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mgatlag · Joined: 02 Aug 2007 Posts: 647 Location: Avon, IN

Well I've finally made some time to pull the motor and replace some leaky gaskets and want to check a few things before I pull it while it's running.

The car starts every time, first time but lately it seems that the power has really started to decrease and acceleration has been horrible. Hell, just getting up to speed with the other drivers is a challenge. Once I'm up to speed, it seems ok though. Just takes too long to get there.

I've checked the fuel pump output and did the 30 sec test in a clear jar and got the proper amount of fuel, so that's ok. When I rev the engine out of gear it revs much quicker than it does in gear which tells me that something is blocked or it's not breathing right. Could the block breather be a cause of this? I replaced it last year and had a bitch of a time getting the new one in. But that was with the engine in place. This time would be much easier with it on a stand.
I also checked the spray of the injectors, which are new also, and they are fine. Timing is also good, set to 6-7 deg atdc iirc, but does idle a little high at 1050-1100 rpm.
Fuel filter is only a year old with maybe 2k miles on it, so I doubt it's that.
One problem I'm pretty sure about is that the rear seal is leaking a little and oozing some oil on the flywheel/clutch and when I get on it I can smell it. I know that doesn't pertain to the power loss though. Just some added fun.
I just bought 20 acres but won't have my house or barn (or motocross track

) done until next spring so all my work will be done in my storage unit, which sucks. I was gonna wait til next spring to do all this in the barn but I have the itch again and don't want to wait.
Any help is appreciated, I figure I should do all my testing now on what I can while it's running and then repair/replace things while it's on the stand
_________________
Michael
'77 1/2 924 N/A- 5 speed Audi box
'04 Ford Taurus - gone!!
'92 Jeep Cherokee Laredo - gone!!

Porsche... better than tea with Miss McGill
(Slap Shot)

924RACR · Posted: Wed Jun 18, 2008 2:39 am Post subject:

Clogged cat?
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

mgatlag · Joined: 02 Aug 2007 Posts: 647 Location: Avon, IN

Cat was removed years ago
_________________
Michael
'77 1/2 924 N/A- 5 speed Audi box
'04 Ford Taurus - gone!!
'92 Jeep Cherokee Laredo - gone!!

Porsche... better than tea with Miss McGill
(Slap Shot)

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

FSM says your ignition timing should be 3° at idle, vacuum lines on, FWIW.

Got an advance timing light? I would check your distributor advance. Should be 41° BTDC at 4.5k, vacuum lines off.

If you don't have an advance light, you can check it with a standard light by putting a 41° mark (using that math stuff) on your pulley. . .but an advance light is good to have.
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

double check that you hace good compression across all cylinders, just to rule that out. while the plugs are out, make sure they're not loaded with carbon (an indication of running too rich).

Also, check for vac leaks...has a huge impact on the "pull" of a motor. replace all the vac lines (now, or later when the motor is out).
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erstwhile owner of just about every 924 variant ever made

mgatlag · Joined: 02 Aug 2007 Posts: 647 Location: Avon, IN

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Set idle timing to 3 (window to flywheel). Remove both vacuum lines from distributor. Start engine, have assistant rev to 4500. Set advance timing light to 42. You should see TDC mark in flywheel window. If you don't, fiddle with timing light advance setting until you do see TDC mark. Make a note of the setting and report back.

BTW, in case you weren't clear, an advance timing light is a special kind with a dial on the back.
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

mgatlag · Joined: 02 Aug 2007 Posts: 647 Location: Avon, IN

Ok Rasta, I had to turn the dial to 45 to get the 0 in the window. My flywheel has two marks, 1 and 0. When I set the timing to 3 with the vac lines on, I set it to 0 just like when I did it when disconnected. What does that tell you?
_________________
Michael
'77 1/2 924 N/A- 5 speed Audi box
'04 Ford Taurus - gone!!
'92 Jeep Cherokee Laredo - gone!!

Porsche... better than tea with Miss McGill
(Slap Shot)

Paul · Posted: Wed Jun 18, 2008 10:03 am Post subject:

Somewhere in this investigation you have verified that you have no vacuum leaks in the intake system and that the camshaft timing is correct, right?

Have you taken a vacuum reading, what's it doing?
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

mgatlag · Joined: 02 Aug 2007 Posts: 647 Location: Avon, IN

Yes I've checked the cam timing and the notch on the pulley is in alignment with the arrow on the cam cover and 0 is in the window of the flywheel. So that all seems good.
I've also checked everything (I believe) and found no vacuum leaks since I replaced all the hoses a few months ago. Is there a special tool to measure vaccuum pressure or am I just looking for leaks mainly?

After checking this stuff tonight, I'm still stumped. What am I missing? I decided to time myself 0-60mph and it took 25 seconds! I know these things don't set land speed records but it shouldn't take almost half a minute to get to 60mph!![/img]
_________________
Michael
'77 1/2 924 N/A- 5 speed Audi box
'04 Ford Taurus - gone!!
'92 Jeep Cherokee Laredo - gone!!

Porsche... better than tea with Miss McGill
(Slap Shot)

Scorpio · Posted: Wed Jun 18, 2008 3:17 pm Post subject:

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Well, its not fuel delivery, and your advance is working. . .

Any indication of a clogged cat as Vaughan suggested?

Does the car roll easily when pushed by hand? Is there gear oil in the tranny? Is the throttle and linkage working right? Is there a potato in your tailpipe?

Listen to Paul too, vacuum gauges are cheap, or maybe loaned out at Schuck's.
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

Joes924Racer · Posted: Wed Jun 18, 2008 4:16 pm Post subject:

something is screwed with your timing.
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1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

924RACR · Posted: Wed Jun 18, 2008 10:07 pm Post subject:

He mentioned - cat was removed some time ago.

Since it seems like it's been a gradual deterioration of performance... I can't help but wonder if maybe the fuel system is no longer up to snuff? Maybe mixture no longer adjusting properly?

Timing should be easy to check; have someone run it up to higher RPMs while you watch the timing with the adjustable light; make sure it doesn't over-advance at speeds up to 5000rpm or so, and is stable... but sounds like you've pretty much been through all of this.

45 is a little on the high side I think; 42 is safer, and what I run on the racecar.

Definitely check the compression. Also conceivable a valve or two are out of adjustment; plugging in a vacuum gauge might give an indication of this.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

mgatlag · Joined: 02 Aug 2007 Posts: 647 Location: Avon, IN

Thanks for all the input boys, this is starting to get frustrating as I just want to drive the damn car now cuz it's in storage all winter.

I'm thinking the fuel mixture is ok, I've checked the plugs periodically and they look good. I'm gonna go to today and pick up some gauges and check compression on the cylinders.
Vaughan, you mentioned plugging in a vacuum gauge, I've never done this before. What kind of tool is it and where/how would I hook it up?

As far as the cam timing goes, I am right with my thinking that I set the flywheel timing mark to 0 and then the dot on the cam pulley with the arrow on the valve cover, right? My haynes book says to line up notch on the V-belt pulley with the pointer on the oil pump. Well my pulley doesn't have any notches...

I did adjust the valves about two months ago, I guess it wouldn't hurt to re-check them again.

Rasta- it does roll fine by hand and I recently drained and refilled the tranny oil, much quieter now. I don't think there is anything wrong with the linkage and throttle, never had an issue before with it.

Thanks again for the help.
_________________
Michael
'77 1/2 924 N/A- 5 speed Audi box
'04 Ford Taurus - gone!!
'92 Jeep Cherokee Laredo - gone!!

Porsche... better than tea with Miss McGill
(Slap Shot)