Hi, I have a 95 xj6 x300 base model. It shifts and drives fine around town. However, when I’m at highway speed 50mph+, whenever I release the gas pedal, the cars jerks a little and I hear a slight sound. I’m worried about the gear box. Is it normal for older car? I took it to the mechanic but he said he didn’t notice, I’m not sure if he took it on highway tho. And he said fluid level is fine. Please help!

 

When you let off the throttle the inlet air control valve modulates to not have the engine stall

Do you have any CEL codes

Is the transmission shifting gears strangely like drooping from 4th gear to 3rd when it shouldn't be or only when you let off the pedal ??

 

it doesn’t have any CEL
the gear shifts up perfectly when I press (hard) the gas pedal. The jerk only happened whenever I release my foot from gas pedal when driving above 50mph. However, when I release the gas Very very slowly, there is no jerk.

 

The IAC valve does not have a sensor the verify it is in the position commanded by the ECU

You can put a meter on the ECU connector ( the black one ) and test the legs or windings of the step motor but it probably won't fail unless the step motor is warmed up or tapped on

See page 88

www.jagrepair.com/images/Training Guides/801S - 2000.pdf

 

Thank you for your reply! Sorry I’m very new to the car scene and completely dumb about cars lol..I did look up the terms iavc step motor and ecu..I only understand about 30% of the instruction here. I guess if the car is not stalling i will probably just have to get used to the jerking..

 

It might be worth taking the Throttle Body, IAC, EGR assemblies apart and giving the a good clean.
Mine were pretty dirty when got my cars and it made a big difference.
The IAC valve would be a primary concern.
Does it feel like a transmission or gearbox issue, or could it be more engine related?

 

Say no to the jerk and enjoy the grace

Good definition of the problem

Some friend may be challenged with electrical meter skills

Their is a good Youtube tutorial on the use of a meter from Fluke meter manufacture

Do not remove the IAC valve yet as can be difficult with bolts breaking because they are glued in with locktite adhesive

The IAC bolts are a odd size like 5.5 or 6.5 torque bit but don't damage them with a loose fitting torque bit

 

Could be some extra play in the U-joints of the driveshaft or axles. Or the driveshaft center mount. Easily checked with car on a lift. Driveshaft U-joints are durable. The 4 axle u-joints have grease fittings and need greasing as they are under heavy duty.

 

What SleekJag12 said .

 

Leave the IAC alone. They are 5.5mm heads and they are loctited in so they will snap if you’re not careful.

I would start with a cleaning of the throttle body. Sticky deposits on the butterfly can cause this issue.

The EGR can also cause this. Wait on this one. It will eventually stall your engine out and, if you’re lucky like I once was, you’ll be awarded with a code….eventually.

In any case, start with the cheap and easy. Clean the throttle body.

 

5.5 mm hex heads is correct and is a good idea to remove and clean the oil residue in the throttle body that causes problems in the idle area ( this is a common thing with this engine )

While you have the TB off you can best remove the IAC valve if you desire

You have little clearance with a 5.5 socket hitting other items with the TB still installed so it gives you room to work

By applying heat to the inside of the TB where the IAC mounting 5.5 mm bolt threads into the TB you can loosen the adhesive locking the bolt from removal

There is no gasket between the TB and the intake manifold

You don't necessarily need to remove the intake manifold

Do not remove the throttle position sensor ( mounted on the bottom ) from the TB assembly

There are 2 engine coolant lines into the TB assembly that heat the TB throat for cold weather operations ( icing of the throat )