thedugger1

Has anyone installed a rebuilt AFM from 928 International? Will it typically be tuned properly stock or should I anticipate having to adjust the air/fuel mixture to the proper CO? I have the factory adjustment tool, but as of yet, no access to a CO meter. From what I've read this can also be accomplished utilizing the O2 sensor as well.

FYI..this is for a 1983 non-euro.

thedugger1

Well, Mark Anderson from 928 international responded that "There should be no adjustment necessary". That sounds good to me unless anyone here ran into any issues I should be aware of.

Landseer

Makes sense.
Besides, Mark Anderson backs-up everything he says and sells.

Its the hot wire MAF on the later fuel management system that may require calibration.

The question is why do you think you need a new AFM? Generally its a pretty robust piece. Did you clean the potentiometer inside with an eraser? Don't want you to chase the wrong issue.

Brett928S2

Hi

Sorry to disagree but they do need setting up with a CO meter...

When they are rebuilt they are set pretty close but as all engines are different you will still need to put them on a CO meter to set them properly...

A few years ago I got a reconditioned one from John Speake and it was set up very well but I still had to adjust it by around 0.5% with my Co meter.... to make it perfect (FOR MY ENGINE)

By the way that adjuster has NO END STOP ...so do NOT SCREW it all the way in as you would a carb mixture screw (before backing out the screw again)

When you adjust it, make sure your engine is fully warm (20 min drive as a minimum) and then put in the anaylser pipe in the exhaust and set the adjuster by very small amounts...say around 1/4 of a turn at a time.....until it reads correctly on the analyser....1% in my case.... (86 S2 -16 VALVE)

All the best Brett

thedugger1

I have a slightly lumpy idle and hesitation, occassional pops from the intake, all more pronounced when cold. The following has been replaced courtesy of Earl Gilistrom: fuel lines, injectors, cold start valve, plugs, wires, cap, rotor, o2 sensor, temp II sensor. I've been unable to find any vacuum leaks and Earl doubted any leaks. I tend to agree as everything looks fresh (well serviced car with mileage in the 40's).

I researched Rennlist extensively and everything pointed to the AFM. Earl also recommended that would be a good place to start. The adjustment cover was already removed and it looks like someone has already been under the cap. So, I attempted to adjust what seems to be a lean condition only to find that the adjustment screw was already to full rich (full CW). I then spent a full day tinkering with the adjustment. While the condition improved somewhat, I did find it odd that no matter where the adjustment was set, the car ran about the same either full rich/full lean.

I've more or less convinced myself that the AFM was at issue. Quite honestly, if it's not it, I'm at a loss. You're probably right that I could have cleaned the unit, but, for the price of the unit I thought a fresh AFM was the way to go.

What do you think!?!?

Landseer

Brett, did you convert your car to an AFM? Your euro, like my 84 euro, use MAF.

His car is earlier, USA with LJetronic and AFM.

thedugger1

Brett, you mention that there is "NO END STOP" on the CO adjustment screw, but my unit definitely won't turn any more CW. It turns smoothly throughout, but definitely hits and end point.

Landseer

Well, it would be even better if you could swap one in then and try it. Little to loose.

Bad O2 sensor or associated wiring will defiinitely give those symptoms, too. I moved exhaust and 02 sensor from one 84 USA to another 84 USA and the problem followed the exhaust.

PorKen

The '80-'84 US L-Jet AFM CO adjustment is an air bypass, like the idle speed screw.

('84 ROW) '85-up LH-Jet have a MAF sensor which has an electronic CO adjustment.

karl ruiter

Actually, several ways these can have problems: electrical problems with the wiped hybird, or mechanical problems with the door sticking. Sometimes a good backfire into the door will tweek it and then it will stick a bit.

Landseer

Did Capt. Earl clean both ground points on the passenger side cam cover?

There is a hidden one located under the emissions valve, just at the top of the "o" in Porsche that is extremely frustrating to access. The only way to do it right --- remove the emissions hoses between air pump and exhaust --- actually easier than it sounds. Then polish it and the cam cover and bolt.

Similarly, there is another closer to the "h" in Porsche that is more visible.

These two ground points are where the computers and sensors are grounded, including O2 sensor, on the 16V cars. When dirty, behavior can be intermittently and subtly poor, exactly as you described. In addition, this is the location where the injector harness grounds one side of all injectors after triggering by the computer. Mission critical. And its NOT and off/on failure in most cases.

In fact, I'd clean them again to ensure certainty, and at the same time inspect the ring terminals for corrosion of solder in the junction. And, clean or replace the groundstrap between engine and frame.

Here is what I mean ---- this is a Euro with no air pump / valving so the one in the left of the picture is very visible ---- remove your valve to address this!

thedugger1

Sounds like I have some homework! Thanks for the insight, I'll check that out and followup.

Brett928S2

Hi

My 86 S2 (310 hp) uses a Maf and LH , I assumed (wrongly I think) that the OP was talking about a MAF...

My MAF has got a manual adjuster though...

All the best Brett

Landseer

No problem.

So you have a hybridized 82?

I might be mistaken, but isn't that ROW car nominally 300 hp with CIS mechanical injection?

Could it perhaps be retrofitted with 84-on MAF / LH / EZ ?

Brett928S2

Hi

Umm not quite....

Mine is a UK (ROW) 86 4.7 - 310 hp S2 (UK designation only)

It has the most powerful 16 valve engine which was fitted only in 85/86 and it also has S4 suspension and brakes (4 pot Brembos all round as an example)

It was a change year model I think....they were preparing for the S4 so gave it S4 suspension and brakes but still an S body and rear spolier etc...

The engine WOULD fit into any S body although you would need both the ecus plus the whole LH injection system.

My brother has an 84 16 valve S2 and mine is a little sharper than his but its only 10hp more (his is 300)

Although I am pretty sure the American 16 valve engine came nowhere near that sort of hp, probably due to the cats that American 16 valves came with...(no UK 928 had cats until the S4 in 89/90 year)

All the best Brett