Time to play "Which sensor's broken?"!!!

[michael]

I don't want to throw you off on a tangent so you can disregard this if you are following a solid lead. In an effort to figure out how many ways there are to seperate the two banks from each other I found several. The key is finding which one was disturbed during maintenance. Since you were changing out the CTS is it possible you upset the connection to the knock sensor? That wiring can get very dry and brittle. It might be worth a quick check.

[yt]

Originally Posted by SVX10

How about why occasionally it only starts w/3 cylinders, then 5 minutes later is running on all 6?

How about revving fine and holding an on-throttle RPM for up to a minute before instantaneously cutting everything and stalling?

Trevor, you have to read it all

Tom

[yt]

Originally Posted by michael

I don't want to throw you off on a tangent so you can disregard this if you are following a solid lead. In an effort to figure out how many ways there are to seperate the two banks from each other I found several. The key is finding which one was disturbed during maintenance. Since you were changing out the CTS is it possible you upset the connection to the knock sensor? That wiring can get very dry and brittle. It might be worth a quick check.

A knock sensor is not dependent upon banks. It mearly detects on both banks. if it does pick something up or a lack of something, it will effect ignition timing on all cylinders. Good idea though, it was on the right track

Tom

[yt]

Originally Posted by yt

The fact that it is isolated to one bank means one of two things

1. The power source to the RH bank coils is intermittent

2. The cam is out of it.

So, check the power feed to all the coils on the RH side of the engine and confirm 12v at all of them when it is running rough.

If the voltage is good all the time.... Then you will need to pull the gear like I had mentioned earlier and confirm the wear issue on the gear & keyway

Tom

Originally Posted by Trevor

Please read the second point I made. Your new identity is rather confusing what gives?

That is why I asked him to monitor voltage during the misfiring on the LH cylinders

Tom

[oab_au]

Originally Posted by SVX10

What should the cold and warm resistance readings be for the CTS?

Can anybody explain the mechanism behind how the cam sprocket being loose/out of alignment with the cam would allow it to run just fine while warming up, then suddenly die at the same point in the warm-up cycle every time?

How about why occasionally it only starts w/3 cylinders, then 5 minutes later is running on all 6?

How about revving fine and holding an on-throttle RPM for up to a minute before instantaneously cutting everything and stalling?

The book says that the Water temp sensor should read 2k to 3k ohms at 20*C/68F. and 300 to 400 ohms at 80*C/176*F.
So unplugging it makes the ECU think it is cold.

It does seem strange that when it is unplugged, it comes good. It is obversley a fault that is overcome when the ECU goes to running a 'cold engine routine',ie increasing the injection time.

The puff,puff,puff, and slowing idle, symtoms are tipical of a lean mixture, why it is confined to the left side only, would make me to start checking the fuel delivery to that side.

Otherwise NFI.

Harvey.

[SoCal LS-L]

Im going to stick to my guns here and insist its a wiring issue..... what the heck could have started this problem ONLY after it sat? I vote for corrosion or rodent issues, since he already put new fuel in.

[yt]

wiring issues are traceable. Lets hope it shows w/ a voltage test mentioned earlier

Tom

[SoCal LS-L]

This is one of the reasons my next SVX will be a 96 or 97, in all of the OBD-I cars I have owned, the ECU has without exception shown a marked insensitivity to sensor and component failures, sometimes even with the car shaking badly and barely running, a MIL would not be lit.

On most of the OBD-II systems Ive worked with, the MIL comes first even when no symptoms are present.... which makes sense why it was made mandatory. It also made retrieving codes from the various mfgrs much easier, as our snap-on scanner required only circuited keys in the OBD-II connector instead of fishing for the malady of different mfgr-specific connectors to make a crackshot attempt at finding memory codes.

OBD-I.... Better for a swap, yes

Better for the nerves, no

Im wondering if poking at the various sensor wires going into the ECU would yield a bad voltage signal between there and the engine bay, as prolific as this problem is it might need some attentive probing, and probably a lot o luck.

[SVX10]

Well, I just played with the MAF again, and ran it with the O2 sensors disconnected just for fun....no change.
Alternator reads 14.6 - 15.1V @ idle.
Resistance @ CTS = 3.7k ohms after warming up, so that doesn't seem quite right.

After all that, I just disconnected the CTS and started it up. It stalled again. I started it again, and it ran continuously. I let it idle for 10min or so checking various things. I'd plug in the CTS and it would immediately lower the idle, so I'd unplug it and it'd immediately recover. I did this about 10 times listening for any sounds that may give me a hint, but no luck.

Finally I just took it out for a drive. It felt very smooth and had no issues. I ran it up to redline a few times and it felt great. Problem is that it's been so long since I drove it I don't remember what the power levels should feel like. The only oddity I felt was a bit of a rough spot around 1500rpm...kind of a shudder as it came off high idle and returned to low idle around 800 - 850rpm.

It was smoking like crazy, also...something burning off of the pipes. I'm assuming it's just oil that's been slowly seeping out of the engine for the past 8-12 months. I checked the oil level after driving and it didn't appear to be burning oil. It actually appeared to be a hair overfilled. It was about 1/8" above the notch on the side of the dip stick. Just before the drive I checked it cold and it was right at the top full circle on the dip stick.

I may just drive it around with CTS unplugged for a tank or two of fuel and see if it gets better. Other than voltage testing individual wires I don't know what to do. I'm trying to KISS, and that approach would say that there's no reason for any component to fail after not being used, but there's plenty of reasons for valves to get stuck, injectors to get clogged, or the like.

Any danger in driving it with the CTS unplugged? My only concern with this is the effects if the cam sprocket and timing are the actual issue. But, it seems to me that if that's the issue, I eventually have to replace a cam and a sprocket anyway (more likely the entire engine just for cost and ease). So if I'm driving with the CTS out and kill the engine via crap timing, I'm right where I would've been anyway.

[michael]

If you have the time to troubleshoot which it seems. You may want to redo the timing belt install. With one bank screwy, and a hot smelly exhaust it sounds like a timing issue. Is one pipe hotter than the other? You are relying after all on where an aftermarket pulley company placed it's label.

[SVX10]

I was looking over the Service Manual troubleshooting procedures, and found some interesting stuff. A few things from there and this thread are combining to give me some thoughts.

1. Timing could be affected in 2 ways. a) timing belt sprocket movement b) ECU reaction to input signals. Concerning the higher RPM (not idle) stalling, knock sensors detecting knock could lead to ECU corrective action leading to stall, yea? Bad fuel can lead to this, yea?

2. When running in the "cold" open loop, I experience no issues. the "cold" open loop is an enriched map, yea? Injector time is increased, yea? Fuel quality/flow/pressure would be less significant in this condition, yea?
Question: What is different about the timing in the cold open loop?

3. Sitting and not running for months on end would allow some crap to build up on/in fuel components, yea? What would it take to clear these things up?

So, it's logical that it could be fuel, but to be honest, I feel like I'm stretching a bit to make that theory work. But, is a fuel pressure gauge easy to install so I can monitor that just in case? Seems like it'd be easy to install one under-hood.
Questions: Does the fuel pump operate any differently in closed loop vs. open loop? ie. pressure, RPM, voltage, etc?

4. Going waaaaaaaay back, something fried my fusible link. It's possible that whatever fried that did some weird other crap to the electrical circuits. I'm going to take an approach mentioned in another electrical gremlin thread and try removing any fuses not necessary to run the vehicle and see if that addresses the issue. If no luck, I believe I have an ECU from a '94 FWD. Question: Is the 94 FWD ECU interchangeable with 92 AWD LS-L?

5. MAF. Frankly, these seem like MAF symptoms. Is this the best MAF check (courtesy of Trevor)?

With the engine idling, connector plugged in :-

Terminal number 1, should have 13 - 14 volts to ground.

Terminal number 4, should have 0.8 - 1.2 volts to ground.

When the engine in my car was revved with the car stationery, voltage rose from 1.1 to 3 volts.

Looking into the connector plug as if it were disconnected, with the catch uppermost, the pins are in a row numbered left to right. Pin 1 is therefore, at the left hand end.



Just had another thought:
In order to link the stalling to the PS bank, could I start the car, let it get warm until it stalls, then disconnect the spark and fuel from the PS and run it? If it's related to that bank's spark, fuel, or timing, it should continue running, right? If it's not, it'll stall as usual, right?

Maybe my logic's off. Dealing with this issue is like trying to grasp eternity...think too much about it and you'll go mad

[Trevor]

Have you re soldered the connections on the MAF ? I recall another member finding a dry joint problem, which was not visible. Better still exchange the MAF with one in another car. See below for a parallel explanation.

Five months ago you had a problem which was cured when I suggested the temperature sensor, this was replaced and all was well.

You advised the problem had currently returned, but only referred to an idle problem. Exactly what difference is there in the previous and existing problems?

The consistent indicator at present, is surely the fact that unplugging the CTS makes an improvement. My experience with intermittent faults is such that, what is hardly possible, is in fact very possible. The replacement CTU you fitted, could very well be now be faulty.

There is no reliable check for an intermittent fault within a component, other than by exchanging it for another absolutely proven OK, having operated OK in a practical test. This can only be achieved by making an exchange with one from another car.

Alternatively, when the CTU is disconnected some other situation is being corrected, e.g. a partial short or open circuit. Not so likely, but possible.

[SVX10]

I'm not convinced it ever went away. I think I just found that it ran when the CTS was unplugged, so I assumed the new part would fix it. I didn't drive it enough to really find out for sure.

I checked the CTS resistance today and it read 1.82k ohms ambient, 270 - 300 ohms operating temp.

Another interesting thing is that the fans don't kick on unless I unplug the CTS, even when the CTS voltage is as it should be at operating temp. I'd say that the signal from the CTS isn't reaching the ECU, but it knows when it's plugged in or unplugged.

How about that 94 FWD ECU...swappable?

[yt]

I'm sorry but you have gone way outside of the logical path with this one.

Stop trying to find new solutions before you write off all the other first. This is only clouding your issue

Tom

[SoCal LS-L]

Can I recommend something? It may be a PITA, but would help your cause to list through the symptoms again and give a brief synapse of everything done so far...... I have been with this thread since the beginning and even im starting to forget certain details. At 104 posts its not feasible for someone new who wants to help, to read through the entire thread before offering advice thats informed of the situation.

About your ECU, its worth a shot since you have the parts car right? At this point, id say try anything.

"Another interesting thing is that the fans don't kick on unless I unplug the CTS, even when the CTS voltage is as it should be at operating temp. I'd say that the signal from the CTS isn't reaching the ECU, but it knows when it's plugged in or unplugged. " This is what I have been recommending for a while now, testing sensor signals at the ECU itself, probing the wires in the connector with a safety pin and a multimeter.

Its got to be frustrating at this point, most of us have been there, just be methodic and patient, and leave no stone unturned..... just think about how you will feel when you find and fix the problem!