3.2 backfires

[mmasse]

My friend wants to buy a 911. We went to try one 1985 today. The car looks in mint condition, but there are a couple of things I would like to check with you guys.

After some spirited driving the engine would backfire. Is this this bad? What could be the possible cause of this? WOuld this be a reason to walk away?


Also when downshifting to 2nd you get the typical grinding noise. I assume this is the second synch, right?

Thanks a lot in advance

[twin plugged targa]

I think you probabley already know the answers to your questions- no the car should definately NOT backfire after spirited driving! and the gears should not grind in any gear/shift. However if the couplings are worn the shifts may be worn causing you to miss a gear and possibly crunch it!.
I would drive it some more or drive a few others to feal if it is either your technique or the couplings or the synchros as suspected.
The only way to know this is to either have someone else drive the car in question or drive a few more and get a 'feel' for these cars!.
2nd gear synchro is usually the one to go as people tend to rush 1st to 2nd when drag starting!.

I had an 86 Carrera which had bad end float on the drive unit of the distributer which caused the car to backfire when driven hard but would be fine after it cooled down. This is rare but still possible- I feel the backfire may be something much more regular/simple

Hope this is of some help
Rgds Ben

[BReyes]

I would ask for history including service records. The backfiring could be a dirty distributor cap. The 915 needs to be shifted slow and smooth. Does is shift into second with out any noise during normal shifting into second from 1st? Who was driving? I remember a 915 I had and due to the nature of the shift into second it was remarkable, yet the car was awesome with proper driving.

Unless I am mistaken the motronic should adjust for altitude.

Who is going to service the vehicle? Have you told him about a PPI? Can they give it a leakdown?

Regards,

[Por_sha911]

Everyone repeat the mantra:
Get a PPI.

[mmasse]

I was driving the car. I have a '76 with a 3.6 engine and 915 tranny. I feel the 2nd gear is a synch problem, since shifting is quite good on other gears in terms of feeling. Actually my 915 feels much looser.

Any more insight into the backfiring?? Any other potential causes??

Thanks

[mmasse]

Some more info. I was following the car while my friend was driving and saw that there is some white smoke coming out of the exhaust when he donwshifted. What could be wrong?

[azasadny]

Is it a $20,000 car? It will be...

[Hugh R]

White smoke on downshift in most cars means the valve guides are going. Backfire, depending on when it happens, can also mean the valves are burned.