RyanPerrella

no i dont idle along in 3rd gear when there is traffic.

i havent driven my car in 4 months but i think first gear at 10 mph is over 2000rpm. When you inch along you let the clutch out give it some gas nit the clutch again and coast to the bumper of the guy in front. You should only be in gear for a few seconds if your inching along.

heinrich

Happens in LH also.

heinrich

DJC, it actually has much to do with the drivetrain, the resonance of the torque tube and the flex in it ..... but the intake volume ... yes, sounds feasible. Ssssay ..... tbf ...

Bill Ball

I'm with Stan as regards the idle switch, but it may be the cable is too loose rather than tight. Take as much slack out of the throttle cable as you can AS LONG AS YOU CAN STILL HEAR THE IDLE SWITCH CLICK just barely off-idle (a degree or two). Just make sure it always clicks reliably and activates at idle. You can verify this by looking at the instant gas mileage readout on the digital dash. It should go very quickly to 90 MPG when you downshift and decelerate with your foot off the gas pedal. On the other hand, make sure there is a good amount of slack in the cruise control cable - it should not be snug. Even if this doesn't resolve your problem, a snug throttle cable, with the idle switch still operating properly, makes it more likely the WOT switch is tripping when you put the hammer down.

Randy V

Model year?

Candleman

1989 S4 5-speed

RyanPerrella

This apparently seems to be a regular problem, not just a putting along at 1000 rpm thing.

I cant recall ever having a problem like this. I need to drive my car!

killav

Mine is an auto, but it did the exact same thing, and it was the idle switch not closing. When I would barely step on the gas and then back off again to lurch forward in stop and go traffic, the throttle would not fully close and my idle would start to hunt up and down. I was able to reproduce this in my drive-way, popped my hood, and manually pushed the throttle blades closed. My idle returned to normal. Tighten up the throttle cables so that you hear the audible click every time you let off the throttle.

heinrich

Mike wouldn't that be "loosen the throttle cables..."? ... I think the scenario you describe is different. In the 5-speeds, when the driveline is engaged, there is not (like the auto) freedom for the engine to rev up or down against the torque converter, and gears stay engaged as opposed to downshifts being completely out of control of the driver. In the 5-speeds, the lurching happens when the engine drags on the driveline and gets into a wave of almost-die ... run ... almost-die. This is the lurching described.

UKKid35

The transmission shunt that you have described could be caused by many things as others have noted. But if you want it to virtually disappear all you have to do is replace your engine mounts. It is the collapsed engine mounts that prevent this shunting being absorbed.

This was the biggest and most satisifying result I found after changing the mounts. Please note that I used hydraulic mounts, which are not in fashion at the moment. I doubt solid mounts give the same anti shunt protection, they may be fine for autos but they don't have this issue, presumably because of the torque converter.

Ispeed

Also, I think the later cars ('91+) don't have this condition because of the thicker drive shaft (which due to less ability to twist, ends up shearing at either end) that twists much less.

shmark

I'm with Heinrich, and it can happen in all kinds of manual-trans cars. It's drivetrain "whiplash" and it comes from twist/slack in the various components. It can then be aggravated by computers/ignition/etc. if they don't have good controls to deal with it (god how I hated controls classes in college). Essentially you're hitting a resonant point in the drivetrain and it quickly amplifies. Try playing with the throttle while moving at idle speed and you can induce it quickly - my wife does it every time she tries to drive the Mini and that's a front-driver. Quick fix is to disengage the clutch and then be more gentle.

Candleman

This is good stuff. I'm on it. And Charley, go take a hike.

RyanPerrella

I didn't know 91's have a thicker driveshaft. Is this the shaft inside the torque tube or the half shafts going to the rear wheels? I never heard this before

jorj7

Thicker shaft on the driveshaft, but thins down for the connection to the
flexplate. I had the thicker shaft on my 90, but replaced it with a straight
shaft from an earlier year (because of the shearing problem).