CAS problem?

[Scooby]

Can anyone please suggest what might be causing the following problem;

Usually the car starts from cold and runs fine. Occasionaly however, it starts and runs OK but but drives sluggishly, with barely perceptible surging/uneveness when driven gently ie approx 50 km/h 2200 rpm etc. Symptoms go suddenly - as if hitting a switch - and car runs very smoothly, slight but obvious acceleration also. Doesn't happen every morning but always happens the same way and goes suddenly within about 5 minutes of driving, like clockwork.

Now...there's a clue. I've watched the timing and when this behaviour is absent, timing @ idle is 20 deg, timing at trailing throttle is about the same, goes to about 44 deg at cruise, decreases quickly under power. When it's playing up, timing starts at 20 deg @ but after moving off it sticks on 10 deg, won't change no matter what I do. Until...symptoms suddenly go and timing jumps to 20 deg etc at which time it acts normally.

Seems clear that the sluggishness is retarded timing, and I can only think CAS related.

Grateful for any suggestions

Mark

[Duncan]

Mark, interesting theory, I had an intermittent missfire in my gtst which we eventually traced to a faulty CAS. Unfortunately I didnt have a PFC so I couldnt see the timing change, that would really have helped as a clue.....

In my car it didn't happen regularly but it was happening often (if that makes sense....) engine check light also came on on two occasions but the consult puter couldn't find anything.

take it to a workshop and get them to swap another cas on to see if its the problem

[Craved]

a mate with a CA18 had a similar issue - turned out to be the key on the end of the CAS had chewed out, try marking where the cas is now, then removed it and check the key - if not damaged check the "lock" on the cam to see.. thats how we found it on the CA -- not sure exactly how the skyline CAS attaches to the cam though!

exactly the same symptoms though

[Scooby]

Thanks Guys;

Did it again this morning - started OK and idled @ 20 deg, driving along slowly then dropped to 10 deg. This time however it would change when revved rather than being stuck on 10 deg no matter what, as it did yesterday.

What I can't figure out is why the change to normal running is so sudden and happens almost exactly the same distance from home. Almost as though it's temp related.

I'll pull off the CAS and see if there's anything out of order.

Mark

[WHITE R32]

my rb20 with microtech as a problem with the timing at the engine and the timing by the ecu are different.... hard to explain... but as they revs rise the timing at the engine gets more and more out of wack with what the ecu says it is... im thinking about trying another cas.... sounds like it could be something similar any ideas?? if i was u id also try looking and seeing what timing u have at the engine when this happens if possible...

[Scooby]

my rb20 with microtech as a problem with the timing at the engine and the timing by the ecu are different.... hard to explain... but as they revs rise the timing at the engine gets more and more out of wack with what the ecu says it is... im thinking about trying another cas.... sounds like it could be something similar any ideas?? if i was u id also try looking and seeing what timing u have at the engine when this happens if possible...

CAS looks fine. Did the same thing today, switched to normal suddenly @ exactly 61deg engine temp, was watching AFM v also but no change at the switching point. Will check out the other parameters tomorrow. Can't help but think it's temp related.

[bbenny]

Scooby, i have the exact same problem. and like yours it always suddenly goes away when i am abou 5 blocks from my place, same place every time. i have standard management with an SAFCII.

Ive been wondering what the prob is, but havent worked it out.

let me know when you find out!

[CrazyMan]

yeah, i have this problem too... i put it down to coolant temperature, or something similar, as most Engine managments that i know of, will retard your timing when cold, so that the motor will heat up faster. not sure i'd realy call it an issue though.

[GTR32]

Scooby,  i have the exact same problem. and like yours it always suddenly goes away when i am abou 5 blocks from my place, same place every time. i have standard management with an SAFCII.

Ive been wondering what the prob is, but havent worked it out.

let me know when you find out!

BBenny;

All the other parameters check out OK, no dramatic change to O2 sensor or AFM v when switching to normal running/timing. Still switches @ exactly 61deg. Must be temp related; I've checked connections etc but not yet tested sensor voltage. I've also noted that timing goes to normal when decelerating ie 50km/h timing frozen @ 10 deg, decelerate and it advances to 20+ as it does when it's running OK over 61 deg.

I'll keep looking...

[aKTiVE]

hahaha, temp related! I had a serious CAS problem on my rb30et. I was convinced it was temp related. Cold start it was fine, i'd drive it for 10-15mins and by this stage it would reach operating temperature, then it would missfire in a BIG way, backfire and shut off... the tacho would be bouncing around everywhere even when the car was off. I'd wait like another 10-15mins, and it would start again as if nothing had happened, and it would run all day.

It sucked.

I got a new CAS from petro-ject - $150 odd bucks later it was sweet.

I would HIGHLY suggest you guys swap Crank Angle Sensors with someone who doesnt have the problem, see how you go.

You dont even have to drive the car, let it sit there and idle till it gets to operating temperature and it will freak out when it gets there. Good luck guys.

[Col-GTSX]

Sound very similar to my problem... check this

http://www.skylinesaustralia.com/forums/sh...ead.php?t=36874

I posted a few weeks ago and have had no luck with finding the problem... but i have reduced the freq of the occurance....

I had a feeling it was the CAS as they get F#@king hot as when up to operating temp... Like its the seconds hottest piece of metal in the engine bay (other than the exhaust of course)

Im sure when it gets too hot the signal breaks down... VL & R31's (Rb30) motor contantlly had CAS problems (i used to be an auto-elec) but they ran a very different system, and the plates were replaceable... I dont want to just go and buy a CAS to see if im right or not....

So maby you can and then tell me if it works... LOL

Read this post maby it will help anyways...

[R31Heaven]

Ok my GTS-X does this as well. when I first start it, it runs fine for a minute then will jump into to retarded state as discribe above and when the temp reaches the same point on the temp gauge every time it will take off as nothing is wrong. I am glad you have actualy got gauges or instruments that show you what it is doing, as I have been guesing it has been retarding itself. It is just trying to work out what is causing it to do it. I dont believe is is the CAS I have changed mine and no diff and most CAS problems surface when the engine is warm/hot. this is a cold start problem. Will a crook injector cause the timing to retard? But the temp thing get me. I have replaced all my sensors as well.

[GTR32]

Ok my GTS-X does this as well. when I first start it, it runs fine for a minute then will jump into to retarded state as discribe above and when the temp reaches the same point on the temp gauge every time it will take off as nothing is wrong. I am glad you have actualy got gauges or instruments that show you what it is doing, as I have been guesing it has been retarding itself. It is just trying to work out what is causing it to do it. I dont believe is is the CAS I have changed mine and no diff and most CAS problems surface when the engine is warm/hot. this is a cold start problem. Will a crook injector cause the timing to retard? But the temp thing get me. I have replaced all my sensors as well.

In light of what others have said I may have to eat my words but I agree with you that it doesn't seem to be a CAS problem. I'm sticking with it being temp related, the point at which the thing starts to run well is always, without fail, precisely 61 deg C. The fact that replacement of the sensors didn't make a difference isn't what I wanted to read though. At this stage I'm just trying process of elimination to think of the things that can send a 'retard timing' message and see if any one of them are temp related. Knowing how cars love to trick us however, the real problem is likely to be masked by two others...

[R31Heaven]

Ok making my own theory here, have been reading some stuff on injector duration from toyota and it talks about cold start duration and how it keep injectors open for an extended time until the motor reaches an expected temp of between 50 cel & 80cel and then goes back to normal cycle. My theory is that for some reason during this cold start the injectors are leaning out or not extending the open duration and causing the motor the run lean and then cause the motor to retard, until it reaches its set normal running temp. I need someone with a Mechanical background here to confirm that this can happen and how and then I may be way off

[GTR32]

Ok making my own theory here, have been reading some stuff on injector duration from toyota and it talks about cold start duration and how it keep injectors open for an extended time until the motor reaches an expected temp of between 50 cel & 80cel and then goes back to normal cycle. My theory is that for some reason during this cold start the injectors are leaning out or not extending the open duration and causing the motor the run lean and then cause the motor to retard, until it reaches its set normal running temp. I need someone with a Mechanical background here to confirm that this can happen and how and then I may be way off

There's no question the thing will/should run rich when cold but even if it wasn't I doubt it wouldn't be running so lean that the engine would retard as much as it does. Given that the timing 'sticks' on 10 deg but fluctuates as per normal when decellerating and also behaves normally when idling also thickens the plot, as does the fact that injector opening time remains the same throughout. Seems to retard only under power, no matter how little, until suddenly - and I mean suddenly - getting its act together @ exactly 60 deg C water temp. Not 59 or 61, but 60. Indicates to me a mullered component that's supposed to have a graduated response to operating conditions but isn't doing its job.

[WHITE R32]

okay hows this for crossing out most of the abouve theories???

my car did it with a std ecu, a mines chipped ecu and now does it with my full aftermarket microtech (which doesnt use afm so cross that out too i say)..... so i really think that it has something to do with cas or tps (though microtech hardly uses the tps when its tuned off vac) ... i think the problem is elsewhere.... since changing to the microtech ive also added gtr injectors and a malipassi and it has also done it with the last 3 turbo setups ive used (std,TD06 and gt2835r).... so i think we should look deeper cause i have even played with the cold tune extensively and it hasnt fixed it... ill be trying another cas also soon so when i do ill tell the results

[GTR32]

okay hows this for crossing out most of the abouve theories???

my car did it with a std ecu, a mines chipped ecu and now does it with my full aftermarket microtech (which doesnt use afm so cross that out too i say)..... so i really think that it has something to do with cas or tps (though microtech hardly uses the tps when its tuned off vac) ... i think the problem is elsewhere.... since changing to the microtech ive also added gtr injectors and a malipassi and it has also done it with the last 3 turbo setups ive used (std,TD06 and gt2835r).... so i think we should look deeper cause i have even played with the cold tune extensively and it hasnt fixed it... ill be trying another cas also soon so when i do ill tell the results

Whitey;

I always thought it was nothing to do with the ECU, good to have the feedback. Ditto AFM. The monitor shows TPS V doesn't change at the 60 deg transition point so I'm not sure that's the problem. For what it's worth I still reckon it's a sensor or some kind of component degredation. Look forward to the results of the new CAS.

Does yours by any chance start and idle low ie 600 rpm, building gradually to normal idle speed over about 10 secs? Another annoying prob I've got but I think it's related to the fuel pump return leaking. Anyway I won't 'go there' now...just thought if you have the same it might be related.

[WHITE R32]

when i start the 32 first thing in the morning it will start good then drop idle if about 3 secs to really low like just running then it will pick back up then its fine ive tried letting the car prime the fuel system longer/shorter etc doesnt seem to change it..... i also think these 2 probs are linked.....

[GTR32]

when i start the 32 first thing in the morning it will start good then drop idle if about 3 secs to really low like just running then it will pick back up then its fine ive tried letting the car prime the fuel system longer/shorter etc doesnt seem to change it..... i also think these 2 probs are linked.....

Sure sounds like it's possible they are linked. Must be something to do with a component that's temp sensitive and can somehow retard ignition also. Time to get the manual out. Will post on the SDU site also to see if the Kiwis know anything.

[R31Heaven]

This is how mine goes. Hit the ingnition in the moring fires up and runs great, so gather the cold start works fine after a minute or so of as nothing is wrong, it must go out off cold start mode, as soon as it does the car coughs and splutters at this stage for a minutes or so then seems to be running ok with only a slight hesitation every now and then, but when you drive off and try and cruise, it drops into this state until the temp gauge just gets over the first mark, sorry dont have temp gauge so cant tell you the temp. How many K's on your cars and what models. I am wondering, these things get hot around wiring on top of the engine and after years if this could have affect on it causing it to degrade, highering or lowering resistance to a sensor. theory #2. surley some one else has nutted this out as it seems to be a plauge with these cars, could be worth trying to chase some one up in Japan in the know.