Which way do you turn the screw?

[Jeff]

I need to know which way to turn the mixture screw on both a 79 3.0 and a 87 3.2?

I want to mess around with the mixture (Both seem to be running rich) and get it close until I can get my hands on a gas tester.

Thanks.

[Paulporsche]

79: Counterclockwise, as viewed from above, will lean the mixture. Be careful! Do this in 1/16 turn increments. If there is no change, or if the engine seems lean, put it back where it was.

Are you sure it is rich? Do you have symptoms? Has something changed to make the car go rich?

[eddiehotrod]

My '84 3.2 turns anti-clockwise to lean the mixture.

[Jeff]

Thanks Guys.

Paul, I am trying to learn the CIS system. I have only had the car for a few weeks. The symptoms I am having are, Hard cold start and fluctuating idle after the cold start (1600 down to almost stall and back up). I have been reading (maybe too much) and thought that would be a good place to start until I get pressure gauges to really dig into it.

[928ram]

Not sure if this will help because it's a different engine/system (K-basic/928), but I had what sounds like the exact problem; cure was a couple small vac leaks plus a faulty decel valve (don't know if 911 uses these). I eliminated the decel valve completely witht he only side-effect being slight "burbling" from the exhaust on decel.

[Paulporsche]

Jeff,

In your reading, you've probably noticed that hard cold starts w/ CIS cars can be due often times to a bad or out of spec Warmup Regulator. I am assuming your ignition items are in good order. If the car weren't starting at all, I would then look at the fuel pump check valve, fuel accumulator, or cold start valve.

Your hunting idle , or a tendency of the engine to want to stall due to a rapid drop in rpm when approaching a light or stop sign, sound like classic symptoms of a too rich mixture. Quite often, though, people set the mixture too rich to compensate for something else, like a vacuum leak, say at the airbox, popoff valve, auxiliary air regulator, or decel valve, which would make the mixture too lean otherwise.

These engines can run at CO readings from about 1 to about 4%, so there is a lot of leeway, and a little fine tuning in 1/16 increments probably won't hurt. Just remember, 1 full turn seems to be somewhere around 8%, so don't go crazy. I've always done this to my car without gauges, but I've been tuning CIS cars since 1977.

3.5% seems to be a good overall setting.

Having your control pressures checked is probably the single best first step to see if your CIS is set up correctly. A correct cold pressure should give you what you need to get the engine started, especially from cold and in cold ambient conditions. Check the graph and see what reading you should have at any given ambient.

Most of the time (but not always) a correct cold pressure will result in correct pressures throughout the entire operating range.

Good luck and tell us what happens.

[Jeff]

Paul, I was not able to turn the adjustment screw as I was not able to figure out what screw head it has. I half heartedly tried different size allen wrenches from 5mm - 3.5mm, but wanted to read your post more closely before I messed something up.

First off let me explain the symptoms I am trying to fix a little better...
The hard cold start is that it takes 2-5 short bursts of the starter to get it started (PO said not to crank long or it would flood. He also said not to turn the key without immediately starting or it would flood).

The fluctuating idle is just that 0-1600-0 etc. until it is warm. It is a very rythmic fluctuation and doesn't stall.

I need to know...

1.- What type of head does the mixture adjustment screw have?
2.- What gauges would you recommend?
3.- What CO tester would you recommend?
4.- Is a Bentley manual a good place to start for learning the CIS system or should I look elsewhere?

Thanks for the help.

[jbrinkley]

good book for CIS and motronic
http://www.amazon.com/exec/obidos/tg/detail/-/0837603005/qid=1130163550/sr=8-4/ref=sr_8_xs_ap_i4_xgl14/103-6514290-2383842?v=glance&s=books&n=507846
the allen size for motronic AFM is 3mm
the LM1 is a great tool and 100 times more cool than a gastester for AFR numbers

[Jeff]

Jerry, Where can I find the LM1 and can I use it to test the AFR on the Carrera?

[jbrinkley]

http://www.innovatemotorsports.com/
PP has it also. There are cheaper ways but if you're messing with a couple cars, I think it's worth it. Check out their website forums for info.

[Jeff]

Jerry, Just found the LM-1 on Pelican. From the picture it looks like you plug it into the bung where the O2 sensor sits. I don't have an O2 sensor (79 3.0) will this tool still work or do I need to search for something else?

[jbrinkley]

one other thing, the only thing on a motronic car that you adjust on the AFM is the idle CO, DME chip controls pretty much everything else, with a little input from the O2 sensor. Still, to be able to see your AFR's under load through the whole RPM range is pretty cool.

[jbrinkley]

they have an exhaust clamp you can buy also.

[Hladun]

If you need to ask which way the screw turns, you shouldn't turn the screw.

[Jeff]

Hladun, Thanks for the great advice and insight on fixing my problem.

JFYI, I just wanted to double check as I let another Pelican use my Bentley manual. You know (or maybe you don't), like in the spirit of this website : Helping each other.

WTF?

[jbrinkley]

but if no one ever asked, we all would still be taking our cars to $100/hr repair shops.

[Hladun]

Originally posted by C U L8R
Hladun, Thanks for the great advice and insight on fixing my problem.

JFYI, I just wanted to double check as I let another Pelican use my Bentley manual. You know (or maybe you don't), like in the spirit of this website : Helping each other.

WTF?

Point well taken. But just to be clear, this and other sites are excellent sources of information (the search function). Too many posts are the result of what I call "1/4 turn" tuning. Their systems are eventually so screwed up that no one can help them. The initial post said "mess around" and that's a recipe for disaster.

[Paulporsche]

Jeff,

Looks like you got some good advice from others. Just to add to it:

The CIS also uses a 3mm allen. It should be something like 5" long so it can fit down in the mixture control/fuel distributor unit.

A lot of the members use the CIS fuel pressure gauge from JC Whitney to check control and fuel pressures.

The Gastester people mentioned is only accurate within about .5%, so if you really have to know what your setting is, go to someone who has a more accurate piece of equipment. I don't know what my setting is. I just try to get the car to run well in the given climatic condition. I usually wind up richening the mix by about 1/16 or 1/8 turn in the fall, and then go back come spring. I have no O2 sensor or DME.

The Probst book is very good. So is the Bentley. Bosch also has manuals out. My car originally came w/ a manual for the FI. There is also a lot of info here for the searching.

Hladun has a good point. If you feel at all intimidated, maybe another Pelican near you can help you, or you can go to a (knowledgable) mechanic and watch him. You will learn the procedure, and it shouldn't be expensive.

If you are mechanically inclined, and feel confident that you have found the CIS screw and are turning it correctly, you should be able to tell by the reactions of the engine if you are doing it right. Just go with small increments. If nothing improves after 1/4 turn, put it back where it was and see your mechanic.

And remember, as I said, sometimes someone may have richened your mixture to make up for a lean condition caused by an air leak.

BTW do you have a popoff valve in your airbox?

[Jeff]

Thanks for the info Paul.
I am mechanically inclined and was using the mixture screw as a starting point for learning the the CIS system. I like to be hands on when I learn the reactions to different adjustments and I can always put them back the way they were and be no worse for wear. Also the PO had a Popoff valve installed.

[Paulporsche]

Good luck. That's the way I learned.