Does mixture need to be adjusted after installing SSIs?
 

I'm pretty comfortable doing just about anything to my car EXCEPT screwing with the CIS. It's been like a sleeping dog since I bought the car. It's worked great, until now.

Before the SSIs: The car always started right up immediately. It would bog down if I gave it a lot of gas right when I started it stone cold, but after about 30 seconds of idling, it ran great. Warm starts were always perfect.

After SSIs: It now always starts, then dies right away. On the second try, it starts but runs really rough for a few minutes. If I try to give it gas, it will die. If I let it idle, I can feather the throttle to get the revs up after about a minute. After a few more minutes, I can rev it up, and it runs fine. When warm, it starts right up and runs fine.

Also, after installing the SSIs, I don't really notice much more power out of the car. It seems to have less low end torque, although it really screams above 4,000 rpm. From everything I've been reading about the SSIs, I would think that I should notice a significant kick in the pants. Then again, it's been sitting for about 3 months since I last drove it, and my daily driver is considerably more powerful, so maybe it's just been a while and my P-car butt dyno is out of calibration.

Do I need to readjust the mixture after installing the SSIs? Is this something I can do at home, or am I going to have to take it to the local mechanic to have them do it? After dropping over $3,000 in the last month on this thing, I'm not really interested in spending much more money on it.

Thanks for any advice from the CIS experts.

we had to tinker with toby's. it was just a click to get it to idle smoothly. i believe he took it for an official adjustment shortly afterwards.

i think you need to richen just a bit

If you don't have the tools to measure your AFR you are better off going to a shop so that they can check it.

A shop should be able to do it in 15-30 minutes. Your best bet is to make an appointment, get the car nice and warm on the highway and then have them adjust the mixture on the spot.

It is always a good thing to verify your mixture every so often. Might as well have them check timing too. Very minimal cost and worth every penny.

Quote: "After SSIs: It now always starts, then dies right away. On the second try, it starts but runs really rough for a few minutes. If I try to give it gas, it will die. If I let it idle, I can feather the throttle to get the revs up after about a minute. After a few more minutes, I can rev it up, and it runs fine. When warm, it starts right up and runs fine."

That sounds like the symptoms my car suffered after being stored for nearly a year...

I emptied the tank and filled it with new gas, Performed a valve adjustment, Changed the oil, New dizzy cap and roter and checked the spark plugs.

My car ran 100% after that! I know installing the SSIs may seem like the obvious cause but...

Quote: "Then again, it's been sitting for about 3 months since I last drove it,"

That's not really long enough to get stale fuel problems but when was the last time you adjusted the valves or did a basic tune up?

To get the best mixture and idle adjustment you really need an O2 meter. Some people here have their own and use it regularly when performing engine mods tune ups etc. I intend to get one soon but I'm tossing up between a permanently installed one with gauge in the dash or a portable hand held one. (cheaper)

When I was much younger (44 now) I used to do lots of work on motor bikes. It was standard practice to re adjust the mixture whenever a new exhaust was fitted or a change was made to the intake. I'm not sure how that applies to Porsches but if it was me I would get it checked by either using my own O2 meter or taking it to a mechanic with Porsche knowledge... Hope it works out OK :)

Thanks for the quick comments guys. I think I will just fork over more money and take it in.

To answer some questions. I had the engine out over the past 3 months and did a valve adjustment while it was out. Also, new plugs at the same time. I suppose the gas could be stale, but I don't think so. When I put the engine back in, I installed the stock heat exchangers and muffler. I drove about 5 miles, and it drove just like it did before I pulled the engine 3 months ago. I only drove about 5 miles though, and it was snowing out, so I didn't really push it at all (this car doesn't usually see snow, summer tires). BUT, it did start right up and ran fine with the original exchangers before I pulled them off again. The change didn't appear until after I installed the SSIs. That's why I am thinking the cause was the SSIs.

My car had SSIs when I purchased but I noticed a BIG difference when I put a home built 2 in 2 out on the car. I was always screwing around with the mixture so I dont know if that was during the time...my point is the exhaust back pressure seemed to make a big difference to the Butt dyno. Not really recomending a 2 in 2 out though it was awfully loud, maybe for the track. I wondered the same thing as you are when I went back to the 2 in 1 out and picked up a set of Megaphones for the track. Would I need to adjust the mixture???? Never got a chance, sold the car before getting back out to the track.

As said above, if you can borrow the tool to measure the gasses its pretty easy, I was never able to get the "by sound measure to work to well. Of course I think I discovered a big vacume leak after attempting that...

Are you sure you did not split a hose or leave one loose (crank case breather??) during your in and out. The leaks really seemed to mess with the CIS.

That's a very good point. I should definitely check that. What is it that I can spray around the engine compartment to affect the idle and check for vacuum leaks? I think I'll check that first.

I did replace the crankcase breather hose, and I had a he!! of a time getting it back on. I'm sure I could have knocked off or messed with one of the other hoses at the same time. If that's the case, just PLEASE let it be accessible. I really don't want to have to climb in the engine bay and hug the engine again to fix those hoses back there. What a pain!

Why would you have to adjust the mixture after SSI? With Carbs I can see a difference because the freer flowing exhaust would lean out the mixture, but FI measures the airflow in and sets the mixture. Maybe just reset the idle screw, right?

Regards,

Jerry Kroeger

Sounds to me like your mixture, especially when cold, was a little lean to begin with. When you added the SSIs your mixture then needed further richening.

If you search, you will see that a too lean mix can be due to several things, including an out of spec WUR giving you a control pressure that is too high, vacuum leaks, or sometimes just a too lean setting. If you have a 5" long 3mm allen wrench you can richen the mix via the screw down in the top of the fuel distributor. A clockwise 1/8 turn may be all you need. You can also verify your control pressures w/ a pressure gauge to make sure your mixture is correct under all conditions.

As mca and others have said, however, if you are unsure about this, or don't have the tools , have a shop check your control pressures and set your mixture.

Also, new plugs at the same time

What kind of plugs ? I have seen this symptom with new platniums vs plain BOSCH. Does your distributor have a vacuum retard ?

Plugs are new Bosch, and this is an ROW SC, which doesn't have vacuum retard.

Follow up:

Allrighty, I went by there on my way home from work and had my local guy adjust the mixture. It was lean. The idle immediately smoothed out and raised a bit when he richened it. He checked my timing too. It was a "hair below 30 BTDC @ 6,000 RPM). It was noticeably more peppy on the way home. I'll have to wait until tomorrow when it stone cold to test the cold start.

I also sprayed carb cleaner in various typical problem areas of the engine. There were no fluctuations in idle anywhere, so it appears that I don't have any vacuum leaks.

So if I'm still having cold running issues, I'm guessing it's the WUR. And at $500, I'll just be dealing with a rough cold start and probably NOT buying a new WUR.

The mixture richening may be enough to take care of it. If not, you may not need to buy a new WUR. Very often, all that is needed is a procedure called "knocking the plug" which is very simply done. This lowers the cold control pressure and richens the mixture for starting and warmup. You can search this site. There is a ton of info on how to do it.

If the mixture @ start is just slightly lean, a very short knock might be all that you need. If you want to be sure, this can be done while you have a fuel pressure gauge attached so you know exactly where you are relative to spec.

As before, any experienced Pcar mech should know how to do this, and have the pressure gauge, if you are uncomfortable doing it yourself.

Just to let you know, I've been adjusting my own CIS cars for 30 years. Only recently did I borrow a gauge from a fellow Pelican and used it to track down a cold start problem. In my case the WUR needed cleaning and resetting to a spec different from the factory; about 1 bar lower both cold and warm, to make up for engine mods and wear (I think). I have a thread on this. I had someone do the repair and recalibrating to the WUR for $175. If you PM me I'll tell you who did it. I don't think you will have to spend as much time on it as I had to.