How test/inspect 2.0L DJet throttle body before swapping it in? Options

[Tdskip]

Hi - the '75 DJet car has a stumble that happens at a couple points in the rev range and at certain RPMs when the throttle is held constant. It rarely happens when the throttle is being exercised up/down the RPM range (like accelerating through turns etc).

I'm thinking worn throttle body "fingers" or the trace pad they travel against (yeah, wrong terms I know) but I believe this could also (maybe) be a sticky advance weight in the distributor.

Any why to test the spare throttle body so I don't swap out the wrong thing?

OR

Should I just pull and open the plastic cover on the one I have to see what is up? Doesn't look that hard to remove it.

What say you gentlemen, and please do liberally apply terminology dope slaps.

Thanks!

[rjames]

The board definitely looks worn, but it's also easy to disconnect the TPS see if the stumbling is still there. I'd do that first before anything else as it may be a air/fuel mixture issue as emerygt350 suggested.

If it's the board, you also may be able to bend the TPS contacts out just a bit so they aren't going over the same worn area on the board. Again, easier to do than replacing the board and worth a try before tossing it- especially if the reproductions aren't reliable (I' not saying they are, just going off of the comment by Jett).

As far as inspecting the throttle body, a smoke test (with it installed in the car, or off the car if you can seal up the bottom and top ends) will tell you if it's worn. Often they leak from the idle adjustment screw and the cure is to install a bushing. However, a leak would more likely result in a high idle, not a stumble in the middle of the RPM range.