Engine running lean

[Ozzy]

Car seems to be lacking a bit of power when floored, and occasionally there is a sort clattery noise which sounds like its from the top of the engine. (For example, coming off a roundabout, say 30/40 mph in second, floor it and you get the above scenario)

It's had new plugs, leads, dizzy cap, rotor arm. But the original plugs look exceptionally clean, very very light brown, so it does look as though its running very lean! It's an EU2 supersport, with the original Rover sealed ECU, so I gather theres nothing can be done with this. If it is fuelling, is there anything else to look for, maybe sensor etc, that could cause lean mixture? I disconnected the Lambda sensor, but this didn't seem to make any difference on the road whatsoever. So does anyone know if anything else controls fuelling/mixture? Also, theres a vacuum pipe from the plenum which goes to the ECU via a small black oblong box mounted on the bulkhead. Does anyone know what this box does?

It's not misfiring or anything like that, all temps are normal. it's also had a new fuel filter, and the fuel pump primes as normal, but I think if there was a problem with the fuel pump, it'd be more noticable/serious.

Bit baffled at the moment! Anyone experienced something similar?

Oz...

[simon_h]

The black box is a water trap.

[revilla]

When you floor it, it most likely runs open loop and ignores the lambda sensor anyway. There have been a couple of instances on here recently I think where ageing and worn fuel pumps on K Series have been struggling to keep up the fuel pressure at full power, resulting in lean running at the top end. Other than that a problem with the fuel pressure regulator or I guess a sensor like IAT or MAP feeding wrong info to the ECU may throw the mixture out but being EU2 I'm not sure what your options are for disgnosing the problem as it won't talk OBDII. Just be careful because the noise you describe is probably detonation and will eat pistons in no time, so take it easy until you get the problem sorted.

[TomB]

I'm investigating a missing 10-15bhp from my engine after mapping, and the mapper thinks it was leaning out at higher engine speed due to lack of fuel. My pump is 20 years old, and as the car was supplied with a 1.4 and is now a 1.8 with TB, I'm going to replace the filter, pressure reg and pump, then get it remapped.  

Im probably going to get this pump fromt Merlin Motorsport

https://www.merlinmotorsport.co.uk/p/fuel-pump-for-caterham-7-motorsport-upgrade-pump-itp144

Which will give plenty in event of further power upgrades in the future.  

[Ozzy]

Thanks, some interesting info.

Can you tell me where the fuel pressure regulator is located? Is this the gadget on the top of the plenum. Also, what do you mean by detonation? 

I know where the TPS is, and obviously the Lambda sensor, but apart from that I can't see any other sensors that might be fuel/air related, so I'm assuming this is all controlled from the ECU with a standard map?

Oz.

[revilla]

Fuel pressure regulator is the little round disc on the front end of fuel injector rail where the fuel return line comes out. Intake air temperature sensor will either be a green sensor screwed into the rear side of the rearmost runner of the inlet manifold or may be combined with the manifold absolute pressure sensor (although it was only combined on EU3 engines) which on mine is a small rectangular box attached to the top front of the plenum. My car has the alloy plenum, if you have a plastic plenum the MAP sensor may be in a different poition on the plenum.

[56]

I'm experiencing similar symptoms of a clattery noise under hard acceleration (1.6 K). Sounds like it's coming from the top of the engine on the intake side. I can't replicate it when stationary. I got carried away over the winter and made quite a lot of changes but it seemed like the noise started when I changed the exhaust manifold (from standard short 4-1 to a 4-2-1 modified to keep the standard silencer). I only gave it a quick test before stripping it down again to change the pistons and head (upgraditis) but I believe the noise was there at that point. I initially thought it must be an exhaust leak or the primaries touching the chassis but I've triple checked for leaks and reassembled with high temp silicone. No sign of anything touching the chassis and it sounds more like its coming from the intake side rather than exhaust. So now I'm considering the fuel system. I've tried different injectors and a different fuel pressure regulator with no improvement. I guess there's no easy way to check the fuel pump is working properly in order to rule that out?

 

Would be good to know if Ozzy managed to sort his issue out but it looks like he's no longer active here.