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93 Geo Prizm chugs in 2nd gear

Now that the ignition coil is fixed, the same issue that started this journey many months ago is still there. And that is that it chugs when it switches from 1st to 2nd gear. It’s an automatic. It chugs (loses acceleration power), as soon as it changes, then I just keep my foot on the gas where it was to begin with and it recovers and takes right off after 1-3 seconds. It mostly happens in morning or when cold/foggy. If I take off faster from a stop light, it pulls through that much easier and either chugs less or not at all. A mechanic has recently looked at my gears and says they’re fine, but I take that with a grain of salt. What’s your magical answer?

(By the way, this is the problem that the dealership couldn’t figure out and told me to keep driving it till it got worse and then it’d be easier to diagnose!!)

Does anyone have a clue about this? It acts like I took my foot off the gas for 1-2seconds after it changes into 2nd gear. By the way, it IS fully going into 2nd gear, but then hesitates and then takes off again just fine. WHAT’S UP?!

This sounds like a driveablity problem, i.e. something wrong with the engine management system. This would be classified as a ‘stumble’. Is the Check Engine Light ‘on’? How does it do in third gear? How is it on at highway speed and on inclines?

Get back to us with more information.

No, the check engine light is not on and there are no codes. It’s fine in the other gears. Drives great. Only happens in this one “place” - after it switches into 2nd gear. That’s what’s perplexing - it seems that if it were a timing belt issue it would happen all over the place anytime. Can’t figure this one out. And I can’t imagine the VSS only messing up in this one spot, either. (Can it??) And the fact that it happens with varying degrees of stumble in different temperatures (ambient or engine temp) tells me it’s not the gears. Cuz like I said, I can floor it off the line and it pulls right through it. If only I could get the Clackett brothers to tackle this one, but they never choose my question for the show. Guess they only deal with easy stuff they can make fun of, like the guy that can’t get the washer fluid to hit the window. (duh.) But I keep trying.

Well, thorough 7, this is a stumper. Yes it is unlikely to be the VSS. It might be the TPS but that should show up when coming back on the throttle at freeway speeds. You are right it is unlikely to be valve timing or the timing belt. The only thing I can come up with is that the transmission is shifting too early and causing the engine to ‘lug’. This engine transmission might still have the TV cable so you might check that for correct adjustment.

Good luck. Post back if you cure this problem.

Shot in the dimness (almost dark) - I’m assuming that the shifts are controlled by solenoids. Find out if there is a way to test and/or easily replace the 1-2 upshift solenoid.

I know, it is a tough one. Thanks for your ideas, guys. I’ll see what I can find out along those lines. In the mean time, if anyone has any other ideas, I’d love to hear them. This one should be on “Stump The Car Talk Guys”.

The tps (throttle position sensor) tells the engine computer when the throttle moves. The engine controls spark and fuel flow in response to that signal. If the signal is erratic, the response will be erratic. The tps can have voltage spikes while moving just off idle position (not to be confused with idle rpm).

If you use an ohmmeter (multimeter) to measure the resistance while slowly moving the throttle off idle, you may see the values “jumping” high and low, or a flat spot where the value doesn’t change (it should). If you see this response, change the tps.

Thanks again for the wonderful advice. I will check this on Sunday and let you know the results. Much appreciated.