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Discussion Starter #1
Did more than a little thread hopping and a few searches...
Still got a question.
1997 4.6 Sport - It's not driven very much lately. I've been painting it and sewing up new seats, etc.

Got all my codes cleared late last year, needed a couple of new downstream O2s. Cleaned the MAF, TB, EGR (orifice?), IAC, the whole she'bang - new plugs & wires, filters, TPS, etc.
I have a barely discernible stumble when idling and a very slight hesitation / stumble at idle when I pop the throttle... It picks up smoothly and runs well...WHEN COLD.
At operating temp, the stumble at idle is distinct, the hesitation on a quick throttle pop is more pronounced... I checked the fuel pressure, and it was on the low side of "good", with no bleed down)
Thread hopping leads me to a few possibles, Fuel pressure (pump or regulator or injectors) , cats, maybe.
Again, I have no codes at all and no CEL.
I thought on an occasion I smelled a "hot metallic" smell after dogging it a little the other day, making me think cats, but I haven't had a repeat of it and it was faint and fleeting when I thought I smelled it.
Help?
Blessings
 

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Why was the TPS replaced? Is the adjustment on?

You could always throw a can of Seafoam in the tank since the car sits, and change the plugs, unless they are new.

Al
 

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Discussion Starter #3
Did the TPS with the tune up in summer. I think I just got one to eliminate the possibility. I use my multimeter to dial em in, but now that you mention it, its TPS-like symptoms, but no out of range code. I check it again
 

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Did you replace the coil packs when you did the plugs and wires?
 

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Discussion Starter #5
I did not replace coil packs. one,is a newer motorcraft, the other is likely original. Ive read thesr coils are not failure prone... (unlike my old SC)
 

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Discussion Starter #6
TPS- 5v
Ground good
1.3(or so) closed, 5v WOT.
 

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I did not replace coil packs. one,is a newer motorcraft, the other is likely original. Ive read thesr coils are not failure prone... (unlike my old SC)
Symptoms of old coil packs are the same as bad wires - bucking at low RPM in high gear when climbing a hill. I know people say they never go bad. I fixed two MN12's with new sets.

It was problem that was on and off for a couple years, the bucking at low RPM. First, plugs fixed it, then it came back. Next, wires fixed it, but also came back. Finally, coil packs fixed it for good.

Al
 

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Discussion Starter #8
well one evidently went bad at some point, or there would be two original stock coils on this red 'bird instead of the one, right?
I will pull a coil off The Crow (my black '96), which I know are firing perfectly, and swap out each one and see if it helps.
I had an intermittent buck under throttle with a bad idle before the new plugs and wires, now I got smooth pull, just the stumbly idle...
Why would it be worse when hot than when cold? That could definitely be a too-hot coil, huh?

What's REALLY driving me crazy is the 1/2 second hesitation when the throttle opens quickly. If I actuate the butterfly slowly, it doesn't hesitate. Would a faulty FPR cause this? Many folk are opining that they're either functional or not. My experience with my Jeep tells me otherwise.

I REALLY HATE that I (secretly) really love these little nit-noid T-Bird problems.
 

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Discussion Starter #9
Did the coil swap thing from the other bird. No difference.
 

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Discussion Starter #10
The more I search, truck forums and mustang forums, etc... It warrants mentioning the roughness of the idle, that is to say a vibration. When in park, it smoothly TACHS up to 2500 or 3000 nicely, but stumbles and vibrates on the way down about 2000rpm. In gear it is the same but a bit less noticeable.
This give any further light?
 

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Discussion Starter #11
Far as I know its original. The PO did a pretty good job keeping docs for stuff. I got receipts for the PI and heads swap, TC recall, coil, plugs, stuff he did ... Even routine stuff. I guess he'd have documented an FPR. Im picking up one today and will put it on this weekend. Ain't gonna hurt to replace it in any case.
Thank you!!!
 

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Discussion Starter #12
Replaced FPR & PCV.
No change.
Going to recheck the fuel pressure again tomorrow... Looking at the pump.
 

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Discussion Starter #13
Also put a can of seafoam in
 

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TPS- 5v
Ground good
1.3(or so) closed, 5v WOT.
At idle it needs to be less than 1V. At WOT it only needs to be over 4.5V. You "should" have enough free play to rotate it so the voltages are within spec by loosening the screws.
 

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Discussion Starter #15
Aha. I will facilitate that change in the am. I have a new IAC in a box-o-parts that I was going to swap out, just to check... I will break out the multimeter turn that tps a bit real quick while I'm freezing my fingers off.
Thank you!
Blessings
 

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Discussion Starter #16
"Adjusted" tps to 1v at idle. Swapped out IAC for a known working one. No change.
Tested fuel pressure. As follows (average of 3 tests)
KOEO 37-38. Idle 30,
As I opened the TB and surged the "gas" to it, it jumped to around 42 then back.
I opened the TB and held it, it jumped to 42 or so and slowly declined. I closed the throttle and it went back to 30.
No bleed down when key off on all tests.
The idle and priming numbers are within "specs" but are low, from what I can find.
Am I looking at a pump replacement?
 

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Discussion Starter #17
I've been reading a lot, found a guy with my problem. His was a bad evap canister.
Could a bad evap can NOT throw a code?
I had the evap codes but replumbed the cracked vac lines and cleared it up.
 

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Discussion Starter #18
Hate to keep blowing it up, but on a whim, I checked for pending codes... No CEL, BUT I do have a pending 0430 code.
Bank 2 cat below efficiency (right?)
Related to hesitation and shuttering idle?
 

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Somewhat similar symptoms for my 93 5.0
Was just a handful of VERY SMALL airleaks.
MAF type cars go crazy with airleaks.
Problem would be worse when it was cold--when the hoses were hardest.
Hoses looked OK, but Ford doesn't like to use hoseclamps, instead used a lot of barbed fittings.
So every hose that that I could TWIST on the fitting, when it was COLD, I replaced.
I think the PCV valve grommet was the worst offender.
 

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Discussion Starter #20
I sprayed ether (starting fluid) all around after making several passes with carb cleaner to no effect. (Pulling hair out)
My PCV is, however, conspiciously loose. But I didn't really suspect it may suck air. I bleeve I will hose clamp it on both joints. I'm going to jack it up, pull off the tire and recheck my plumbing job on the evap can.
I drove over to an old car restoration guys place. He took one listen and proclaimed "I'd say a vacuum leak, but with all those sensors..."
But, thank you for your help.
 
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