Stg3 CA18DET big running problems

[Adams]

Hi guys,

I'm after some help with a CA18DET S13 running like crap... Basically the specification of the car matches Jez Stg3 chip which is also equipped. The entire thing started some time ago with what we thought was a broken injector and turned out to be a knackered ecu. The symptoms are:

After firing up the car runs perfect. Idle is fine, but with time as the engine warms up the revs start to float a bit. While driving at first everything is ok but soon after the car starts to overfuel, won't rev properly, experiences something similar to boost cuts (cuts off) and maybe even misfire - basically not driveable.

Things we checked/done:
- replaced the ECU (inc new Jez stg 3 chip installed by a professional)
- new (used) 444cc injectors
- z32 maf installed
- changed the knock sensor (original one was broken)
- fixed all leaks in the intake system
- installed new ssqv3 in place of an old leaking bov
- timing checked and set to 15deg
- compression checked and by the book
- all the fueling/ignition components checked via FSM procedures - everything seems to be fine
- ECU diagnostics show no errors....

I've done quite a bit of reading and can't come up with any decent ideas on where to look/what to do...
One thing that might potentially be a problem is that the car has slightly altered timing namely +1 tooth on the intake cam. This is a simple mod done to the car on the previous map when it was running a piggyback which gives it a bit more low end torque. I don't see a real possibility of this being the issue as this mod didn't require mapping (on the piggyback) and the car was running perfect (worth mentioning though)

Any input greatly appreciated as I'm running out of ideas by now

Cheers!

[R3K1355]

That sounds like your problem, the cam being a tooth out will make it run like shit.

Take the belt covers off and make sure it is correctly timed, by both checking the cam markings align properly and counting the number of teeth between each belt run.

[Christian]

Hi

You say you have already replaced ECU, so mayby this is not much help...

Are you using a european ECU or a japanese one?
Reason I ask is because some years ago I put a japanese OEM chip into a european ECU and the car fired up fine, idled fine etc.
I could even drive about 10-15km without issues, but once the coolant was up to temperature the engine started stuttering, bogging and misfiring.

But I would try cam timing first, +1 tooth sounds a bit odd tbh as you have changed the timing by 15°

Best of luck with your search
Christian

[Adams]

Thanks for the input guys.

It's a European ECU so shouldn't pose any problems with the chip.

Concerning the +1 tooth I know it sounds a bit odd but it used to be a very frequent modification in Poland some time ago. Performed on a bog standard or modded car without any changes to the map didn't cause any bad symptoms... The car was running fine with it for the past few years but I guess the next step will be reversing it as it's the only thing I can think of...

ps. I reckon if the oem engine temperature gauge works fine the coolant temp sensor must be working properly right? (slight thoughts about replacing it...)

[Christian]

Gauge and ECU use different sensors.

Have a look at the factory manual, ECU diagnostics is covered very well in there with which voltage should be under which circumstances etc.

Christian

[monsterer]

Sounds to me like it could be the coolant sensor - get yourself a multi-meter and do a diagnostic as per the s13 workshop manual.

[martinbattye]

there is no benefit from altering the stock cam timing.

perhaps if its had an exhaust cam fitted in the inlet side..

still pointless as you need a vernier to do it properly..

go back to basics with the motor and check the simple things first.