Grady/ Sherman(72 Guys) Ok now what?

[deoxford]

Guys
I was working on the car last weekend, I found that the airflow didn't match so I got them all very close. After that you could really hear how much better it was running. I took it for a ride and it seemed to feel good.
I did notice I had a exchust leak from the muffler gasket,but it seem to run better, I also timed it and got the idle down to about 900 with engine warm.

I stopped there, I ordered some new plugs and wires. they will be put in this weekend.

So Monday I go out to and replace the gasket with some high temp sheet gasket matrial. They still leak so I need to make a new one . So I take it for a ride anyway. IT was very cool out and it never seem to warm up , But It ran really bad. NO power and missing and back firing really bad. I had to limp home , and then I would not stay running. When it did run it missed and back fired really bad.

What did I do? How can it run good one day and like **** the next?
Could this just be the plugs , fouling up bad or the cold
Help, this sucks

Derek

[Early_S_Man]

Derek,

Cold weather snaps [which I assume you had this past weekend] can have some strange effects on old auto parts ... distributor weights that were working fine when it was warm can get stuck like glue to the plate, and a constant retarded setting can play havoc with power and driveability! My suggestion is to check the timing with a timing light, and let us know what you find???

If you haven't had your distributor out and apart for a checkup/clean/relube ... here is all the data to help, including the advance curve data you need to check immediately:

distributor lube...

[deoxford]

bump

[JSDSKI]

Well - if you're certain the plug wires are connected solidly to the plugs and the cap, and point gap is ok. Make sure you've got a complete connection on the hoses that go to the MFI thermostat. Start up on the left heat exchanger from under the car. Make sure that hose has a tight and clean connection from the exchanger to the "elbow" that runs through the left side sheet metal up inside the engine compartment. Then check the hoses from the elbow to the MFI thermostat. Pull the hose off at the MFI and start it up. Make sure hot air is coming through. If it is - then make sure the enrichment rack is moving freely. HTH.

[deoxford]

Scott,
All the hoses going to the thermostat are correct.
What is the enrichment rack?
Derek

[deoxford]

I checked the timing , It is right on. It ran good for a little bit at idle then started to back fire and stall. It would not start again after that with out giving it gas, before it would start with no gas just turn the key.... am I chasing my tale here.
Derek

[Grady Clay]

Derek,

Link me with the prior threads so I can tell where we are.

I searched MFI+deoxford here
But I’m not sure where we are in the process.

It is best to keep a continuous thread so lame old sots like me can review what everyone, including me, has posted.

I think Scott reference to the “enrichment rack” is the main mixture rack adjustment. Leave that alone – at least for now. You don’t want to get lost in the system.

Warren’s suggestion is good. Let the 911 sit in the cold and measure the timing when you first start it and the distributor is cold. Incorrect advance is a distributor problem.

Give us some more details on what you did. Exactly how did you balance the stacks? Where is the timing set at idle with and without the vacuum? How did you get “…the idle down to about 900 ….”? What did you do to accomplish that?

When you undo the muffler, carefully inspect the top and seams of it that is not visible from under the back of the car.
I much prefer the OEM muffler and header gaskets that our host sells. Keep yourself a personal supply of them. Carefully look for other exhaust leaks. Make sure the flanges are flat and have good surfaces for proper sealing. Keep the hardware in good condition.
When installing the muffler, have the two muffler support straps loose and inspect for proper mating of the muffler to the heat exchangers. Only then, slide in the muffler gasket, install and tighten the hardware. Finally tighten the muffler support straps making sure the seam of the muffler is over the bracket lip.

Sorry for not posting earlier but I was working on this Colorado Porsche shops & Dealers list – then a siesta.

Best,
Grady

[deoxford]

Ok here is what I did , The order is not correct, I put the optical pick up on before the everything else.

1. I used a air meter to look at the air flow in the stacks . Three were good at 10.5 and three were bad.
a. The CMA said to adjust the air screw, I took that to be the screw with the spring.
b. I adjusted that screw with no change.
c. So I adjusted the linkage between the stack till the air flow matched.
2. the idle adjust ment. I adjusted the stop screws when the engine was warm.
a. That still did not work
b. Car was hunting between 1100 and 1500
c. but a spring to pull the linkage all the way back
d.This worked I got it to run a 900, this is not the fix, need to correct it
e. This was done to make sure I timed it a 900
3. Timing. I timed the car with the vacumm on the car.
4. I also changed out the points with the optical pick up.
5. Will the leak in the exchust make the car run bad(loss of back pressure?)

I hope to change the plugs and wires this weekand.
Thanks
Derek

[john walker's workshop]

1c,2,and fouled plugs may be problems.

[Jay Auskin]

Don't forget the simple things. When I had my gas tank out to be sealed (crud in the tank was my MFI problem), I also did a valve adjustment. Well, I had the #2 and #3 plug wires swapped. You'd be amazed how well it still runs, and just feels like it's a bit "out of tune".

Just double check the simple stuff.

[tobluforu]

Not sure if you have done this, but the ports that control vacuum advance/retard-make sure they are not blocked. One of mine was when I first got my 72. Pull each idle adjustment screws out and clean them. I could not believe the amount of crud on them Make sure those ports are also clean and not blocked. These are little things that get overlooked.
Can you confirm the new optical ign. is still working properly?
I have had leaks in the exhaust and they did not change the way my car idled from one day to another. Listen to warren, and johnny w.
Oh Yeah, have you timed the MFI pump as well (lined up the marks on the mfi cam sprocket?. Maybe it slipped a few teeth???

[deoxford]

Ok, So I went outside started the car,and let it warm up
I checked the timing again and make sure it was correct.
So I took it for a drive
And it ran great I just drove it for about 45 mins around town.

Very little missing and power is back.....THe idle was pretty good too
I have no Idea what the deal is.


John. what is=1c,2 did I do that wrong ?

__________________

[deoxford]

I wish there were some early cars/ and shops out here. I would pay in a second to have someone tune it. I what to get out there and enjoy it not try to tune it for the next year.
I asked one shop guy here , that is the local Porsche man about the hunting from 1000 to 1500. Do you know what he said?

"That is normal, porsches do that to keep cool"

Of course it was the mirco switch , but do you see what I am dealing with down here.

[Grady Clay]

Derek,

This is why it is so important for you to be very methodical about this. CMA and extensions are critically important.

The treacherous path too many mechanics and DIY follow is fixing symptoms. Usually those are the easiest (or most profitable) to do, needed or not. The whole point of CMA is the Check & Measure part. Without that knowledge, many are adjusting inappropriately and replacing expensive parts blindly. Yes, there are some parts that should be summarily replaced for testing purposes. Yes, there are some parts that should be replaced for reliability.

MFI (or any other complex system) is poorly served by just replacing parts until the problem disappears (or not). Too often I have seen cars (MFI and other) sold because of poor diagnosis and the owner ran out of patience and money.

2c

Best,
Grady

[deoxford]

Grady,
I have been reading/following the CMA, please don't give up on me now
Derek

[Grady Clay]

Derek,

Not to worry, I’m not going to give up on you at all. Most of my post is to educate others of the importance of the process. When I post here, I try and address the larger issues as well as the current problem. I may get a little preachy (sorry) but I try and address the whole issue.

I am just as guilty as any other, upon hearing a symptom, proposing a solution without knowing ALL the details. I know first hand that mistake.

When Porsche built these cars, all the components were new. If something didn’t work properly, they simply replaced everything necessary and sometimes a lot more. The difference between ROW and USA MFI pumps was the best pumps went to California to meet emissions.

Today, we deal with MFI issues Porsche never envisioned 40+ years ago. The good news is that they are all solvable.

Best,
Grady

[deoxford]

SO I took it out again for a 35min run around town stoping /going, and it ran great.....once it got warm.
If this the issue?

[Shuie]

sorry for not responding any sooner. My 1st guess was timing. Sounds like its ok now. You set the timing at idle without the vaccum line and then checked it at 600RPM with the vacuum, right? Maybe it wasnt advancing . 2nd guess is fouled plugs, but again, everything sounds fine now

Unless you find an MFI expert in your area, dont let anyone touch the car. You will find that you already know more about MFI and CMA than your local pcar mechanic remembers. A mechanic who doesnt know any better, doesnt remember, or doesnt have the time to read the CMA manual you bring them will adjust things until he makes the car run. You will wind up with a car that runs like crap, BTDT.

[derek murray]

Derek… I would recommend (and please disregard anything I have to say for the opinions of Grady and Warren) that you work to set the MFI system back to baseline. I say this because when you were trying to synchronize the air flow between the stacks with the air screws there should have been a change. No change suggests, as one possibility, that the air channels are carboned up. Adjusting the push rods to the throttle valves to compensate may have evened out the air flow, but there is a good chance that the throttle body butterfly valves are now out of correlation.

As Grady suggests follow CMA to the letter. I would start by removing your air screws and cleaning the air channels with something like Berryman’s B12 Chemtool. Reinstall the air screws full in and back out 3 half turns as CMA suggests (you have a 2.4 litre, I presume) then make sure the rod / linkage lengths and the position of the butterfly valves are also to specification...

Good luck.

edited for spelling

[Bobboloo]

Ditto what Derek Murrray said only include John Walker.
Warren (Early-S-Man) has only given jewels of wisdom when it comes to these early cars. Particularily when it comes to the electrical aspect of them. In CMA they express the importance of making sure the electrical is in order before any adjustments are made to the MFI system.