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Discussion Starter #1
A bit of a long story, but here's all the details:
I ported and polished my MAF last fall. After doing this I disconnected the battery to reset the PCM. Afterwards, the car would idle incredibly rough at startup, but when it warmed up, it was fine. it would do this for a couple days, popup a MIL, and then run fine every startup afterwards. I just left the light on, because Autozone didn't have a reader for OBDII at the time, and didn't think much of it. Well, I ordered a chip from American MOtorsport a couple weeks ago, and when I talked to they guy, he said that a ported MAF will screw the computer up. So I went to a junkyard, bought a MAF off of a 96, switched out the actual sensors with the housings, and put the MAF in my car. Reset the computer, and it worked fine for a week - no codes, no rough idle, nothing. Put the chip and larger 19lb. injectors in on friday, and the old problem of rough idles has come back, along with the MIL. Went to Autozone today (they finally got an OBDII scanner in), and they pulled a lean condition, banks 1 and 2. So my question is: do I need to replace all four O2 sensors, only 2, or is there something else I'm missing.
 

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Ive had the same problems with my car including the MAF...

Running lean banks 1/2 usually means you have a post MAF leak: TB, intake.

Another thing you might just want to look into is how large the sample tube is. and FYI you can clean the MAF sensor, I use lighter fluid like ronsonal....spray it on the sensor and let it dry or blow on it.
 

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I'd take apart the MAF and clean it with electrical contact cleaner and put it back together. Then reset the battery to make sure all the learned data gets erased.

I doubt that both of your o2's are bad. And if they were, you would only need to replace the front two.
 

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To add to what Alberto has already posted. Try this procedure for clearing the memory...

Take off both leads on the battery and turn on the highbeams, and hazards to use any remaining power.

Wait 15-30 minutes before reconnecting

After you reconnect the battery, turn off the lights and hazards and start the car
let the car find its natural idle, should be no more than 30-45 seconds

Once the idle has been learned, turn on the headlights & highbeams, turn on the hazards, place your foot on the brake AND HOLD IT, put the car into drive, and slowly turn the wheels making sure NOT to hit the stops. 1 turn in either directions should be sufficient. Do this for approx 1-2 minutes until you can see the tach idling around the normal area for your vehicle.

Then shut everything off including the engine, restart and go for a drive.
 

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A major vacuum leak will usually set a rich code as the computer would have advanced to the end of the data tables. I cannot add any more fuel to compensate for the extra O2.
 

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A vacuum leak will show rich when you have a forced inductiion car and are at WOT. A vacuum leak will show lean otherwise, as you are taking in unmetered air..
 

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Originally posted by Grn96Taurus@Feb 24 2004, 07:15 PM
To add to what Alberto has already posted. Try this procedure for clearing the memory...

Take off both leads on the battery and turn on the highbeams, and hazards to use any remaining power.

Wait 15-30 minutes before reconnecting

After you reconnect the battery, turn off the lights and hazards and start the car
let the car find its natural idle, should be no more than 30-45 seconds

Once the idle has been learned, turn on the headlights & highbeams, turn on the hazards, place your foot on the brake AND HOLD IT, put the car into drive, and slowly turn the wheels making sure NOT to hit the stops. 1 turn in either directions should be sufficient. Do this for approx 1-2 minutes until you can see the tach idling around the normal area for your vehicle.

Then shut everything off including the engine, restart and go for a drive.
Disconnecting the negative battery terminal for about 5 minutes is enough to clear the KAM.

You can also pull a fuse that does the same thing, ifyou find it.
 

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Discussion Starter #9
The injectors are stock fords off of a 99(?) v8 mustang - orange (#19). The car was running fine before I worked on it, with the same MAF. There isn't a vacuum leak that I can find - no sounds of rushing air in the engine bay. The rough idle only happens when it's cold - when the O2 sensors aren't warmed up yet. I have already bought 2 new O2 sensors off ebay, so I will go ahead and put them in when I get them (even though I know that's not the problem).

I have a spare MAF off of a 96, will that work in my 97?

EDIT: the code on the 96 MAF is:
F67F-12B579-EA: same as my 97, but then it's
6F20-2. Not the same as my 97.
 

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Originally posted by americanmotorsport.com+Feb 24 2004, 08:42 PM-->QUOTE (americanmotorsport.com @ Feb 24 2004, 08:42 PM)
<!--QuoteBegin-Grn96Taurus
@Feb 24 2004, 07:15 PM
To add to what Alberto has already posted.  Try this procedure for clearing the memory...

Take off both leads on the battery and turn on the highbeams, and hazards to use any remaining power.

Wait 15-30 minutes before reconnecting

After you reconnect the battery, turn off the lights and hazards and start the car
let the car find its natural idle, should be no more than 30-45 seconds

Once the idle has been learned, turn on the headlights & highbeams, turn on the hazards, place your foot on the brake AND HOLD IT, put the car into drive, and slowly turn the wheels making sure NOT to hit the stops.  1 turn in either directions should be sufficient.  Do this for approx 1-2 minutes until you can see the tach idling around the normal area for your vehicle. 

Then shut everything off including the engine, restart and go for a drive.
Disconnecting the negative battery terminal for about 5 minutes is enough to clear the KAM.

You can also pull a fuse that does the same thing, ifyou find it. [/b]
Eh, what can I say - I want to be thorough.
 
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I would suspect a vacuum leak, check again. You had to take the upper intake off to get to the rear rail of injectors. There's possibility of vacuum leaks at the gasket, and at the EGR. Get some carb cleaner, and while the car's running, spray it around the intake, EGR, etc. 98.5% of the time, lean on both banks=vacuum leak.
 

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Discussion Starter #13
UPDATE: New 96 MAF didn't work. Checked for vaccum leaks again, couldn't find any. My o2 sensors come in tomorrow. I will change them out, and try using carb cleaner arounf the UIM, TB, MAF, and EGR valve tomorrow.
 

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What do you mean it didn't work? Still get the code?

Are you sure you fully physically disabled everything in the EGR and capped it off and unplugged all of the sensors?

You're sure you are not sucking unmetered air from anywhere? Did you make any modifications to your PCV system?
 

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Discussion Starter #15
Yeah, the leans condition codes came back. The EGR tobe from the exhaust manifold to the intake manifold broke, so I cut the exhaust manifold bend off and capped the line with a brass compression nut. the EGR valves and sensors are intact. I did this after I started getting the codes. The PCV system is still stock. I can't find any places where unmetered air is getting in, but I will go over any possible leaks with a bit of carb cleaner tomorrow to make absolutely sure.
 

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Discussion Starter #16
Well, this is really starting to torque me off. I replaced both o2 sensors today - made no difference. Also sprayed carb cleaner around EGR, UIM, MAF, TB, and all the vacuum lines I could find - nothing.

Another thought crossed my mind while I was working on the car today. Maybe the IAC is stuck open. I know the air is still being metered by the MAF, but would it make any difference? The car is now running lean even when the car is hot, when idling or not. I am out of ideas at this point.
 

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I told you I didn't think it was the 02's. Also, as far as setting the code, remember that it is not necessarily that it is runing lean atthe actual moment you set the light, but rather, it can set a while after the code itself has been set to memory. So the exact timing of when the light comes on does not have anything to do with at what conditions you are actually running lean. Codes are stored inmemory until the EEC completes certain tests before it will set a light.

Now you have always had a probelm with this car throwing those codes? Since whwne? What did you change just before it started to happen?

The IAC would have nothing to do with this.

Do you have any exhaust leaks?
 

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Discussion Starter #18
I knew that it wouldn't be the o2 sensors, but I had already purchased them off of ebay, and the old ones were original.

I can fell and hear when the car is running lean. it sputters at idle in gear, and the idle RPMs oscillate between ~450-1100 when the transmission is engaged. My low-end toruqe has gone to crap, and I can hear the valvetrain rattling from detonation.

I can't remember exactly when the MIL came on, but it was sometime in the fall, after I ported my MAF, and before I had to cap my EGR.

The exhaust system is stock, other then the aforementioned EGR. I just remembered that the muffler has been removed. Would a drop in backpressure cause this? If so, what about those who get custom cat-back exhausts made? I can't smell anything in the cabin or engine compartment that would signal an exhaust leak.
 

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No, a loss of backpressure would not cause this.

You may not smell an exhaust leak sometimes.

Why don't you remove all the rest of EGR tube and cap where needed. Also, remove all of the EGR sensors, remove any and all lines, and cap the vaccum lines where needed.

I somehow suspect you did not properly disable and block off all of the EGR system...
 

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Discussion Starter #20
UPDATE:

I replaced the fuel filter and checked the fuel pressure. It is 37 psi with key on, eninge not running, and 34 psi with engine at idle.

I decided to reconnect the EGR system. I ordered a new EGR tube from the dealership and it will be in tomorrow. The junkyard here wouldn't let me pull one off their cars; the guy knows about the ford fragile EGR tube problem.
 
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