MFI problems

[tom dance]

A good friend has a 70E, just rebuilt motor but still has some problems that I suspect are from the MFI. Here are the symptons. Most are when the car is cold.
- Very hard to start cold.
- Then runs rough and backfires.
- Low on power, especially in lower revs.
- When hot is will run good.
- Seems to be quite rich.
I know there is alot of knowledge here on these things. This guy would really like to use this car as a dalily driver but this problem is vexing him. Anybody got an idea what this could be?
tom

[mobius911]

There are numerous threads on this topic both here and at the Pelican bulletin board. Much of the Pelican stuff has been distilled and can be linked form the Tech page on this site (http://www.pelicanparts.com/techarti...FI/TipMFI.htm).

Many people find MFI tuning daunting, but it can be done by someone with a moderate mechanical ability and the willingness to learn. Your friend will need to get a copy of the MFI Check, Measure, Adjust manual from Porsche, which can be downloaded from the above link. This manual has all the critical information in it.

The first step in MFI tuning is to make sure that the basics are set properly: correct and good condition plugs, wires, rotor, cap, etc.; ignition timing, dwell, and injection pump timing set properly; cold start enrichment working properly, and the injection butterflies set properly to their stops in the closed (idle) position. Only at that point should you begin to mess with the injection system itself, and I can tell you from experience that diving into the injection adjustments without having the basics set correctly just leads to many hours of frustration.

Key tools for MFI tuning:

1. Timing light
2. Dwell meter
3. Air synchrometer tool for adjusting the stacks
4. Bosch MFI adjusting tools (3 tools that cost around $40)

I also ended up buying a CO meter but I've subsequently found that I can get the adjustments right without it.

There are numerous potential causes for your friend's symptoms. Start with the basics to get a proper baseline and take it from there.

Jeff

[304065]

Broken thermostat hose, either lower or upper, or defective thermostat.

There is no substitute for a thorough run through check measure adjust. Have your pal download it from Pelican and perform each step in detail. Don't jump ahead-- each step is very important.

You can search under my name over on Pelican for about a dozen threads with photos I've taken on the MFI system. In particular, there's one about the thermostat.

Also search for the cold-start system-- this could be part of the problem if it's running continuously.