Can you but wiring harnesses?

[sjcurtis]

I take it that you are running a nissan computer on the L28, if you are running an anilog system then you can reduce your rich run by checking that your cold start valve is closing off( the thermotime switch functions. then go to the mass air flow meter this item has a variable in it other than the bypass air you can increase the spring pressure on the airflow flap lying about the amount of air going thru, that will in turn lean out your running mixture To check for a analog system go to the airflow meter again check the imput wiring plug it should have five contact pins. to confirm go to the throttle valve switch it should have three contact pins. the most probale reason for the rich running is age of the spring on the mass airflow flap, it has gone soft.

For the computer you have if it is nissan it will have a tag with part numbers that nissan will be able to date and tell what model it came from.

good luck

"inject them all"

Steve

[Hallaian42]

Thanks for the info sjcurtis. I dont know if it matters but the airflow meter apears to be aftermarket. It's made by vane. Would that change anything? Is it possible i have the wrong one? The computer is made by bosch and it has all the numbers for the bosch stock numbers but i dont see anything by nissan. The egr has been disconnected because of the headers. And the coolant temerature switch (not temp sensor) doesnt appear to be connected to anything...what is it's significance? Thanks again

[sjcurtis]

I found this by Dave Hoerl and It explains theairflow meter well.

Airflow Meter Calibrating & Repairing

From: dfh@ariel.com (David Hoerl)

Date: Wed, 25 Sep 96

Subject: <MISC> RE: Air Flow Meters

If you have a mechanical Air Flow Meter (with a vane and an embedded

potentiometer), you can calibrate it. These things are factory calibrated

to a spec, not to the car. Metric Mechanic sells for $5 a procedure to

calibrate one. Don't know how good it is as I haven't gotten it yet (I ordered

it in August, they cashed my check, but no procedure yet :-<).

Basically, to calibrate it, you need to first pry off the plastic cover. After

that, you position the thing such that you can access the springs and

adjustment screws. The O2 sensor is disconnected, and you put a voltmeter on

it. While monitoring the voltage, you first adjust one of the screws (probably

the arm angle offset) to get a .5Volt reading from the O2 sensor. Then, you

increase the engine RPM to a higher setting, and adjust the big round spring

tension adjuster so that the voltage is again .5 Volts. If the Air Flow Meter

is good (ie, all resistors good, carbon track good), you can get it dead on,

and it will now be "calibrated" for your car.

NOTE! I'm guessing at what the exact procedure is - so don't follow the above

as gospel.

Generally, older engines tend to run "lean", so you need to richen them with

less spring tension.

Good luck. And, if you are a DIYer, call Metric Mechanics.

David Hoerl

84 633CSi

Okay now that tells you what you need to optimize the running and also to add spring pressure to reduce rich running.

with the system now running at good mixture stabalise the air bypass or leaks to achieve a more acceptable idle 650 to 700 rpm with no cold start running.

the bosch computer is the basis for the nissan ones, so it should have cold start capability in it.

you will need the cold start circuit wired up for ease of cold engine start/running.

also check that the throttle switch is not stuck at full throttle (max fuel imput).

good luck

Steve

[Hallaian42]

Thanks again for all that input. Sounds like i need to do some investigating with my cold stat valve/cuircit and air flow meter. That was an interesting tech article thing you had there. The only problem is that my car doesnt have an oxygen sensor. I heard that was normal because some of the earlier F/I systems didnt have them until early 80's. Am i correct with that statement? All sensors hooked up to my computer are as followed...Coolant Temperature sensor, thermotime switch, air regulator, cold start injector, air flow meter, throttle valve switch. The only thing that doesnt appear to be hooked up is the coolant temerature switch. And im not sure where its supposed to do or go. Am i missing anything? Thanks again

[sjcurtis]

I am not to sure, as I said before about the aftermarket stuff. The oxygen sensor is not nessasary It really only interests the smog fiends in Cali. or a digital fuel managment computer to control the rate at which your catalitic converter clogs up, costing you money and stalling the car. In your case the oxygen sensor might have leaned the mix a bit. I would have thought that a coolant temp switch would have picked off on the pin next to the thermotime switch to cut the start injector in and out. Maybe this model computer direct reads the resistance from the coolant temp and controls start injector internally.

wish I could see what it looks like, I am sure we could have your engine screaming in no time flat.

Good Luck

Steve

[Hallaian42]

I have a digital camera...I'll take a few pics of my setup and post them up for you to see. Thanks alot...i appreciate the help