gravelexpress

Upon import my car required a new MAF and lambda sensor in order for it to pass SVA emmisions. I have just carried out a ECU diagnostic that indicated both faults - and then reset the ECU.

Do these items failing point to anything else that could have caused them both to fail? The car is MY 99 wrx sti V type R. The car is modded with apexi induction and thedocuments that came with the car indicate that the owner had an apexi exhaust fitted at some stage (currently standard STI full exhaust fitted).

JusH

What mileage is the car? I have read that O2s only last between 30 and 50k (mine went at 46).

gravelexpress

spot on 51 k. miles

ozzy

Induction kits have been know to cause MAF failures either through excess vibration or poor filtration. The MAF from the MY99/00 cars seems a bit fragile compared to older or newer cars.

O2 sensor has a life around 3 years (varies with milage), so it's feasible it just came to the end of it's life. Mine, for example failed just before my 3yr warranty expired.

Other than physical damage when changing exhausts (e.g. dropping the sensor), the car would need to run rich to coat it with excess carbon causing premature failure.

Other than that you'd need to check the actual wiring at both to see if a wiring fault was the cause.

Just thinking logically, but I'm sure someone else would come up with other ideas.

Stefan

gravelexpress

I suppose im thinking of it pointing to something nasty. I brought the car on a "test drive" up to 125 mph when the CHECK ENGINE light came on. I immediately backed off, stopped, cooled it down then ignition off and restarted - the light was extinguished.

Boost is indicating about 0.5 - 0.6 kg/cm2 - but i dont really know what that means.

ozzy

No idea what that boost means either. Would need to convert it to psi or bar to make sense of it.

The important thing with JDM cars is their fuelling. Make sure it's on Optimax+Booster to get as close to 100RON and check that it isn't running lean and/or detting under heavy load. That's what usually leads to them blowing up.

Other than a boost gauge, does it have anything else?

Stefan

gravelexpress

Im running optimax and booster, I use the turbo timer. Other guages are oil temp steady at 90 degrees, volts and another guage labelled PRESSURE also in kg/cm2.

Everything is pointing at getting knocklink fitted - but I did want to avoid this.

gravelexpress

Just found a conversion table - boost is about 0.59 Bar / 8.5 PSI. I have to wire in the additional HKS boost guage with electronic memory in order to see what peak boost is indicating.

ozzy

Why avoid a KL? It could save your engine. All other gauges can read OK, but your car could be steadly detting away to it's hearts content.

Then one day - boom.

You can get the ECU remapped, but it still wouldn't show a bad batch of fuel, for example.

Stefan

dowser

Boost is too low, sounds like there's a pipe connected between turbo outlet and wastegate actuator (ie; no boost solenoid in the circuit to bleed air off, so boost control is around the .7 bar actuator pressure).

This *could* be because whoever had the car before didn't understand the MAF problem, but it could be more sinister.

It's normal to need to replace both MAF and lambda at same time, and I also frequently find that the air idle stepper motor will be very gummed up and require a good clean before it idles smoothly too.

Get some det cans on it to be safe. To fully diagnose could require wideband to check fuelling too.

Richard
PS: check the MAF has a green spot on it (by upward facing bolt hole) - I've found these to be far more resilient than the earlier types. If it's not there, still suspect the MAF without a professional diagnosis.......

gravelexpress

Thanks Dowser,
can you point me in the right direction to locate the stepper motor. I am going to clean out the pipes using some carb cleaner this weekend.

dowser

Round thing bolted into the throttle body - undo the 2 philips screws and out it comes. Perform an ECU reset after putting it back in.

Have you put det cans on it, or have any idea of the AFR? Such low boost could be the result of many things, most of them bad (ECU could be in safe mode to protect you from your setup). Be careful....I'd advise someone proficient with DeltaDash takes a look, it'll save you time/money/hassle in the long run.

Richard

gravelexpress

I cleaned the stepper motor today - it was full of gunk. I also tried cleaning all the turbo hoses around the solenoid. But still no good. boost still at 0.6 bar.

I noticed on one of the hoses from manifold to solenoid in the middle a denso filter type thing - what is that for?

I will be seeking additional help. It sounds as if that solenoid may have a fault.