VWGUYGOESPORSCHE

Hey to all. I am new to the Porsche game. I am a VW guy by blood but just picked up a sweet little gem in the form of a 81 928. This baby has the original burgandy-ish paint with tan interior. 32,000 original miles. Been sitting since 95 and I am trying to resurrect this baby. I did get her started but is idling rough, popping through the intake and just running crappy in general. I did pull the tank and completely douched it, new strainer, put a new pump and filter, cleaned out the lines but did nothing to the injectors. I am assuming this is where my problem is but wanted to get some tech help. Is there a way to clean the injectors or should I just bite the bullet and buy new ones? Thanks in advance for any help. Steve

The Forgotten On

Popping through the intake is usually caused by the timing on the distributor being off or the cam timing being off. I had it happen with my 81, turned out the distributor was 1 tooth off.

Most likely your injectors are fine but may be clogged by varnish and could use a clean by either sending them out and having them refurbished or just using some MMO or techron.

VWGUYGOESPORSCHE

I was thinking the same thing in regards to the popping and rough idle, however, I didn’t touch the belt or the distributor and before it sat for 23 years it ran and drove like a champ.

Billu

They all ran “like a champ” when they were parked.
And they all nomally fire right up.
All of them.
Seriously, every single one.
But, on the outside chance yours is different, change the oil, replace the plugs, set the timing, add Techron and drive it 30 miles.
Then report back.

jpitman2

Is it L-jet or K-jet? K-jet has hard metal injector lines...Do as Billu says - fresh fuel, Techron, drive some.
jp 83 Euro S T 57k K-jet

VWGUYGOESPORSCHE

So I guess a little more background is needed. Thanks for the comments guys. So I did completely clean the tank, new strainer, new fuel pump and filter, new plugs/wires, new intake gaskets, complete oil change and filter, full coolant system flush. I will Get back to you guys. I am going to take your advice and we will see what happens. Thanks again and more comments are welcomed. Steve

VWGUYGOESPORSCHE

It is the L-jet setup. Looks like rubber lines.

fiatrn

I know this sounds dumb, but triple check that your plug wires go to the correct cylinders. Two cross wires can cause oddball idle problems.

karl ruiter

Never a bad idea to check cam timing and plug wire order. Keep in mind also, that the harmonic balancer can be put on backwards which throws timing all to hell. Worth a glance. Should not be issues of the report of it running perfectly 23 years ago is correct, but I doubt my memories from 23 years ago are totally correct, so maybe the POs were not either.

Check the door flap in the AFM. On L-jet cars it can be bent by a back fire and then hang up afterwards, causing all kinds of problems. You can just move it with your finger to make sure it moves smoothly. Also, if not in a rush, you might consider sending your injectors to witchhunter. I have the experience of spending years putzing around trying to get my 91 944 (L jet also) running right only to find out later that one of my injectors had an issue. It's pretty cheap and gives you a solid starting point.

Also, you can grab the rotor and make sure the mechanical advance seems to move the way is should. I have seen them lock up from sitting.

A big air leak can also cause poor running on a Ljet car. The biggest hidden bit in that regard is a rubber boot between the center of the spider and the throttle body. I have seen them fall apart while sitting for a long time.

Could easily have a bad plug wire from the long sit. You can get an econo kit from 928 intl that is only the wires, not the plug ends, for about $100.

VWGUYGOESPORSCHE

Double checked the firing order and all is good there. I did a one for one when changing out the plug wires. Will check the distributor. Got some brake cleaner and started checking for intake leaks. Seems possible that where the AFM goes into the intake might be an intake leak there. Def spiked in RPM's when spraying on the top side. The AFM flap was good. I def can hear that thing smack when it is backfiring through the intake. I checked the boot at the throttle body with brake cleaner and seemed fine. Definitely spinning here guys. I'm off tomorrow so I am going to go through everything. I appreciate all of the input. Steve

VWGUYGOESPORSCHE

Quick question guys. As I stated I am new to this beautiful car so I am in learning mode at this point. While testing and diagnosing, does the air filter box need to be installed or is it ok for for it to be off until I get this thing running right? Thanks in advance. Steve

Hilton

Just to be clear - when you double-checked, you checked against the Factory Workshop manuals or the distributor markings, and not just "was it the same as the old ones"? Don't assume that it was all correct before you replaced stuff - its moderately common for long-term parked cars to have had issues after being worked on, which led to them being parked, due to 928-unfamliar mechanics.

VWGUYGOESPORSCHE

Correct. I did check each and every wire according to factory wire location starting with #1 and going around clockwise to ensure each was in the right location. Steve

The Forgotten On

At least Bosch made it easy with the distributor cap to see if the plugs are in the right order. Just match each wire from the cylinder to the spot labeled with its number on the cap.

VWGUYGOESPORSCHE

Wanted to ask this one more time. Thanks.

Quick question guys. As I stated I am new to this beautiful car so I am in learning mode at this point. While testing and diagnosing, does the air filter box need to be installed or is it ok for for it to be off until I get this thing running right? Thanks in advance. Steve