Brittania

I'm trying to figure out if the o2 may have gone bad. Gas milage is crap, 400 km off a tank in stop go highway driving (not using boost too much to try to conserve) . Also failed emission test with high co at idle. Thing is po had replaced o2 within last 5000 km according to his receipts I found. Are there any other symptoms I should look for that may point to a bad o2 sensor? I find the car is crap in stop go traffic, not very smoth on decelaraiton closed throttle. Chip is vitese afm

Cheers

Tom M'Guinn

You can jumper the test port to bypass the O2, to see if it makes any difference, or put a multimeter on the O2 signal to see if it is even functioning. Based on your description, I'd wonder if the AFM and TPS are faulty? Have you tested those with a multimeter?

Brittania

TPS, Has been replaced. Air Fuel meter reads stoich and bounces around nicely. The main noticable problem is in traffic 1st,2nd gear on decelaraiton it's not smooth when she comes back on the idle aorund the 1200 rpm mark. I can see the fuel come back on at 1200 and its almost a shudder thats felt . Is this typical or is there a problem , would the O2 effect this?

testarossa_td

Gives me the TPS feeling.....

http://www.arnnworx.com/tps-repair.htm

Shudder
http://www.frwilk.com/944dme/shudder.htm

AFM
http://www.frwilk.com/944dme/afm.htm

Brittania

thanks Mate, that 944 shudder does sound like it - but I didnt think it was present on the 86 944 turbo. Shouldnt the vitesse chip fix the fuel shudder issue. The TPS was replaced . Anyone else with a 951 have the fuel economy shudder?

wi54545

Try disconnecting the sensor at the back of the intake manifold to see if that clears it up. The DME will revert to stored maps like some ROW cars.

Brittania

I let the engine warm up and then diconnected the o2 sensor , there was no noticable change in rpm. The air fuel guage stopped working when disconnected so I guess the o2 is working well enough to be sending a signal to the a/f gauge. Shouldnt the rpm change if the o2 is disonnected?

symptom,
When the car comes back on idle - its just not a very smooth transition, In second or fist I have to be ready to jump on the clucth to stop the shudder. With clutch in the idle is nice at 1000 / 950 ish and does not drop any lower. Should I not be able to crawl along in second during heavy traffic and not have to worry about pushing down on the clutch before she returns to idle.

hally

if u are planning on doing further mods, maybe now is a good time to bring forward purchase of a wbo2, will answer all your a/f questions.

Brittania

I have one of those narrow band light show gauges. I dont have the funds to upgrade to wideband. I'm thinking the car runs a little rich, high fuel consumption and black tailpipe, failed emmisions at idle. I'll test the o2 , change fuel filter and pressure test intake vacuum. My FPR got replaced last year , when FPR failed the car ran rich ,I'm thinking this may have fouled the o2.

Scooter

I get about 470 km's with my 86 951 with an autothority chip and no cat, is that bad for a mix of hwy/city driving?

Brittania

I got around 450 km's off my last tank, thats stop/go highway on the 401. I think these cars are great on gas if driven at cruise speed, once you have to stop start they get very thirsty. I'm using a vitesse afm chip. 3 bar and shimmed gate coming soon. Then I expect to see if drop even more

cheers

skene

I've got basicaly the same setup, and the same symptoms you have. I'm going to be replacing my 02 sensor in a bit to see if I can pass emissions as well.
I'm getting much better mileage then you though, ~400 miles per tank with a good mix of stop and go and highway.
I think I fixed my funny off gas/closed throttle bit by adjusting my tps some more. It wasn't completely closing when off throttle, so it was probably using the part throttle map instead of the idle map. It also seemed to fix the idle dropping to ~750-800 then going back up to 900 when giving it a bit of gas.

Brittania

Skene, do you have a narrow band air fuel guage? Mine shows the air fuel is perfect yet my tailpipe is black ,fuel consmuption is high and the "back on idle "is less than smooth. The car does idle ok, at 950- no dipping. The TPS is clicking closed at the correct point, and when it does click closed I can see on the A/F gauge that the fuel is off until the revs drop to 1600.00 - then the fuel comes back on and the car shudders slightly. This is much more noticable in 1st and 2nd.

skene

Actually no, I don't have an air fuel gauge. My tail pipe is pretty sooty as well. Something is funny in my 4th cylinder too since the plug has a lot of ugly build up on it but the other three look normal. I should probably do a compression test on it to check what's going on.

Stiletto

Along these lines, I just recently put in the Vitesse AFM chip, and noticed that the (narrowband) mixture gauge now takes a long time (around 5 minutes) to get into the normal "lean-rich-lean-rich" dance, which if I read right means you're in closed loop mode.

Before installing the chip, it only took about a minute to warm up and get into closed loop mode. Now, it sits there at full-rich for about 5 minutes after I start the car. I can only imagine how much fuel I'm blowing through the system in these first 5 minutes.

Should I be worried about this? Is there a way I can get back to normal without pulling the chip? It's a brand new O2 sensor, so that's probably not the problem!