CAS problem?

[Penfold]

I’ve got a really similar problem with my R33 GTR. Symptomps include:

- Running very rich ie. 300km / tank (tank = 72L)

- Cold Start

- Starts Ok

----- Idle is a little erratic & diff exhaust sound

----- Feels like timing changes slightly when water tmp reaches 30°C

----- Surging & running pretty poorly (boost builds very early)

----- AFM voltage is about 1.2 at idle

------ Injector Duty is at 2.1at idle

- Timing advances at 60C

------ Runs perfectly

------ AFM voltage is about 1.0 at idle

------ Injector Duty is at 1.5 at idle

- Start with waterl >40C and it runs fine.

As the car runs very well at over 60°C its pretty safe to assume that there is nothing physically going wrong with the car/engine. Thus, it is more likely to be a sensor/ecu making an error. So its time to check the sensors.

1. Run ECU diagnostic

Short the driver side fuse & check the ECU code:

11 Crankshaft position sensor

12 MAF sensor circuit

13 Coolent temperature circuit

14 Vehicle speed sensor circuit

21 Ignition circuit

31 ECU (ouch!)

34 Knock sensor

43 Throttle position circuit

45 Injector leak

51 Ignition circuit

54 Auto signal to ECU

55 All OK

2. Check for faulty O2 sensor

- Check its earthed properly (the braided line is usually earthed to exhaust manifold)

- Three wire is heated occupying two wires with the third being the signal and the body being ground.

- Find the wire for the O2 sensor going to your ECU and put a (+) probe from multimeter

on it and put the (-) probe to the chasis and drive your car. it should vary between 0-

1volts. if it stays at 0v its dead.

- If you have an aftermarket ECU then disable closed loop to diagnose

- http://www.gt-skyline.net/maintenance/oxyg...gen_sensor.html

- O2 Sensor Check

- Summary

-let engine warm up to normal operating temperature.

-Measure voltage in engine bay O2 sensor plug, with everything still connected, between the MIDDLE wire out of the three in the plug, and chassis ground. The O2 sensor is screwed in a bung just after the turbo dump.

-if its OK you should see the voltage fluctuate several times a second from a minimum anywhere between 0V and 0.3V to a maximum of anywhere between 0.6V and 1 V.

-if no fluctuation is occuring the sensor is dead.

-this test should only be conducted during idle as only then is the ECU in closed loop mode (except for cruise) causing it it to alternate the mixture in opposition to the current sensor reading.

3. I doubt its the Coolant Temp Sensor as your °C readings seem ok but its work checking:

- It sits on the rail that comes off the top radiator hose, yellow plug 2wires

- The sender should read:

2.1 - 2.9 k Ohms @ cold (17 or so degrees

0.68 - 1.00 k Ohms @ approx 45 degrees

0.30 - 0.33 k Ohms @ approx 74 degrees

4. Check Cold Air Regulator - cold idle valve between cyclinders 4 & 5. (FIDC)

- gives the fast idle when cold and is located on the manifold.

5. Check Crank Angle Sensor (CAS)

6. Clean AFMs with electrical contact cleaner (eg CRC electrical grade Contact Cleaner) and use multimeter to check readings. Spray gently as the wire is pretty fragile so keep a decent distance. If u want to know wheather your AMF fault, just unplug it & start the car (it’ll use default enrichment tables). If ide run OK but can't run over 3500rmp which is normal. It's mean problem from your AFM but if the ide still go up & down, its something else.

Check for leaks in the air intake pipe out of AFM &the clamps.

http://www.skylinesaustralia.com/forums/sh...t=AFM+AND+clean

Air Flow Meter Check –

-with the engine running and warm, and everything still connected, measure the voltage between chassis earth and the first wire after the blank on the AFM plug.

-the voltage should be somewhere over 1 volt at idle, raising to about 1.5V at about 2500 RPM.

-everyones voltage will be slightly different as each engine will always breathe slightly differently, the important point is that a voltage exists, and increases with RPM.

If these fail time to check:

- Give the ECU a reset

- Remove & Clean Auxillary Air Control (AAC) Valve

- Check TPS (throttle position signal) voltages

- Clean throttle body

- Check coils & replace spark plugs

Other options:

Unlikely to be a physical problem as it wouldn’t always be spot on 60°C as something expands to fix the problem. BUT:

1. Check for leak at inlet manifold (dried and cracked or broken inlet gaskets?).

2. Check vaccum lines & in particular anything near the fuel pressure regulator.

3. Fuel pump & fuel filter – Visual inspection (not clogged, etc) & maybe some injector cleaner

4. Other theory I’ve seen “think is the ECU is going into closed loop mode way to early, before the motor warms up and stops using the cold temp fuel map, which is why if you accelerate a liitle bit it goes away, the ECU won't go into closed loop under accel, but as soon as you back off and cruise under light throttle it goes into closed loop and because the ECU is running the cold fuel map it it very rich and in closed loop it basically freaks out and thinks there is way to much fuel and trims it down” on Skylines Downunder.

I'm in the process of going through all of these,

Penfold

let us know how u go

[R31Heaven]

What you describe as the symptoms are excatly what mine has to the tee, With the checking I have done every thing on your list and cant find a thing wrong the sensors all tested fine. just to add to things, the other day when I was hunting around under the bonnet I was moving the main injector loom and the car started to hick up slightly and when I took it for a drive and planted the foot it started to burble and fart and just run bad. I stopped lifted the bonnet and moved the loom and it started to run fine again and since I have done this the cold start is slightly better. I have just had all the injector plugs replaced a couple of weeks ago, so there not the problem it is higher up in the loom. I am more into the ECU comming out of open loop to early, just need to find out why

[Scooby]

Thanks Penfold that was a great post. Checked most of this, no luck. The sudden 60 deg thing leads me to believe it's a sensor or ecu problem, however, the AAC has also attracted my suspicion although voltages etc check out.

Mine has an intermittent start up caper that seems related - starts quickly and idles at 600 rpm building to 900 rpm over 5 secs hot or cold. Thing is the retardation occurs only when cold. When it starts cold and idles @ 950 the retardation doesn't happen however.

Anyway...I've had it and I'm going to get Advan to see if they can find anything.

[ferni]

to me it just seems like the engine protecting itself, until it has warmed up a bit ?

[GTR32]

to me it just seems like the engine protecting itself, until it has warmed up a bit ?

It should be to some extent but this is strange behaviour. Retardation when cold is understandable but not this much with these effects.

[Penfold]

Well in my case Im leaning towards a leakin head gasket or o2 sensor(grounding) combined with my default timing being slightly retarded (but the other things can all be causes).

Ill see how it goes with mechanic

P.S. When its cold get a mate to give it a bit of throttle (in neutral of course ) and have a look at whats coming out your exhaus.t

[Scooby]

Well in my case Im leaning towards a leakin head gasket or o2 sensor(grounding) combined with my default timing being slightly retarded (but the other things can all be causes).

Ill see how it goes with mechanic

P.S. When its cold get a mate to give it a bit of throttle (in neutral of course ) and have a look at whats coming out your exhaus.t

Penfold;

Any luck with your mech on this? Mine is not having much luck.

[pstanbis]

just my 2c on CAS troubles - Mine was making a scraping/rattling noise, and car was running REALLY rich - black stuff up back of car type rich - and when i pulled it off, pulled it apart, gave it a bit of a twist and 1) very hard to turn and 2) metal shavings in pile on ground - so went a got a replacement ($250 - WA is exy) and slapped it in, car now pulls better, more economical, and doesn't rrattle - good result all round i thought. Not a lot of help for your problems, but its some other symptoms.

Catcha,

Phil

[Scooby]

Well Yip Yah!!

Of the two probs one - excessive cold running retardation - seems to be fixed.

So far so good, 10/10 starts and it seems fine. The problem appears to have been an incorrectly adjusted TPS. Now it cold starts fine, goes straight to and stays at 1200 rpm or so for a while, and when it hits 60 deg C water temp there is no perceptible transition. At last.

As for the hot start problem it's still there but I reckon its days are numbered now. At this stage I'm betting it still has something to do with the ATTESSA pump. On hot starts the revs still remain low - about 600 rpm - for a while and then build to about 950, they hit 950 almost exactly the same time as the pump stops running. Process takes about 5 sec. Almost as though the idle up for the pump, if there is one, isn't working.

Will report back when I know more.

[mindflux]

Man theres alot of talk in this thread..

So whats the outcome?

was it the CAS that was causing these starting problems?

[The Alchemist]

Cam angle sensor ....just scoped my mates 300ZX with similar probs to your decriptions.....

the 120 degree signal was dropping out causing earratic timing problems...not enough to cause a hard fault in the Ecu but none the less enough to cause the rough running.

my two cents...

if in doubt swap it with a mates and see if the symptoms resolve, or get a tech to scope the CAS outputs and the fault will stand out a mile !!

Mike