Poor CL behavior, WOT = OK, help ???

[DonMaximo]

The wife has a 2001 GT SOHC stock engine.

This 80K car recently has began to stumble upon acceleration...and you can hear what sounds like a "mild" miss when idling. The only time this car seems to be doing it's job is at WOT.

- I've used throttle body cleaner on the TB
- Electrical cleaner on the MAF
- Cleaned/reoiled the K&N air filter
- Replaced plugs and plug cap wires

Several months back and for regular maintenance reasons only, I replaced the rear O2 sensors. I had intended on replacing the more important front sensors, but did not have the special socket to make that job easy.

In short, it seems the car is having issues when idling and/or under load. I would presume this is under Closed Loop operation. At WOT (Open Loop), I cannot discern any problems...she (the car) screams.

Would disconnecting the battery (ie. resetting the PCM) and reconnecting 30 minutes later provide any more valuable information to this forum ?

Any ideas or suggestions would be appreciated.

Thanks in advance.

-D

 

[wmburns]

Do you have access to an ODB2 scanner? If so, post the long term fuel trim at idle and part load. Fuel pressure, IAC percent, evap purge valve, MAF, injector pulse width, and O2.

Even better is to data log this through a take off.

The 4.6 is bad about water pooling in the spark plug holes. Try removing the COP's and blowing out with compressed air.

Some ODB2 scanners can activate the Ford cylinder power balance test. This helpful trying to locate a misfiring COP.

Might try disconnecting the battery. Not really sure it will make any difference in this case.

Note, my 2003 has a slight bump in the low part throttle take off. Usually happens around 2k. Goes away at heavy throttle. It's not bad enough to make me try to find it (lazy learned to live with).

 

[DonMaximo]

As mentioned, we are planning to keep this car for some time... So I have thought about scanners for diagnostic purposes. I've just been avoiding the subject as I didn't want to drop 100's of dollars on a tool I did not yet need.

I'm working with Tweecer and other software components for my 5.0 projects, so I'm not adverse to spending money on tools and equipment.

I obviously need to do some homework for this 4.6 engine as I know the PCM is much more advanced than my EEC.

Any suggestions on make/model scanner ? Do they all provide datalogging functionality ?

Point me in the right direction...I'll do the homework.

TIA

 

[oxfordgt]

It's the TPS.

 

[DonMaximo]

It appears that these TPS units cannot be adjusted as they could on 5.0s.

Are you recommending I replace the TPS ??

Is there a means to confirm (with voltmeter) that the unit is not working correctly -OR- is the expectation that these units begin to fail with higher mileage/time ???

I twice attempted a search in the 4.6 forum for "TPS" and got nothing. That can't be right.

 

[Pearl02]

It appears that these TPS units cannot be adjusted as they could on 5.0s.

Are you recommending I replace the TPS ??

Is there a means to confirm (with voltmeter) that the unit is not working correctly -OR- is the expectation that these units begin to fail with higher mileage/time ???

I twice attempted a search in the 4.6 forum for "TPS" and got nothing. That can't be right.

Look in here for answers about you TPS http://www.stangnet.com/mustang-forums/583369-4-6-tech-important-threads-newbies-here-first.html . Also I have a Equus Innova 3130 scan tool. It's does datalogging much easier than that xcal along with other things. I paid 135 for mine on ebay. You can also check out their web page. When you pull up the thread look under "Engine" heading. Pearl02

 

[trinity_gt]

The wife has a 2001 GT SOHC stock engine.

This 80K car recently has began to stumble upon acceleration...and you can hear what sounds like a "mild" miss when idling. The only time this car seems to be doing it's job is at WOT.

- I've used throttle body cleaner on the TB
- Electrical cleaner on the MAF
- Cleaned/reoiled the K&N air filter
- Replaced plugs and plug cap wires

2001s don't have wires or a "cap": They have individual COPs (coil-on-plug), one for each cylinder and thus no wires and no need for a distributor or its cap or rotor. What did you actually replace?

Also, do not clean the TB with solvents or sprays. You can remove a special factory coating and that can lead to idling problems.

Do you see an MIL (check engine light)?

 

[DonMaximo]

Sorry... didn't have the specific technical term... I replaced the COPs & plugs.

As for cleaning the MAF, there is a product called Mass Air Flow Sensor cleaner and it's made by CRC. And it is a good idea to use for a higher mileage vehicle such as ours. Particularly when you're having problems and want to rule out the simpler/cheapest solutions first.

No MIL light.

I went to the NEWBIES site listed above and found no reference to how to test the existing TPS.

There are 3 wires on the TPS. If I knew which to test for "+" and "-", I could determine what the default voltage is at idle and could determine if voltages bounce around as I smoothly open TB. In all honesty, I just learned that the TPS will cost $40, so I'm just going to replace it.

Will keep the old one if this provides no fix.

**********************************************

I'll be doing some reading about scanners today. Already got a thumbs-up for the EQUUS, but in good conscience I need to understand all options before opening wallet.

Thanks for the reply

 

[DonMaximo]

It's NOT the TPS

Cleaned MAF again... I've heard about K&N oil messing these up sometimes = No Help

Disconnected battery, allow KAMs to zero out. Will restart in 1 hour.

Will replace fuel filter, but I seriously doubt that's the issue as I can here gargling at idle.
It's a cheap part.

Unless any one else has some idea, no matter how crazy, I'm planning to purchase a OBD2 scanner.

 

[oxfordgt]

There are only 3 things that will give you your symptoms.
1. bad TPS
2. vacuum leak
3. fouled plugs.

I just changed my TPS the other day because I had a stumble during acceleration, surging idle, and hard starts so I knew what it was right away. Tested the TPS first and it tested fine but still replaced it and all problems were fixed.

Since you changed your plugs I doubt its that.

Check for vacuum leaks, if you have a vacuum leak it is more then likely the evap vacuum source.

 

[bboylobo]

did you try cleaning or replacing the IAC? has it ever shut off on you randomly?

 

[DonMaximo]

Good points...

I just cleared the KAM (ie. disconnected battery for 2 hours)... now it's running worse.

Even WOT is worse. Almost like the Keep Alive Memory was helping the car prior to clearing KAM...

Really starting to wonder if O2 sensors have had better days. They are original on this 80K car.

It's my understanding that KAM set a baseline for WOT. At WOT the PCM would go into Open Loop and check on O2 sensors for modifications. Anyone disagree ?

Definitely gotta get scanner on this before I dump $100 on a pair of O2 sensors.

 

[patman0911]

Nope, computer ignores the O2 sensors in open loop.

It's unlikely that the O2s are so far gone at 80K that the car won't run OK with them. Sounds to me that whatever the problem is, clearing the computer wiped out whatever adjustments it made to work around the issue and so it will take a while for the car to readapt. You may be on to something with your vacuum leak idea but your original description sounds like a run of the mill misfire except that you should notice some loss of power and a some vibration at WOT too, although they do smooth out some at higher RPMs if it's not so bad that you can't rev under a load at all. If it's an auto, maybe the torque converter is helping to smooth things out too

Go through everything again thoroughly. Make sure all COPs are seated firmly and connectors are secure, check the plugs holes for fluids and debris, make sure no plugs have backed out, check gap on plugs and inspect for fouling or other symptoms, inspect COPs for any sign of damage.

 

[DonMaximo]

Patman,

I did find 2 minor vacuum leaks and repaired them, but that provided nominal improvement.

I started checking plug wells...2 from each side...they're dry and clean as a whistle.

I agree with you on the O2 sensors... I was reaching...If they failed to work altogether, I would have expected a MIL.

Not intending to get off course, but we did have to replace the fuel pump 2-3 years back...and that makes me wonder.

Our intent is to keep this car so I was going to shop for OBD2 scanners/tuners. I already received a recommendation for Equus...but I'm also curious about these Predators. There's a hefty price difference between the two and I expect we'll always keep this car stock.

Any recommendations on a OBD2 scanner would be appreciated.

-D

 

[oxfordgt]

It's the damn TPS. The computer ignores the o2 sensors during open loop, hence the reason it is called open loop. The computer only reads ect,iat,maf and tps to determin fuel tables at wot. Change out your tps.

 

[oxfordgt]

Patman,

I did find 2 minor vacuum leaks and repaired them, but that provided nominal improvement.

I started checking plug wells...2 from each side...they're dry and clean as a whistle.

I agree with you on the O2 sensors... I was reaching...If they failed to work altogether, I would have expected a MIL.

Not intending to get off course, but we did have to replace the fuel pump 2-3 years back...and that makes me wonder.

Our intent is to keep this car so I was going to shop for OBD2 scanners/tuners. I already received a recommendation for Equus...but I'm also curious about these Predators. There's a hefty price difference between the two and I expect we'll always keep this car stock.

Any recommendations on a OBD2 scanner would be appreciated.

-D

Yeah go to auto zone and have them scan it for free.

 

[GDawg]

Do a search on "AC Ripple". Seems most times people forget to check that when they are having this sort of problem. Could be bad diodes in your alternator that's affecting your computer.

 

[patman0911]

Do a search on "AC Ripple". Seems most times people forget to check that when they are having this sort of problem. Could be bad diodes in your alternator that's affecting your computer.

What is the procedure for testing for this at home - I did a search a while back and couldn't find anything other than "do a search for 'AC Ripple'"

I was getting odd behavior on the dash voltage gauge so I tested mine - it seemed to check out by the book procedure for DC but I still suspected something was wrong so I tested for AC with first a digital multimeter at both the battery and at the alternator and I was getting 30V AC. That sounded unlikely so I tested again with an analog meter in case the digital one was getting freaked out by non-sine wave AC but it also showed 30V AC which would have to be pretty much fully unrectified AC coming out of there. Then I took it to Autozone and had them test it and they confirmed a bad diode in the alternator. I didn't have any driveability problems (unless it was contributing to the poor mileage I've been having lately) but, like I said, the gauge was not showing the usual charging patterns and I'd just replaced a battery and I didn't want a bad alternator killing the new one too.

 

[DonMaximo]

Was thinking...


8-9 months ago, I replaced the stock throttle body & upper plenum and a C&L unit. Now I'm wondering if that resulted in minor changes to my PCM KAM since that time.

I'm going to put my original unit back on, disconnect battery for a while, and see if this mitigates the stumbling.

 

[wmburns]

Hasn't it run OK for 6 months? Haven't you allready disconnected the battery with the aftermarket intake?

IMO, you are reaching to think this is a PCM KAM problem from an intake swapped out 6 months ago.

The PCM KAM is erased each time the battery is removed.