Cannot solve this issue: hesitation at anything more than part throttle

svtpower

New Member
Apr 30, 2005
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Wisconsin
My car hesitates badly at more than 1/4 - 1/2 throttle.

Ok, so I have searched about every keyword I can think of on this forum and others. I can't solve this issue. My car has 89,000 miles on it, still original speed density.

It's worse when cold, but even after the car warms up it hesitates BADLY at tip in throttle.

If it's cold and I am in a hurry I will usually get a intake POP or backfire when I try to go WOT after shifting into 2nd gear.

Starting off from a dead stop, if I try to burn the tires and mash the gas pedal and let out the clutch quickly the car just falls on it's face. And this is with 3.73s! If I use like 1/4 throttle or so and slip the clutch it goes much better.

Shifting from 1 to 2nd, if I try to do it quickly and go WOT immediately after shift, it stumbles and hesitates badly for about half a second, then continues on ok.

If I give it gas like a grandma and use like 1/4 throttle or so between shifts and when taking off from a stop it does ok, just pud slow. :bang:

It seems to me much worse at low RPMS, on the highway at speed it's much less noticeable but still there.

I have a DIGITAL OBD1 code reader and the only codes I got were something about the A/C and the "system ok" code I think it was 11.

I have replaced:

Plugs with Autolite ones, properly gapped (old plugs looked good)

Plugwires with Ford Racing 9mm ones.

Cap and rotor with Motorcraft ones.

Fuel filter with Purilator Gold one.

Checked timing with timing light with spout out (was at 10deg, now at 12deg)

TPS adjusted to .98

Replaced air filter with new OEM one, now currently running a new MAC CAI that I got cheap on Ebay.

Ran a can of fuel injector cleaner in the last tank of gas.

I just put the Magnaflow catted H on, so the cats are brand new. The smog hole on the H is blocked off.


Smog pump delete pulley is on the car and openings in the back of the heads have bolts in them with sealant.

Where do I look next guys?

Does this sound like a :

vacuum leak? (I checked the hoses and couldn't find a leak)

bad injector?

bad fuel pump?

Any ideas are really appreciated guys. I am out of ideas.

EDIT *This is not a new problem, it's been like this since I bought it a few months ago, I was hoping it just needed a tune up, but I guess not.*
 
Personally, I would completely SKIP setting the TPS and go right to swapping it for a new one.


Start the car, Pop the hood, rev lightly by hand. If the sound of air being "sucked" past the TB blade is evident then your TPS is toast. "Yes", you can set a bad TPS to .98 V and it will still be a bad TPS.

If you're not hearing that sucking sound then perform one final vac leak test with a can of engine starter (ether).

If no leaks are detected then you may want to consider swapping out the MAP sensor (an auto-parts store may even allow you to slave in a new one in the parking lot to see if it's what you need prior to purchase).
 
Thanks

Thank you for the input about those sensors.

In all the threads I had read I had no idea the TPS could be bad and still adjust within spec.

I will start on your suggestions.

Thanks again, atleast now I have some things to try.
 
I often sound like a broken record when incidents similar to this pop up, but based on my previous experience with a similar problem on my 93, it ended up being a faulty TFI module on the distributor. I bought an Auto Zone version which didn't help squat. I bought a Ford TFI module and it fixed the problem.
Like yours, if I went easy on the gas the car accelerated ok, but if I got into the gas pedal and the RPMs climbed, it would start bucking and/or fall on it's face.
Just something else for you to check out.
Ken
 
If you buy a new TPS I would suggest getting one from Ford. These cheap aftermarket sensors keep failing on me. I have decided that since the original equipment from Ford lasted this long it is a good idea to spend the little extra and get another good quality part.
 
My TPS went bad and would cause the car to about die when taking off from a dead stop with a 1/4 to 1/3 throttle. If you stabbed it to the floor it would hesitate for a second and then burn tire. 47 bucks for new motorcraft from my local parts store.

Adam