S4 N/A

I put a rebuilt engine into my car last monday. Nearly everything that was used for the rebuild is used, but the compression is good, it seems to run and idle fine, no smoke.

I have the 3800 RPM hesitation, which was a problem before the old motor went, but I still haven't found a solution to it. That's not the issue here though.

I started the car today, the ambiant temperature was about -1C. I let it run for about 2 minutes while I got the snow off of the windows, then I jumped in it for a cruise.

Between 3 and 4 thousand RPM it lurches violently. And not just once, but multiple times. It happens in every gear. I shift at 4k right after I feel the 3800 RPM hesitation so I don't know if it does it beyond that, but it's usually lurching so bad that you can't even get there. It does not lurch if you are driving at a constant RPM, but as soon as you accelerate (no matter how softly you press the pedal) it lurches.

One the car starts to get warm enough that it registers on the stock temp guage

As soon as the engine gets warm enough to register on the stock guage the lurches dissapear, and the car drives perfect as far as I can tell.

 

Let the car actually warm up...?

 

Yes I know, it was a damn rookie thing to do. I usually do let the car warm up. However, if I would have done so I wouldn't have noticed this issue. On the occasion that I jumped in and drove before my motor went, it never did that. I would like to know the cause of it.

 

Full tuneup including a TPS adjustment. Check http://www.aaroncake.net/rx-7/grounding.htm for some info on correcting the 3800 RPM hesitation.