I've had this problem a while now and it seems quite random. All I know is that when I accelerate from a stop it hesitates only when I floor it or push on the pedal rapidly. If I slowly accelerate no problem. I'm in the process of replacing vacuum hoses on the car but I really haven't found a leak. My idle is normal. I set it using the adjustment screw and it hasn't change much in the past 6 months since the last time I set it. I recently had the fuel pressure regulator and fuel filter plus fittings replaced as I had a severe leak. The problem was there before that and after. Car runs normal when driving and normal idling. Could it be a timing issue? I'm really confused. I did notice the car drops RPM rapidly when I disconnect and plug the vacuum hose that does to the pcv system ( at the flame trap). I plugged both ends. It seems like it doesn't react fast enough when pushing hard on the pedal. Also if I do this at speed say 60km/hr and acclerate to 100 no hesitation. My top speed hasn't changed either. So no loss of power there.

Thanks in advace
Chris

Something else you can check. When you stomp it, the motor torques to one side and exposes splits in the intake snorkel tube. Sometimes they can be hard to see, and the problem would be exacerbated with old/soft motor mounts.

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Gary Gilliam Sumerduck VA, '94 940 Regina 168k '86 240 198k, 93 Camry 4cyl 5spd 245k

Maybe your IAC is sticking - not closing when you punch it, so the mixture goes too lean?

What happens if you:
1) punch it half way
2) wait till it gets past the hesitation
3) punch it the rest of the way

If it gets past the hesitation in 1), and it doesn't hesitate when you punch it the rest of the way in 3), then I would think it could be the IAC, in that it would have closed by step 2), and wouldn't be a problem in 3)

If it hesitates in 3) also, I would think it's more likely a fuel delivery or ignition vacuum advance issue.


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David Armstrong - '86 240(350k km?), '93 940T(270k km), '89 240(parts source for others) near Toronto

Thanks for your response.
If I punch it half way it doesn't do it. If I accelerate smoothly it doesn't do it. I think you might be right with th aic because if I'm already moving and I punch it no problem. Its only when it comes to a complete stop. I'll try the old remove and clean trick. I've never cleaned it since I've owned the car. Seems all my problems started after switching to synthetic oil. Maybe some sludge loosened and went down by the aic.

I'll let you know how it turns out.

Great weather here in southern ontario eh? Glad I didn't buy the snow tires this year.