble shooting guide.

MAF sensor voltage testing.
Voltage checks with DVOM:

* Key ON - engine OFF; 10.5 volts from RED to GND (OK)
* key ON - engine running; 1 volt from LT BLU to GND (???),
* key ON - engine running; near 0 volts from TAN to GND (???)

According to Autozone:

key ON eng Off, VPWR (red) to ground is 10.5 volts
key ON eng running, SIG to ground is 4.5 volts & SIG RTN to ground is .34 - 1.96 volts.

So what do I really have? Is AZone correct? Is my system OK? Do I have something wrong?