ECU fault codes - 34 knock sensor

I hope you get your problem solved VC....I'm holding thumbs.

looks like i'm in for the long haul draco.

doing my time, paying some school fees along the way!

i ripped out the engine bay harness. the one that goes runs from the computer box. i checked all wires for continuity, and rewired those wires that were brittle and old. also fixed connectors where possible etc, etc.

put it back.

and guess what...

the problem is back.

i've now troubleshooted so much that i am totally disheartened!

i've had it running on a different computer box, no difference.

different MAF, same problem.

different TPS, same problem.

different combinations of the above, same problem.

i dont think it is the coils or injectors, because it is still idling fine.

i do get a strong fuel smell while trying to rev over 1500rpm and it starts missing, so the coils aren't firing intermittently. i checked the coil harness with a timing light - and all signal is lost intermittently.

i've checked fuel pressure while driving, and under boost, before the problem occurs its fine. its at about 36psi on full vacuum, and moves up to about 45-50psi under full boost.

so i'm convinced its electrical, and somewhere along the following flow diagram something is going wrong:

CAS + TPS => Computer Box => Power transistor => Coils => plugs.

CAS = i'm not sure if its this because i dont have a replacement to test with. but the car drives fine while cold, and idles fine while hot.

TPS = i've replaced this with another used one, and i still get the same symptoms.

Computer = i've replaced this with another used one, and it still has the same symptoms.

Power transistor = i've replace this with another used one (that was cold at the the time) and i get the same symptoms.

Coils = i havent replaced these while the symptoms show, but i could. i'm not convinced its them though. the car idles fine while hot, and if i use a timing light on the trigger harness for coil #1 i momentarily lose power at the exact time that the misfire happens. and that happens on each coil too.

plugs = i've changed these to the old ones i used to use because the new ones were terrible. the old ones worked well on the ca18. they are gapped to 0.8mm ATM. and are displaying spark when held outside the bay. hte car also idles fine.

so somewhere i'm experiencing a loss of signal when the car, or one of its components gets very hot.

anybody???

Gees VC you have basically checked everything, I hope someone has some advice...I don't have a clue.... 🙄

forgot to mention that i got some strange readings when checking earths, both body and engine earths.

on the copper strand it measured 0.3 ohms - but on the connector 3.0 ohms!

so i fixed that thinking that a stupid earth disconnection had got the better of me. but i still got the problem.

then i noticed that the relays for "ign coil", "EGI" and were getting very hot in the engine bay. there is one right next to that for something called "N&P" (???) which was warm, but not too hot to touch for more than a few seconds!

i dunno - can a relay work when its cold, and then fuck out when its hot???

Jeez dude, I hope you come right. Have you tested with another coil igniter? (Dunno if this is the "power transistor" you've mentioned)

thanks sokar,

its the same thing. i drive around until i get the problem, usually when things are VERY hot.

then i change the ignitor, while trying to avoid 3rd degree burns from the turbo. and the problem persists!!! so i swop the hot one with a cold one, and get the same symptoms!!!

its mind boggling i tell you.

So have you eliminated the Knock sensor as the problem?

Daniel wrote:

So have you eliminated the Knock sensor as the problem?

i have. we were getting that code on the ecu. i removed it to check that it was operating properly. and it is.

we are also no longer getting taht code as a problem on the ecu. its now 55 (everything OK) all the way!!!???!!!

veecee wrote:

CAS = i'm not sure if its this because i dont have a replacement to test with. but the car drives fine while cold, and idles fine while hot.

Phinx has a SPARE CAS for you to TEST with (i.e. he definately wont part with it) PM Him, he might be going to wesbank on Wednesday. If you chat nicely to him he has other extra's of a spare motor he'll let you test with (Knock sensor, water temp sensors etc...)

I suspect you are all barking up the wrong tree.
Have you checked the mixtures before and during the"missfire"?
What is happening to to the injector open period when the issue starts?

You have checked a fair bit of stuff however this is one where experience comes into play.
Remember, Om te meet is te weet.

THANKS ever so much to everybody who has replied.

thanks sokar for the tip on phinx, but i managed to convince toby to "lend" mr his CAS. i fetched it last night.

caver - the mixtures i am sure are not 100%, but i do know that i have proper fuel pressure, and that the injector solenoids are being activated.

two things i noted:

1. the timing light does not flash when the problem is there, as long as its off idle - otherwise its normal. this tells me there is a total loss of signal in the coil harness.

2. there is a strong smell of fuel when the problem is there, and there are wet spots all over the driveway at the exhaust outlet!

BUT i think we've solved it. and you would NOT believe me when you hear it!

THE SOLUTION:

it was the cas, and perhaps the engine temp sensor too!

the reason i say perhaps the engine temp sensor, is while the engine was cold this morning i took out the temp sender unit. i then plugged the hole with something else, and used a hairdryer to heat it up very hot.

so with everything else cold, the computer thought that it was hot.

it struggled to start, and when it did, it would not rev up past 1500 just like before. when we unplugged the sender the car ran fine.so i thought that i had solved it, but i was wrong - and murphy was kicking my ass.

it was also my CAS.

i drove around to find a new temp sender, but noone had stock. and this time it took much longer for the problem to come back. but it did eventually. i then unplugged the temp sensor, but it didnt solve it.

we then got home eventually when the car had cooled a bit, and made the problem come back before we swapped CAS's. and the problem went away!!!

we drove around for hours all afternoon, and it never came back. then later this evening i decided to open up my CAS. this is where i found what i think coul've caused all these faults!

the CAS:

the CAS has two bearings on each end of its shaft. mine felt and sounded fooked. but i had no idea how bad it was until it was open.

when i got the housings apart, i noticed a wet dark grey substance on the outside surface of the smaller bearing (NSK 6000). the same substance was on the inside of the housing that held the bearing.

conclusion? the bearing was turning inside of its own housing! not good!!!
it was the same pasty grey substance you get when sanding aluminium with 1200 grit and water!!!

once i got the rear housing open - the bearing there was totally stuffed. it wasn't broken, but didnt have any lube left, and was running freely, metal on metal!

i'm convinced that these problematic two bearings were probably the cause of eddy (???) currents generated that confused either the optical pickup, or the signal that it generates.

so if the CAS sends a strange signal to the computer, then the computer sends a strange signal to the coils - and BAM...

very erratic running of a certain CA18det.

i took lots of photos while dismantling and "mantling" the CAS, and i will post a long thread with photos in the articles section.

thanks again guys!

and huge thanks to those who donated parts for testing:

Vlade
Toby.

fank!

knock knock

Awesome man, just sorry I cant be at wesbank tomorrow to watch you strut your stuff 😛

Sokar wrote:

Awesome man, just sorry I cant be at wesbank tomorrow to watch you strut your stuff 😛

are you two in durbs??? or the south coast somewhere??

how's the waves??? believe it or not, i used to be a surfer!

Woohoooo... light at the end of the tunnel!! Glad to see this whole saga is coming to an end 🙂 ChemCool - his car was exhibiting similar symtoms to yours, albeit much worse, but maybe you should have your CAS and temp sensor checked out?

The symptoms you described sounded like a to rich mixture which is verified by the strong fuel smell and the fuel running out of your exhaust.
If you measure the resistance on your coolant temp sensor you will probably find that its going open circuit or to a very high resistance. This will make the ecu think its like -40deg and cause the flooding you described.
As for the cas issue a scope on the ouput would have picked up the fault straight away.
Like I said om te meet is te weet.
Well done on getting to the bottom of it eventually.

The Calibrator wrote:

The symptoms you described sounded like a to rich mixture which is verified by the strong fuel smell and the fuel running out of your exhaust.
If you measure the resistance on your coolant temp sensor you will probably find that its going open circuit or to a very high resistance. This will make the ecu think its like -40deg and cause the flooding you described.
As for the cas issue a scope on the ouput would have picked up the fault straight away.
Like I said om te meet is te weet.
Well done on getting to the bottom of it eventually.

LOL - there were a few wet black splatters out the exhaust, but it wasn't running out. you make it sound like a tap!!! then i would agree about the mixture being too rich. when the car was idlng, it was fine. the splatters and the smell were unburnt fuel because there was no spark!

we did measure the temp sender and although i cant remember the exact figures - it wasnt an open circuit. but it did show a big range dependent on temperature.

i first thought it was temp sender, but nissan wanted R350 exvat, and they didnt have stock - luckily. i used the car on the track yesterday without hassles - so now i dont think it was that. so i dont think i will swop that part out yet.

it was my CAS. and the symptom was what people on other forums call the ECU "limp" mode. the FSM actually describes it, and states that two conditions would cause it. faulty engine temp sensor, and a faulty AFM.

i didnt think a faulty CAS could cause it too, and my idling limit was 1500rpm, not 2000rpm like everyone thinks.

if you try to run your car with your AFM unplugged, you get the same symptoms.

engine temp sensor should be around 2.5 to 3k cold and 200 or 300 ohms at operating temp.
Sure was a lot of work to find a faulty cas.