General Tech Good at troubleshooting? Have a non specific issue? Discuss general tech topics here...

now it runs poorly

Old 05-12-2008, 06:54 PM
Thread Starter
Join Date: May 2008
Posts: 2
Default now it runs poorly

I have a 73.5 911t that has PMOs on it. The car was located and tuned toan altitude of about 4000'. When I drove the car home(about a 1,000 mile trip)andit ran finebut the carbs would pop, burp and hiss at startup. They did this when I picked up the car as well as when I got it home. I took it into a "Porsche Specialist" for a tune-up, valve adjustment, and carb re-jet. The car starts and idles much better than it did, but, now it starts to miss (very badly) at about 2800 rpm. I took it back to the shop that worked on it and he tried everything to get it to run right. He changed ignition modules(MSD) and tried to put a set of webers on the car. He tried 3 different distributors, check fuel pressure and flow, new gas, and it still runs horrible when trying to maintain a constant idle above about 2800 RPM.
The mechanic says my camshafts are not compatable for the carbs, but my car never missed like this prior to my expensive "tune-up". It's really not drivable.

Any Ideas?
Old 05-12-2008, 07:56 PM
Join Date: Mar 2008
Posts: 380
Default RE: now it runs poorly

Good chance the C/O (the fuel distributor adjustment) will need to be checked and reset, and that is likely the cause of the backfiring you’re getting. You'll need to do this with a C/O machine as it is very difficult to do this accurately enough by ear. You will likely also find it necessary to set the C/O higher than the original specs due to the different gasoline we have now, about 4 to 5%. Also, check your fuel filter at the bottom center of the tank and make sure it is clean.
Related Topics
Thread Starter
Last Post
Porsche 944
12-04-2008 08:14 AM
Porsche 944
09-24-2008 08:10 PM
General Tech
09-05-2008 02:56 AM
Private For Sale/Trade Classifieds
08-08-2006 02:30 AM
Porsche 924
03-21-2005 10:55 PM

Thread Tools
Search this Thread
Quick Reply: now it runs poorly

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to and affiliated sites.