1998 Taurus SE high/low idle and stalling

My car has been having problems for a week a so. Sometimes when I start up my car or am at a stop sign, my car will idle really low and sometimes stall. When I'm driving faster though, it idles high to the point where it will speed up without pressing on the gas.

I took my car to Autozone and got these codes:
P0133
P0135
P1131
P1507

After getting my car briefly looked at by a mechanic, he managed to fix a vacuum leak and replaced the IAC Valve. It didn't fix a darn thing :mad: but after getting the computer reset and making a second trip to Autozone, I only got two of those codes:
P0133
P0135

Can anyone help me figure out whats wrong with my car?

Also, is that black cap still supposed to be on the IAC Valve after it's installed?
http://smg.photobucket.com/albums/v330/cereal_killerxx/?action=view&current=IACinstall2.jpg

One last question. When you buy a new IAC Valve, does it come with the motor for it or do you have to buy that seperately? (because the mechanic said that the motor was dead not the valve). Thanks for absolutely any help you guys can give me. I feel like I'm gonna crazy if I don't figure this out :crying:

The P0135 code indicates a short to power, short to ground, or open in the Bank 1, Sensor 1 heated oxygen sensor circuit. I'd start with that code and determine what the cause is, fixing it will likely solve the P0133 and stalling. The P0133 indicates the same HO2S is outside of a calibrated window, which would be expected if it is shorted or open. If shorted to battery positive, that would certainly be outside the expected 0-1 V range of the sensor.

The little black cap on the IAC is normal. Apparently the IAC is using ambient air rather than having a tap to the air intake tubing. Where does the large metal hose fitting connect to? And when you buy an IAC it comes with the motor as part of the assembly.

The P1507 code does in fact point to an issue with the IAC, so replacing that was not an unreasonable place to start for your driveability issues.

-Rod

The P0135 code indicates a short to power, short to ground, or open in the Bank 1, Sensor 1 heated oxygen sensor circuit. I'd start with that code and determine what the cause is, fixing it will likely solve the P0133 and stalling. The P0133 indicates the same HO2S is outside of a calibrated window, which would be expected if it is shorted or open. If shorted to battery positive, that would certainly be outside the expected 0-1 V range of the sensor.

The little black cap on the IAC is normal. Apparently the IAC is using ambient air rather than having a tap to the air intake tubing. Where does the large metal hose fitting connect to? And when you buy an IAC it comes with the motor as part of the assembly.

The P1507 code does in fact point to an issue with the IAC, so replacing that was not an unreasonable place to start for your driveability issues.

-Rod
So... what do you think the problem could be? I'm just starting to learn about cars so I'm a bit confused. Do you think it could be the O2 sensor? The mass airflow sensor? Or another problem entirely?

Without seeing the car, I'd suggest you start by inspecting the wiring for the bank 1, sensor 1 (B1S1) HO2S. Get out the multimeter and unplug the B1S1 sensor, then measure for a short between the gray/red and gray/light blue wires. If they measure shorted to one another, you need to trace back to find out why. If those two wires don't measure shorted to one another, then check to see if the gray/light blue wire is shorted to ground. If not, then check for a short to battery. This wire goes to pin 60 of the PCM for the 12V Vulcan engine. If you have the 24V DOHC Duratech, the wire colors and PCM pin may be different.

The gray/red wire is common to many other sensors, so if that wire were shorted to ground or power you'd have fuses blowing and many other codes I would expect.

-Rod

Without seeing the car, I'd suggest you start by inspecting the wiring for the bank 1, sensor 1 (B1S1) HO2S. Get out the multimeter and unplug the B1S1 sensor, then measure for a short between the gray/red and gray/light blue wires. If they measure shorted to one another, you need to trace back to find out why. If those two wires don't measure shorted to one another, then check to see if the gray/light blue wire is shorted to ground. If not, then check for a short to battery. This wire goes to pin 60 of the PCM for the 12V Vulcan engine. If you have the 24V DOHC Duratech, the wire colors and PCM pin may be different.

The gray/red wire is common to many other sensors, so if that wire were shorted to ground or power you'd have fuses blowing and many other codes I would expect.

-Rod
Well, I just bought a heat oxygen sensor from autozone with a 1 year warranty. Tomorrow (or whenever the weather is good), I'm gonna install it and see if it fixes the problem.

Also, I just went to a mechanic earlier and he said the problem could be one of 3 things:
Heat Oxygen Sensor
MAF Sensor
Throttle sensor (can't remember exactly what it was called)

Does that sound pretty accurate?

Well, I just bought a heat oxygen sensor from autozone with a 1 year warranty. Tomorrow (or whenever the weather is good), I'm gonna install it and see if it fixes the problem.

Also, I just went to a mechanic earlier and he said the problem could be one of 3 things:
Heat Oxygen Sensor
MAF Sensor
Throttle sensor (can't remember exactly what it was called)

Does that sound pretty accurate?

Not really. As I mentioned, the codes you have point to an issue with the HO2S circuit, of which the MAF and Throttle Position Sensor are not part of. Based on the P0133 code, there's a chance the HO2S itself is not the problem, but it could be in the wiring. It would be pretty easy to check for the open or shorted condition of the existing sensor and the wiring if you have an ohm/volt meter. Especially if you're going to be down there changing out the sensor anyway.

-Rod

Not really. As I mentioned, the codes you have point to an issue with the HO2S circuit, of which the MAF and Throttle Position Sensor are not part of. Based on the P0133 code, there's a chance the HO2S itself is not the problem, but it could be in the wiring. It would be pretty easy to check for the open or shorted condition of the existing sensor and the wiring if you have an ohm/volt meter. Especially if you're going to be down there changing out the sensor anyway.

-Rod
Well, hopefully today or tomorrow, I'll get a chance to pinpoint precisely what the problem is. If it's the wiring, then maybe I can save myself 65 bucks in the process :cool:

Also, I just noticed today that whatever the problem is, it's most definetely affecting my gas mileage. I think this even further points to a problem with the HO2S. I will post my findings soon XD

Just installed the O2 sensor. The check engine light is no longer on but it didnt seem to fix anything at all. My car is still idling just as bad, maybe even worse.

Go back and follow Rod's advice. You are jumping the gun on the repair. There is a systematic madness to automotive repair. The codes only give you a general area to start looking. Good luck and slow down and take your time. Oh yeah, welcome to the forum.

Took my car back to autozone and got the following codes:
P0133
P0135
P0155
P1742

The first two have been addressed above. P0155 is just like P0135, except for Bank 2 Sensor 1.

Code P1742 is transmission related, TCC Solenoid has failed ON by electrical, mechanical or hydraulic concern.

-Rod

http://www.automotiveforums.com/vbulletin/t647288.html

I think I may have found the fix i was looking for! I just have one question. What is trans oil? Is that referring to the transmission fluid?

A stuck TCC would typically cause the car to stall when coming to a stop after cruising at speeds above 35 mph prior to the stop. That does not match the description of your problem from your first post. But a sticking TCC is something to address because it will be a problem eventually.

Remedying the TCC issue will not fix the HO2S issues though.

-Rod

Agreed. But a HO2S will not likely cause the symptoms my car is experiencing. It would more than likely be something involving the transmission like the solenoid (unless the other HO2S is to blame, but that still doesn't seem likely). Either way, it's atleast worth a shot. Besides, from what I hear, a TCC Solenoid is around 400 bucks and replacing the transmission is completely out of the question.

Any ideas on any specific things dealing with the transmission that could cause this other than the solenoid?

Edit: After re-reading my first post, I realized I forgot to add that part. After my I take my car on 45+ road (sometimes lower depending on how long I've been driving) my car will surge and/or stall at stop signs and red lights. Sorry, I'm really bad at wording stuff sometimes =/