735iSE

My 1988 E32 is running rich as a bitch and guzzles fuel like there's no tomorrow...

I had one of these krypton tuner guys down and he didn't have a clue what was wrong. He spent all his time fiddling with the box in the engine that controls the airflow ( I mean whatever the thing is that sits on top of the engine right after the air intake/filter)and it didn't make the slightest difference. The CO and CO2 levels are way up there...

He even tried recalibrating the control... Took the bottom off and rotated that toothed wheel thing (potentiometer)...Not the slightest effect on the gas levels.

I had myself previously replaced all the plugs, leads (boy are they expensive...had some made up for half the price), coil, rotor arm and cap to see if that would help clear the problem.

The krypton readout

The OBC doesn't show any errors...
Where do I look next? Any ideas how I should approach diagnosing/fixing this problem myself?

BTW are there any on-line technical manuals for this car that I can access?

Thx

i hope you didn't let the AirFlowMeter (AFM)tooths slip by fucking wit it...the afm should effect the air/fuel mixture though..
AFM needs adjustment
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Posted by KC Ron Carter on February 07, 2003 at 09:16:50:

In Reply to: Help erratic idle posted by Harly Quin on December 30, 2002 at 03:38:34:



I would suspect the AFM


AFM it is a mystery to most drivers.

Here is a picture and the instructions to adjust.

If you do not feel comfortable with them just print and take them to the shop of your choice.

Do a good leak check using a spray ether starting fluid on the intake.

Here is the adjustment procedures.


Air Flow Meter Testing:

Before you test the AFM, you need to make sure you have NO AIR leaks anywhere. Check and double check!

A simple way to determine if you NEED to ajust the AFM is as follows:

- Remove the air filter housing and elbow leading up to the AFM.

- You will probably have to put a small piece of wood or rubber under the AFM to support it on the Valve Cover.

- With the engine idling, gently push on the AFM flapper-door. If the idle rpm increases and the engine smooths out, then your AFM needs adjustment.

- An additional test. Repeat the above step, but hold the throttle as steady as possible at 3,000 rpm. If the highest rpm and smoothest operation occur only when you advance the door position, then you need an AFM adjustment.


Several things I NEED to point out. The toothed wheel mentioned below MUST be held firmly as you loosen the retaining. If you let this wheel slip uncontrolled or rotate freely, you will be SO SCREWED! Also, I found that I only had to adjust my wheel by two cogs, i.e. VERY little. What this did, was loosened the resistance of the flapper door and hence enriched my fuel mixture slightly. You will be tempted to adjust it much more, but you shouldn't even think about doing this. Small increments are better. I would try only one cog first and you can always increase another cog or two if you feel the need. Also, you will want to rotate the wheel in a counter clockwise manner. This will loosen (or enrich you fuel mixture) the flapper door. IMPORTANT: Be sure to use some type of bright paint to make a mark on both the wheel and the reference hole, so you will know where you started, in case you want to return to the original wheel position. I've scanned and posted a diagram of what you'll see under the black cover.

Also, I chose to not reseal the black plastic cap on the bottom of the AFM. Rather, I secured it temporarily with a couple of linked zip ties wrapped around the AFM in such a way to hold the cap on. I then ran the car for a few days to see how it perfomed. If I like it, I took the zip ties off and resealed with silicone sealant. I've done several this way and it is pretty straight forward.


Calibrating the AFM
Theory:

The amount of fuel fed to the engine is determined by the 1)FUEL PRES and 2)PULSE WIDTH (length time wise) to the injector.

The pulse width is affected by several factors (inc. but not limited to PROM, Temp Sensor, O2 Sensor, AFM Flap Position*...)

*Up to about 3500 rpm only

We are going to modify the Flap Pos'n Sensor by making LESS air open the flap WIDER (Wider=More Fuel). Usually these engines are set at the edge of leanness when new, and as they age, they go leaner, making for poor performance and idle. By "calibrating" we are simply maximizing the engine output for the other parameters using the AFM to "tune" the system.

Doing the Job:

1)Unhook the air cleaner elbow from the AFM.
2) Rotate the AFM 180 deg (M30) so the black plastic rounded-corner plastic cap is on the top (watch the wires).While the AFM is upside down, center the idle CO screw (count turns) in its range.
3) CAREFULLY cut the sealant (RTV) and pry the cap off.
4) Notice the screw holding pressure on the toothed wheel (looks like a gear).
5) Paint a mark on the wheel and the post as a reference mark for future re-setting if desired.
6) Disconnect O2 Sensor @ firewall, start car and warm to operating temp.
7) Set RPM to above idle (1500-1800 rpm is fine)and hold it there mechanically.
8) Loosen clamp screw and rotate to maximize rpm.
9) Tighten screw.
10)Check idle smoothness. If it is rough, note present toothed wheel position and try moving 1 to 2 teeth either direction until idle smoothes out.
11)Adjust idle CO screw for edge-of-lean smooth idle. (remember screw works backwards from carb idle adj.) (i.e. CW=Richer)

As an alternative, you can simply adjust the toothed wheel for the smoothest idle (at idle rpm of course) in step "8" above and have done with it. You probably won't notice a big difference at running speeds anyway.

have you checked the coolant temp sensor and its wiring going back to the ECU.i just had a same problem and it was a broken solder joint near the conector for the coolant temp sensor.

mark

It's been in the garage for the last two weeks and they have no idea what's wrong. They claim that they've checked the coolant sensor, the spray pattern, the airflow meter, the leads, the coil, cylinder pressures, the distributor, the fuel pump pressure...they have no idea what's wrong and can only suggest that I take it into a main dealer and let them look at it for £100/hr.

The result... I'm taking the alloys off and the radio and going to scrap the car. It just isn't worth spending more and more on it in what seems to be a vain quest to fix it. The pity is it's a great car but by 10 am tomorrow it'll be scrapped...Unless anyone wants it... It's in London.