VP surging. Could this be related to aircon?

[Frogman]

My '92 VP Commodore is occasionally surging.

This is most noticable when idling, sometimes when the engine is cold and sometimes when hot.

Now I am thinking it could be related to my aircon motor which might be occasionally seizing (and possibly on the way out)? When the aircon is on it doesn't always blow cold, it seems to cut in and out. I can't say that when the aircon isn't blowing cold that the engine then surges but I just have a hunch that they are connected.
With the main drive belt running around the aircon motor, if it is seizing would this cause the engine to surge?

Any help would be appreciated.

[Just_a_stocker]

hmm interestin.

Im told the air con is a complete seperate unit to the engine.

Hows your drive belt?

sorry mate, not much of an idea on that one, but you could try cleaning the TB.
it could be--
*a vacum leak
*fuel filter needs replacing
*alternator giving poor voltage
* a crap tank of fuel
* whatever you do dont touch the base idle to fix it, it won't (unless its already been fiddled with.

just a few ideas mate but sounds like one of thos probs you will have to troubleshoot for a while, it could even be your CAS.
yeah and check your drive belt operation, if your air con is seizing ( which i have never heard of) im guessing you mean it is not spinning then of course it will surge the idle.


cheers

[vxcalais_01]

Yes, alot of commodores seem to do this. Cause as you turn on air con, it activates the aircon clutch and now the belt is spinning an extra pulley now, which in turn affects the Alternator, cause it to sieze/surge/lunge whatever. Try doing it while your driving. Mine only seems to do it for a little when im stationary.

[Frogman]

Thanks for the tips/info. On top of the surging problem the radiator boiled today!

I have found that I am getting the following error codes at the moment:
14 Coolant temp sensor (voltage too low)
42 Electronic Spark Plug Timing
and 45 Oxygen Sensor Rich

I'm thinking to replace the Coolant temp sensor as the next step. Where is this located and is it easy to replace? That might fix the problem with the fan not coming on and the radiator boiling obviously, BUT do you think it will rectify the surging problem?

These issues have followed on from a month of car trouble during which I have replaced the Oxygen Sensor, Throtle Body Sensor and the ECU (computer)...

So what do you think? With the air conditioner not working all the time and the car surging I now have these codes indicating problems. I know you shouldn't just keep on replacing sensors all the time and something sometimes causes the sensor to register a fault. Does anyone see any interrelation to these issues?

Thanks again
Frogman

[Just_a_stocker]

remove your alternator behind it on the manifold are 2 sensors screwed into it.
The one on the left (the smallest one) is the coolant temp sensor ($15).

Mate I am having the same problems, so i am f%cked of I now, but replacing the coolant temp sensor will improve it a little, not sure if it will stop the surging but it does effect fuel mixture so it might be it, but of course who knows?

Just remember people post up here what they "think" it is, i do it myself.
Once when my CAS went i got it replaced and it ran like a dream, and for all those weeks leading up
to the breakdown i was none the wiser thinking it was somthing else because I always thought they died a certain way (fairly quick and affected driving), but not so.

[IvegotaCommy]

If it makes you any happier (as in misery loves company) I have the same problem with air con. however I have no error codes at all so I don't think your problem has anything to do with the errors you have.

[Cheap6]

Thanks for the tips/info. On top of the surging problem the radiator boiled today!

I have found that I am getting the following error codes at the moment:
14 Coolant temp sensor (voltage too low)
42 Electronic Spark Plug Timing
and 45 Oxygen Sensor Rich

I'm thinking to replace the Coolant temp sensor as the next step. Where is this located and is it easy to replace? That might fix the problem with the fan not coming on and the radiator boiling obviously, BUT do you think it will rectify the surging problem?

These issues have followed on from a month of car trouble during which I have replaced the Oxygen Sensor, Throtle Body Sensor and the ECU (computer)...

So what do you think? With the air conditioner not working all the time and the car surging I now have these codes indicating problems. I know you shouldn't just keep on replacing sensors all the time and something sometimes causes the sensor to register a fault. Does anyone see any interrelation to these issues?

Thanks again
Frogman

The usual procedure is to clear the codes, drive the car and see what returns. The coolant temp. code may be the result of the overheating rather than the cause. If you have a multimeter (ohmmeter), and for the $10-15 that one suitable (>10M Ohm impedence on voltmeter is the only essential criteria) costs there's not much excuse not to, you can check the resistance of the coolant temp. sender against temp.

Another thing to check would be the inlet manifold gaskets. If the are leaking externally you can see a residue of dried coolant along the edges of the manifold. if they are leaking air as well as coolant, that could be the cause of the surging, particularly if it is occurring at idle and light throttle loads.

Coolant temp. sender resistance:

http://forums.justcommodores.com.au/...-switch-2.html

(Bottom of post #39).

Here for code 42 diagnosis:

Fault Code 42

[Not_An_Abba_Fan]

The coolant temp sensor can cause the codes to come. They are all related. Change that first and see how it goes. I would be doing a coolant flush while you are at it, also fit a new thermostat and radiator cap. Check the pulley on the water pump by giving it a wobble, it shouldn't move apart from a barely noticeable wobble. Spin it by hand as well to see if it feels tight or noisy.

[levymetal]

I get the problem when driving with the air con on, I don't know what the hell it's doing but when I accelerate I get an extremely noticeable fluctuation in the cars acceleration, as if I am putting my foot flat, then half throttle for half a second, then flat again, then half for 200 milliseconds... Stupid air con. It's not even that cold in hot weather, and it makes this really weird sound that continues even after the car is turned off for about 30 seconds, kind of like the sound darth vader makes...

[Frogman]

Thanks Cheap6 for your comment

"Another thing to check would be the inlet manifold gaskets. If the are leaking externally you can see a residue of dried coolant along the edges of the manifold. if they are leaking air as well as coolant, that could be the cause of the surging, particularly if it is occurring at idle and light throttle loads."

I did have coolant coming out of the inlet manifold gasket, with some dried coolant visible also. I spent the day fitting a new inlet manifold gasket set. Fired up the car and it is surging straight away when ildling. The engine sounds stable and good when giving it some throttle. Straight away it registered the fault codes

14 Coolant temp sensor (voltage too low)
42 Electronic Spark Plug Timing

I did take out and clean the temp sensor when I took the inlet manifold off today. It was dirty (not really corroded but chalky looking). I havn't taken the car for a drive yet cos I now need a new bypass hose which was very brittle when I did the work today and when I put it back now leaks.

Next phase of my drama is to fit a new coolant temp sensor (and new bypass hose) and see where that gets me. I would have fitted a new temp sensor today when I did the other work but our stupid supplier didn't have it in today like they said they would after I ordered it in the week.

Stay tuned for more ...

[Frogman]

Hey everyone I ordered a coolant temp sensor from Coventreys (told them its the one that goes to the engine computer) and they soldme,via my son who picked it up, the larger sensor with the blue cap and two wires that goes to it. I quizzed them about this not being the right one. They were adamant that it was the one that goes to the computer.
I checked a wiring diagram and sure enough the coolant temp sensor that goes to the comp has two wires going to it. It was $15.

I'll let this forum know what happens when I replace it.
Cheers,

Frogman

[Cheap6]

That's definitely the correct item. The small brass single wire one next to it is for the gauge.

Was the resistance vs temp. of the old one wrong?

If the codes come back straight away, and there are two of them, otherwise unrelated, it's more likely to be something like the ECM than the sensor though. If the CTS code only showed up after overheating, then it could have been an effect rather than a cause.

[Frogman]

This is getting rediculous.
I have replaced the inlet manifold gasket and the coolant temp sensor. Took the car for a run yesterday and it seemed fine. I even got good old code 12.

But today it surged a little and stalled when idling AGAIN! And I am getting codes

14 Coolant temp sensor (voltage too low)
42 Electronic Spark Plug Timing
and 45 Oxygen Sensor Rich

back again.

I really don't know what to do. The car seems to run normally at all speeds, it just surges and stalls when idling??

ANy ideas anyone?

[Just_a_stocker]

have you reset the ecu?
It always pays to reset it after you have replaced a part.
It sounds like an electrical fault..

how is your battery charge?
maybe the alternator is weak.

[Frogman]

have you reset the ecu?
It always pays to reset it after you have replaced a part.
It sounds like an electrical fault..

how is your battery charge?
maybe the alternator is weak.

Yes I reset the ecu by disconnecting the battery for a few seconds.
My multimeter shows the battery has full charge.

Perhaps its as simple as muck in the fuel filter?

But with 3 codes coming up all at once I'm also wondering if the new (reconditioned) ECU is faulty.

[vn calais manual]

hows your fuel economy?

[Frogman]

Prior to these dramas it was good. About 440 k's from a full tank of reg unleaded. 3.8l v6 VP Vacationer wagon driving around the city.

[Cheap6]

But with 3 codes coming up all at once I'm also wondering if the new (reconditioned) ECU is faulty.

That is a possibility. Is it still under any warranty?

Was the code 42 diagnosis link any use? (Better if the code 42 comes up as active, I know).

One type of failure in the ECMs is:

A resistor is bypassed in the CTS circuit at higher temp. readings, > ~50C. (This is done because the CTS is not linear and it increases the available resolution at the higher temps.).

If the circuit for bypassing the resistance in the ECM is broken (it's a transistor short circuiting around the resistance), the ECM doesn't "know", and the CTS reading is wrong for the actual engine temp..

This is what the voltage at the ECM terminal C10 should look like:

Coolant Temperature Sensor Waveform (Vauxhall Multec System)

(The Vauxhall system is similar to Aust. Holdens).

While you won't have a 'scope (I don't think?), watching and recording the CTS voltage every few seconds as the car warms to running temp. is a reasonable substitute. (The first paragraph in the link shouldn't be there and the voltage should slope down again rather than flatline after the step up at "50C" = a double peak).

[Just_a_stocker]

Frogman tell you the truth
My car reved and chugged
I replaced ..
The IAC Valve
Temp sensor
manifold gasket
MAT sensor
Oxygen sensor
Flushed radiator
Renewed injector O-rings and filters
Replaced ECU control unit and memcal

I have fixed my main problem of high rev on startup.
But the damm thing still missess on idle to the point of distraction.

Towworrow I am having a mobile mechanic come around to check it out, he may help me he may not

But its better to get experienced advice when you really need it.

keep at it and I hope it workS out.
post your progress . everyone here wiill do their
best to help you if they can.

[Frogman]

Progress today...
Fitted a new fuel filter and reset the ECU/ECM and started the car maintaining about 2000 rpm for over 30 secs to reset the idle.

Still the same
She is still running rough but most noticable when idling.

This time though only 2 "new" codes came up
14 Coolant temp sensor (voltage too low)
42 Electronic Spark Plug Timing

Perhaps my next move should be to replace the IAC valve (because I have "cleaned" the throttle body and might have caused a problem there.

I will be very interested to see how Just_a_stoker went with the mobile mechanic guy troubleshooting his car.

[Just_a_stocker]

Nope the prob has gone away again, so i didnt call him.
I had replaced the whole control unit from wreckers and it fixed a lot of problems.
It has not been doing it again and is running fine..It could have just been a bad batch of fuel.

Possible your IAC is gone, but before you replace it..do this....

Remove the MAT (manifild absolute temperature) sensor from the rear of the manifold,
check it for gunk, if it is gunked up give it a hit with carb cleaner then put it back.

Also check your MAP sensor vacum line is connected and not perished.

Hard to say if it is the IAC valve, especially when you just cleaned the whole TB, I would suspect not, but cant say 100%.

You can reset the IAC by removing it jiggling the end of it while pushing it back into the seat till the tip is < 26mm from the base

[Cheap6]

Progress today...
Fitted a new fuel filter and reset the ECU/ECM and started the car maintaining about 2000 rpm for over 30 secs to reset the idle.

Still the same
She is still running rough but most noticable when idling.

This time though only 2 "new" codes came up
14 Coolant temp sensor (voltage too low)
42 Electronic Spark Plug Timing

Perhaps my next move should be to replace the IAC valve (because I have "cleaned" the throttle body and might have caused a problem there.

I will be very interested to see how Just_a_stoker went with the mobile mechanic guy troubleshooting his car.

I feel bad about this because I don't seem to have been clear enough in what I have suggested.

That the codes come up straight away after they have been cleared is good as it means the fault(s) is/are present at all times which makes diagnosis easier.

I doubt it is the IAC and it does point more towards a fault in the (reco.) ECM.

To address the coolant temp. sensor code first:

1) Check the wiring between the coolant temp. sensor and the ECM:

To do this, disconnect the wiring harness connectors at the ECM (behind the LHS kick panel, under the glovebox) and find the connector terminals D2 and C10. The numbers/letters are cast into the ECM harness plastic connectors. Push at dressmaker's pin into each terminal and measure the resistance between the two - the resistance will vary with the temp. of the sensor so the setting on the multimeter will need to match.

Here is a proper data table for resistance vs temp. for the sensor:

http://www.pe-ltd.com/Downloads/coolant_temp.pdf

It doesn't have to exactly match the resistance for the given temp., just be close. If you check it at room temp., it will be in the 4-3Kohm range.

Then compare the reading across the ECM terminals with that measured across the sensor terminals directly. They should match. If they don't, there is a fault in the sensor wire(s).

2) Check the ECM via the CTS voltage:

Reconnect the ECM wiring harness and push one of the pins into the back of terminal C10. Temporarily removing the plastic "comb" from the connector makes this easier.

With the multimeter set to "volts" - the voltage will be from 0-5V, so select 20V or 40V on the meter - and connect the red wire to the pin (C10) and the black wire to a convenient earth (car body, ignition key etc.). The connections need to be reliable to get accurate results.

Start the car and bring it up to operating temp. while recording the voltage reading and the time from start. Every 20 or 30 seconds will be OK but the more readings the better the result, and it is important to match the time with the voltage reading. Plot the results, voltage (vertical) vs time (horizontal) and it should match the plot in the previous (picotech) link. No "step" = ECM fault. (This is the poor man's oscilloscope.)

[Frogman]

Well I think the "Chronicles of my VP" are over.

I got a mobile auto electrician over today and his diagnosis was that the ECU (Computer) was probably faulty, even though it was a new (reconditioned one, less than 2 months old).

Mine was under warranty so I replaced it and the car started fine, idled properly, no engine warning light, engine fan worked ok etc.
I know this is early days but I'm saying it is finally fixed.

The motto of my saga ... reconditioned ECUs are not always relaible.

Good luck to everyone else having these dramas.