R31 Won't Run

[B0oStEr]

I can't get this aussie r31 to run.

I had trouble starting it and once it started it would only run for a few seconds and stall.

I got a mechanic to have a quick look at it.

He came out to my place and got it to run after a few tries and I asked him what he did and he said 'nothing'.

It revved up and ran great but then it got rough and stalled.

He restarted it and it idled but wouldn't rev past 2000rpm

He checked fuel pressure and flow rate which was normal.

He extracted the fault codes which he said were only there because he didn't run the full procedure and they didn't tell him what was wrong.

Then he backprobed the afm and the readings were normal even though it was barely able to keep from stalling.

Oddly the fault might still be the afm because the car idles and runs perfectly in limp mode with the afm

disconnected.

The mechanic said he'd need to get it into his shop so he can put a scope on it so he can be sure it's not the ecu.

I don't want to fork out for a new afm only to find out it's something else causing the problem.

[SKY031]

He extracted the fault codes which he said were only there because he didn't run the full procedure and they didn't tell him what was wrong.

That sounds a bit odd.....

Do it yourself and see if anything is showing up.

Details here

It's unlikely to be a problem with the ECU.

Other common culprits...

Ignition leads

Distributor/rotor button

Timing - a bit hard to check if it isn't idling properly.

AFM (the engine should cut out when it's disconnected)

AAC

TPS

Keep us updated.

[66yostagea]

I had similar probs with an R30 I just got.

Check all the injector leads.

And temp sensors etc. It may be necessary to pinch up the female part of the cons to get good contact. Also a bit of RP7 helped.

Cheers, Hugh.

Also after you buggerise around, reset the ECU by disconnecting the neg terminal of the battery and pump the brake pedal 5 or 6 times.

Reconnect the battery and the ECU will be rreset.

Edited January 11, 2007 by 66yostagea

[B0oStEr]

That sounds a bit odd.....

Do it yourself and see if anything is showing up.

Details here

It's unlikely to be a problem with the ECU.

Other common culprits...

Ignition leads

Distributor/rotor button

Timing - a bit hard to check if it isn't idling properly.

AFM (the engine should cut out when it's disconnected)

AAC

TPS

Keep us updated.

The fault codes that were logged were

14 speed sensor

23 TPS

24 neutral/park switch

31 A/C switch

To save time he didn't operate these sensors as part of the procedure so they were logged as a fault.

I drove the car to the workshop with the afm disconnected.

It stalled six times on the way there.

The mechanic thought that because fuel from a jerrycan was put in the car the day before the problem could be fuel contamination.

He set up an independent fuel supply using an on-car injector cleaning kit.

It still ran like sh!t until he increased the fuel pressure to >60psi which seem to make it run ok.

He said it just needs a bit more fuel.

He checked the ohms between pins 1 and 6 on the airflow meter.

It measured 383 ohms which was spot on factory spec but he increased it by screwing the afm pot in a couple of turns to make it 500 ohms which seems to be the recommended setting.

Unfortunately this made no difference to how the car runs.

He backprobed pin 3 on the afm plug to moniter the output voltage.

It was 2.1 volts at rough idle and rose to 3 volt with a bit of a rev.

He said that seemed ok but he disconnected the afm plug and substituted the afm with a regulated voltage supply to no.3 pin on the afm plug.

He started feeding the ecu 2.1 volts and the idle was as rough as before but by gradually increasing the voltage the idle improved until by 2.3 volts it was perfectly smooth.

I was surprised how much difference such a small change in the voltage makes.

Even though the afm checks out as working ok when the fault is apparent it's output is 0.2 volts lower than the ecu needs.

He cleaned the hotwire but that made no difference.

I'm pulling the cover off the afm to see if I can find a reason for the intermittent problem.

It looks like new inside but I'll resolder the pin connections to be sure.

There doesn't seem to be anything else I can do to it.

I'll try it on the car in the morning.

If it doesn't run I guess I'll have to get a new afm.

[blind_elk]

Get the injectors cleaned. Replace the fuel filter.

Also, I once fitted new injectors to my L24E. The engine kept stalling because the crap injectors weren't capable of maintaining the low duty cycles (like 1 - 2%) at idle.

[KamikazeR33]

get a mate with an r31 and put his afm onto urs, that will help u find ur problem, otherwise it sounds like a fuel/timing problem. if it stalls on idle id b doing a compression test

[kudos.motorsports]

I personally would suggest that the CAS within the dizzy is stuffed. It's quite common with VLs so I can only assume that the R31 wouldn't be any different.

[B0oStEr]

All fixed

$50 second hand afm did the trick

Thanks all.

[KamikazeR33]

I personally would suggest that the CAS within the dizzy is stuffed. It's quite common with VLs so I can only assume that the R31 wouldn't be any different.

acutally ur quite wrong andrew, the r31 runs a mitsubishi unit where as the vl runs a quite different one (and unreliable)

[SKY031]

You're both right.

Bosch and Mitsubishi were both used.