Air /Fuel mixture

[B Komar]

I think I have the FI dialed in and my timing/dwell done (thanks guys) but I can tell that I am running rich. I can smell unburned gas/ rich smell. I also get a small puff of smoke (hard to tell what color) when I switch gears. I know about the air/fuel screw on the ECU but I dont know how to properly adjust it....any suggestions? Thanks, Brian

[pbanders]

The knob on the ECU adjusts the idle mixture, it has no effect under other conditions. If you're getting mixture problems under part-load, you need to check elsewhere (e.g. head temp sensor, MPS, fuel pressure, etc.).

Brad Anders

[John Rogers]

I would try to find a shop (small and friendly) that has an air/fuel system so you can see what it actually is instead of guessing. That way you will rest easier when you're done. Good luck.

[pbanders]

I agree with John, have a shop put it on an A/F meter and check it against factory specifications at idle. My car has a 73 2.0L engine that is nearly stock (euro pistons), and across most part-load conditions, the A/F ratio is about 13.6:1 (about 2.5% CO).

Brad Anders

[kena]

Originally posted by B Komar:
I think I have the FI dialed in and my timing/dwell done (thanks guys) but I can tell that I am running rich. I can smell unburned gas/ rich smell. I also get a small puff of smoke (hard to tell what color) when I switch gears. I know about the air/fuel screw on the ECU but I dont know how to properly adjust it....any suggestions? Thanks, Brian

The initial setting for the screw on the ECU is as follows: turn left to lean mixture / right to richen mixturer. Mechanic at Porsche garage said there are 22 clicks total on this screw adjustment and they start initially by setting it in the middle ie. 11 clicks from right or left.

[B Komar]

Thanks, I will check to see where the adjustment screw is set at now. I imagine with all the manipulating I have done to the system it may need re-adjusted. I think the richness is mainly at idle...I am getting 34 MPG and have no problem with driveability but I can sure "smell" it when it is idling. Thanks guys, Brian

[pbanders]

If you're getting 34 mpg - and you have a 2.0L - you're definitely not rich at part-load. Check the idle setting with a shop. I've found that if you have a stock setup, and correct and matching FI components, the correct idle setting is within +/- 3 clicks of the "factory" setting - the mark on the plastic surround of the ECU idle knob. Note that this mark isn't always in the center of the range.

Brad Anders

[pbanders]

BTW, one of the reasons to get a puff of smoke on a gear change is worn valve guides. When you shift, the throttle valve is closed, and your intake vacuum is high. If the guides are worn, the vacuum pulls oil down the valve shaft into the intake, where it burns and you get some smoke. How many miles are on the engine?

Worn guides are fairly common. The problem is that when the guide is very worn, the thermal transfer between the valve and the guide is poor, so the valve gets very hot. Eventually, the valve fails, often breaking off and falling into the cylinder and causing general destruction. Check it out before you have any big $$$ problems.

Brad Anders

[This message has been edited by pbanders (edited 05-28-2001).]

[B Komar]

This engine has <15,000 miles on it but it sat for four years. Euro P&C, stock everything else. It is a VERY strong engine that now runs very well. I had just noted that little puff of smoke and wondered if it was related to mixture. This is only my third tank of gas since the transplant, but I gotten 33-34mpg on the last two tanks. I have a 50 mile one way commute at 70 mph and I just couldnt be happier. I dont know if you remember past posts...this was Chuck Bass' engine from a car that had been totaled in Seattle, Wa. I have complete receipts detailing the engine and 911 clutch build up and EVERYTHING was replaced with new items, including all sensors and injectors. He parked the car in the garage and didnt touch it again for 4 years. I flat towed it home to KS. in April. I am hoping that the puff of smoke will clear with a few more tanks....and I will be taking it out to Heartland Park Topeka for a PCA DE meet towards the end of June...this will either make or break the car(or me) I guess. Thanks again, Brian