SuperPorsche928

Hey everyone, so i own a 1985 Porsche 928S ( 4 speed auto, 5.0L V8.) This morning on my way to work, when i stepped on the gas, the car would hesitate to go any faster, sounded like the engine was cutting out. The RPM's would drop, but i drove it a few minutes more, super light foot, it got a little better, but again when i would step on the gas, it would bog down and decelerate and cut out again. but in high RPM's, it would do just fine. So i downshifted into 2nd, going 40, and got it up to about 5200, and after that it drove completely fine.

Any ideas?

dr bob

Welcome to the 928 Forum!

Spend some time reading through the "New Users" thread at the top. It has links to many common issues and solutions.

Knowing virtually nothing about your car my first instinct is to replace the three critical relays in the central electrics panel, forward of the passenger's feet. These are the fuel pump relay, the EZF/Ignition relay, and the LH/Injection relay. These are common Bosch 53b-type relays. Buy good name-brand replacements like Bosch, Potter & Brumfield. Avoid the cheap carded relays at the local parts store if you can.

Ground points need to be clean for all the sensors and other "final elements" like the fuel pumps to work. There's an annual electrical maintenance protocol that includes inspection and cleaning of all these connections.

The three relays mentioned above each receives power via its own dedicated feeder from the battery. Look at the smaller wires in the battery well where they attach to the positive battery cable clamp. The ring terminals need to be clean and bright, the nut needs to be snug. This is also part of the annual electrical maintenance protocol, along with cleaning the main connections to the battery.

What was last worked on? Sometimes I do a little collateral damage as part of a procedure. Symptoms that show up shortly after some work I've done on the car are usually tied somehow back to the work I just did, even if there might not otherwise seem to be a connection.

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After that basic stuff, you get to answer questions about miles on the car, use patterns, and major work already done. Fuel delivery starts with power to the fuel pump and injection, then goes to metering including temperature senors and the mass airflow sensor. And their wiring. Ignition is generally pretty bulletproof, but suffers when sensors and wiring deteriorate. Signals start at the crankshaft position sensor, go through the EZF controller for ignition, then to the coil, coil wire, distributor rotor and cap, plug wires and plugs.

Tell us more about the car, including miles and history. Share some about work done on it recently too. With some clues, the brain trust here will help you zero in on the cause.

Again, welcome to the group!

M. Requin

After following Dr Bob's excellent suggestions, you might look at the high tension side of the ignition system. Your symptoms fit pretty well with a high tension leak, such as a carbon trace in a plug cap or distributor, a "leaky" plug wire (easily found with a firefly test- do a search), and also with a bad distributor to spark plug or coil to distributor lead. The last is very common, just pull the leads out of the distributors and coils, a visual check will identify any problems quickly and unambiguously, if nothing, then move on to plugs..

SuperPorsche928

Okay thank you guys. My plan is to get new caps/rotors/plug wires here pretty soon. I'm changing the timing belt and water pump, and rebuilding the tensioner this weekend. Again thank you for the input! Any more help would be greatly appreciated

DeWolf

When was the MAF last rebuilt? I send mine to Injection Labs every few years or when I purchase a new 928. It makes the world of difference.

SuperPorsche928

not exactly sure when it was rebuilt. I'm finding new things as I go as I replace them. I've replace a bit so far.