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-   -   Condition worsens.... Help!! (http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/129888-condition-worsens-help.html)

Pike 10-01-2003 09:55 PM

Condition worsens.... Help!!
 
What is going on here?

The Symptoms:

_ The car stumbles when the gas is pressed. The idle is ok, once it gets past a point, the car gets real power and takes off. The RPM that it stays dead at is getting higher. It only does this if you 'punch it. If you ease onto the gas, the rpms just go up no problem.

What I have looked at / done

_ Gas quality. Have tried several stations and grades. This did not affect it. I have tried both injector cleaner and the stuff that takes water out of the gas. The fuel filter is rather new < 4000 miles.

_ Vacume lines. The lines seem to be ok. I have noticed that if I take the small line off at the big one to the brakes, the rpms go up. If I unplug the vac line anywhere else, nothing happens.

_ The air filter is clean

_ The problem has seemed from time to time to be related to how well the brakes were working, but there was not enough of a collaborating between the two. This would make me suspect the vacuume system again.

Current Ideas

_ Fuel pressure regulator. I think the loss of power is related to the lag between air and gas getting to the engine. (CIS) This could also be related to the fuel distributor, but it works ok at rpms over a certain point. What happens when your FPR goes out?

_ Something in the vacuume system, like the vacuume advance on the timing. Not nessisaraly caused by a bad distributor.

_ What do you guys think? This seems to be an odd problem! The car is weak enough at low power that it is almost undrivable.

Pike 10-06-2003 08:12 AM

_ I did some more looking around under the hood, and have not yet found the problem. I checked the vacume lines, the fuel filter, realigned the airflow sensor, and made sure that the sparks were not loose. Help, what should I check next??

goingboeing737 10-07-2003 05:53 AM

Fuel pressure reg and dampner on the fuel rail. Replace them both. PITA to remove, be careful, I ended up with a new (used)fuel rail...ouch !!

Will make a world of difference in throttle response, idle and overall running codition.

My .02, it worked on mine...YMMV...

Britwrench 10-07-2003 06:47 AM

924 models don't use the Motronic system installed on the 944 so there is no fuel pressure regulator, fuel rail or damper.

You need to get the fuel pressure checked and injectors removed and tested. Sounds like a fuel pressure problem.

SoCal Driver 10-07-2003 07:49 AM

Side draft Webbers.

Pike 10-07-2003 09:17 AM

_ I like SO Cal's idea. =) I am very close to buying new injectors and seals. I am pretty sure that the seals are leaking (slight hissing, might just be the injectors). Would there be a difference between the FPR from an '81 and a '77 924? I am using one from the '81.

_ Other interesting stuff: I removed the cold start injector and it was not running even when the car was cold; ~50 degrees or so, Should it have been? Also, after letting it sit for a couple of days, the car is running great now. !?!?!? I am sure that it will revert back soon though.

Roger Hall 10-07-2003 06:23 PM

Test the thermo time switch it controls the cold start valve.

Pike 10-07-2003 07:31 PM

Will do. I also noticed tonight that the brake lights stopped. I only touched one thing back there though. I am pretty sure that it is going to be the ground. The right turn signal only works if your foot is off of the brake. I will try and fix that and test the thermo switch.

Buddy 10-08-2003 03:45 AM

If you've never replaced the rubber boots from the fuel distributor to the intake manifold, this would be a good time. But buy new ones. The old ones have a tendency to get very small, undetectable cracks under the hose clamps from being removed and installed and from the heat under the hood. They're not that expensive. Vacuum leaks will cause the problem you're describing, as well as low/incorrect fuel pressure, which may be the result of the wrong WUR (aka FPR). May want to cross check the part number and be sure they're the same from '77 to '81. When my WUR was acting up, it stumbled on start, would idle but not rev up until it was warm. After that it ran normal. If you can get the pressure checked, that's the best way to diagnose the problem. But even if it turns out to be the WUR, I'd still change the boots. Between the boots and the injector seals, it's cheap insurance on the CIS system.
Changing injectors and injector seals is an excellent place to start. All that kind of stuff is probably brittle with age and heat from being under the hood for 25+ years. The difference will surprise you. You have to be sure there are no vaccuum leaks. After that, you can look to the more expensive possibilites like the fuel distributor, etc. Start w/the cheap stuff.

Has this car been sitting awhile?

Pike 10-08-2003 08:54 AM

I have been working on it and driving it for about 6 months. I have already put on about 3-4K miles on it, most of those with no problem.

_ I also am going to reclean and put new spade connectors at the ground for the fuel pump.


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