Need Help! Keep Killing Cas Sensor

[i4dat]

Hey Guys, I'm new to your forum, but was hoping that someone here could help.

I have tried to get suggestions from the guys at GTR.CO.UK, but as of yet no luck.

SO.... here goes with my ongoing saga.

I bought my 1996 BCNR33 GTR in November of last year, and it came with a bog/stutter/hesitation/misfire? from the get go.

It would only do it when the engine was first started after it had been sitting overnight. I would get the problem between 1600 rpm up to 2800rpm in 1st and 2nd gear. But as soon as the car's water temp gauge got to about 100degrees F, it would stop doing it. And besides for a bubbling burble off of throttle thru the exhaust, everything would run ok. The idle rpm would fluctuate between 920 and 980 and settle at 950 for a few seconds then move back and forth again.

At first I thought that she might just need plugs/filter etc so I started with them. No change.

Then I got an Ign amplifier that I knew was in working order.... no change.

Then I got AFMs that I knew were working.... No change.

Changed the Coils to Splitfires..... no change.

At this point I ordered a BlaZt Datascan/logger and found out that when the car was accellerating, the Ign Timing would start to raise and then when the bog started it would become fixed at 13 degrees.

Of course after it was warm, it didn't do it anymore.

I tried to check my water temp sensor, and unplugged it after the bog had gone away, but the problem didn't come back so it wasn't that.

Mark at Abbey's in the UK suggested it was the CAS sensor going bad and to change it.

This I did and presto, it was fixed! I had a rock solid idle rpm of 950 give or take 10 rpm. Everything was perfect.

Or so I thought.

Four months later and the problem has returned. (I haven't checked it with the BlaZt yet, but the symptoms are the same). And when it warms up the problem goes away.

The RPM is now jumping around from 920 to 970/80 again and everything.

What could be causeing me to kill CAS sensors?

Do I have a bad wiring harness or something?

I don'w want to have to keep buying CAS's three times a year. At $600 a pop thats expensive!

Has anyone had a similar situation happen to them?

Or any suggestions?

Any help would be greatly appreciated.

David.

[i4dat]

Has no one experienced a problem similar to this?

And is your CAS Sensor supposed to be extermely Hot after the engine has warmed up?

Just throwing something else in there.

D.

[Duncan]

Nope I killed one but never more than 1.

Are you sure your cam is straight?

Or maybe you were just plain unlucky with 2 in a row?

[MANWHORE]

Was the cas brand new? Unfortunately, there are some dodgy people otu there. If someone was selling the cas, it could be because they suspected that it wasn't working

Are you runnign the cam gear cover?

[seeyagtr]

for a RB26 fpr the idel to raise and lower between 920-970 thats not too bad.....

Are you running a standard air box? If not do you have custom inake piping? is do do you still have a balance connection between the air flow meters?

If they are not balanced, under light loads or idel the air flow meter become un-balanced and cause fuel and loads cause some of the problems above.

[i4dat]

Ok, to try and answer the above questions.

I have no idea if the cam is straight or not.

Yes the CAS was brand new, came in a sealed Nissan Box.

Yes I am running a Timing belt cover.

No I do not have the factory airbox, using stock intake piping, but HKS pod filters (the metal screened one's with K&N drycharger covers).

If I get the car sorted out I want to get the Trust Greddy Suction kit with the polished pipes that do away with the "twin turbo" pipe and the rubber accordian pipes that are visable now.

That is a big 'IF' right at the moment.

What I don't understand is why did the problem go away when I changed to the new CAS?

And why is it now back after a few months.

Maybe we should look at this from a different angle.

What would cause a GTR to have its base timing change from 20 degrees at idle, to 13 degrees when it gets to 1600 rpm (or so) and then return to normal above 2800rpm. After about 5 minutes of this condition or when the car is warmed up (I think it is more a time issue than a engine operation temp issue),it will act 'normal'. Until the car goes thru a complete cooldown cycle (usually overnight). Then it starts all over.

Thats what got me stumped.

I reset the base idle timing (using the wire loop so it still might not be perfect) and it seemed to make it better but the problem was still there.

I also tried to adjust the AAC valve but I couldn't get the damn plug off like the manual says to. I guess you need to either have the engine out or have Telekenisis Powers to get it off.

Still I am very frustrated.

And maybe selling the damn thing and getting a R34 GTT might be a better choice.

ARGHHHH!

Still any help you guys can give is greatly appreciated.

[skytemplar]

Hey Dav,

I had a similar problem to your with engine's rpm fluctuating in idle and it stalls easily on low speed. However my ECR33 didn't suffer misfire.

I took it to service and the mechanics told me the fuel injector was dirty and almost blocked. In your case, you may also want to check this out. Gd luck with your car

Tim

[i4dat]

Hey Tim, thanks for the advise, I will keep it in mind.

Like I have stated above, what kills me is it only does it during warmup, after the car is warm (or not as cold as it would be overnight) it will NOT do it.

I'm getting very close to running it off of a cliff right at the moment (not with me in it of course).

I'm at my wits end. I can't come up with a solution to the 13 degrees timing issue when its cold. Nor why replacing the CAS fixed the problem for a few months and now its back.

I could see if it happened all the time, but its infuriating that it only does it under certain conditions.

This car is turning more and more into a bane on my existience.

[Penfold]

Yeh my car did the exact same thing.

I got a PowerFC and it ran fine but my CAS is fuxored & difficult to turn so I am rebuilding and buying a new one.

[SLIPPERY]

Try a powerFC in there and see what happens. See if you can tune it out. Also with your idle, a little fluctuation isnt too bad. At least its below 1000rpm. Hundreds of other GTR owners here would kill to have an idle below 1000rpm. Mine sits between 1800 and 2200 lol

The stock ECUs are known to provide cold running problems and as soon as the temperature reaches normal, then the car runs beautifully. Theres been many threads of late of hesitancy when cold with the OEM ecu.

My car killed a CAS but that was due to not having the timing belt cover on but in your case this isnt an issue.

[i4dat]

Thanks guys, I appreciate all of the help so far!

I have been thinking about changing the EMS to something else.

I have seen a lot of talk using the Emanage Ulitmate instead of the PowerFC.

Any suggestions with that?

We do not have any reputable Tuners or a 4wd dyno here so I would be having to do it myself using a wideband sensor and road testing. So.... the easier EMS to tune would be really what I am going for.

Thanks.

D.

[i4dat]

Here is something else to throw into the mix?

When I had my laptop hooked up to the car (using blazt datascan 1.52) I noticed that when the car is warming up by itself, the timing is set to 20 degrees.

Now when I use the blazt to tell the ecu that the temp is lower than normal, it will go into warm up mode, which advances the timing from 24 to 30 degrees, depending on what base temp I set, which raises the rpm to around 1300 or so.

Why doesn't it raise the Timing from 20 degrees when the car is doing a normal warmup?

Can this be an indication that something is amiss?

Any suggestions?

[i4dat]

Someone mentioned something else to consider.

That the car might be running lean at this point.

Any reason why it might run lean between 1600`2800rpm only until the engine gets to about 100degrees F?

Then not do it anymore (or at least not be noticable)?