Rough idle? maybe not

[busteif]

1976 - 930 (12,100 miles)

So I receive the car a month ago and drove off the trailer into my garage, amazed at the idle smooth revs and everything else. a week later I take the car out of the garage and wash her down let her run and put it back in the garage. meanwhile for the next couple of weeks I would start her up daily for about ten minutes.

Weather clears up in the upper 50's I decide to take the car out, as I drive uphill from my home it backfired twice, no issues kept driving, but felt a little roughness in the idle. since then the weather went sour again and I've been starting the car up in the garage but could feel the idle a bit rough and when I step on the gas I don't get the smooth VROOM feeling you normally do, rather VBBBBROOM (hesitation) issue.

Yesterday, took the car out and went for a drive, still with a bit of idle roughness, after 10 minutes of driving I stepped on it a bit and was coming up to a light and had to slow down quick - downshifted and it backfired twice. revs got normal again and no issues - step on the gas and it was as new again with no hesitation.

What caused the issue?
Is it going to comeback again ?
What should I check to prevent it again?

Thanks all for you input.

[Miguel Antonett]

First of all, don't crank a 930 for few minutes in the garage and turn it off - don't do that - it is a killer for the turbo and fuel system. You are better off just leaving the car alone until you can run it and heat it up to "operating" temps. I would wait until you can do just that, and open it up, take it up in RPM's (blow/flush the system out) may be put some Techron in it before that "long ride", burn a full tank of gas. If the car still hesitates after that run, then start looking for other things. Seldom/casual/once in a while mis-firing/poping is not unusual in 930's. During that first run watch for oil level, temp and pressure.