How do you know if O2 Sensor needs to be changed?

[Redsquall]

My engine has been running rich and i cant get the idle to stay constant from cold to warm.

[Bitsyncmaster]

My engine has been running rich and i cant get the idle to stay constant from cold to warm.

Did it happen suddenly or has it always been this way?

[sdg3205]

If it has run rich for a long time it MAY be dead, however my lambda system still worked with a half dead, dented, original unit that was held into place with coat hangers and picture wire, so the 02 sensor probably isn't your issue just based on what I'm reading in other threads you have going.

[Jonathan]

Agree with what Dave(s) said. Sounds like you have more than one issue to contend with.

Figuring out idle issues, or fuel mixture issues, isn't usually a one, general rule of thumb solution, unfortunately.

I would suggest starting at the beginning and making sure each and every component is connected correctly, operating correctly individually and then also as part of a system.

- compare fuel lines, vacuum hoses and all electrical connections associated with those to the diagrams and make sure they are all installed correctly.
- adjust the idle speed microswitch lever arm off of the throttle spool, including making sure the lower rest screw allows the butterfly valves to come to rest in a fully closed position, and the upper screw engages the idle microswitch correctly. The 3 brass screws in front should all be threaded in all the way and closed. Throttle spool spring should be clean and lubed enough to not fight extra resistance. Deice shield recall kit came with snap ring washers (4 of them) that should be clipped over the post to ensure the extra end of the throttle cable doesn't snag on it. Confirm the full throttle fuel enrichment microswitch on the lower portion of the throttle spool is getting engaged correctly as well as releasing when the throttle is not full. Same for kickdown microswitch in the same spot if you have an auto trans. You may need to test all three of those switches separately if you don't think the wiring or switch itself is good internally. This assumes your idle speed motor is not sticking or otherwise misbehaving.
- the Lambda ECU behind the driver's seat and the sensors feeding it may be next. One of those is the O2 sensor and another is under the Valley. Testing this portion is via a procedure in the workshop manual. It'll also assume your frequency valve is working.
- there are a lot of different places you can have problems that affect the engine idling. A small air or vacuum leak somewhere as well as poor connections somewhere between the engine bay, through the bulkhead connectors and into the fuse and relay area including the terminations under those relays or fuses.

I suggested starting with the easy things like confirming everything is per the drawings and connected correctly, because you might get lucky and find something easy. Sorting out some of the more hidden issues can be a big pain in the butt. This can be an area where you decide that it is "good enough" if you get it idling reasonably well but not perfect.

[Redsquall]

Did it happen suddenly or has it always been this way?

Daves, I feel like I have the idle pretty good today. It ran great for about an hour. I'm going to test it cold again tomorrow and see if it's OK. Thank you for your help. Let's see what happens tomorrow

[Redsquall]

Agree with what Dave(s) said. Sounds like you have more than one issue to contend with.

Figuring out idle issues, or fuel mixture issues, isn't usually a one, general rule of thumb solution, unfortunately.

I would suggest starting at the beginning and making sure each and every component is connected correctly, operating correctly individually and then also as part of a system.

- compare fuel lines, vacuum hoses and all electrical connections associated with those to the diagrams and make sure they are all installed correctly.
- adjust the idle speed microswitch lever arm off of the throttle spool, including making sure the lower rest screw allows the butterfly valves to come to rest in a fully closed position, and the upper screw engages the idle microswitch correctly. The 3 brass screws in front should all be threaded in all the way and closed. Throttle spool spring should be clean and lubed enough to not fight extra resistance. Deice shield recall kit came with snap ring washers (4 of them) that should be clipped over the post to ensure the extra end of the throttle cable doesn't snag on it. Confirm the full throttle fuel enrichment microswitch on the lower portion of the throttle spool is getting engaged correctly as well as releasing when the throttle is not full. Same for kickdown microswitch in the same spot if you have an auto trans. You may need to test all three of those switches separately if you don't think the wiring or switch itself is good internally. This assumes your idle speed motor is not sticking or otherwise misbehaving.
- the Lambda ECU behind the driver's seat and the sensors feeding it may be next. One of those is the O2 sensor and another is under the Valley. Testing this portion is via a procedure in the workshop manual. It'll also assume your frequency valve is working.
- there are a lot of different places you can have problems that affect the engine idling. A small air or vacuum leak somewhere as well as poor connections somewhere between the engine bay, through the bulkhead connectors and into the fuse and relay area including the terminations under those relays or fuses.

I suggested starting with the easy things like confirming everything is per the drawings and connected correctly, because you might get lucky and find something easy. Sorting out some of the more hidden issues can be a big pain in the butt. This can be an area where you decide that it is "good enough" if you get it idling reasonably well but not perfect.


Thanks Jonathan, so far I've been able to adjust the mixture and the idle screw and it was coming for the gently. I'm going to test it cold tomorrow

[David T]

A bad/old O2 sensor doesn't put out as much voltage. The first sign is that the dwell will cycle up and down slower than it should. When it is really bad it won't cycle at all because it can't react to changes fast enough.

[Redsquall]

I pulled out the one and only plug that had most imposture under the boot. See pic. Seller changed spark wires 6 months ago. How much of the problem is this plug? Remember a few days ago I had it mixed well enough to run great after warm and next day it is cold and too chugging to go. Also can I just clean these with dremel? The exhaust is lightly black smoke sometimes. Not solid black but you can tell it's dark sometimes when chugging41867

[Redsquall]

What's best way to clean rust particles off the hole?

[Redsquall]

Also did spray test to find vacuum leaks. None found. These connectors in pic are disconnected. What are they? They don't quite reach. (Don't yet have shop manual- is it online?)
thanks again. I'm on the way to getting it sorted.

[Redsquall]

Also did spray test to find vacuum leaks. None found. These connectors in pic are disconnected. What are they? They don't quite reach. (Don't yet have shop manual- is it online?)
thanks again. I'm on the way to getting it sorted.

heres pic41869

[Rich]

......(Don't yet have shop manual- is it online?).....

Yes, it's it's online, sort of...

Spend 50 bucks and save yourself a lot of searching. Nothing like having it sitting next to you in your garage: http://store.delorean.com/p-9201-workshop-manual.aspx

[Jonathan]

Dirty spark plug:

One bad cylinder/spark plug/wire can make your engine run bad, yes. Seeing the condition of the spark plug you pulled, I would suggest changing them out with new. All six of them. Yes, they aren't free, but at $50 for the six, especially when they are a pretty big unknown on your car, I would not try to clean this one and instead get new ones.

Dirty spark plug hole:

Ideally none of that falls down into the cylinder, but seeing the plug you pulled out, it probably did. What I would do now is get a vacuum and put the end directly over that hole and suck out whatever it can get to. You can gently wipe the threads on the hole trying to bring out any grit still sticking on those threads, then go back and vacuum again. I would not use anything rough or coarse on the threads. Just a soft cloth and the vacuum.

Workshop manual:

There are links to it here on the forum. Search for it or look in the resources section. Or buy it from a vendor as Rich suggested.

Plugs unplugged:

The plug you have in your hand on the left side of that photo doesn't need to plug into anything. I don't remember what the story was for why it is there, but it can be left as is. The one on the right side though I'm not too thrilled about. I believe it needs to go somewhere but not sure right this second. I suspect it also should have more than just a black ground wire in it. I am thinking it goes to one of the components down the backside of the engine, but I'll need to go out and look at my own car to say for sure. There might have been a wire pulled out the back of it, or some other change. Keep that on your list of things to resolve.

[Redsquall]

I was able to clean it out just like you were saying. I clean the spark plug back up really nice and put it back in. I plan on changing all of them, but the thing is I have had the motor running very very smoothly idling and accelerating and going down the road and 50 miles an hour just fine exactly 2 times in the past week. I had adjusted the idol screw in the mix with the O2 sensor in – and it let me do that. Then I turned off the car and turned it on call the next day and both times the car went back to being really chunky. This makes me think that the spark plugs and wires are not the issue right now I need to hone in on the root cause before changing those out. Because he will probably get black again. Today I will try unplugging a few things and see if I can get any more clarity. There is some shiny liquid around The seams in this picture – is that normal? 41873
Thanks again for continuing to help me figure this out

[Bitsyncmaster]

There is some shiny liquid around The seams in this picture – is that normal? 41873
Thanks again for continuing to help me figure this out

That could be just some grease on the edge or it looks like a gasket sealer was used between the two halfs of the fuel distributor. Factory build did not use any gasket sealer there so maybe someone has tried to rebuild that FD.

[Redsquall]

Ok guys - so some progress:
1) I had the car running (still idling very chunky) for about 30 seconds or so trying to see if unplugging the frequency valve electrical plug did anything. It made the engine stopped almost right away. The engine was not warm at this point.

2) with the engine off and only have been running for about 30 seconds or less (so still cold) - I found this bronze colored vacuum device behind the engine with a missing vacuum tube. (photo below)
I then found the miniature vacuum tube with a drillbit stuck in it. When I remove the drillbit I can hear the vacuum was sucking in air. I connected the vacuum tube to this thing (I forget what it is) and started the car up. The idle immediately sounded almost normal and much much smoother. I then let the car warm up why was looking around and when I warmed up the idle got chunkier and chunkier again.
41876


3) I looked at all the connections behind the driver side seat and took a couple pictures. Besides that seemingly extra coil of wire hanging there in the hidden compartment it looks normal to me. (Photos below)
4187441875

4) with the car now very warm and idling very roughly, (adjusting the fuel and idle speed sometimes seems to make it better and then it gets worse again) - I unplugged the O2 sensor and the engine sounded a lot better (still a little uneven and rough but not nearly as chunky). I took the video below so you can see exactly what happens when I Connect the O2 sensor again. Video video also explains my concern with The throttle. It is super gummy and does not actually rest back on the stopper at Idle - I am wondering if the butterfly Springs could be week and keeping the butterfly open because you can see after I rabbit up that the new idle it Is much higher around 1200 or 1400. Sometimes if I use my finger to push the throttle all the way back to the stopper– the idle can get lower.

VIDEO: https://drive.google.com/file/d/0B8QCSG-KgyVNblhrZTFkRmc0ZjQ/view?usp=sharing

What do you think next steps should be?
hmm, what are the symptoms of a bad idle speed regulator?

[bfloyd]

The bronze colored vacuum thing is your hot water valve. Yeah, it needs it's vacuum line to work.

My car had that same "extra coil of wire" in that same compartment. Pretty sure it's the speaker wire. Mine even extended down into the locking compartment behind the seat. I ran all new wire when I upgraded my speakers over the winter and removed all of the original wiring.

[Jonathan]

Yes, definitely speaker wire.

That ECU compartment behind the driver's seat actually looks really nice. More so than many other cars I have seen.

The heater core vacuum line and drill bit plug isn't technically a direct influencer on your fuel and idle control system, but unmetered vacuum leaks are.

Next steps? Yea, go back and confirm all your vacuum lines, fuel lines and electrical connections are the way they should be like was suggested to you already.

[DMCMW Dave]

Ok guys - so some progress:
1) I had the car running (still idling very chunky) for about 30 seconds or so trying to see if unplugging the frequency valve electrical plug did anything. It made the engine stopped almost right away. The engine was not warm at this point.

That made it go lean which killed it.



2) with the engine off and only have been running for about 30 seconds or less (so still cold) - I found this bronze colored vacuum device behind the engine with a missing vacuum tube. (photo below)
I then found the miniature vacuum tube with a drillbit stuck in it. When I remove the drillbit I can hear the vacuum was sucking in air. I connected the vacuum tube to this thing (I forget what it is) and started the car up. The idle immediately sounded almost normal and much much smoother. I then let the car warm up why was looking around and when I warmed up the idle got chunkier and chunkier again.

That is the hot water valve. Vacuum should only be on that hose if the A/C is on MAX. Plugging it richened the mixture, but it should not be any different than with the drill bit stuck in the hose. This also turned off the hot water to the water valve (A/C was on max?)



3) I looked at all the connections behind the driver side seat and took a couple pictures. Besides that seemingly extra coil of wire hanging there in the hidden compartment it looks normal to me. (Photos below)

4) with the car now very warm and idling very roughly, (adjusting the fuel and idle speed sometimes seems to make it better and then it gets worse again) - I unplugged the O2 sensor and the engine sounded a lot better (still a little uneven and rough but not nearly as chunky). I took the video below so you can see exactly what happens when I Connect the O2 sensor again. Video video also explains my concern with The throttle. It is super gummy and does not actually rest back on the stopper at Idle - I am wondering if the butterfly Springs could be week and keeping the butterfly open because you can see after I rabbit up that the new idle it Is much higher around 1200 or 1400. Sometimes if I use my finger to push the throttle all the way back to the stopper– the idle can get lower.


If you can push the throttle closed and pull the idle down, it is not the butterfly springs. Its a sticky or out of adjustment linkage. When the throttle closes it should click that microswitch to turn the distributor vacuum off. If that isn not happening the distributor is at full vacuum advance at idle which will make the engine idle too fast and not very even. There should be slight preload on the linkage from the spool to the throttle arm to help push it closed. If the spool is sticky, or the ball studs on the linkage are dirty, or the spring is missing, or the nut on the end of the throttle shaft is too tight, any of these contribute to the sticky throttle.



What do you think next steps should be?
hmm, what are the symptoms of a bad idle speed regulator?

It is very easy to check the idle speed regulator (motor/valve). Go in the electrical compartment behind the driver seat and unplug the plug on the idle ECU (black plastic module in the center of your picture) while the engine is running. The idle speed should quickly ramp up to about 2100 rpm. Plug it back in and it should immediately come back down. If that happens the ECU is good and the idle motor is good.

You are messing with a couple of systems (vacuum advance/timing, mixture, mixture enrichment, and idle control) all at the same time which makes it hard to tell what you are really doing.

[Redsquall]

Regarding what Dave said about the hot water valve – I noticed now that the fans don't kick on until the needle is about 1/5 above the second temperature Mark. They used to have the fans kick on right at the second temperature Mark. I don't think the air conditioning works. At least when I tried it last week nothing happened – I don't suppose having a drillbit plugging up the vacuum hose would prevent the air conditioner from working?

I am going to take a look at the linkage on the throttle and more vacuum routing today and see where that gets me. Thank you all again

[DMCMW Dave]

– I don't suppose having a drillbit plugging up the vacuum hose would prevent the air conditioner from working?



No. Just not as cold on "max".