Alex Sol

Mark,

Thanks for follow up question.

Took the 964 into indy to check over.

found:

1. vacuum leak
2. distributor needed rebuilding
3. grounds - cleaned
4. idle running fine until it warms up and then seems to go into limp mode

suggestions:

1. replace o2 sensor and it could have been telling dme to retard timing- which i did and no difference
2. replace knock sensors and they could be seriously retarding timing? - coming next week

currently 964 starts and runs and doesn't have the smoky unburned fuel and much less (if any) afm door slap which was due to a serious back fire through the intakes. i had the 964 warmed up and checking through all the injectors and decided to pull the intake and run the motor. there was serious back fire through left hand side banks and seemed to lessen once up in the rpm range.

now seems to be in a limp mode and not allowing me past 4,500 rpms - as if my limiter is there...

also stalls like mad when coming to a stop so i am heel and toeing every stop... guys in the car next door think i want to race...

Mark Brook

I've got the same problems as you it seems. I've used the OBD Scantool which is coming up with fault code 23, which is 'rear right speed sensor'.

Its actually coming up with 'Oxygen regulation at stop (intake air leak?)

Maybe we both have inlet leaks???

Cheers,

Mark 90C2

Alex Sol

update:

after rebuilding the distributor, the idle is excellent when starting but... as soon as it gets warm it starts to stall and sputter.

it also feels like there is a `delay`in getting fuel

another symptom- i cannot control the throttle between 1000 and 3000 rpms- it jumps around like crazy and will stall

over 3,000 rpms i can hold at pretty much any rpm..

checking today.. fuel pressure - as i found that a dead or dying fuel pressure regulator can trigger all of these misfire and rough running problems

looking for a fuel pressure system method of checking...

-nick

Alex, This kit has everything that you need to check fuel pressure.
http://www.harborfreight.com/master-...kit-97706.html
There is a port on the front left fuel rail to connect the gauge.

I haven't read through the whole thread. Odd sounding problem. Have you checked afm voltage? And cht and iat resistances?

Good luck!

Alex Sol

thanks for the harbour freight lead. i picked one up from local store in Toronto area made by Innova- Equus 4630 for $60. pretty basic set up and no proper connections and fittings but lots of hoses and clamps.

i started with my 944 turbo as it also has a misfire that could be due to fuel pressure regulator and or diaphragm. 964s don`t have a separate diaphragm or maybe it`s built in? some please clarify here.

i started the car, pulled the fuel pump sender fuse 15 amp on the 34 spot for fuses, and it seems to relieve the fuel pressure on the system, removed the fuel test port (there a ball bearing in there so remove carefully) and got the rubber hoses clamped on. Replaced fuse then started car and...
i got... 35 psi and after 30 mins it was down to 28 psi which sounds low on the 944

then did the same on the 964 and got...

50 psi running, 55 psi when turning off and 30 mins after i got 48 psi

so my conclusion, the fuel pressure regulator is doing its job.

speaking of cht - i had removed the cylinder heat temp sensor and connected to a volt meter, the resistance was right on spec, put a heat gun on it and watched the ohms slowly drop as the sensor heated up. then once it got to a certain point (maybe heat gun can only heat up so much) and it was stable and in spec....

i left it off as the 964 runs pretty well in cold program maybe due to rich fuel mixture. and took for a quick run, it ran so well and didn`t stall that it reminded me of how my 964 used to pull and was magic. there was a very significant stutter just off idle. like a major turbo lag where nothing is happening and then boom! i`m at 3,000 rpms and quickly building speed

iat - idle air or intake air temp sensor? maybe the culprit. i have an old afm and opened it up and rejigged the sweeping arms on a fresh strip. applied a little contact cleaner and also found one contact in the afm was not making contact so bent the arm also... prior to that i cleaned up the contact and replaced in the 964. ran like crap once heated up

my `new`afm from FUEL INJECTION CORPORATION in California is a rebuilt unit with about 30,000 kms on it and i haven`t opened it up to check... maybe my next move...

Alex Sol

mark, what scantool are you using?

i borrowed a jennikens from a rennlister with a 928 but it didn`t show any codes and did show a lot of knocks

i think this is also my issue. i replaced my two knock sensors last week and suspected that i was in some kind of ignition retard mode. thinking maybe i over tightened them or that they were faulty

checked my old knock sensors using an osilloscope and found they were NOT faulty and should be working

what have you done to fix your issues?

Alex Sol

as far as intake air leaks, i have checked extensively and will look closely at the boot where the afm is connected as i `upgraded`my air box to a Evolution Motorsport K N filter set up and it just sort of dangle and rested on the right hand side air intake plenum and maybe... there`s a small tear in there.

will get the fire extinguisher and a can of brake cleaner out to test... i had found a slight intake situation using the same process earlier and fixed... also had replaced all six rubber gaskets that go between the intake / fuel stack and cylinder head intake...

-nick

Pressures look good. You can rule out fuel pump and regulator.

I read through the thread and am a little confused. It sounds like you've confirmed that cylinders 1-2-3 are not firing? But those plugs are wet with fuel? That would point to an ignition issue.

Then you wrote that it ran better with the idle/wot switches unplugged. And now again with the cht sensor removed. Both of those things will push the mix very rich. That points to a lean mix issue.

So I'm confused.

General, and easy, things to put on your checklist-

1. afm voltage. Easy to test. Put a +12 lead on pin 3. Ground pin 4. Then check the voltage at pin 2. With the door shut, you should see ~0.26V. With the door completely open, ~4.6V.

Also check the input voltage from the harness. It should be very close to 5.0V.

2. Go to a shop and have them use a smoke machine to look for vacuum leaks.

Good luck!

Alex Sol

nick, i have some crazy issues.

once the cht sensor gets to temp it seems to tell my car to start stalling, running rough, misfire, cannot hold rpm steady in the 1,000 - 3,000 rpms but works nicely in the driveway from 3,000 rpms up to redline.

but when driving, different story, i have to slip the clutch in at 3,000 rpms and it will not rev past 4,500 - 5,000 rpms like a rev limiter kicking in.

i am going to carefully check for vacuum and intake issues because i may have damaged my intake boot that connects to the afm when i changed my air box to evoms k n air filter...

i'm pull out my fire extinguisher and brake fluid and spray it around the intake to see if there's any change in operation / idle.

then step 2 will be the smoke test

Alex Sol

the cylinders all seem to be working and it was a distributor issue.

strange thing is that my 964 ran quite well prior to my tear down, split case, reseal, fresh gaskets, seals, bearings, rod bolts, head bolts, spark plugs, wires, caps, rotors, intake air gaskets, refreshed fuel injectors, msd coils,

i had already replaced: crank position sensor, idle air control valve, got a fresh afm from california,

and recently replaced: knock sensors, 02 sensor, engine harness (used), rebuilt distributor,

and my fuel filter, not that old

my 964 seems to be stuck in some kind of limp mode or ignition retard due to message from computer...

would a plugged up catalytic converter cause these issues?

Alex Sol

nick, i did the afm bench test using a 9 volt battery

got the idea from www.the944.com

i put 9volt power into pins 1 and 2 and tested voltage on pins 1,4

it was a very steady, increase in the voltage as the door opened

i have two afms and they both tested the same. steady increase in voltage as the door opened with no sudden spikes up or down on the voltage.

i also test the resistance on the intake air temp and it was a steady drop as the afm warmed up from being outside (winter in Toronto) to room temp...

that said, i have one afm that causes the engine to run very rough idle and cannot go over 3,000 rpms and the other afm runs a steady idle when cold then idles rough once warm. cannot hold the idle at a steady rpm under 3,000 rpms but can do so from 3,000 to 6,000 rpms