Low power in low RPMs after reconnecting O2 sensor

[tirwin]

Good stuff, Jim! Sometime when I know I'm going to be out of town for a week or two I'll be happy to ship you my ECU for the sake of testing for posterity.

I have an update, although it's not much of one.

I got my hands on a free oscilloscope but I think it's a lost cause. It powers up but I can only get the display to occasionally flicker.



I also found an old school dwell meter on eBay. It's a 1969 Milton model and it's in great condition. Has the original box and user's manual. Still no dice on reading the duty cycle. I'm back to looking for a loose connection between the test port and the ECU.



Feeling a little frustrated I drove over to our Fry's to see if I could find a multimeter with a duty cycle function. The only one they had was a Fluke 87V for $399.95. No thanks. I ordered the Innova I previously posted about from Amazon.

Funny story... As I pulled into the parking lot at Fry's I noticed another older 911 and parked near it. Just as I was getting out of the car the owner was getting in and we stopped to chat. His name was Dave and he was the 2nd owner of a beautiful 86 Carerra. Turns out Dave races a 79 and is a local DE instructor. So we got to talking about why I was there in the first place and he said a lot of what you guys are saying about lambda CIS. The lambda cars just really like factory stuff and that's it. And they don't like not having the O2 sensor. Ok, I give up on my wideband O2 idea (for now - more on that in a bit). We talked until we were both frozen and Dave gave me a bunch of great advice on a lot of different topics.

OK, so I know javadog said to get the stock O2 sensor. I thought I remembered that Pelican offered an "original Porsche" and an "OEM" version. I thought the original was about $120 and the OEM was less. But when I went to look, I only found the OEM version for $23 dollars. Am I remembering this right? I just want to make sure I don't mess up and order the wrong thing. The one that's listed just looks like it has a short (couple of inches) pigtail. I went to another parts store online and found a different version of the Bosch that I think is a better match (18.5" wire and comes with the rubber grommet). The website said they could have it have it to the store in a day but when I talked to the store they said it was NLA. Is the $23 one ok to use? I'll have to figure out how to wire it into what's left of the old green shielded wire.

One other thing that I want to ask you guys about. I have been thinking about going to SSIs for a while but now I'm having reservations. You guys have convinced me that I really need to keep the O2 sensor for the lambda unit on this car.

Here's my dillema. The existing heat exchangers are starting to get in bad shape - lot of rust/corrosion. I've got a minor oil leak that I was going to fix at the same time as I did the SSIs too. Can I weld in an O2 bung on one bank of the SSIs?

The state of the existing cat is also questionable (might be clogged which could be part of the problem - can't really rule it in or out at this point). I don't want to invest in anything now and then do something different later. I'm kinda at the point where I want to go one route or the other and get this fixed so I don't have to think about it for a long time.

Options:
1) forget about SSIs, ditch old cat now and install cat bypass w/ O2 bung
2) forget about SSIs, ditch old cat now and install magnaflow cat, weld in bung
3) go ahead with SSIs & new exhaust (assuming I can weld in an O2 bung on 1 bank of SSIs)

If I do SSIs I either go without a cat or I go the route Craig_D went using a cat for each SSI bank and a custom exhaust. Right now I'm leaning towards not doing the SSIs but I'd like to hear from you guys.

[tirwin]

Jim,

I know you said a modern version of the old ECU would be a labor of love but I'm starting to think that it is in the realm of possibility. Have you ever seen the Arduino platform? I've found a few people building ECUs using Arduino and there are even some open source projects. It looks like between the info you and javadog have, it could be done. I'm just thinking that Arduinos are really cheap and fairly easy to program. Just kicking the idea around.

I was also looking at oscilloscopes and I came across Bitscope. Just curious if you or anyone else has any experience with it (or similar ones)? Wondering how they compare to the more expensive standalone units?

[javadog]

I'm going to wade back into this briefly, to voice an opinion.

I have always used the correct O2 sensor. I've never used one where I had to splice the wires. To me, that's just asking for trouble that I don't need.

I have a couple friends that have worked their whole lives for a company that makes wiring harnesses and other related products for the military and aerospace industries. I've seen how they make the harnesses and circuit boards. They are very particular about how they connect wires. They use expensive tooling, expensive connectors, etc. What they do makes the typical backyard automotive wiring jobs look like the hack work that it is.

I've bought and owned a bunch of cars. Dozens and dozens. Every single wiring splice installed by a previous owner has been a source of trouble. I've seen it all, from the cheapo connectors sold by any auto parts store, scotchlocks, soldered joints, twistlocks, even wires that were placed next to each other (not even twisted together) and wrapped with cheap electrical tape. I should have kept a picture collection of all of the stupid **** I've had to fix.

I look at it this way. The most expensive O2 sensor out there is dirt cheap, given that it's good for at least 30,000 miles (and often longer) and none of my Porsches ever gets any serious mileage put on them in a year. Even 30 years ago, when a 911 was a daily driver for me, it wasn't a serious expense.

Good luck,

JR

[tirwin]

JR,

The problem is which one is "correct"? Bosch 11027 or 11047? It looks to me like 11047 is what is "plug and play" for an 83.

But according to our host, Bosch has recently changed the part and now it is the short wire (not plug and play) version.

So is there a different sensor or part number?

What seems to be even more confusing is that when I search on the part numbers on line some seem places seem to show the same picture for both so unless I can talk to someone who can physically look at the part, I am not really confident in what I'm getting.

If this has really changed then this could be a problem for others going forward.

[tirwin]

I dug out the old sensor. It had a piece of shrink tube over part of the wire. Cutting it back reveled a simple crimped connection.



Part number is 0 258 001047.


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[javadog]

I think the correct sensor was 911.606.123.00. No idea of the Bosch number for that, or if that's still a good number. I also couldn't tell you if there is a difference in that one, vs. the generic Bosch equivalent, since I never used the generic ones. Pelican does sell both.

JR

[tirwin]

I tested the 15C switch and it appears to be good.

I had to get the AC compressor out of the way. I disconnected the wire and connected red lead of multimeter to the male spade in the switch and black to ground. Set meter to ohms. With the car off, reading was 0. I also have a laser temp gauge so I was able to monitor temp at the same time. Ambient temp in the garage was 54F. Switch temp was 12C with a stone cold engine. Started the car. Ohms reading 1.0. I watched the temp climb. As I watched the meter, it started reading about 40 Ohms. Temp was 17C and climbing.

Bentley doesn't state what the resistance should be, just states switch closes to ground at 15C.

[tirwin]

Originally Posted by javadog

I think the correct sensor was 911.606.123.00. No idea of the Bosch number for that, or if that's still a good number. I also couldn't tell you if there is a difference in that one, vs. the generic Bosch equivalent, since I never used the generic ones. Pelican does sell both.

JR

JR,

Searching Pelican for that part number showed the genuine Porsche sensor at $113.50. That part DOES NOT show up when you click through "911 (1974-89) > Exhaust". Weird. I thought I remembered it being in the Pelican catalog.

I found a helpful guy at a local parts place. He thinks the only difference between the Bosch 11027 and the 11047 is that the 47 comes with the rubber grommet and the female connector that is a plug and play. The 027 was $13 so since I have the next few days off from work, I figure it's cheap enough it's worth a shot. If not, I'll order the genuine Porsche one. I suspect they are the same thing though.

Right now I'm checking the test port wiring harness for loose connections and removing the wideband ECU components.

Also going to try to get some time at a local shop to dial in the AFR with an exhaust gas analyzer.

I'll report back. In the meantime, y'all have a Happy New Year!

[tirwin]

Here are the old and new sensors side by side. The left is the old sensor from the car and the right is the new.




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[javadog]

I looked aroiund to see if I had any single wire O2 sensors and didn't see any. It's been a while since I had a car that needed one of those. If I find one, I'll let you know.

JR

[Bob Kontak]

Just saying that I have purchased the $18 generic Bosch at Advance Auto and it seems to work just fine. I get me some dithering, at least..........with the Actron.

More to come - my shop mates are into the Storage Wars thing and they brought home tubs of car stuff. In there, is a gigantic JC Penney dwell meter, believe the name they use is "Penney". It is awesome (ummm, looking). Gigantic needle swinging in a 70 pound iron box.

Prepare to be jealous.

[tirwin]

Hey, Bob - you know the scene in Christmas Vacation when Clark finally gets the lights on and the ret of the lights in the town go out until the guy throws the "Auxilliary Nuclear" switch. Yea will that's what happens when I power on this oscilloscope.

[tirwin]

Hey well welcome to 2013 everybody! One of my New Year's resolutions is to be more detailed-oriented this year.

So I made some progress today. I ditched the wideband O2 module (can I interest anyone in a barely used wideband O2 module?) and installed the single wire Bosch 11027 sensor.

In case you don't recall the male end of my O2 sensor wire (the wire that goes to the ECU) was broken and frayed, so I clipped it off completely.

In order to connect the new sensor, I cut back the outermost layer of the shielding on the green wire (maybe 1/2") and exposed about 1/4" of the inner wire. After that I put on a little piece of shrink tube. (By the way, this is what is recommended in the instructions that came with the sensor.)



Next I used a waterproof crimp connector to make the connection and slide it over the shrink tube.





Finally, I covered the whole thing with another piece of shrink tube. Here is the end result.



Then came the moment of truth. I cranked the car and let it warm up. At first, the idle was a little high so I let it warm up a little longer just to make sure it didn't start to fall on it's own and then dialed it back. Overall it was running MUCH smoother.

Next test was that I turned it off and let it sit for about 10 minutes. When I started it the 2nd time it idled low (600-700 rpm) for about 30 sec and then it settled at a normal idle. (I'll have to think about this some more and do a little more poking around)

After that was the road test. Very noticeable difference! I wouldn't say it was more power on the butt dyno but it was just much, much smoother.

Tomorrow my new multimeter should be here so I'll (fingers crossed) be able to get something more reliable on the duty cycle. I will report back on that.

The other thing I'm going to do is take it to a local shop and get the AFR dialed in with a gas analyzer and check the timing.

Lessons learned:
1) the '83SC does NOT like a narrowband output from a wideband O2 (I still want to investigate this further)

2) the Bosch 11027 seems to be a good replacement sensor (also confirmed by Bob)

3) the '83SC does NOT like running without an O2 sensor

Thanks for all the help!




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