hdteran

Continuing with my rebuild (keeping the threads separate for every issue).
My car starts and idles with no problem. Once i get it on the highway at 75mph the engine seems to cut off or something happens, the revs fall about 250 rpm for a split second. The gremlin comes and goes, it is hard to repeat. In the old days one would say "bad gas" however the tank was cleaned less than a year ago and the injectors serviced. Again no issues on idle or even acceleration from moderate to high... it's more at cruising speed. The tiptronic light on the clock comes on every once in a while however it goes off on it's own. I ran the codes and none of them are coming up. Any ideas? Thank you

Jacke2c

Check the 19 or so grounding points on your car..... I know that can cause this type of issue.

hdteran

Thank you I will check that out.

cjoenck

Fuel pump? Do you have a way to test fuel pressure?

RicardoD

FYI, I just went down the Fuel Pump Tester rabbit hole. This is great solution, with the right fitting that mimics the ball bearing seal, to test the fuel pressure regulator and fuel flow on our cars. Please see the workshop manual on how to do this.

http://www.arnnworx.com/catalog/index.php?main_page=product_info&cPath=65&products_id=348#.XtBVny2z1Bw

https://rennlist.com/forums/964-forum/840679-1990-c4-engine-rebuild-diy-4.html#post16629063

tbill

Had somewhat same issue with my ‘88 911 G-50. Startup was great, drove for ten minutes just fine. Then began cutting out. Replaced gas tank, Plugs, fuel pump, Distributor cap, injectors an who knows what else!

Then read on Rennlist about someone else having the issue. They replaced the cylinder head temp sensor, which fixed their issue. Did that with mine also an has not missed since! Just a suggestion.