k20 Running Lean at all engine speeds, help!


JohnTurbo

Well-Known Member
Joined
Oct 3, 2013
Messages
942
Hi folks,

Took the exige to the Dyno to get it looked at.

I will dump graphs in here when i get to a PC.

In short though the AFR was about 15 all through th rev range and over 15 in the power band.

Otherwise the graphs were similar to another k20 with RBC manifold saved on the Dyno, though making less power - 200.5 vs 235. The line was basically offset downwards due to the unfavorable AFR.

What could cause this as it must have been right when it was originally mapped?

All I found was the fuel pressure reg vacuum was not connected (but i believe this is for idle typre speeds) - there is also a solenoid on the TB with a disconnected vac line, I don;t know what thats for.

:-(
 
What ecu does your car run? Is the vtc system active? No fault codes up etc?
 
Other than a possible tune or ecu issue.

Fuel pump? Although I'd expect that to get worse as fuel demand increases.
Stuck or sticky injector?
I do doubt that though.
Pressure reg issue? Usually you'd see fuel spitting out of the vacuum port if the diaphragm was split.
Map sensor perhaps?
If the ecu is seeing a lower load than it actually is then it will be fueling for that lower load, I'd expect drivability issues though.

Tbh I think I'd start at the tune/ecu and go from there.
 
Its on DTA s60. VTC active.
Fuel pressure reg is aftermarket...I guess this is my first area to investigate, but its not old.

Map seems to be responding as i would expect.

RBC inlet and bespoke exhaust, no cat.
 
OK. Aftermarket as in adjustable? This could well be your problem if it's been adjusted too hold too low a pressure.
 
Although from 15s to what mid 13s afr? Is quite a jump for a regulator to cause
 
Ah right. I'd be surprised if that's the sole cause of your issue then. Although I wouldn't rule it out and I'd get an Oem one (or whatever they are tuned on)
 
I'd definitely get a vac line run to the pressure reg if you haven't already, see if that makes a difference or like Jesse888 said try and change the reg out for an oem one if that's an option

was there a vacuum line that should have been connected that wasn't, causing a leak?

Other than that it's a hard one to diagnose without playing around with the map to see if it's just a lean map to start with, you got any friendly tuners nearby to take a quick butchers?
 
Adding a vac line to fuel reg won't help the matter. 1st step would be to verify fuel pressure and after that you will need to plug into ecu to verify all sensors are reading correctly. If fuel pressure checks out ok I would guess it is faulty TPS sensor, on the DTA ecu the "load" axis is TPS based.
 
Bought a dta lead off chris (tuner). He would have looked for me but we couldnt find the ECU. Ive found it now and plugged in. - Chris was wondering if the tps was not reading correctly - but if I graph the output and jab the accelerator it does read 100%.

Have ordered an inline fuel pressure gauge off ebay.

Thanks Vtec6k..your hunch was correct last time (lean on b18c due to fuel pump).

Thanks everyone else too.
 
Does The DTA have closed loop enabled and a target lambda set?

My old dta had this option, to run full time closed loop.

If the sensor is reading richer than it actually is it will lean itself back to what it thinks is the target
 
So fuel pressure is 2.7bar.
Reg is a weber 3 bar unit. Neither of those seem right (3.5bar?) so I wonder how long its been wrong.
 
that does seem on the low side, not much more to give either if its only a 3bar unit
 
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