924Board.org

[xr4outcast]

I am trying to get my new 1982 931 running properly. I had an old Porshe mechanic set the timing and the CIS. The car starts very easy when the temp outside is not to cold. I have not tried it when really cold yet. The problem I'm having is when you start to drive it pops an will not rev. Just sitting it revs up ok. I noticed the other day that the O2 wire was cut and there was a plug in the pipe. I'm not sure if this old system relys on the O2 for proper performance or not. The car seems to be pullIng good vacuum at idle, it around 13 on the boost gauge. Not sure what it's supposed to be.

Any help would be appreciated.
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So many cars so little time.

[924RACR]

Refresh my memory, you have the Euro-spec car, right? You may want to put that in your .sig, so we can keep track.

The car should run reasonably well without the O2 sensor working, as long as the wire isn't grounded maybe. Certainly better than you describe. Main impact from that should be mileage.

Idle speed is adjusted using a timing light, at least on the US cars; changes the ignition timing to control idle speed, so the speed won't change, but the idle timing will. Kinda wierd. Hopefully this is what he set; otherwise the timing is non-adjustable (computer-controlled).

Idle mixture also needs to be set, he probably did this. But usually when they won't rev properly or make power, you've got a mixture problem. That could be caused by an air intake leak (very likely, on these cars) or a CIS control pressure regulator problem.

To check the latter, you need the proper gauges for checking CIS pressures (not just any fuel pressure gauge). To check the former, you just need to hunt around spraying WD-40 or brake cleaner or the like, listening for a stumble, then finding that leak and replacing the necessary hose.

Lots of them are obvious, if a rat's nest. However I did find one large one under the intake manifold, #1 runner, about 1/2" dia, that was a bitch to see/fix. It goes to a pipe that goes to the turbo (another well-hidden elbow). As mine both leaked, my performance was quite poor.

Of course, since your DAPO took off a lot of what he thought were emissions plumbing, it's very likely you no longer even have the right connections in there. You may very well have to restore that all first...
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[xr4outcast]

Thanks for the reply.

The car is a U.S. spec. I was wondering from posts I read the difference between the two types. Just to see if I could kill the O2 or if I should restore the entire system.

What Vacuum should a 931 pull at idle?

The previous owner killed off most every hose but I managed (between my old car and the box of parts I got) to put everything back.

The car starts and idles really well. It has now sat in the cold over night so I will try it this morning and see if there is a cold start issue.
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So many cars so little time.

[924RACR]

Cold start will be different issues/sources than poor running. Certainly it's less likely to start when cold if it doesn't run well warm, but... best to first fix the warm-running issues.

Sorry, can't relate a decent idle vacuum reading - just disassembled the motor from my car for complete overhaul/rebuild.

I would restore the O2 function - but wouldn't worry about it right now, it won't be the cause of what you're describing unless it's really far off. I guess that does raise the question - do you hear the freq valve buzzing at idle? I've found that when my car was running well, I could hear it (hood up leaning over engine). When the settings etc were in the weeds, I wouldn't tend to hear it cycling... not sure if that relates well to others' experience, but one of my observations...

You definitely should try the vac leak test spraying WD40 or carb or brake cleaner etc; 13 does seem on the low side, I'd guess more like 20 or so... (I assume you're looking at an aftermarket gauge?)
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[xr4outcast]

I started the car this morning and everything was good. Started just like it did when warm. Let the car warm up the hit the throttle to see if it would climb RPM and it did. So I took it for a spin around the business park and it ran ok. Well enough to lay down 15' of double rubber. But it is still not right. It wanted to stall when I came to a quick stop. But started right up again.

I was thinking of going EFI instead of changing all the rubber boots an hoses. I just stumbled across the fact that a ford 2.3 turbo distributor is almost exactly the same as the 931. So I was thinking of using a 2.3 harness and sensors, throttle body... And see if it would work. The Merkur Xr4ti has about the same power levels and I have lots of that stuff just laying around.

I will post pics of the car later. I just finished the suspension and brake mods. Should be a fun car once the power is right.
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So many cars so little time.

[924RACR]

You do realize that's a bigger job than simply fixing the car, right???
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[xr4outcast]

Yes Yes cooler headed have prevailed, I am goin to visit Ideolas Garage and order the necessary bits to get this thing on the road.

But later this winter I think I will work on the conversion and offer it up on the forum so people can have an easy EFI for the 931.
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So many cars so little time.

[924RACR]

Cool...

I aim to megasquirt mine - but will wait till after I get it reassembled and working properly. Then, once the megasquirt is happy, I'll pursue adding the IC and cranking the boost way up there.

Then I'll probably be shopping for brakes, rims, and tires, to keep it under control.
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[stevekat]

Getting the car running nominally, and laying down 15ft or rubber on a 30 year old DITC 931, I would say, are not mutually conducive.
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"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.

[xr4outcast]

Are you planing on distributor less? I was looking at the Megasquirt option as well and though it would be easier if I use the ford distributor and the MS for the 2.3.

I went backwards with my build because I have had all the parts since 1996. I just installed 1986 951 suspension, breaks, and transaxle. As well as Bilstine shocks and struts with coil over perches, stainless lines and 928 S4 flat wheels. I cut 1.5 coils in the front and skipped a tooth on the torshion bar (inner) oh and 951 sway bars.
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So many cars so little time.

[924RACR]

I haven't decided for sure on the ignition side, but I do wish to get away from the stock ignition. The distributor seems pretty robust, so I may not bother with coil packs, but I would like to get away from the stock crank trigger; while it's not delicate, not being able to find replacements worries me.

Yeah, that suspension setup should be pretty decent. Mine's still bone-stock other than Bilsteins... but refreshed - I do like the softness of the stock suspension, for the Detroit roads...
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype