Jim @ EuroWerks

no it was not because the o2 was disconnected. It was ck'ed this way to see if the line (wire ) was going ground without input from the o2. If there is no input from the o2, then the control unit will give it something to run on kind of a fail safe. John, it seems that you and Carl are going the same way as this. If I ck the injection timing and it's ok then it either has to be crappy injectors or a combustion problem. If the ignition is ok that is . Is that what you guys are thinking? Thats smart. Hopefully I can get back on the car monday. I'm doing honey do s today mothers day and all. I hate the mother inlaws honda passport.

Steve Cattaneo

Yes the 2.3 LH does have adaptive memory, but that is only when it SEES a sensor out of range. When it sees a total failure the emergency run program; Limp home mode is a rich map default, a short to ground in the 02 circuit will cause a low 02 voltage reading

The car runs rich yet the 02 reading is only .523mv which is a little rich but normal, were as the reading should be 600 to 900mvs; That 02 sensor can not recognize a rich mixture,
Or it sees a high amount of oxygen in the exhaust; unmetered air, a vacuum leak.

I would start with the 02 sensor and injector pulse width. Do a voltage drop test on the LH ground wire with the car running in closed loop (hot). back probe the LH ground wire. MP VIII terminal #17. A good reading is .003 volts a perfect ground is 0V.



Check the 02 signal wire on the LH by back probing terminal # 24 with the engine running hot in closed loop at 2500rpms. . Use the battery ground terminal for the meters. A normal reading on a hot engine is a rich to lean sweep. Induce a lean mixture by removing the brake booster hose. The reading should be below 450mv = lean = wide pulse width = longer injector duration.

Enrichen the mixture by removing the vacuum hose from the FPR the reading should be above 500mv = rich = narrow pulse with = shorter injector duration. Check the injector pulse width at the same time, the normal reading on a hot engine in closed loop at idle is 1.5 to 3.5 ms. The readings will tell the story.

My guess is unmetered air is getting into the system. Vacuum leaks or a dirty air mass sensor hot wire.

Jim @ EuroWerks

ok guys here it goes. The injection time at idle o2 connected is 4.5 ms.Also co% is 5.5 to 6.0 per side air pump disconnected. I'll have to tell you the not so funny ocsilosope problems. The first one someone cleaned the screen so well all the #s were taken of the bottom so you could not read the time. The second one the guy had never used it was a bear unit. The bear has adjustable time as most do but only showed a random # at the bottom of the screen. Yes I am sure of the results. I'm afraid to drive this car much further because I'm afraid of setting the cats on fire.

John Speake

OK Jim,
The idle injector on time should be nearer 3mS at idle with those MAF volts. And the CO is correspondingly high, so that figures.

Did you measure that time with the engine at normal temp ? If it was cold, then a longer pulse would be expected.

I can take some readings for you tommorrow , it's a bit late here now.

While measuring the injector times, you could do some tests, like unplug the temp sensor 2, and see if that affects the pulse length. If it doesn't it means its signal is not getting to the ECU, or that the ECU has gone into some kind of limp home mode. You should do this with the O2 snsor connected.

Also, try and measure the O2 sensor voltes when it is connected, and running closed loop.

Regards,

Jim @ EuroWerks

yes the car was at operating temp. It's funny how all mechanics that I know are dumbing down. I remember taking a class on sun diagnostic when I was 18. Now I'm teaching people alot older than me how to use their equipment that they have had for years. John, I know the ntc2 readings are getting to the LH unmolested. However, now from what you've got me ck'ing it looks like the LH to me? Just speculating what do you think?

Steve Cattaneo

Jim,
There are too many variables missing.

Did he LH have a ground signal?
Can the 02 recognize a lean or rich mixture?
If so is the LH receiving the signal and commanding the right adjustments; lean / rich?
And what are the 02 voltage; injector PW readings when all of the above is happening?

At 4.5 at idle the CO will be high.

There are tuner shops that can provide a print out of all these parameters.

Garth S

When the engine goes rich, does it do so on all 8 - or one one bank only?

John Speake

Hi Jim,
I've just run an LH /10 ('87 MY) on my test bench. The injector time at idle and MAF volts 2.7 is 3mS with the engine at normal operating temp.

With engine cold at normal ambient (about 60 deg F) it increases to 3.5v

When I O/C the O2 sensor, it defaults to 3mS. However the pulse width is quite sensitive to MAF volts. At 3.5v the pulse width shoots up to 10mS.

What I can't understand is that this happened after water ingress.

Steve's questions are good, you need to monitor the injector times, and see what effect the external sensors have on them.

Did the rich running start imediately after this incident ?

Jim @ EuroWerks

Ofcourse the cust thinks it happened after I put a radiator in the car, but the engine ran like crap when it came in leaking but thats another issue. So you and steve suggest trying to get the ms to change and measure o2 voltage while running. Yes steve the ground to the airmass cks fine while running.

John Speake

Yes, you've got it. It sounds as though the customer is not being honest about this one.

You say you swapped the LH, was this a known good one ? Do you still have access to it ?

I am wondering if there were two faults with the car, one you may have fixed along the way, the other might be the LH. Might be worth going around that loop agian.

I know this sounds a daft question, but does the tach read correctly ? I mean about right, rather than twice as many rpm as it should.

Jim @ EuroWerks

not readily, But I expect one anyday. So stupid question, the o2 voltage on a engine running rich, the o2 should swing which way to reduce co%?

Jim @ EuroWerks

John, Steve, years ago my shop foreman ( a very smart guy) would test o2 ciruits by disconnecting the o2 sensor then put one hand on the pos. battery term and the other to the o2 feed wire and watch the co%. then one hand on the ground post with the other on the o2 lead and watch the co% does this sound right to you guys?

John Speake

Jim,
At high CO, rich mixture, the O2 will put out a higher voltage - greater than 900mV. This should then make the brain pull it back towards stoich - roughly 500mV.

Because of the very sharp slope of the curve, a properly working loop will "hunt" between rich 800mV and lean 200mV.

The sensor gives out a voltage, but your friend was actually introducing a leakage resistive path through his fingers. It would depend on the internal circuits in the ECU whether this would work on a particular car.

I don't think O2 sensor processing circuits in the 928 would allow you to do this on a 928, but I can't easilly simmulate this on my test bench to check for you.

John Speake

Another thought on your friend's trick - if you short the O2 sensor pin on the LH to ground, this will make the LH ECU think the engine is running weak, it should then richen up the mixture about 20%.

Jim @ EuroWerks

John, I don't know what happened with us swaping the LHs before, but your expertise were very helpful. I hope more people will give your business a chance. The rebuild was returned very fast, it was always easy to get you online and whats nicer is you were even able to tell me which circuit was messed up and how. Oh, by the way, the car has been running for about an hour now and still running great.