Quest jerks at high speeds on the highway

[mckenziepiping]

I know there are many other threads about jerking, but they all contain too many variables for me to relate them to this case.

As soon as I go faster than 110km/h (65mph), my van starts to slightly jerk every 2-3 seconds. It feels like I'm releasing the gas pedal for a fraction of a second and then pushing on it again.

I think there may be an issue with the transmission because lately it seems to get stuck in a low gear when I'm accelerating and doesn't want to switch to a higher gear, so I have to release the gas for a second to make it do so. But could a transmission problem have an effect when cruising (i.e. not shifting gears)...?

The van does NOT:
- display any warning lights on the console
- jerk at any speeds below the one I mentioned
- jerk when accelerating at high RPM, I've tried tramping down on the gas to make the RPMs go up to 5-6 and this does not cause jerking
- jerk when accelerating without downshifting
- stall when parking
- show any loss of power

My mechanic said it could be due to the fact that my thermostat is broken (the engine temperature is always on "cold"), but this has been the case for over a year, yet the problem started only a few weeks ago.

I've tried using fuel injector cleaner and it doesn't seem to be helping. I've read on other threads that spark plugs could be a candidate, but wouldn't that be ruled out by the fact that the problem doesn't occur when accelerating from lower speeds?

[tempfixit]

Originally Posted by mckenziepiping

I know there are many other threads about jerking, but they all contain too many variables for me to relate them to this case.

As soon as I go faster than 110km/h (65mph), my van starts to slightly jerk every 2-3 seconds. It feels like I'm releasing the gas pedal for a fraction of a second and then pushing on it again.

I think there may be an issue with the transmission because lately it seems to get stuck in a low gear when I'm accelerating and doesn't want to switch to a higher gear, so I have to release the gas for a second to make it do so. But could a transmission problem have an effect when cruising (i.e. not shifting gears)...?

The van does NOT:
- display any warning lights on the console
- jerk at any speeds below the one I mentioned
- jerk when accelerating at high RPM, I've tried tramping down on the gas to make the RPMs go up to 5-6 and this does not cause jerking
- jerk when accelerating without downshifting
- stall when parking
- show any loss of power

My mechanic said it could be due to the fact that my thermostat is broken (the engine temperature is always on "cold"), but this has been the case for over a year, yet the problem started only a few weeks ago.

I've tried using fuel injector cleaner and it doesn't seem to be helping. I've read on other threads that spark plugs could be a candidate, but wouldn't that be ruled out by the fact that the problem doesn't occur when accelerating from lower speeds?

What year vehicle?? When was last tune up? Plugs, wires, fuel filter, etc. Have you checked the distributor shaft for any looseness or the bolt being loose that holds the rotor on?

[mckenziepiping]

It's a 94 with 260 000 miles

[mckenziepiping]

Last tune up was over a year ago. Not sure what a distributor shaft is but I'll google it

[tempfixit]

Originally Posted by mckenziepiping

Last tune up was over a year ago. Not sure what a distributor shaft is but I'll google it

Welcome to AF.

Take off the distrubtor cap, ( Here is a link that shows distributor)
http://www.oreillyauto.com/site/c/se...994&vi=1212512

Inside there is a rotor on the distibutor shaft, see if there is any side to side play.

Also try disconnecting the upstream oxygen sensor for a few days of driving to see if it still produces the jerk.

Have you owned vehicle since new?? Has the timing belt been changed??

Yes a cold operating engine can cause the engine not to fuction at its best, the pcm does not get the correct info from all the sensors thus it will not operate at peak performance. How is the Gas mileage???

PM also sent.

[tempfixit]

When was the last time the transmission filter and fluid was changed. I assume tranny fluid is at proper level.

Have you ever cleaned the Mass Air Flow Sensor on the air filter housing?? Clean with either mass air flow sensor cleaner or carb cleaner. Spray the sensor and the screen clean but be careful as the wires are quite delicate.