Hesitation under steady throttle

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rubydist

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you need to fix the speed sensor problem. I have had cars run stupid, including bucking and jerking if the speed sensor is sick. on the auto, a sick speed sensor can also make the transmission randomly shift up or down. you need to get that fixed.
 

zach44102

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Generally speaking, 80% of ignition problems (bucking/surging) are caused by plugs and wires, 10% by the DIS, and the last 10% are shared by the coil pack and the cam sensor. The cam sensor going bad will usually present other symptoms. The not wanting to start first time up is one of those symptoms.

also another .5% are from a exhaust valve not seating correctly.:wave:
guess which ignition problem i have?
 

Terrorizer

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you need to fix the speed sensor problem. I have had cars run stupid, including bucking and jerking if the speed sensor is sick. on the auto, a sick speed sensor can also make the transmission randomly shift up or down. you need to get that fixed.

I cleared the codes and re-checked them and the speed sensor didn't show up again, only the lean condition. But I will keep my eye on it, it could be the problem.
 

Brett

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Good luck buddy. If you find a solution to your problem PLEASE, please PM me. I have had no codes but 1, the "running lean on bank 1". My car hesitates under steady throttle like yours. ive done a full front and top 60k including valve lash adjustment and things like plugs, wires, o2's, etc. i still have the problem. Ive asked before to no avail. i think im gonna try replacing my old crappy vacuum lines.
 

msteiny

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Have you guys tried new/different injectors? There was a question on here not long ago about missing at start-up, not sure on the specifics. Anyway, this person changed out the injectors and I guess the it runs like new now. If it were my car, and I have been everything you guys have done and I am still getting a lean code I would think I have some type of restiction in the injector. Just my 2 cents.
 

RedDemonSHO

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my 94 MTX is doing the same thing. i have a 92 MTX i have pulled every sensor off of it and put it on the 94 and it was still doing it and the only codes i would get was a running lean or running rich for last resort was going to pull the vehicle speed sensor but havent got one i ordered yet so i unpluged it and the car is running 97% better no more jerking or misfiring or smelling gas and it only kinda cuts out at 4k rpm when the short runners kick in but i think its cause there is no signal (because its unpluged) to advance the timing for the boost in air at 4k will know if it fixed it when my part comes in try unpluging the speed sensor and seeing if that helps on yours
 

Terrorizer

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I just checked my cruise control and it isn't working, the light doesn't even come on the dash. I figure this could have to do with the speed sensor. Where is the vehicle speed sensor located. I can't find it in my service manual and I did a search but I only found posts about auto transmissions.
 

TYSHO

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Bottom Arrow:

shospeedo1.jpg



New:

sho-mtx-vss.jpg
 
Last edited:

RedDemonSHO

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this is a question off subject but what is the plug in upper right that isnt plugged in i have it on my 94 mtx but not on my 92 mtx and have no idea what it goes to justs wondering thanks
 

Terrorizer

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How do I disconnect the VSS to see if it helps the bucking. Should I just pull it out or do I need to unscrew it?
 

TYSHO

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this is a question off subject but what is the plug in upper right that isnt plugged in i have it on my 94 mtx but not on my 92 mtx and have no idea what it goes to justs wondering thanks

It goes to a time machine.
 

hawkeye18

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this is a question off subject but what is the plug in upper right that isnt plugged in i have it on my 94 mtx but not on my 92 mtx and have no idea what it goes to justs wondering thanks

That is actually a test port for the VAPS system. Few people know that VAPS has a test routine/plug, but it does, and that's it.
 

TYSHO

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Do I need to pull the pin out to the side to release it?

The pin, or whatever you want to call it, is for the speedometer cable. You do not pull this, you need to pull the electrical connecter that has electrical wires.
 

Terrorizer

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I pulled the speed sensor and drove it around the neighborhood. The bucking/surging seemed to get slightly better but it was still quite noticeable. It wasn't 97% better as red demon SHO described his car got with it unplugged.
 

Terrorizer

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Does the fact that unplugging the speed sensor didn't help the hesitation rule out a speed sensor problem or is there a better way to test it. Currently that is my only code I'm getting but I haven't been driving the car much.
 

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