por4ever

Hi all. I recently picked up a 968. After I have been driving for a while I get the Check Engine light during steady cruise. If I let off the gas the light goes out after about 5 seconds. The code is a 2 23 intermittent oxygen regulation. A description I read for fault 23 talks about the oxygen regulator. Is that the O2 sensor? I don't get a code for an O2 fault. Is it the MAF? I don't get the code for that either.

When pulling away from a stop light I get knock. CEL does NOT show a knock sensor code. The plugs and fuel filter were replaced last week with no change. I have sprayed some MAF cleaner around different vacuum lines and connections including around the throttle body but no result. (Is MAF cleaner flammable enough to detect vacuum leaks?) But at idle the CEL is not lit so the leak may not exist at that time.

The car runs great otherwise. Feels like it has all the power it should. No stumbling even when I hear the knocking. Knock is not constant so I don't suspect rod knock. There is a very slight stumble while cruising on the highway but not while accelerating. That with the knocking makes me think I am lean but I can't find any leaks yet. Intermittent issues are the worst. Any ideas?

thomasmryan

are the ignition components original? rotor, cap and wires?

por4ever

I looked through the records the PO gave me. I don't see a bill for those. When I had the fuel filter and spark plugs replaced they checked and cleaned the cap and rotor. He said they were dirty but not worn. I did notice on the way home from work today if I keep a constant speed the CEl comes on. If I accelerate or decelerate the light will go out until I get to a constant speed again. I just received the throttle body reseal kit from Paragon. That will be done this Sunday.

thomasmryan

reseal kits may not be compatible with the 968.

start your car n a dark place with the hood up to see if you see sparks.

oem plugs should have three grounding electrodes.

por4ever

The TB kit I bought does say it works with S2 and 968 but I'll compare parts that come off with the ones I am replacing. I'll contact the shop on Monday if the invoice doesn't say to confirm what plugs they used. This shop has been around forever so I feel confident in their work. I don't think the plug wires were checked so that's an idea.

931guru

Vacuum leak. Find it with a smoke tester.

thomasmryan

Tiger03447

On the ignition wires..like the other poster said, find a dark spot..dusk is good, and use a spray bottle with some water in it..spray it on the wires..while the engine is running....if they are bad, you'll see the electrical display.

thomasmryan

por4ever

I re sealed the throttle body this weekend. CEL still lights while at steady peddle position. I did find that if you repeat the procedure to pull the code with the gas peddle other codes will display. Second code is for TPS. I should have that by tomorrow. The 968 TPS is not just a switch as in the 944. It's a potentiometer. I can't find resistance values for it anywhere but I'll compare them before I put the new one in.
I'll see if the new TPS fixes anything and troubleshoot from there.
Does anyone have the 968 shop manuals in pdf? The link on the archived Cannels site does not work for me.

Lognet

Did you find the source of trouble? I experience exactly the same ting in my 968 1992, change almost everything and rebuilt almost everything. run like a charm, but still feel a minimum of not quite perfect at idle speed check engine light on and oxygen regulator code, when accelerating or reducing speed, light go off like you.

Stebo

I cured this code by replacing all of my vacuum lines and fittings. 1/8" rubber hose (non reinforced, windsheild washer tubing) bought at Napa worked best for me. I also tried 5/32", which worked okay but it wasn't as good in my opinion. I originally ordered 5mm ID silicone hose, but it was slightly too large - so if going silicone, I'd recommend 3mm or 4mm. Whichever hose you choose, buy some samples first and test it on the manifold nipples and what not before committing!! I didn't get to fully verify which was better. I found what worked on my '92 968 and just went for it. I bought 30' of hose, and had tons leftover. I think the Linsey kit is 20'. I didn't want to go back to the store! LOL. one hitter quitter.

I replaced all of the hoses and fittings to renew the whole system. For the fittings, I only needed tees - no wyes, no butt connectors, no Us, and no 90s. This did not immediately eliminate the CEL upon starting the car.

Lastly, I disconnected the negative battery terminal for 10 mins (a trick i used on my hondas back in the 90s) and that reset the CEL. Good to go! Hope this helps



I used these links to help with the diagrams:
https://rennlist.com/forums/968-foru...l#&gid=1&pid=4
https://rennlist.com/forums/attachme...ing-hvac-3.jpg


**EDIT** Well it worked for 4 days... code 23 is back again. haven't rechecked the vac lines yet - maybe i'll give the plug wires a try...

Tiger03447

You might spray the ignition wires with a water mist while in the dark place..that will make it light up better. Intermittently, of course. You WILL be able to find the electrical leak if you spray it continously.

Stebo

I'm still fighting this a year later. New O2 sensor didn't fix it. I also inspected the MAF and it looks brand new inside the cover - i'm not ready to change it or have it rebuilt yet - the circuits are all potted and connections look great. Spark plug wires are new and look fine too.

Upon changing the oxygen sensor, again resetting the ECU by removing the negative battery cable, and then putting everything back together - the car runs AMAZING for a couple days until the CEL comes back on (and stays on). Power is up and it just runs smoother. I'm starting to wonder if my ECU is messed up. I plan to keep chipping away at this issue, one thing at a time until I find what works. We'll see.

I could just keep removing the negative cable every few days to reset the computer, but that seems stupid. If the vac leaks, spark plug wires, MAF, o2 sensor; were the problem I think it would still run badly even when the computer is reset.

Does anyone have any thoughts on that?

orig944