air flow sensor plate adjustment help needed..!!

Jc924turbo · 01-31-2008, 07:23 PM

my 81 931 air sensor plates got messed up in adjustments during repairs of other things.. found out that the plate needs to have some little space around the plate, but how do I adjust that..?? I did make a stopper with a screw, using the plug hole, but.. I don't think I suppose to do that.. and secondly..; hex adjustment in the flapper adjustment balances the air and fuel mixture.. richer and dryer.. but when I have it in good sounding/good running position, can't get it start .. engine turns, but does not fire the sparks.. so I have to mess with the screw that I had put on to start.. I know I'm not suppose to mess with it,,.. but too late.. someone out there must know this set up and hope htat I can get some help.. thanks... KEEP ON PORSCHEING...!!!

Makis · 01-31-2008, 11:44 PM

I don' think the plate needs to have any space. So you will have to remove the screw adjustment and make sure the plate moves freely. When the engine is running or when you start the incoming air keeps the plate open. Now if you adjust the plate spring too hard then you create to much restriction in the flow thus causing the engine to start more difficult. You will need to reduce the tension and see if starts.

The correct tension in the plate is important to achieve correct fueling. Too little tension will make it run richer. Too much tension will make it run leaner. Also too little tension can cause the plate flap to be too sensitive which can cause running problems on an engine especially at idle as small vacuum changes in the inlet can cause the flap to close and open widely. Too much tension will restrict air flow which will loose you power too. If the engine does not run properly with the correct adjustment then there is some problem with it and should be fixed you do not need to temper with the AIR flow meter normally.

drew1 · 02-01-2008, 01:18 AM

I go along with Makis & will give a suggestion for setting. Take off one of the lines going to the injectors. With the fuel pump running, jump the relay don't crank the motor over, & the allen wrench out, fuel should barely run over the edge of the injector line fitting. It's kind of aggravating because the weight of the allen wrench affects the tension. You have to adjust, remove the allen wrench, & check, & maybe do again. This should get the motor to start.

If you loosened the plate on the lever, you need to get it set back even all the way around. If this won't run good with the motor warmed up, you may have a problem in the warm up regulator or frequency valve.

Jc924turbo · 02-01-2008, 05:18 AM

Thanks guys.. for your inputs.. O.K...;1.. I don't need a stopper for the flapper, so I'll take out the screw, to start out.. (when I do that, I get very low and harsh cold idle.;I mean barely idles, and when I push the gas pedal engine does not run faster,,wants to turn of..etc..until it warms up..)when it's warmed up it's fine..hey.. Drew.. you mean you want me to run the fuel pump without engine crank..; give voltage to the fuel pump with another cable..??? is that what you mean..??and taking out the injector line on the engine side..?? or the distributor side..??I suppose it's the engine side, cause you mentioned the line fittings.. right..??

924RACR · 02-01-2008, 05:51 AM

Actually there is a spec in the Haynes for clearance all around the plate in the cone - to be checked with a feeler gauge. It's adjusted by unscrewing the 10mm hex bolt that holds the plate to the arm and moving the plate around.

The plate should also be level with the base of the cone - again, explained in Haynes. Drew's got it right - the setting while warm and running is correct, and when you have starting problems beyond that, you need to look at the rest of the injection system, including warm-up regulator and cold start valve (including thermo-time switch).

Jc924turbo · 02-01-2008, 07:11 AM

That sounds awsome... let me work on it.. today/tomorrow.. and I'll let yu know the results.. that sounds right at the target... thaks guys.. for all your help...

drew1 · 02-02-2008, 03:14 AM

"run the fuel pump without engine crank" - Thats right. You can do it on the plug under the hood by the fire wall or pull the fuel pump relay & jump terminals." I remember the fuel pump relay, so I will explain that. Get a piece of #10 or 12 wire, 6 to 12" long. Strip the ends & crimp spade terminals on each end. 3/16 wide terminals work, but are hard to find so you may have to file 1/4 terminals. you want them the same width as the wide blades on the relay. The socket where #30 relay blade goes id the battery. I'm trying to remember, it's either 82 or 87 for the pump. With the jumper in these slots the pump runs. I'll check some info & get back on the pump blade # if nobody else does.

" taking out the injector line on the engine side..?? or the distributor side..?? = Take it out of the distributor side.

Hope you haven't loosened & moved the plate. You probably did though. All of us do once. It's like sticking something in the electric socket when you are a little kid. 924RACR's instructions will get you back right. If you can get a light up where the turbo hose goes, from the top eyeball the difference from side to side on the blade after the feeler gages to double check. As you are going to find out, the first couple of times it will probably be off until you get the feel of the arm & plate giving.

Did you take the car on the road with it warmed up? If not it could be a couple of a bad Oring in the fuel line pressure regulator in the fuel distributor. Vaughan probably has shimmed his up & can make sure I'm telling you right. It's under the big bolt beside where the fuel line comes in. It has a pin with Orings, Spring & shims. Easy parts to loose.

Jc924turbo · 02-02-2008, 10:35 AM

O.K... That took a while.. this morning... well I did take off the distr. side of the line.. and checked... and looks all right.. not as easy as I thought... well the starting problem is better now... with adjusting the hex... again.. and again.. it runs much better.. I did put some wd-40 inside of the fuel distr. so hopefully the flap would be little better to adjust the mixture.. I still did not get full info on the adjusting the plate.. so I'll get to it little later.. but my rpm seems little high....; at 1,200 to 1,400 or so... how can I adjust the rpm to go lower..?? isn't it supposed to be like 900-1,000 or so..?? I don't want to adjust the hex.. for it is good now..just the rpm lowered..

drew1 · 02-02-2008, 12:41 PM

There is a bypass valve on the throttle body. It has a slotted head for a screw driver. You should be able to see it from the top of the throttle body. This will probably be the easiest thing you have done on the injection. Just don't tigthen too hard & scar the valves seat.

924RACR · 02-02-2008, 01:31 PM

OK, but that won't change the idle speed if the ignition is working properly - only change the timing. Though it can affect the starting ability, and you are right, it should idle around 1000rpm if not lower. Mine usually idles around 900rpm IIRC - haven't been able to drive it for a few months!

(too much snow, sometimes, in Detroit!)

I don't know if you've been through this before, but have you gone through every bit of the intake to fix all the vacuum leaks? These will cause poor starting and running, not to mention high idle. Plus they're inevitable given the age of the cars; there are many hose elbows and straight bits that die after 20+ years of heat cycles. I've since replaced ALL mine with 3/4" silicone hose elbows - pretty easy and cheap to get, when the originals are NLA. Just sucks having to have those bright shiny blue silicon hoses in there, looks like a ricer, but I'll take that if she runs well! I got mine from Racer Parts Wholesale.

There's even two that are hard to get to and usually forgotten, the plumbing to the compressor bypass valve. One is a straight tube directly below the front of the intake, can see it if you get the alternator out of the way; the other is over the turbo, on the front of the engine by the water pump, and a real PITA to get to. But worth the trouble when it's leaking!!!

HTH...