Hi All,

Need some help. We recently did a my99 car that has a persistent lean running problem.

When we first checked the car out we were told it had a new short motor fitted following failure. Pre-check showed MAF to need replacing.

However, after changing this and remapping, it was still running low MAF voltage and pretty lean. Tracing through found the following problems;
- Home made cold air duct was blocking airflow (we removed it)
- Hole in signal pipe to FPR (replaced)
- Crappy joints on an aftermarket inlet pipe (same as MRT one, but *very* soft - wouldn't like to run this at high boost!) - we fixed all the joints/leaks.

All of this brought idle without the ECU's lambda to 17:1 instead of the more normal 14-15:1. WOT is 12.5:1 at 1.1 bar on a base map that should be giving 11:1. MAF voltage at 1.1 bar is still low (4.19 volts at around 5k).

Fuel pressure is correct (3.25 bar idle without signal connection, 3 bar with). Replacing the FPR, fuel pump and fuel filter also made no difference.

I also checked ECU connections/wiring and can find no add-ons.

HELP! I'm at a loss what to do now. I *could* just remap the fuelling, but this feels like cheating.

I'm also not sure whether the low MAF is caused by the fuelling, or is a root cause. The MAF in my car works fine and the car is running the stock airbox.

Reconnecting lambda for ECU sees closed loop to be operating fine.

Does anyone have any ideas or advice? A Subaru mechanic suggested it would be worth checking that the cambelt timing is all OK, as this could cause problems? Any other ideas/suggestions?

Thanks
Richard

 

possibly worth checking inlet manifold is not leaking/loose after rebuild.

how about a blocked injector? possibly over the failed piston on earlier failure.

 

Thanks - whole intake system was checked for leaks and is (now ) OK.

Do you think a single blocked injector could cause this? And do injectors get blocked (with 3 bar pressure behind them!)?

Can we just unplug them one by one to see what difference it makes?

Car has a lumpy idle at 17:1, and is not particularly smooth on WOT either, but I just put this down to a general lack of fuel.

Cheers, Richard