Alex Sol

has anyone ever experienced this?

you start your 964, take a spin around the block, in cold weather (Winter in Toronto) and drive around for about 45 mins in mixed highway and traffic.

Stop for 1/2 hour then go out again.

well after this, i was going about 30 miles an hour in second gear and felt the car chug, sputter, and not rev past 3,000 rpm.

i quickly pull over to the right, find a side street the car stalls.

I start it up again, same thing happens 150 feet down the road - car chugs, sputters and dies...

I start it up again but this time i rev it past 4,000 rpm and take off briskly thru the gears 1,2,3.

Then drive the 964 home another 20 mins and no problems.

This has happend two or three time now... other times no problem.

i've pulled the dme looking for cold solders

i've replace dme relays and keep a couple on hand

i've ordered a new cps (crank position sensor, reference sensor)

and a new iacv (idle air control valve) - the 964 has all stock clutch and flywheel but would stall from time to time when coming to a stop sign while coasting in second gear and decelerating. (i did clutch in when it got to about 5 mph)

spark plug wires are new

fuel pump new

rotors, caps, coils, plugs (40,000 miles on them)

total on the chassis - 225,000 miles with very poor rebuild at 175,000 miles.

anyone had this experience or just me?

xdecock

I had the exact same problem it was my mass airflow meter dead, changed it, and everything went fine,

the problem was purely random sputtering, and limited power (being distanced by a tractor) and as random self healing.

Xavier.

Richard Curtis

Try this easy thing first: Clean the ground (earth) between the negative post of the battery and the chassis. Clean both ends of the cable, the chassis where the cable connects and the battery posts.

Shamus964

Yeah, I've been looking at my AFM also for loss of power symptoms... check out these threads and see if you see the same symptoms... good luck!

https://rennlist.com/forums/964-foru...-downhill.html

https://rennlist.com/forums/964-foru...t=afm+downhill

https://rennlist.com/forums/964-foru...t=afm+downhill

Robbie Ravioli

Check fuel pressure as well. After a long drive engine bay warms up. When engine is turned off for 30mins, temp in engine bay rises. If fuel pressure gets low you may get vapour lock, specially with high volatile winter fuel with higher rvp.

Alex Sol

I don't particularly care for beating a dead horse, but shortly after thinking I found the solution Nessie reared its ugly head again. Although the problem is far far less trouble than it was with that broken vacuum line, the problem is still there.

Specifically the problem happens when you press the throttle enough to bring the car off of idle, but not far enough to really open the butterflies. This is a slight downhill attitude. As mentioned in previous posts, a quick full throttle to trigger the wot switch cures it (closed loop, ignores the ox sensor adjustments). I still whole heartedly believe during this situation the car is running either way lean or way rich and the system tries to compensate. I realize this is an unpopular opinion, but it fits my observations. When you trigger wot it immediately reverts to normal settings and thus is fixed.

I have a problem in my AFM that the resistance surface is cracked near the low angles. Seeing as low demands are where I am seeing the problem, could this be the problem. I do notice when checking the afm voltage outputs that it doesnt work like I would expect it; it doesnt go up smoothly, and in fact, drops quickly for a short throw then goes back to climbing. This seems to me that it could be the problem. I did tinker with the afm to get the arm to ride on a slightly different track, but it did not help (yes I did my best to adjust the 0 properly, which miraculously I think i did). Anyone ever repaired one of these things?

Anyone have any thoughts? Besides my annoying squeeling pig (the brakes) which I intend to fix this weekend, this is the last serious annoyance I have to cure. Please o please help me if you can.


Shamus, I am definitely not alone with this problem. I read thru the links and quoted this 2005 issue...

i have some oil leak issues from a poor rebuild and suspect the oil is getting onto hoses.

i've rebuild the twin rotor with the belt and vent

i've replaced the battery strap with fresh oem part

i haven't tried to change or service the AFM so that may make sense that it could be the culprit.

i've replaced the fuel pump and fuel filters though i wasn't aware of the one in the gas tank.

vacuum lines? leak - probably causing the hunting issues so i may be looking a replacing a bunck of vacuum lines...

i've had extensive discussion about dropping a 3.3 litre 965 motor in this narrow body 964 which may be a challenge with wiring etc.

also very tempted to do a v8 conversion... duck for flying tomatoes!!

will definitely be dropping motor (again) to look at the various issues

btw, i had stalling issues fixed by flooring the throttle (similar to the solution to some of the links sent by Shamus) and got the 964 home once and another time to a local firestone shop. they found a spark plug had dropped down

i'm missing most of my engine tin due to erosion, rust, age so need new sheet metal down there...

i'll check the fuel pressure robbie

Alex Sol

back in 2005, Adrian had some very interesting comments including air flow sensors, air temp sensor confusing the dme when under light load. this is normal for the 964!

the fix... floor it then drive it normally...

i figured this out on my own under survival mode about 400 kms from home!!

and have gotten used to it at times... crazy car!!

peterC2S

Ditto that with a previous 964 C2 Tip (I posted in the first of Robbie's quoted threads). Changing out the AFM fixed the problem. A few of us also noted that the problem always occurred on the same downhill grade on the daily commute.

Shamus964

Yeep - AFM is where I'd start

xdecock

the fix... floor it then drive it normally...

Got the same issue, playing with throttle till things normalize (flooring, releasing, flooring, releasing, ...) and all of a sudden, the motor will breathe normally, but got a few times it had not fixed the problem (and @ 130 kph+ on an highway while overtaking on the third line, it's damn stressful to loose control of the power delivered while trying to reach the far right side with clutch pressed in)...

So try to confirm maf is the problem, and you'll probably fix this definitively (at least for a dozen + years)

Alex Sol

afm ordered and will be installed in a few days

Alex Sol

quick update:

replaced crank position sensor - 964 is a completely different car!

starts up right away, within 1 second of cranking

engine pulls stronger than ever - once warm

car would stall on decel in second gear once in a while... no evidence of this anymore...

idle has settled down and does little to no hunting

once warm idle is between 800-850 rpm = i haven't even installed the iacv yet

old AFM still feels like it's not opening and creates a slight hesitation when motor cold

new AFM coming later this week.

can all this be attributed to CPS?

a couple of things i'm watching for: mileage used to be up to 700 kms on 60 litres when cruising on the highway... hope to get that back also....

xdecock

700 km on 60l i'm impressed my Best score was around 600

Alex Sol

this was on a cruise from Toronto to Montreal then into Vermont. going a steady 110-120 kms/hr with some bits in the 80-90km/hr... that was the best though normally i would be 475-525 kms in mixed use city /hwy driving.

Alex Sol

quick update: ordered a rebuilt AFM from Fuel Injection Corp in California. Service good, price reasonable.

$230 for a rebuilt AFM plus core charge.

Installed by removing the harness to the Idle Air control valve and then loosening one clamp. Careful not to lose the metal clip.

I have the K & N cone air filter from Evolution Motorsports. Sounds great when accelerating...

Removed the harness to the AFM, careful not to lose the clip.

removed the K & N plus Evolution housing, replaced on the AFM. Slapped everything back in.

Car runs.... excellent! no hesitation on acceleration !!

next project... cut off primary muffler and bypass...