The dashpot on the TB of my '90 GTU does not appear to be adjustable. It is unlike the one shown in the on-line FM or Haynes in that it doesn't have an adjustment lock nut on the outer side of the device (see the attached image). There is a nut holding the device in place on the inner side, but it doesn't seem to have threads that would allow adjustment. Would appreciate it if someone can tell me if this type of dashpot is adjustable and, if so, how to do that. The nut is nearly inaccessible where it is located. TIA

 

Don't think I've ever seen a dashpot that really needed adjusting, but if yours does, I think the only thing to do is to create a little extension to the 'plunger' part with epoxy or something.

 

Thanks for the idea. That may be an option and I'll consider that.

The dashpots shown in the manuals are easily adjustable since they have a threaded central shaft with a lock nut on the outer side so that you can loosen the lock nut and rotate the dashpot to make the adjustment. This one ....?

 

I can't recall exactly, but I don't believe this can be adjusted on my '91 either. The engine is in pieces in the garage right now, so I can easily check this later today.

 

Thanks johnny. It's almost impossible to see what the thing looks like because of all the stuff around it.

 

Did you get a chance to check out your dashpot? I think mine is similar to the dashpot on the TII and that one is adjustable. Just gotta figure out how to get a wrench in there to loosen the lock nut.

 

Geez, I forgot completely...sorry 'bout that. Will do tonight for sure.

 

OK..it just look decieving. The shaft of the dashpot is threaded and threads into the holder. The nut is just a lock. By far, the easiest was to adjust this is going to be to remove the throttle body or the upper intake manifold.

 

Many thanks for checking Johnny. I suspected that was the case but just couldn't see the dashpot well enough to tell. Was that the only locknut or was there another one on the other side of the mounting plate? Maybe I'll pick up one of those small mechanics mirrors and see if I can get at the nut(s).

I just had some of that apart yesterday when I removed and cleaned the BAC. Guess I could have taken the next step and removed the TB. I'll check the TPS today and run the car to see if I still have the intermittent stalling problem.

Thanks again!

 

Yup, that's the only locknut. Loosen it up and you'll be able to turn the dashpot.

Describe your stalling problem? Does it just die at idle, or when you let off the throttle, or...?

 

I tried to get to it with an end wrench but that doesn't look too promising. May have to remove the TB. I did get one of those mechanics mirrors so that I could get a better look at the lock nut area and I see the threads on the shaft on the other side of the mounting bracket. So, I will tackle that one in a day or so.
Car goes through the "standard" startup sequence--3K initially dropping to 1.5K then when fully warmed up dropping to about 700-750. Idle is very stable when idling. Blipping the throttle and watching the revs drop, the idle usually drops to the 700-750 range with noticible damping expected of a functioning dashpot. However, the occasionally the idle drops to ~500 before jumping back to 700-750. The occasional stalling happens when underway, not sitting and idling. For example, driving along in 2nd or 3rd slowing down preparing to stop and/or turn and pressing in the clutch, the revs will sometimes drop like a rock to the 500 level without any noticable damping, occasionally stalling. Sometimes the revs will just bounce off the 500 mark and the car will shudder a bit as if getting ready to stall.

After cleaning and testing the BAC, I adjusted the TPS today using the 2-bulb method and then checked the resistance on the relevant connector pins and all checked out fine. I did make a minor adjustment to the TPS, but a test drive indicates that this didn't make any difference. So I will continue to troubleshoot other components. Fun!

 

When you take off the throttle body, also inspect the thermo wax thingy that controls the fast idle cam. If that isn't working properly, it usually gets stuck in the extended position, which keeps it in fast idle, holding the butterfly open in the throttle body. Then, when you set the TPS, you set it wrong (the throttle isn't fully closed), which has the BAC valve pumping more air into the engine than it's expecting at idle.

 

Thanks for the idea Johnny, I'll certainly do that.

 

Removed the thermovalve and using the testing procedure in the FSM it checked out OK. Only thing remaining I figure is to adjust the dashpot, but according to the FSM and Haynes, you need to have the car running in order to properly adjust the dashpot. So removing the TB to get at the dashpot doesn't seem like the answer. Just testing the dashpot manually and watching it in operation it seems to be working as designed, but I suspect it needs a little tweaking to solve my idle drop problem.

Thanks again for your help! I'll figure something out.

Larry

 

Larry, if you loosen the set nut while the TB is out of the car, then you should be able to grab hold of the dash pot and turn it while it's mounted in the car. Although, I'm hardly optimistic that the dashpot has anything to do with your problem, but I really can't come up with anything else.