Gevo

I did double check for stored codes and still was clean. The car runs strong, but wow I am going through a lot of fuel. Another 1/4 tank today for about 25 miles of driving. lol. that's 100 miles per tank, roughly about 2 1/4 times more fuel usage than most others are reporting.

I had an emergency at work, so had to run back before I could do the O2 sensor swap. If that shows same results as above then I will chase wiring. I would be very surprised if it's wiring again (remember my no spark condition) because for my bud to make two mistakes like this is blasphemy!

muddmadness

He wouldn't smog the my truck...paperwork glitch screwed up the smog standard year for the truck. Have to get it changed and then go back again for smog test.


But my truck went 200 miles today with no problems. First distance trip since rebuild began

Sturmcrow

Gevo, I didn't say anything before, but that picture you showed of the first short you tracked down made me cringe. I did not see any heat-shrink or electrical tape separating the bare wires. Without seeing it first hand, I am not going to bash your bud, but it did seem a bit slap-dash from what I did see.

Edit: Here: https://www.yotatech.com/forums/f199...l#post52163747

Gevo

Mudmadnes... sucks!!!

I on the other hand am an extremely happen man right now. Be back to add the news!!!!

Gevo

RJR, Sturmcrow, Famefreak and all the others who have been helping me keep my sanity and think straight.. I thank thee good sirs (unless one of you is a girl in that case thank thee good maddam).

Basically, it's blasphemy. It seems I must have pissed off my good friend Pete.. indeed I found an electrical short. I'll share picture soon. After seeing the results of the first driving test as per RJR's advice, I was going to swap the O2 sensor to test a different one, but I thought, before it gets burning hot again let me test the harness. After a few minutes I found the OX (shielded black wire) showing continuity to ground. I looked at the wiring diagram and determined that this should not be the case (all sensors were disconnected from harness of course) I started tearing into the harness at the diagnostic connector, lucky for me I started on the right end. There is a factory splice where the OX wire comes from the O2 sensor, splices to two wires one to the diag. connector the other to ECU. This wire is shielded, and the factory splice had a rubbery thick sleeve over it, the sleeve had worked it way up a bit, enough for the splices shielding to wrap around the core of the wire has my buddy wrapped it with flex loom and electrical tape.

At this point I was happy, but trying not to get to ahead of myself. I connected my brand new awesomely yellow analog multimeter to the VF1 and E1 (shorting the E1 and TE1) and went to pick up my niece from school. I observed the poor ECU desperately trying to adjust the air mixture. It was bouncing to 4-5 volts about 10 times in 10 seconds (FSM says count minimum 8) ... smiles smiles smiles... Then I went to Autozone to return the TPS sensor I bought in a haste a few days ago and on the way I disconnected the TE1 and E1 terminal wire. The ECU was, on some cyclical basis, adjusting for the rich condition. According to RJR's linked Autoshop 101 link, it said that a lower voltage on these terminals means the ecu is adjusting, decreasing the fuel, which makes sense for as per the smog pre-test. According to the autoshop 101 document the learned value should be between 1.25 to 3.75, my voltemeter was reading .75 everytime it was showing a voltage. I am assuming since the conditions are extremely rich, this value is normal to be out of the 1.25-3.75 range.

ANyway, I'm on call this week and I got a call....


Question, what is a normal amount of driving before I should be seeing the ecu leveling out the adjustment?

I can't thank you all enough!!!

Next time any problem shows up, I will go to the harness first.

Now, let me call and give my friend some crap.. poor guy spent bunch of time on this, including buying all the flex loom and shielding...

RJR

Sounds like you've made a breakthrough! At last! Congratulations. Hope this is the solution.

As long as the O2 sensor voltage is cycling, the control loop is in closed loop mode and the ECU has the mixture under control. Assuming the cat is good, you should pass smog.

The low voltage you see with T1 open indicates the open loop settings of the system are on the rich side. Mine does the same thing but still passes emissions. I've thought about tweaking the AFM to make the ECU think slightly less air is coming in. That should make it inject less fuel and help to bias its operation slightly more lean. Not sure if I'll bother, though, as long as the truck is running well and passes emissions.

Gevo

Sturmcrow, in my friends defense, I rushed him a bit. He has heat shrink and shielding and such all over. Just missed a couple spots. Hopefully this is it. Lol. I gotta tell you, Iv learned so much through this. In a sick way im glad I went through it. I will understand the symptoms better in the future.

muddmadness

I am really happy you found the problem, I understand how wiring on these engines can really screw things up. I was following your progress and it totally seemed overwhelming. I just spent two weeks doing the same thing, but I figure your newer engine can be a little more complicated than mine. I really hope it corrects your emissions issue. Keep us updated


I will find out on Tuesday whether DMV and CHP are going to help me correct the paper problem...if they do the smog ref(called me, long story)will pass my smog because a 1980 with an 89 engine is far beyond standard smog regulation for 1980 standards. I still have to go and see the ref again but I will probably be there for 15 min. and then on my way. Keep your fingers crossed

Gevo

I'll cross my fingers for you muddmadness

Update: I drove for 15 miles since the repair of the wiring harness. I took it in to my guy for smog, he said let's do pretest again, I said. do it. He started, and then some weird things started showing up, the Nox was good, the CO and HC were jumping all over, for a while it showed good and then jumped for a couple seconds, then again green. etc... So, the O2 sensor wire revelation did in deed make a big difference, now there is something that is causing it to spike around. He thinks it's the O2 sensor that is messed up from the short and or the rich condition. I told him, maybe if i drive around a bit more it may make a difference? He said he doesn't think so. Anyway, I am confident there is nothing to this now, it may have something to do with the PAIR reed valve coming on at cold start and staying on for a while.

RJR

The short shouldn't have damaged the O2 sensor. It's basically just a wimpy 1 volt battery that can deliver about 1uA max.

Speculation mode on: I'm thinking that you are just on the edge of where the ECU can maintain control of the mixture, and that periodically it loses control. Earlier you reported that when you measure the VF terminal with T1 open, you read voltages near zero. That means that the basic system is very biased toward running rich, and the ECU is very close to its limit of being able to control the mixture. I'm speculating that occasionally it loses control and the system goes open loop. At that point your emissions spike up. Then, after a few seconds, the ECU regains control and the emissions drop again.

You could test this by putting your awesomely yellow analog voltmeter on the Ox1 terminal and watching it closely under the emissions pretest conditions. You should see the voltage continuously swinging between 0 and 1 volt. If it ever "sticks" at near 1 volt for a few seconds, that's an indication the system is going open loop rich and the ECU has briefly lost control of the mixture. (BTW, what analog meter did you get, and where? Seems like a good tool to have.)

Ideally you'd like to see that VF terminal near 2.5 volts. That means things are centered and the ECU has a lot of room for short-term adjustments.

Gevo

RJR, this is the volt meter... it's surprisingly decent!

As far as your speculation, seems interesting and falls within the parameters of what's happenning right now. I have been drivign around today with the VF1 terminal voltage showing on my analog meter... I tried to see some sequence to when it shows voltage and for how long etc, couldn't find any sequence to it. It seems random to me. I will try the OX terminal check as you suggested and report back!

Stipulating that you are correct, what will fix that situation?

RJR

Thanks for the meter link, Gevo. I'll check it out.

As far as fixes, here's what I suggested back in my first post in this thread (#62)
Among others, the following things will cause the ECU to improperly enrich the mixture: (essentially, all of these things cause the ECU to operate on the wrong part of the "map" which tells it how long to pulse the injectors.)
- Coolant temperature sensor giving an inaccurate, cold reading. Colder engines require richer mixtures to run well.
- Air temperature sensor giving a cold reading. Cold intake air requires a richer mixture because it doesn't vaporize the fuel as readily.
- AFM set wrong. If the ECU thinks more air is entering the engine than is actually happening, it will inject too much fuel.
- Injectors too large for the engine. The ECU determines proper injector timing based on a specific injector design. If that changes, it has no way of knowing it needs a shorter time. It can "learn" a new setting from the O2 sensor, but the range of learning is limited. Once it hits the limit, the engine is essentially in open loop mode all the time and will fail emissions.

Of all of these things, it seems like tweaking the AFM would be the most feasible. I haven't looked into this, but if one could modify the spring to have slightly more resistance, it would cause the AFM to report less air flow. The ECU would compensate by injecting less fuel, moving the mixture away from rich.

I may tinker with this myself sometime in the near future, since my system runs with the VF terminal closer to 0V than it should be as well. So far no problems passing smog, but I'm up for a test again in a few months, so I want to be heads up on this.

RJR

Just a quick update. After looking at the analog meter, I don't think it is high enough input impedance to measure the O2 sensor at the Ox terminal directly. You'll likely load down the senor too much for it to work properly. However, you can make the same test on the VF terminal with TE1 shorted to E1. to see if the ECU ever loses control of the loop.

Gevo

I have checked and checked all of the sensors you have listed. As far as resistances and continuity goes from tests listed in the FSM the ECT sensor (new) and air temp sensor (inside AFM), and the rest of the AFM check out with excellent marks. I have in fact leaned out the AFM by 4-clicks. There is a balance though, I think if i go any further my cold idle will get worse than I am ok with. Already since the O2 sensor wire fix the idle on cold startup has roughened out a little. Before the O2 sensor the idle was good. Ofcourse once it warms up it runs like a champ! I am very happy with the smooth engine and even the power that most seem to be complaining about. (and it's not like my other car is a go cart so im used to a very well running car)

From what you mentioned above, the injectors are the only uncertainty at this point.

However, there are still other things that are happening that are still not explained for me.
1. the ECU steps the timing right up 15 or so degrees as soon as the TPS is out of IDL mode.
2. On cold startup the PAIR reed valve stays activated for some time. The VSV is allowing the flow, it is not a bad PAIR reed valve.

I simply don't know how those would relate to the sporadic smog pretest situation so I can't comment.

Right now I am removing my carpet and in denial that something is wrong still... lol... will post pics in my build thread.

Gevo

Oh. Good point.. will test tomorrow with TE1 E1 connected!!!

How would the high impedence affect when checking the VF1 and E1?

RJR

No effect there. Those terminals are buffered by the ECU and will drive any reasonable meter. It's only when you're measuring the wimpy O2 sensor directly that you can have problems if your meter isn't up to snuff.

Gamefreakgc

So many posts... can't read them all! Glad you're enjoying this, even though I don't know why.


Hopefully that will do it! Your issue was so odd... I kinda figured it was wiring. Be prepared to fix shorts in the future! You probably know the wiring better than most now though.


If you gas mileage goes up, you know you've got it. Might want to adjust the fuel cog back if it does. Glad you got it fixed!

Gevo

Gamefreak, I am enjoying this because of finding the solutions... and ultimately knowing the engine better and better. and thanks!

For some more uneventful good news... I drove it to corona today and got er cleaned up well. I put about 130 miles on it, and it ran like a champ the whole time. Power is back where it should be and where ti feels strong. Going up long inclines on the freeway in 3rd is not a problem. here is a picture showing everything is doing well


Here is a picture of it being handsome (minus the damage to the front left corner )


Ahh, not gonna take this thread off topic. I think there is a lot of good info for future searchers...

RSR

I'm running NGK Platinum and have no complaints with them.

From my research, the Bosch are the ones to stay away from. The only reason to run basic copper NGK/Denso (either works pretty well) is if you want to increase gaps to Supra specs w/ the supra AFM, bigger gauge wires, supra igniter, etc, b/c you can't do so as easily, if at all, w/ the premium metal offering.

RSR

Actually, open loop if running rich at idle you'd want to increase/open/widen the AFM bypass screw -- but this *shouldn't* need to be adjusted if everything else is working properly. When adjusting this on Supra it's b/c it's factory set for a different engine.

For closed loop, the spring basically biases the initial start of engine idle mixture but with the 02 sensors help it will eventually get it back to its preset factory sets. Best case you'r'e playing in the margins and fighting the ECU.

Where the spring adjustment really matters is for wide open throttle, >70 or 75% throttle. Loosening spring means more air gets in (less tension=easier for flapper to open), while tightening it will lean it out.