SimonR Posted October 16, 2006 Share Posted October 16, 2006 Having just completed my engine rebuild (which included moving from 440 injectors to 800s), I was somewhat surprised to find that the only way that I can get AFRs in the 12-13 area was to add +ve values to the airflow adjustment table. I was expecting to remove approx %40 here – not to add %10-%20! I'm not using the correction factor or any additional injection map at the moment. ECU diags revealed two errors: 1/ Main Heated Oxygen Sensor signal Either: a/ Open or short in heater circuit of main heated oxygen sensor for 0.5 seconds or more or; b/ Main heated oxygen sensor signal voltage is reduced to between 0.35v and 0.70v for 60 seconds. 2/ No Number 1 knock sensor signal to ECM for 3 crank revolutions with engine speed between 1,600rpm – 5,200rpm. Note: Incurs max timing retardation. The knock sensor needs sorting obviously but as for the fuelling I’m guessing that the unhappy oxygen sensor is telling the ECU that the engine is running rich so the ECU is pulling fuel, which I’m then replacing via the Emanage map. Part of the rebuild was to go single so the sensor has been moved from its previous location to the downpipe. Could this just be that some wiring has been disturbed? The sensor was working fine before the engine rebuild. Any thoughts? Quote Link to comment Share on other sites More sharing options...
SimonR Posted October 16, 2006 Author Share Posted October 16, 2006 Thinking further about this, I believe that the sensor should be returning a voltage of between 0v and 1v. The fact that it is returning an (unknown) voltage in a narrower range than this doesn’t suggest on its own that it is returning a rich value – just that the sensor could be knacked, in which case it could be returning anything. Quote Link to comment Share on other sites More sharing options...
Alex Posted October 16, 2006 Share Posted October 16, 2006 Are you using a Wide Band 02 meter or just your stock O2 sensor? You won't get an accurate reading with the stocker. If you're using a WB02. I'd say; 1. You're fuel pressure is very low 2. You don't have 800cc injectors. 3. You are running global correction. Quote Link to comment Share on other sites More sharing options...
SimonR Posted October 16, 2006 Author Share Posted October 16, 2006 Thanks Alex. I'm using both the AEM wideband and the stocker. 1. So you think that the oxygen sensor is a red herring? Wouldn’t low fuel pressure show up at high revs only? This problem occurs at low revs. In fact, I haven’t ragged it at all and won’t until I have this problem under control. 2. Hmm. Any way I can tell without pulling everything apart? 3. Nope. Not according to the Greddy Tool anyway. Quote Link to comment Share on other sites More sharing options...
Alex Posted October 16, 2006 Share Posted October 16, 2006 You should be able to overfuel it massively...but if you take away fuel pressure you can open the taps as much as you like and nothing will come out. Best to speak to the trader and find out what the static fuel pressure is? Are you using an adjustable Fuel Pressure Reg...or the stock one? The AEM AFR gauge won't display beyone 11.3:1 by the way... Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted October 16, 2006 Share Posted October 16, 2006 Just where is the wideband sensor fitted now? if its to close the the turbo they can throw some funny readings. Quote Link to comment Share on other sites More sharing options...
SimonR Posted October 16, 2006 Author Share Posted October 16, 2006 Confused as to why my fuel pressure should be low. Never was before. Using a CW uprated Skyline GTR pump. I know about the 11.3 on the wideband, ta. It’s located about 5-6 inches behind the turbine but I don’t think there is a problem with that – it seems to be reading OK. If the AFR goes way outside the reading on the gauge the engine sounds and feels unhappy. If I keep it within 11-13 on the AEM it drives fine, so I think that the AEM is telling the truth. Hmmm. I see why you are talking about fuel pressure now Alex. Quote Link to comment Share on other sites More sharing options...
Ian C Posted October 16, 2006 Share Posted October 16, 2006 There is no way you should be adding airflow, the last time I heard this the fuel pressure regulator was before the injectors instead of after - not done that have you Fuel pressure could well be the issue, can you measure it easily? If the narrow band is shagged it'll read an artificial signal, so in fact you'd get even more fuel in so it's probably not that. Are you using the stock sensor or a 1v output from a wideband? No-one seems to know if the stock ECU likes the 1v output from a wideband, what it thinks 0-1v means is probably different to what the stock ECU thinks it is... I can have a look at your map if you want, see if there is a nasty tucked away in there? -Ian Quote Link to comment Share on other sites More sharing options...
SimonR Posted October 16, 2006 Author Share Posted October 16, 2006 There is no way you should be adding airflow, the last time I heard this the fuel pressure regulator was before the injectors instead of after - not done that have you Can you expand on that please Ian? I didn’t build the engine myself and I wasn’t aware that there was more than one way to set this up. Got any pics? I can have a look at your map if you want, see if there is a nasty tucked away in there?There's not much to see. No compensation and no additional injection. Just airflow adjustment. I wouldn’t know how to measure the fuel pressure but I’ll have a go if someone can tell me how. I’m using both the stock narrow-band and the AEM wideband. Quote Link to comment Share on other sites More sharing options...
Ian C Posted October 16, 2006 Share Posted October 16, 2006 Well, there is a right way (regulator after the injectors) and there is the slowdog way (regulator before the injectors) Your regulator should be after the injectors in the flow, otherwise all the pressure is between pump and reg, and drops off for the injectors! How lean does it go if you remove your airflow? -Ian Quote Link to comment Share on other sites More sharing options...
SimonR Posted October 16, 2006 Author Share Posted October 16, 2006 I gathered that was what you meant . What I meant to ask was can I tell by looking at it? I sounds as though it's obvious to those who know. If I remove airflow it goes rich, not lean. I can only get it idle properly by adding %20. I then take that down to %5-%10 up to 3,000rpm and that keeps the AFRs between 12-13. Knowing that it's unhappy I haven't caned it at all so I can just assume that as revs go higher I would drop that airflow down further. The odd thing is, the engine builder was idling it (roughly) and it was defo rich as there was a tail of black soot on the floor behind the exhaust. The previous map (being for 440s on a 1JZ ECU that was expecting 370s) had reduced the airflow already. Which is why I am mucho confused that I then had to add +ve values on the map (with 800s) to get it to idle and run at reasonable AFRs. Making any reductions in the airflow map had the AEM diving off the rich end. Yes, that's the grren bit for anyone who was wondering if I knew which was rich and which was lean! Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted October 16, 2006 Share Posted October 16, 2006 Don't know if its actually possible for it to work this way but could the input and output wires to the emanage of got mixed up? Quote Link to comment Share on other sites More sharing options...
Ian C Posted October 16, 2006 Share Posted October 16, 2006 Hang on are you saying if you put in e.g. -20% airflow it gets richer and if you put in +20% it gets leaner?! -Ian Quote Link to comment Share on other sites More sharing options...
SimonR Posted October 17, 2006 Author Share Posted October 17, 2006 No, sorry. I meant that I have to put a +ve value and then reduce it in order to lean off - but still +ve vlaues, only lower. These numbers are from visually monitoring the AEM, I haven't wired it to the Emanage yet. Quote Link to comment Share on other sites More sharing options...
Matt Harwood Posted October 17, 2006 Share Posted October 17, 2006 I've got my fuel pressure set to 20psi on vacuum at idle, and as such, my airflow adjustments are around -7 to -10 in the idle area. so if your FP is very low, that may explain the positive adjustments. I think you need to get the fuel pressure checked before you can do much more. The other time I experianced something similar, there was a large vac/boost leak at the gasket from lower runner to cylinder head. Hopefully that isn't what you have... Quote Link to comment Share on other sites More sharing options...
Alex Posted October 17, 2006 Share Posted October 17, 2006 Send Ian your map and get us pictures of your setup - this may enlighten us all. Quote Link to comment Share on other sites More sharing options...
SimonR Posted October 19, 2006 Author Share Posted October 19, 2006 OkeyDokes, I think that this is a fuel pressure issue. I didn’t notice this before (that’s what stress does for you) but the fuel pump that I have is noisy…very noisy. So much so that it is audible outside the car even on tickover. Everyone comments on it. That is until now. I have noticed this evening that the fuel pump doesn’t make a peep when the ignition is on (it used to make a lot of peep). With the engine started it whines a bit but nothing like before. There is a frig on the Soarer where you bridge two diag ports to make the pump run permanently at max voltage (usually used to diagnose faulty fuel pump ECU). With the pump running at max voltage it is audible again (just) and when the engine is started the AFR sits at 12.5:1 for about 20 seconds or so before it goes lean off the scale and the engine dies. This is with a sensible map that cuts the fuelling back to where it should be with 800cc injectors. For the short period that it does idle it sounds sweet. Best it has so far in fact. Before I rush out and buy a new Walbro, does this sound like a knacked fuel pump or am I grasping at straws? Again. Quote Link to comment Share on other sites More sharing options...
Alex Posted October 19, 2006 Share Posted October 19, 2006 I think it does sound like a fuel pump issue. The only other thing to try is a replacement fuel pressure regulator Quote Link to comment Share on other sites More sharing options...
SimonR Posted October 19, 2006 Author Share Posted October 19, 2006 Thanks. I feel better now. Edit: That was premature, but I did feel better for a while. Quote Link to comment Share on other sites More sharing options...
SimonR Posted October 22, 2006 Author Share Posted October 22, 2006 Replaced the fuel pump with the Walbro. Symptoms remain the same. Chatting to an Australian expert last night and he reckons that the noise from a fuel pump when priming is indicative of it working against pressure. Together with the fact that I have to up the pulse width dramatically just in order to get enough fuel to run, current advise (already above from Alex and Ian) is that "you don't have enough fuel pressure you pommy drongo". I've scrounged a fuel pressure testing kit so testing will resume when the rain stops. Quote Link to comment Share on other sites More sharing options...
SimonR Posted October 31, 2006 Author Share Posted October 31, 2006 'kin ell! The MAP sensor wasn't connected properly. Looked OK but hadn't clicked into position. Engine behaviour changed immediately. No fuel pressure problem after all. Only noticed this after spending £133 on a new Lambda sensor. Anyone want a used one? This situation probably wasn't helped by the fact that the No 1 knock sensor wire had come adrift. Quote Link to comment Share on other sites More sharing options...
Ian C Posted November 1, 2006 Share Posted November 1, 2006 I thought I heard a very faint "doh" in the distance the other day -Ian Quote Link to comment Share on other sites More sharing options...
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