85 Porsche 928S Rescue p4 -- Alvin diagnoses the rough running engine

After getting the engine to run well with a new fuel pump, plugs, wires, and driving it a bit, the fuel pump died. We had it replaced under warranty, installed it, but then the engine started running really rough. What's going on?

[@kbar5821]

I have had an 85 since 2007, and from experience these engines can still run kinda ok with multiple issues (even down a cylinder!) until they don't so you did the right thing by taking it down to Greg. Basically at this point in their life anything on top of the engine that hasn't been replaced/rebuilt will need it done which is kinda why buying a high mileage but maintained car is a MUCH better proposition than a low mileage barn find.

[@alvinsautos7527]

Greg Brown at Precision got the 928 running great, drives really well. Car has since been sold.

[@fairmont___d]

Guessing it might be dirty injectors or plugs or stale fuel is a diagnosis?

[@DEEuroworks]

How did you get the fuel pump to start working? Having the same issue on a 87 928 as you guys had in part 3 of this series. Thanks

[@alvinsautos7527]

We installed a new fuel pump.

[@stereolababy]

that wall of bottles is great

[@alvinsautos7527]

Cool. Some of it is 50 years old, or more!

[@gazfish]

Have you checked the valve timing, done a compression test, check the injector spray patterns, got the MAF tested, CPS, temp sensors, engine cpu, ignition cpu....there's a lot that can go wrong on these engines. Sounds like your down to 4 cylinders so pull an injector lead one at a time to confirm. Highly recommended you download the workshop manual

[@alvinsautos7527]

Gary, yes indeed, a lot to sort through. We just had the car sorted by Greg Brown at Precision Motorwerks. Injectors/rails needed cleaning, some vacuum leaks were fixed, new plug wires/plugs...and now it runs STRONG! Compression is EXCELLENT across the board, runs like a beast now...like it should. We'll soon post another video. Thanks!

[@redbug3485]

Cool vids

[@michaelg492]

Have you tested for vacuum leaks?

[@alvinsautos7527]

Yes we did, finally got it running great, and the car was sold. Thanks!

[@patrickcoyne8624]

I wouldnt have driven it until a timing belt was replaced.Yhe euros and 32 valve US models are interference motors.Just sayin..I have a 1985,1982 and a 1981

[@alvinsautos7527]

When we got it we knew the belt had been changed a couple of years prior. Greg Brown at Precision Motorwerks confirmed it was in good order.

[@peterschmidt1453]

I 've had an '87 S4 since 2007. I had the timing belt done 2019, 12 years on and the old timing belt was still perfect, no wear or cracking of the rubber. Glad I changed it but the old one had plenty of life still in it.