Bri Bro

Steve, If I were you I would just replace the cat and O2 sensor since it is almost 25 years old and they are the main components that clean emissions. You might also pull the injectors and have them cleaned. Think of it as PM. I am sure this is the correct steps to take to avoid these problems year after year. Ca is a tough state to live in with a older car due to the regulations.

ArcticSteve

Specifically what is the issue with using acetone and 10% ethanol blended gas?

Bill

My 944 NA did not pass, so I bought a new cat. Still did not pass. I had a second second cat lying around so for fun I installed it and it now passes.

jonnybgood

I was chasing better fuel mileage at and replaced my O2 sensor at one point. It did not make any difference so I assume the old one is still good. You are welcome to it if you want it. It is sitting in the garage. If you are going to the swap meet this weekend I could give it to you. They appear to be interchangeable from looking at the parts on Paragon's website.

I also installed a high flow cat that bolted up to the exhaust system. I don't know who the manufacturer is but it works fine. I have passed smog with ease since. Oh, I had the injectors balanced at Witchunter as well.

genikz

High CO with low NOX means your car is running very rich. You have plenty of room to increase your NOX emissions (which are a result of high combustion chamber temps, e.g. running lean). Try replacing your 02 sensor. If that doesn't work, your AFM might need to be adjusted.

KuHL 951

That's the plan Brian. I picked up a Bosch universal (heated for Cali) for $63 and will have a new cat section installed with a 'test pipe' next week. The injectors were serviced by Witchhunter about 6K ago so they are good to go. I'm not sure if I should trust one of the other two exhausts sets, one has 91K and the other has 170K...like a fool I didn't mark them

Thanks for the generous offer Jon but I won't be making it down to the swap meet today. I'm surprised the 951 and NA are different part numbers, at least on Pelican they are.

I'm selling the 951 and have to do this first as required by law here. Luckily the smog test is good for 90 days for sales purposes because these cars are not selling fast.

jonnybgood

You had me worried there, the swap meet is tomorrow.

Yeah, my sale on eBay is does not have any bidders. It is my first run and I am not in any great hurry.

Good luck with the smog testing.

KuHL 951

Dooh, I thought today was the 7th. Must have been a Senior Moment. I decided to go with a new cat also so the next owner doesn't have to deal with it. What a nice guy I am

KuHL 951

Thought I would provide an update and another headscratching question. I had a shop install a new quality cat and new Bosch O2 sensor. The old cat had the rear two baffles wasted so I felt good about the retest. After install last week I couldn't smell any fuel in the exhaust anymore but the dyno broke down so I couldn't finish the test. Today the car smelled very rich when I started it. I took it in today for retest and the car was even worst than before on HC (222>261 and 121>173) and CO (2.51>5.09 and .89>2.71) 15 and 25 mph respectively. WTF? NOx dropped as expected (new cat) to very good levels. Nothing has been done to the car since the last test. The shop had some issues fishing the O2 new wires up from the bottom. Do you think it's possible that the O2 wires were laying against the downpipe, melted, and shorted out? It's like the O2 just stopped working today. I'm at wits end here. Is there a way to test the O2 at the sensor plug. Does black wire to ground have a known value; I assume if resistance is zero something must have shorted. There are two interchangeable white heater wires and the black sensor wire. If the sensor wire or heater wire shorts will it default and run rich like this? I guess what I'm asking is does it sound like a bad O2? Thanks for previous and any new advice.

Calmchaos

Most definitely sounds like a bad O2 to me.
Are you sure that it is plugged in?
You can test it like I described at the end of page one.

KuHL 951

The plug is the first thing I checked while on the dyno. I soldered the splices myself then used heat shrink. Your test description was a bit confusing. You said to set my ohmmeter to mV which doesn't make sense at all. Are you saying to measure the voltage drop in mV or resistance in ohms? It seems resistance would be more valid that a mV drop.

Techno Duck

Something to consider is you are not supposed to solder O2 sensor connections. The wires need to breath a sample of reference air to compare to the exhaust. By soldering you essentially cut the reference air sample and can cause the O2 sensor to malfunction. Whether or not that is your problem i dont know, but something to consider.

BTW, i feel your pain. I went through hell trying to get my 951 to pass emissions last summer. The AFM CO adjustment was so far out of whack. I reset everything and eventually got it to pass..ended up replacing all of the suspect items (reset AFM, replaced O2 sensor, new plugs..etc). I was so fedup with that AFM setup after that i just bought the Vitesse MAF.. .

KuHL 951

Thanks Jon. This subject came up a few months ago and the general consensus that most people soldered them and tossed the vampire splices. The Bosch kit I had came with a water tight connector that would have resulted in the same water/air tight connection as heat shrink. After I've had one more beer I'm going out there with my DVM and check a few things out. I was just too frustrated to even open the hood for the last 3 hours.

944Ross

Years ago when trying to trouble shoot an O2, I bought some tips for the DVM that are like a hook with a very sharp metal point that punctures the insulation. They allow you to hook up to the complete, installed system and drive around while you (or better a passenger) watches the DVM, you can see how quickly the O2 responds, which is just as important. (PS -- ONLY use a DVM!)

I can't swear to it w/r/t these Bosch systems, but many EFI systems don't use the O2 signal when the TPS indicates closed throttle (idle). They use presets and defer to the IAC with RPM a priority.

Another thing that causes the kinds of readings you are getting is oil sucking past the valve stems.

KuHL 951

Well the O2 sensor just like two other O2 sensors that are off the car, no short using an ohmmeter when cold. The sensor wire is not shorted 'at the moment'. That's what I'll look for tomorrow when I get it on a rack I'll the sensor wire contacting the exhaust. This is getting ridiculous unless my FPR failed in the last week which is unlikely. There was a definite change (failure of some component) since the O2 was installed last week and today. It's beer o'clock and I'm bagging it for the night.