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Car jolts/jerks

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Old 04-09-2012, 09:54 PM   #1
cepowers18
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Default Car jolts/jerks

Hi all,

I have a rebuilt 1994 Mustang GT (306) with TFS heads, cam, and intake, and it jolts or jerks a lot when cruising and it makes is a noticeable clanking noise. It seems to happen in any gear when the RPMs are 2K or below and I'm simply cruising down the road giving it a little bit of gas. When I'm giving it a good bit of gas everything is fine - it only seems to happen when decelerating or when I'm only giving it a small amount of gas. The RPMs don't fluctuate when it happens. It also jolts/jerks quite a bit from 55-65 mph in 5th.

My first thought after reading some other threads were that it was running lean, so I've replaced the spark plugs, fuel filter, and O2 sensors but that hasn't helped things. I thought that it could also be in the tune but I haven't tried pulling out the chip to see how it runs without it.

Any suggestions? Is it possible that this could have something to do with motor mounts?
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Old 04-09-2012, 10:12 PM   #2
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Hard one for anyone here to diagnose without hearing and feeling that. My first guess would be a deadspot in the TPS, coming back alive creating the jolting. Overheating fuel pump might do the same.

Clanking might be something as serious as the flexplate to converter or flywheel to pressure plate bolts coming out. Don't ignore it. The jolting is creating the clank, which means something is loose.
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Old 04-11-2012, 04:05 PM   #3
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I thought it might be the clutch as well. That may be a good place to start. I suppose it might be worth pulling the chip, too.

The TPS and fuel pump are both new parts from the engine swap, so in theory they shouldn't be malfunctioning but I'm sure anything is possible.
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Old 04-12-2012, 10:11 AM   #4
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I pulled the chip and it still seems to jerk/jolt a little at the same RPM ranges and speeds, but not as much as with the chip in. After I pulled the chip and started up the car, the idle surged a bit more but once it smoothed out I think it ran better than with the chip. The lope and the shaking from the cam isn't as violent as it is with the chip either

Any other suggestions for the jerkiness? Now it almost seems like a sputter or something.
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Old 04-14-2012, 04:25 PM   #5
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Update:

The chip is no longer in and I've driven it several times to see if it would smooth out. Turns out that it still jerks and jolts without the chip in, but not as violently. I've also cleaned the MAF, air intake sensor, IAC, TB, checked the TPS voltage, and re-gapped the spark plugs to .054. TPS voltage is .94 and at WOT it's 4.6, so I believe that is fine.

Does anyone else have any suggestions? Would taking a video and posting it help at all?
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Old 04-17-2012, 12:38 PM   #6
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Bump. Any other ideas, anyone?
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Old 04-17-2012, 12:39 PM   #7
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You need an oscilloscope to check the TPS, not a multimeter.
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Old 04-17-2012, 09:12 PM   #8
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mine jolted and stuff and i replaced the TPS and it stopped, its not that expensive just 35 bucks
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Old 04-19-2012, 06:15 PM   #9
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Ok, I've done a ton of searching and I can't find an answer to this anywhere. Apparently there are two TPS sensors for 94-95 5.0 Mustangs - part #'s F2SF-9B989-CA and F1SF-9B989-AA. Does anyone know the difference between the two?? My car has the F2SF part # on it, but I can't find a replacement part anywhere! Auto Zone, Advance, Napa, O'Reilly's, Rock Auto, nowhere. People have the F1SF-AA part, but I don't know if that will work with my car.

Anyone know the difference between these two?
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Old 04-19-2012, 07:08 PM   #10
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As I remember, the difference was how the connector socket is positioned on the sensor. You will have to look at the sensor to get the number.
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Old 04-19-2012, 09:32 PM   #11
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Quote:
Originally Posted by fl1a View Post
As I remember, the difference was how the connector socket is positioned on the sensor. You will have to look at the sensor to get the number.
My car has the F2SF-9B989-CA part on it, but I can't find a replacement part anywhere. Anyone know of a place I can find one, or does anyone have one they will sell?
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Old 04-20-2012, 07:40 AM   #12
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Here is where I got mine, It looks like there are both types here still.

http://motors.shop.ebay.com/i.html?_...506.m270.l1313
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Old 04-20-2012, 05:43 PM   #13
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The CA designation means california emissions, that might help your search. The contrary sensor, AA, is federal emissions.
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Old 04-23-2012, 12:36 PM   #14
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Quote:
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The CA designation means california emissions, that might help your search. The contrary sensor, AA, is federal emissions.
That's helpful to know. I've heard the AA sensor won't fit on 94-95 Mustangs that came with the CA sensor. Does that seem correct, or should the AA sensor fit?
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Old 05-04-2012, 01:44 PM   #15
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Update:

I replace the TPS sensor and I'm still having driveability issues. The car still jerks/jolts/hesitates, sometimes cuts off after I've been driving it for awhile, etc. My research online tells me that the car might be running lean.

I've cleaned the MAF, TB, IAC, replaced the TPS sensor, replaced the plugs and wires, replaced the O2 sensors, replaced the fuel filter... nothing.

Any suggestions?? This car is really getting on my last nerve. It's been almost two years since the car has gone under the knife to swap out the engine and it's been running like crap since.
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Old 06-06-2012, 05:23 PM   #16
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Update:

So my car is still jerking/hesitating quite a bit when cruising. Also, it runs like crap once it's reached normal operating temp. When at operating temp, it struggles to turn over and once it does, the exhaust crackles a lot and it jerks more. Here's a list of things I've done so far (the chip for my custom tune has been removed, FYI):

- Cleaned MAF
- Cleaned TB
- Cleaned IAC
- Replaced TPS sensor
- Replaced spark plugs (gapped at .054) and plug wires
- Replaced O2 sensors
- Replaced fuel filter
- Replaced distributor, cap, and rotor

Before I replaced the distributor, I ran a KOEO test using a Ford EEC-IV code scanner and passed (111 codes) and ran a KOER test and got codes 137 and 411. During KOER, the car shut off once the test was done revving the engine.

After I replaced the distributor, I passed KOEO again and during KOER, the car shut off again and I only got the one 411 code.

I'm pretty much at my wits end with this car. Any other suggestions as to why my car is still jerking / running like crap when at operating temp?

Thanks!
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Old 06-06-2012, 07:58 PM   #17
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I have a 94 with an auto that has done exactly the same thing. I have corrected every code present in the system and it came up with no codes the last 3 times. It still has the same problem as yours has. At least this rules out any transmission problems as yours has a manual. Out of curiosity, how is your oil pressure?
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Old 06-06-2012, 08:32 PM   #18
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Quote:
Originally Posted by fl1a View Post
I have a 94 with an auto that has done exactly the same thing. I have corrected every code present in the system and it came up with no codes the last 3 times. It still has the same problem as yours has. At least this rules out any transmission problems as yours has a manual. Out of curiosity, how is your oil pressure?
Hmm, that doesn't sound good for me even if I get rid of all of the codes. My oil pressure is low (around the N or O on "NORMAL"). I'm not sure if I'm leaking oil or something else is wrong. I figured I would get to that after this issue... then again, they could be related.

Ideas anyone?
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Old 06-06-2012, 09:49 PM   #19
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Also, my fuel pressure is around 42 or 43 at idle. Not sure if that is too high for my engine and mods.
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Old 06-07-2012, 07:49 AM   #20
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Does your oil gauge move or twitch after the engine is at operating pressure or stay steady? Your factory gauge is connected to a 6 psi pressure switch, as opposed to a linear sender that gives a range of readings.
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Old 06-07-2012, 07:49 AM
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