Tampa 928s

86 S/C
With S/C disconnected and blowing in to the air direct up no stream interference to Maf.

From cold to warm these are the readings:

With a John Speak rebuild from my euro installed for testing I am finding the following:

Speak Maf: Car idle: wants to stall idle fluctuates from 0-1,200 have to feather gas for about 30-Seconds.
Cold start: Warm idle
A/F 10.7 13.1
Rpm 760 840
Maf-V 2.70 265
Maf From Pin 3 to 6 its at 315 Ohms Pin 3 to 5 4.1 Ohms

Modified Maf with two adjustments: Car starts right up idles great.
Cold start: Warm idle
A/F 14.7 15.1
Rpm 760 830
Maf-V 2.42 242
Maf From Pin 3 to 6 its at 427 Ohms Pin 3 to 5 4.1 Ohms


I had to adjust this Maf but now it seems lean under Wot I will test this later.
I am sure I can adjust it out.

Mt question is why does the Speak work fine on my 85 Euro but not on my 86 S/C and the Co adjustment is not at factory from the Speak Maf unit 316 Ohms.

I have my Idle screw all the way in and smoke tested and the only leaks are from the idle control valve. I found this leak on every one I tested and it is small.

Tampa 928s

Could this be because of the chips I have installed?

John Speake

If the MAF can be adjusted for idle CO of 1% when used with your stock Euro, then that pretty well rules that out as the problem. Have you tried a stock 85/86 LH EPROM with your s/c car (with s/c disconnected )?

Tampa 928s

No not yet; I can only believe that your Maf is correct although the readings of 315 Ohms was a little high but the Euro runs fine. With your Maf the car has all kinds of idle issues when cold so I am assuming I am adjusting out these issues with the adjustable Maf. I will install my stock chips tomorrow and see what happens, do I need to do both chips or just one?

Thanks

John Speake

As far as idle CO is concerned, you only need to swap out the LH ECU chip.

Tampa 928s

Thanks I'll try that tomorrow, if this corrects it should I keep out of boost until I get a good replacement?

John Speake

You probably need to modify the car back towards a stock intake to see which of your mods are upsetting the MAF readings. Obviously no boost is part of that back tracking.

Tampa 928s

All this testing was done with the S/C removed to make sure not to effect the base line operation.

John Speake

Yes, understood, but you have a very different intake than stock, feeding air into the MAF.

Tampa 928s

LH 928-618-123-04 24 pin chip 28 pin socket also 2 284-986-516
Lh chip stock 2287355631
on Lh board 228 832 1495-4 and 2 284 496 516

Johns Maf
Lm voltage at idle: 2.70
Lm voltage between pins 6&7 car not running 1.7 volts
10.2 A/F at start up cold
12.2 when warm

Johns has cold start issues but after 20-Seconds idles fine

Tampa 928s

Is there an orientation for the Maf I believe the Co adj pot faces front DS is that true?

John Speake

Orientation of the MAF isn't critical. Is the filter and pipework into the MAF intake stock now ?

Tampa 928s

The s/c piping is facing up into the air venting and not hitting the Maf.
I just have the Maf open to the air while testing, no air box or filter.

John Speake

Can you restore the intake to the MAF as per stock ? This can make quite a difference to how the MAF behaves. The car was mapped with that intake, warts and all.....

Tampa 928s

Well thats if I can find the box, I thought that was next
When and if I can put it on what should I be seeing for the readings?