Running rich - advice please

[grim_d]

Hi all, I have recently installed an aem wideband and the car seems to be running quite rich. with 11.5 at idle and rich down to 10 or below at WOT.

When I got the car back on the road it was running a bit rich due to knackered det sensor so replaced that, this then caused the car to run lean, judging by the plugs, this is what prompted me to get a wideband, at the same time I also wired the fuel pump directly from the battery as I suspected the original wiring wasn't up to the task and was causing my lean running.

It would seem it was but now running rich and struggling to track down the cause.

So far I have checked..

Timing - ok
TPS - ok
Plugs look ok if a little sooty as to be expected.

Boost/vacuum leak, have checked everything over and I am confident I have no significant leak, pull 0.4bar vacuum at idle and 0.6bar off throttle.

Fuel pressure maybe too high although on the stock FPR, changed for another one but no change, waiting on some fittings to come through to test it.

Have a new coolant sensor on the way just in case too, although im not getting any fault codes and the fans come on as normal.

I am wondering if when it was mapped it was done so to account for standard wiring on the last car and now that the pump is delivering fuel as it should that the injectors are putting too much fuel in? I don't know much about mapping unfortunately.

Something else of note is that on startup I usually have the give the throttle a little blip or it will stumble for a few seconds or even stall, probably not related.

Any advice appreciated

 

[fubar andy]

Check injectors are not stuck open like mine were

 

[campbellju]

MAF sensor not reading right? Rather than buying bits with these problems, you're better off hooking up with another owner ans swapping bits until you find the issue or rule out those parts. Starting with an AEM was a good move

 

[grim_d]

Check injectors are not stuck open like mine were

How can I check? I think they are ok though as it was running lean before on standard fuel pump wiring. Plugs are dry and the exhaust doesn't stink of fuel

MAF sensor not reading right? Rather than buying bits with these problems, you're better off hooking up with another owner ans swapping bits until you find the issue or rule out those parts. Starting with an AEM was a good move

I'll give it a test, Was thinking about re earthing it anyway for good measure.

 

[Jon Olds]

My AFR probs were caused by boost leaks. I made a blank for each end one with a tyre valve in and pumped the system up with a footpump.
Jon

 

[grim_d]

Cheers John, going to get a leak tester from a mate. Where were your leaks? All my intercooler piping is sealed up pretty tight, unless the intercooler itself is burst.

Checked afm, 1.25v at idle and has been grounded through the chassis so no problems there by the looks of it.

 

[Jon Olds]

1st 90 degree out of the IC
Jon

 

[grim_d]

Leak tested today, at least until the tester gave way,

The turbo outlet hose had a hole in it, so changed that, made no difference. Still mid 10, low 11 are on idle.

No significant leaks elsewhere, I'm sure there will be some tiny ones about.

Fuel pressure is 3.2 - 3.4bar at idle, a little high, enough to cause it to be this rich? rises to about 3.7 when revved. Standard FPR.

Not sure what to try now or if the next logical step is to have it mapped.

 

[The Doc]

Your AFR gauge could be out, which is very common and some cars need to be rich at tick over due to cams......mine is in the 11s at tick over so it maintains a steady tick over......and your engine has the same cams.

 

[grim_d]

The sensor could be out, although it has only done about 20 miles, seems redundant to have one if they are so unreliable.

I'm really just concerned about bore wash. I'm glad to hear yours are similar at idle, what are yours at WOT?

 

[PobodY]

How close to the turbo is it? - I'm sure there was some issue with having the sensor too close; the instructions on mine says something like 36" from the turbo (although I can't find it at the moment).

 

[The Doc]

Mine drops to 10.2 or so, people keep on about bore wash and petrol smelling of fuel etc....these are some facts of forged pistons and race cams, high lift and long duration on cams causes reversion in the inlet hence the need for more fuel at tickover as because the valve is still open when the piston is rising and the turbo is producing no positive pressure it is forcing the ingested charge back out of the engine, overlap on cams will cause the ingested charge to go out of the exhaust as well.........hence high readings at tick over! As long as the engine sounds happy ticking over it is, and as for oil smelling of fuel that in the majority of cases shows that the engine and oil is not being run hard enough and the oil is not getting hot enough to evaporate the fuel in it and that the pistons are not expanding enough to fill the bores, basically forged pistons and cams on a road car that you pop down the shops in is not a good idea, this is why manufactures use cast pistons for faster piston expansion and better sealing and mild cams, now oil should be run at 100+ degrees as this is when the oil and water vapour evaporates. Now I know the people keep on about mapping and bore wash etc but this is not the case at all.

 

[grim_d]

How close to the turbo is it? - I'm sure there was some issue with having the sensor too close; the instructions on mine says something like 36" from the turbo (although I can't find it at the moment).

The sensor is 36" from the turbo, I followed the installation instructions for it, it is just in front of the bulkhead.

Mine drops to 10.2 or so, people keep on about bore wash and petrol smelling of fuel etc....these are some facts of forged pistons and race cams, high lift and long duration on cams causes reversion in the inlet hence the need for more fuel at tickover as because the valve is still open when the piston is rising and the turbo is producing no positive pressure it is forcing the ingested charge back out of the engine, overlap on cams will cause the ingested charge to go out of the exhaust as well.........hence high readings at tick over! As long as the engine sounds happy ticking over it is, and as for oil smelling of fuel that in the majority of cases shows that the engine and oil is not being run hard enough and the oil is not getting hot enough to evaporate the fuel in it and that the pistons are not expanding enough to fill the bores, basically forged pistons and cams on a road car that you pop down the shops in is not a good idea, this is why manufactures use cast pistons for faster piston expansion and better sealing and mild cams, now oil should be run at 100+ degrees as this is when the oil and water vapour evaporates. Now I know the people keep on about mapping and bore wash etc but this is not the case at all.

Interesting reading, The engine is happy ticking over when warm, it's a bit lumpy when it's cold and can take a little blip on cold start to get it to settle but after that it runs great.

That settles my mind though I would still like to have it checked on the dyno simply because everything has been tinkered with recently, but that's a big spend that will just have to wait.

Thanks for the information.

 

[The Doc]

Well there is nothing wrong with the mapping then, if there was the car would not run correctly, now if you have checked your spark plugs they should be a very light grey verging on white colour on a hard run, tick over will not tell you much as explained why before, the reason they should be a light colour is so that they are running the correct tempreture to burn the carbon deposits off of them.....now colours can vary depending if any addetives have been used ( castrol lead replacement can give them a brown tinge) but you don't want dark colours and you don't want burnt white with grey aluminium flecks, have you got a picture of the plugs?

 

[grim_d]

I didn't take the plugs out today,

Here is one from before which prompted me to do the pump wiring mod and get a wideband.

Here is the most recent one I have which I think was after the mod and after a bit of a run, they do soot up black if left ticking over as to be expected

I'll take it out for a good run over the weekend and check the plugs after that.

 

[The Doc]

Top looks about perfect ( hard to tell on the net as colours change from computer to computer ) , bottom is a little rich as it is not burning deposits of the electrode insulator.

 

[grim_d]

The thought the top was quite lean. I'm not 100% sure on how much of a run it had before the 2nd picture but the only change between the 2 pictures was the fuel pump wiring.

 

[The Doc]

Nope, did you run the car hard or just tick over between the two pics?

 

[The Doc]

If the car was running way to lean, the plugs would melt the electrodes , you would get misfires , there would be grey flecks of aluminium on them from detonation.

 

[grim_d]

I'm not sure how hard the car was driven between pics it was about a month ago. If the weather holds out over the weekend I'll give it a good belt and check the plugs and take it from there.

Having said that before the first pic the car had a good run but not a hard run, a very sedate run over about 40 miles, only going full boost once.