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post #1 of 51 (permalink) Old 02-01-2016, 06:22 PM Thread Starter
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hesitation, no codes, etc.

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?
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post #2 of 51 (permalink) Old 02-02-2016, 09:11 AM
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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

97 T-Bird LX 4.6 - 80k miles
94 Supra TT Auto - street/strip car
04 CVPI- Brenda's car - 76k miles
Previous Fords:
95 T-Bird LX 4.6 - fully optioned, owned 15 years, 220k miles
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post #3 of 51 (permalink) Old 02-02-2016, 10:05 AM Thread Starter
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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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post #4 of 51 (permalink) Old 02-02-2016, 10:51 AM
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Did you replace the coil packs when you did the plugs and wires?
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post #5 of 51 (permalink) Old 02-02-2016, 01:34 PM Thread Starter
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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)
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post #6 of 51 (permalink) Old 02-02-2016, 02:44 PM Thread Starter
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TPS- 5v
Ground good
1.3(or so) closed, 5v WOT.
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post #7 of 51 (permalink) Old 02-02-2016, 03:22 PM
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Quote:
Originally Posted by toid View Post
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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94 Supra TT Auto - street/strip car
04 CVPI- Brenda's car - 76k miles
Previous Fords:
95 T-Bird LX 4.6 - fully optioned, owned 15 years, 220k miles
96 Cougar XR-7 4.6- Brenda's car, owned 11 years, 187k miles
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post #8 of 51 (permalink) Old 02-02-2016, 04:02 PM Thread Starter
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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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post #9 of 51 (permalink) Old 02-02-2016, 05:27 PM Thread Starter
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Did the coil swap thing from the other bird. No difference.
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post #10 of 51 (permalink) Old 02-02-2016, 08:54 PM Thread Starter
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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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post #11 of 51 (permalink) Old 02-04-2016, 10:38 AM Thread Starter
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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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post #12 of 51 (permalink) Old 02-04-2016, 05:22 PM Thread Starter
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Replaced FPR & PCV.
No change.
Going to recheck the fuel pressure again tomorrow... Looking at the pump.
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post #13 of 51 (permalink) Old 02-04-2016, 07:14 PM Thread Starter
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Also put a can of seafoam in
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post #14 of 51 (permalink) Old 02-04-2016, 09:26 PM
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Quote:
Originally Posted by toid View Post
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.

-Brandon
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post #15 of 51 (permalink) Old 02-04-2016, 09:46 PM Thread Starter
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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!
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post #16 of 51 (permalink) Old 02-05-2016, 10:30 AM Thread Starter
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"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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post #17 of 51 (permalink) Old 02-05-2016, 11:50 AM Thread Starter
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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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post #18 of 51 (permalink) Old 02-05-2016, 12:35 PM Thread Starter
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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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post #19 of 51 (permalink) Old 02-05-2016, 07:13 PM
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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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post #20 of 51 (permalink) Old 02-05-2016, 07:28 PM Thread Starter
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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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post #21 of 51 (permalink) Old 02-05-2016, 09:05 PM
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The 96 runs fine? Swap MAF sensors between the two and see if it changes anything. Cleaning the MAF doesn't automatically rule it out as a culprit. Swapping in a known good one will.

Fuel pressures look fine.

You can unhook the vacuum lines from the plenum and plug them to rule out "distant and unseen" vacuum lines as leaky points. The evap system lines are usually the most troublesome due to their length overall, but a leaky brake booster or lines to it could also be a source.

A cat below efficiency code is usually always legitimately a cat going bad - whether it's crumbling internally and blocking flow severely enough to cause problems is going to be an unknown until they get replaced. Usually though with clogged cats the car loses power over a certain RPM/throttle position or starts/stalls instantly.

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post #22 of 51 (permalink) Old 02-05-2016, 09:29 PM Thread Starter
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A shutter at 2K rpm maybe?
It runs like a beast, smooth. I blasted it up past 110 today, testing. Its just at idle or in gear braking.
I haven't checked the booster yet. No hissing and brakes are good, but that doesn't mean its not sucking air, just that the booster is functioning.
I was sweating the fuel pressure all morning, convinced the cats weren't the problem until a pulled that code.
It cranks well as soon as the key is turned... But that initial throttle hesitation. If it were carbureted, I'd swear the accelerator pump was squirting too much fuel. That's GOT to be a vac leak... Or am I smoking what I'm selling?
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post #23 of 51 (permalink) Old 02-06-2016, 09:08 AM Thread Starter
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Yeah, There was, something like, 3 or maybe 4 codes for the evap system... All I needed was a purge valve and the whole thing was one giant vac leak. 2 upstream O2 codes and evap codes..?
If the brake booster or other vac lines don't pan out, I'm going back under there to check it out. I haven't been able to spray any CC or starting fluid under there to "check for a leak".
I haven't been able to tach up the engine, while I spray... That may be just the thing...

Thanks!!
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post #24 of 51 (permalink) Old 02-06-2016, 11:08 AM Thread Starter
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Thanks.
When I say the booster looks brand new, I mean like it was replaced yesterday. The underhood landscape on this car is incredible for a 1997, heck, its incerdible compared to 99% of the 2007s. The lines are as pristine as they were off the line. Ain't even dirty. Tight and shiny. Can't be original. The sticker is still perfect. If its bad its inside. The vac connector made no sound nor idle change when sprayed, but I am going back out after lunch to replumb and regrommet the PCV. Can i replace the grommet without pulling the valve cover? Its a valve cover gasket job on my Jeep.
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post #25 of 51 (permalink) Old 02-06-2016, 11:25 AM Thread Starter
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Yeah, I'm selling it in the spring. So I just want it put in shape
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post #26 of 51 (permalink) Old 02-06-2016, 12:05 PM Thread Starter
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154k. Navy. New Jersey for a year then Fla. Then (retired?) to Ga in 03 or so. Between oil changes, tires, dealership receipts, etc.
My black 96 sport (The Crow) has less than 100k and purrs like a Cougar. This one was a good deal and filled that "project" hole after I got through with The Crow.
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post #27 of 51 (permalink) Old 02-06-2016, 12:07 PM Thread Starter
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BTW The grommet is pop out/in off the HELP! Rack. Good as new, $2.69
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post #28 of 51 (permalink) Old 02-06-2016, 02:39 PM Thread Starter
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Re checked vac lines and all junctions. Took off tire and clamped all the joints at the evap assembly. Either I had a broken green vac line under the air tube or I broke it while checking. I cut out the brittle length and replaced it. Good as new.
But still the same miss at idle.
Back to the chalkboard... Without assumptions.
1- Misfire = tune up. Ignition first. I've swapped coils, MAF, & PCV from a perfect engine all that in last several days. The plugs and wires were summer.
New plugs and wires?
Perhaps the last new wires were faulty.
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post #29 of 51 (permalink) Old 02-06-2016, 03:15 PM
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Quote:
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The plugs and wires were summer.
New plugs and wires?
Perhaps the last new wires were faulty.
What brand plugs and wires?

Bosch, champion et al. don't seem to work well at all in Ford engines.

Motorcraft FTW
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post #30 of 51 (permalink) Old 02-06-2016, 04:40 PM Thread Starter
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Autolite double plats on Napa's one step better than OEM wires.
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