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Discussion Starter #1
Hi again,
After cleaning out the MAF and IAC, the car idles at 750 now instead of the 550 it used to idle at. The car starts a little better and is running better, but... when I accelerate from a dead stop or from a slow stop, or just romp on the gas peddle the engine hesitates and then takes off, runs fine, etc.

From what I read about this issue in particular, it points to the MAF and / or TPS. Since I don't have codes to read either, am I looking at a MAF that is going bad or a TPS going bad (or both)?

The other two parts mentioned are the injectors or the fuel pump. The injectors are rather new, all 6 and the fuel pump is fine because I can go up a steep hill and not have a problem.

With the MAF, the only symptom of the 4 symptoms listed is: hesitation on acceleration (hard acceleration) and crappy gas mileage. The MAF itself still looked good without any fraying of the wires, poor coloring or other failed MAF symptoms.

The symptoms of the TPS are poor acceleration and poor fuel economy. Both of which I noticed.

But as I said, after cleaning the IAC and MAF, the car's idle returned to normal and the engine ran better, but the acceleration was poor.

I will pull the TPS and clean it too and see if makes a difference. Is the MAF cleaner good enough to clean the TPS with or should I use something like Seafoam?

PS: I pulled two of the plugs and they are burning really nice and the gap was fine and within limits. The plugs are the ones that used to give me issues in the past.

Any suggestions on the TPS while I have it out?
 

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I would start by looking for vacuum leaks.
 
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Hesitation = lean. You need to find the source of why it's lean. If it didn't have that issue before your maintenance, I would make sure everything you removed is installed correctly.

On some cars, re-adjusting the TPS can be a real bear. I have no experience with the Ford TPS, but I don't believe cleaning it will do anything, nor would I mess with it unless I was replacing it.

On this "cleaning" of the MAF, the only thing that needs cleaned is that little wire, with electronic cleaner only, and a Q-tip if necessary. You need a tamper-proof torx bit to remove the cartridge, and the MAF housing can stay on the car. I always use a magnifying glass to look for dirt.

Al
 
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If yours is like mine, you will likely strip the screws trying (unsuccessfully) to remove the TPS. Clean the throttle body, check for vac leaks, check the PCV. If you suspect a failed MAF, you can unplug it and see if it runs better without it. If so, replace. If you suspect the TPS it will probably be easier to swap a complete TB from a jy car unless you buy a new sensor and then deal with the screw situation. I believe those phillips head screws have some sort of thread-locker on them.
 
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The TPS screws are a pain but they are possible to get off, you need the exact right Phillips head for it to grab, I have an assortment of screwdriver tips and only one ever works on the TPS, so you usually can’t just grab a plain old screwdriver from the tool box and not mangle them. You also need to press all your body weight on the driver while you turn on it, otherwise the tip jumps out and mangles the screw as you twist.
 

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It's the "Steel screws in Aluminum" problem.

Knocker-loose, or other penetrating oil applied to the threads in back helps a lot.
 

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I tried once to remove them and stopped before it got out of hand. If I ever need to remove my TPS I am just going to cut the heads off, pull the sensor off then vice-grip the screws and replace with a hex head. I have a pile of spare TBs so it's easier for me to swap the whole deal.
 

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The TPS screws are a pain but they are possible to get off, you need the exact right Phillips head for it to grab, I have an assortment of screwdriver tips and only one ever works on the TPS, so you usually can’t just grab a plain old screwdriver from the tool box and not mangle them. You also need to press all your body weight on the driver while you turn on it, otherwise the tip jumps out and mangles the screw as you twist.
It's more important on Japanese motorcycles & cars (which use JIS screws) but I found that using JIS screwdrivers seem to help NOT mangling during removal of phillips screws as well. The JIS screwdrivers fit better even in phillips screws so I bought two of them a few years ago from Amazon to complement my random drawer of "found/scrounged/free HF screwdrivers"



https://www.peterverdone.com/jis-cross-head-screws-and-drivers/

I bought the Vessel IMPACTA P2 and P3 since these can be hit with a mallet to loosen stubborn screws. They were <$15/ea.
A multi piece set of non-impact JIS screwdrivers will only be <$20 though.
https://www.amazon.com/Hozan-JIS-4-JIS-Screwdriver-3rd/dp/B00A7WAHTU
https://www.amazon.com/Vessel-Megadora-Impacta-P2x100-Screwdriver/dp/B003BI8HHQ/
https://www.amazon.com/Vessel-125943-P3x150-Impacta-Screwdriver/dp/B003BGTTSE/
 

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WOW! Thanks for all the input!

If I recall, I used a socket wrench with a Phillips that fit snug in the screw and would not come out easily.

Some great points here, best idea I liked was to just unplug the TPS, drive it, unplug the MAF and drive it. If there is not effect to the engine, the items are not performing as they should.

Excellent feed back folks, I will update soon with results.

The car is running much better, but still has the slight hesitation when accelerating so I am suspecting the TPS.

It's more important on Japanese motorcycles & cars (which use JIS screws) but I found that using JIS screwdrivers seem to help NOT mangling during removal of phillips screws as well. The JIS screwdrivers fit better even in phillips screws so I bought two of them a few years ago from Amazon to complement my random drawer of "found/scrounged/free HF screwdrivers"
Beautiful write up. Thanks for taking the time to point this out to others!

I would start by looking for vacuum leaks.
I recently went over the engine and replaced any vacuum lines related to the engine and the only ones I have not replaced are the canister lines. But a good point and something to consider. Thank you for the input.

Hesitation = lean. .... On this "cleaning" of the MAF, the only thing that needs cleaned is that little wire, ... Al
Thanks Al for the input. If the car was running lean, that would show up on my tester as it has before, so I suspect that if lean, it is due to a sensor (TPS/ MAF) acting up.

As for cleaning of the MAF, simple, 2 Torx and a can of MAF cleaner. Done. (lol) The wires still looked good and for others doing this, it should be considered to look at the wires with a magnifying lens, especially the heat wire for wear and damage after 20 years.
 

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Discussion Starter #12
Well, ran the tests with the TPS and MAF sensors unplugged and...

With the MAF unplugged, Check Engine came on, some rough idle, but very little. No diff in hesitation.

With the TPS unplugged, Check ENgine light cam on, no notifiable rough idle and hesitation was the same.

Going to research some more in the Service manual and on line to see what else it could be.


Question: Why does the idle take several seconds to drop to 750 and not as soon as you let off the throttle like most cars? Is this a "feature" of the EEC or is this an actual issue? It has always done this since I have owned the car (over 20 years) to the best of my recollection. (V6, 3.8l)

Thanks!
 

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Just because you cleaned the iac doesn't mean it operating correctly...i would buy a new one ,try it and if it doesn't change anything just return it.
I had an idle issue like that on my 4.6 and I made an iac restrictor plate to fix it.
Also,you sure your front 02s are still good, they cause hesitation and sluggish symptoms ..mine were bad but never threw the cel but did show up as other error codes on the scanner.
 

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Discussion Starter #14
Just because you cleaned the iac doesn't mean it operating correctly...i would buy a new one ,try it and if it doesn't change anything just return it.
I had an idle issue like that on my 4.6 and I made an iac restrictor plate to fix it.
Also,you sure your front 02s are still good, they cause hesitation and sluggish symptoms ..mine were bad but never threw the cel but did show up as other error codes on the scanner.
LOL! Yes, I ordered a new IAC from RockAuto and they listed the wrong one for my 3.8l so I had to send it back. Waiting on the new one to get here.

As for the O2's, the have about 30k on them and are about 11 years old. If I had any codes from the scanner, I would say yes, but that is usually something that will throw codes. I will take a look at them when I have the car up on jacks.

Thanks 94!

FYI: The MAF did have build up on the heat wire and I cleaned that off with a tooth brush, sprayed it again and got the same results. So I am not sure at this point which of the sensors is the issue if any of them.
 

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I recently went over the engine and replaced any vacuum lines related to the engine and the only ones I have not replaced are the canister lines. But a good point and something to consider. Thank you for the input.
If your tranny, alternator and ignition block aren't having problems, then I vote +1 on vac leakage.

It [almost] never hurts to replace vac lines, but you also need to check for leaks elsewhere, such as the manifold gasket. Hand pump vac gauges are handy for finding leak sources, as well as testing the various vac-operated components for proper operation.
 

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Discussion Starter #16
Tracking down vacuum leaks is like programming in Cobal. Old processes when there is a better way.

Thanks Torque, I will go over them again and see if I find any of the new ones loose.

I did find that forgot to put the plate to the MAF sensor back on, so I will see how much better the car runs after putting that part back on.

Thanks everyone for your feedback.
 

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You can use your scanner to determine if you have a vacuum leak.

Read the short term fuel trim and long term fuel trim at idle. Is the long term fuel trim at or near zero? Or is it a positive number?

Read the short term fuel trim and long term fuel trim at a steady 2,500 rpm. After a few minutes do the short term fuel trims and long term fuel trim equalize with the short term fuel trim quickly changing from positive to negative?

After seeing your readings I can explain more. If you want to use this method youtube has tutorials on fuel trims. Using fuel trim data is very handy when determining engine running poorly problems.

Richard
 

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I did find that forgot to put the plate to the MAF sensor back on, so I will see how much better the car runs after putting that part back on.
I had a feeling something didn't get installed back to original. Though I am not sure what a plate on a MAF sensor is? It is all one thing on a 4.6.

Al
 

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I had a feeling something didn't get installed back to original. Though I am not sure what a plate on a MAF sensor is? It is all one thing on a 4.6.
That stumped me, too, as I'm only aware of the o-ring as the only sealing component, the bottom metal "plate" being permanently affixed.
Unless.. he's referring to the shipping protective tube over the elements -- obviously, not to be replaced prior to installation.
Pics of the 3.8L maf: https://www.rockauto.com/en/moreinfo.php?pk=6284328&cc=1140589&jsn=10
 

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Discussion Starter #20
My apologies gentlemen, I am referring to this plate inside the MAF tube:
 

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