car jumping for first few seconds

[micbrody]

This has happened twice in one week. Other times no problem:
I start car in garage. It starts fairly easily. About 15-30 seconds later I back out of garage in reverse. I get into street, put in first gear, and car violently jerks while trying to go forward. Thinking maybe my transmission is not fully engaged, I press clutch and put into first again. It gets better; and after 10-15 seconds, everything seems fine. And remains fine for rest of drive to work. Great acceleration; normal shifting

My differential diagnosis:
1) I am not fully engaging first gear; or clutch released too soon. I don't think its that, because it lasts 5 seconds longer that it should when I redeploy clutch and gear shift
2) Can clutch be failing? or can there be moisture or something causing slippage of clutch plate. Eventually, after some revolutions, the friction becomes normal (just a mental theory; never heard of it)
3) Temporary fuel starvation. Why would occur about 30-60 seconds after starting? unless increased load of going forward on level street vs backing down driveway in reverse.

Any thoughts apppreciated

micbrody

[TX82FIAT]

First, assume about 1 inch of travel before the clutch starts to engage indicating proper adjustment. Also assume you know somewhat the condition/age of your clutch and it is not a worn clutch.

The fact that the car shifts fine after the initial bucking assuming you have to go down to 1st a few times on your way to work makes me think you clutch, cable and fork are properly working with respect to movement. If you think it is fuel starvation then let the car warm up for a little longer and rev the engine a few times before engaging 1st gear. It could be cold start related or fuel related, but I doubt it.

Your second hypothesis may have some insight. oil leaking on the clutch plate could cause a lack of friction or slip as it gives. The clutch would eventually have enough friction to run. However, if there is fluid on the clutch plate is could glaze and contribute to further issues. I would try to inspect the clutch plate. I know easier said than done.

[azruss]

what year is the car, what motor. does it have a cable linkage to the carb.

[micbrody]

Fiat 2000 Fuel injection 1981

[bradartigue]

I doubt it is in the fuel system. Within that 15-30 seconds of idling you've pressurized the entire system, the cold start injector is off. Nothing else is going to cause a bucking like that, especially if it runs fine after...anyway:

Does it do this after you stop and restart, or only after it sits all night? Oil, etc., on the clutch may have an odor, does anything smell funny when it does this?

[76was124]

Have you check'd the trans oil level and know the type and history of when it was put in there?

[RoyBatty]

IS it the same as this problem?
http://www.fiatspider.com/f08/viewtopic.php?f=5&t=31192

[bradartigue]

IS it the same as this problem?
http://www.fiatspider.com/f08/viewtopic.php?f=5&t=31192

It wouldn't be; the jerking described in the prior post is very common on cars with the rod accelerator linkage and small carburetors e.g. 1970 Spider w/1438 and DHSA1.

My Mazda GLC would do this - 1981 GLC that is - "bog down" because we used the cheapest gas you could find. Until it warmed up it had some problems ingesting the leaded 86 or so octane fuel we fed it.