G Man

My 84' has been running a bit rough lately and I have been going through things in an attempt to resolve the issue. I found a crack in the cap and replaced that. Still running rough. Replaced the plugs and still running rough. After doing some research here on Rennlist I decided I would go through and open up the gaps on my plugs to .32. I had originally set them to .28 and even though that is spec it seemed to small for my liking. When I was in there yesterday I had to unbolt my airbox and move it out of the way in order to gain access to the rear plugs. Taking out the drivers side plug I discovered that the fuel pressure regulator on that side did not have the vacume line attached to it. I have no idea when this came off. The rubber connector was not broken and was still flexible. Since the two regulators share the same vacume source I am guessing that the passange side FPR was suffering from very low or no vacume as well. I reconnected the vac line and finished gapping the plugs. The car runs and idles great now. So, did this simple act of reconnecting the vac line to the FPR solve my rough running issue? I don't know for sure but it seems to have quite a positive effect by hooking it back up. What was happening with the vac line disconnected that would cause my car to run rough?

dprantl

Most definitely. That disconnected line was a vacuum leak, and that will affect idle stability. The FPR being disconnected would also affect the mixture, although the O2 sensor should compensate once the engine is warm unless it goes outside of its adjustment range.

Dan
'91 928GT S/C 475hp/460lb.ft

G Man

When it warmed up it ran ok, but at cold temps it seemed like it had a very noticable miss. Since the repair I have only had it around the block. I really need to get it out on the road to make sure all is well.