1991 Running Rich

[E Sully]

I have a friend with a 1991 928. Mileage is only in the low 20 thousand range. It was stored for a while but came out this year.
The shop has sent out all the electronics which check out good and has a new MAF.
It does not like to idle and can be driven but runs rough. The belt has been changed and timing is good. Fresh gas and fuel pressures all measure good. Problem is it seems to run rich. The spark plugs are all on the dark side from carbon. Temperature and other sensors test good. Could it be all the injectors are in need of cleaning, replacing, or possibly a relay?
Suggestions?

[harborman]

I would run a couple of bottles of Techron in it. See if that works.

[stepson]

E Sully,

Check to make sure the correct spark plugs are being used. Don't use the platinum or iridium plugs. There have been reports in the past about idling and running issues with those versions of spark plugs. Just use good old copper plugs

[76FJ55]

Also it would be worth checking the vacuum lines attached to the fuel pressure regulator and dampers to ensure you don't smell any fuel in them . if the diaphragms start to leak on any of them the fuel pressure will still be in the correct range, but you will get extra fuel drawn in through the vacuum system and this will cause rich running.

[E Sully]

It turned out to be injectors. It started to run better after some mileage with cleaner added. They are being sent out, and hopefully cleaned and re-used.

[harborman]

Originally Posted by E Sully

It turned out to be injectors. It started to run better after some mileage with cleaner added. They are being sent out, and hopefully cleaned and re-used.

Did you use the Techron cleaner ?

[E Sully]

Drained tank and used Techron with fresh gasoline. It was improving, but want the injectors tested and cleaned to make sure it runs as good as possible.

[harborman]

Originally Posted by E Sully

Drained tank and used Techron with fresh gasoline. It was improving, but want the injectors tested and cleaned to make sure it runs as good as possible.

All I would do is run a few more bottles of Techron in it and drive it.

[E Sully]

Owner wants them serviced. He'll feel better after seeing the spec sheet showing flow and spray pattern, and if any fail will want that addressed. It's only money, and the car is in great shape.

[E Sully]

There is a Service Bulletin on using Techron.

[harborman]

Originally Posted by E Sully

Owner wants them serviced. He'll feel better after seeing the spec sheet showing flow and spray pattern, and if any fail will want that addressed. It's only money, and the car is in great shape.

All I am saying is the Techron did the trick on my 928 which had been in storage a long time. It is a simple fix. No need to spend a lot of money.