Ford Taurus Severe Hesitation

[tblake]

Hey Guys!

Switching gears over to the Ford forums for a bit (please be gentle)....

My cousin owns a 1998 (I believe) ford taurus with 150,000 miles on it. It has the 3.0 V6 24valve DOHC motor in it.

He stopped by today and asked me if I would take it for a test drive. The first thing i noticed was the "Service Engine Soon" light was lit. Apparently it had been on for some time.

So i started the car, started fine, idled ok, when I put it in drive and hit the gas, it hesitated, then lurched forward, then hesitated again, and finally went. Once you get it moving, it drives fine. Once you stop, and try to go it hesitates. I also noticed that while coming to a stop, it acts up. It seems as though you are driving a manual and not releasing the clutch when you come to a stop.

Thinking maybe a stuck TCC, I put the car in 1st Low and took it for a drive, the same thing, severe hesitation.

When I got home, I plugged in my OBD2 scanner and pulled these codes: P1744, P0135, P1131, P1504. The scanner didnt really give any descriptions of the codes other than the O2 sensor heater circuit.

I also checked out the obvious things, Plug wires look good, plugs are motorcraft, but were replaced at the dealership about 50k ago. I also unplugged the bypass (iac) motor and started it. The car idled low, and when I plugged it back in, idle jumped back up to normal. (so I assume its working). I then removed the MAF and cleaned it with some MAF cleaner and a q-tip. Same deal.

One other thing I should note is that when ideling with the AC compressor running (defrost), the car will idle at about 900-1000, then randomly will increas in RPM's to 1500-2000 and slowly go back down to 900-1000. It will keep doing this in conjunction with the compressor cycling on and off. When the Defrost or AC is not on, it will not have this idle problem..... ODD

I have worked on a few 3.0 V6 ford motors and rebuilt a couple. One past 3.0 motor I worked on in a Ford van had a problem similar to this. It had a severe hesitation that was fine after the RPM's were increased. That issue turned out to be the timing belt had skipped a cog on a camshaft. I'm almost wondering if this is the same issue with this car, unfortunatly. Next time I have a chance I will pull all the plugs and do a quick compression test to determine if a camshaft has skipped. What readings should I expect? If you guys cant give me a ball-park figure i will just compare the front bank to the back bank.

Any ideas what else to look for? Thanks for the help!

[shorod]

According to the factory service manual, Diagnostic Trouble Code P0135 indicates a short to ground, open, or short to VPWR in the HO2S heater circuit.

DTC P0135 = HO2S HTR-11

Possible causes:
-- Shorts to VPWR in harness or HO2S.
-- Water in connectors.
-- Cut or pulled wires.
-- Disconnected wiring.
-- Open VPWR circuit.
-- Open GND circuit.
-- Low battery voltage.
-- Corrosion or poor mating terminals.
-- Damaged HO2S heater.
-- Damaged PCM.

Diagnostic Trouble Code P1131 bank 1 (Cylinder 1) indicates the fuel/air ratio is correcting rich for an overly lean condition. The HO2S voltage is less than 0.45 volt.
Possible causes:

Fuel system

-- Excessive fuel pressure.
-- Leaking fuel injector(s).
-- Leaking fuel pressure regulator.
-- Low fuel pressure or running out of fuel.
-- Contaminated fuel injector(s)
-- Vapor recovery system

Induction system

-- Air leaks after the MAF.
-- Vacuum leaks (vacuum lines and gaskets).
-- Restricted air inlet.
-- PCV system.
-- Improperly seated engine oil dipstick.

EGR System

-- Leaking gasket.
-- Stuck open EGR valve.
-- Leaking diaphragm.

Base engine

-- Oil overfill.
-- Cam timing.
-- Cylinder compression.
-- Exhaust leaks before or near the HO2Ss.

DTC P1504 indicates that Self-Test has detected an IAC circuit malfunction. [Did you by chance perform your IAC test before reading the diagnostic codes?]
Possible causes:

-- IAC circuit open.
-- IAC circuit shorted to PWR.
-- IAC circuit short to GND (P1504).
-- VPWR circuit open.
-- Air inlet plugged (P0505, P1507).
-- Air inlet leakage (P1507).
-- Damaged IAC valve.
-- Damaged throttle body (P0505, P1507).
-- Damaged PCM.


And finally, P1744 indicates excessive Torque Converter Clutch (TCC) slip was detected.

-Rod

[tblake]

Originally Posted by shorod

....And finally, P1744 indicates excessive Torque Converter Clutch (TCC) slip was detected.

Yeah, I did research a little bit and found this out also. Does this code mean TCC sippage or TCC stuck on? Because the hard hesitation and lurching as slowing down seems to go along with a TCC problem. That was my first gut feeling when I drove it.

Can anything be done at this time or is a trans rebuild the only cure? Becuase of the cars milage and condition, I dont think it is worth it.

Originally Posted by shorod

...DTC P1504 indicates that Self-Test has detected an IAC circuit malfunction. [Did you by chance perform your IAC test before reading the diagnostic codes?]

No, actually I hooked up the scanner, read the codes initially, then played with the IAC, started the car, wrote the codes down, and plugged the IAC back in. So it is very possible I cause this code to pop up.

Thanks for the reply Rod! I will check everything out like you said. Thanks again.

[shorod]

Originally Posted by tblake

Yeah, I did research a little bit and found this out also. Does this code mean TCC sippage or TCC stuck on? Because the hard hesitation and lurching as slowing down seems to go along with a TCC problem. That was my first gut feeling when I drove it.

Can anything be done at this time or is a trans rebuild the only cure? Becuase of the cars milage and condition, I dont think it is worth it.

I expect that this is detecting slippage, and I suspect that it detects this by knowing that TCC lockup is requested, but the input shaft speed sensor and intermediate shaft speed sensors are not reading the same shaft speed, indicating the TCC is slipping. If this guess is accurate, that would indicate either the TCC is not able to lock electrically or one or both of the shaft speed sensors are faulty. The speed sensors should not require a rebuild, nor would I think the TCC lockup device would require a rebuild. It would require removing the transmission from the car which could be some significant labor costs. But, I must say, I've virtually no transmission experience so don't make decisions based on my suspicions. Hopefully someone with lots 'o tranny experience will pipe in.

-Rod

[tblake]

ok, thank you!