Lean AFR due to fuel pressure regulator vacuum pipe
 

Hi all again.Yesterday i went for a ride in my 2003 Impreza Sti Jdm which has a 2.1 stroker engine with mahle 2618 pistons running the vf37.I gave it some 'beans' and sustained wot changing gears at approx 6,500rpm even in 5th gear and when i looked at the afr aem gauge at some point i was seeing 13.2-13.5 AFR's at wot while my engine was tuned for 11.5's by Bob Rawle.I dont know for how much long it was running like that as i only saw the afr gauge in a random check as normally i look at the rev counter and the road when im driving a little spiritual.Afterwards I drove slowly back home to investigate the problem which at first i thought it was the fuel pump or the aem wideband sensor.I know for sure that last week it was good so this has happened recently.When i went to investigate the problem i found that the fuel pressure regulator vaccum line had come undone from the inlet manifold nipple.I managed to put it back and put 2 tie clips in place to hold it still.Went for a quick ride and bingo 11.5 afr's at wot and was feeling more powerful than before.I know that the 2618 pistons can take a little detonation/abuse + i have some loose clearances and running a 'small turbo' compared on what they should handle, but is it possible that i made some kind of damages?The engine is newly built and has covered only circa 1,400miles,It is not making any weird noises(my previous stock jdm engine died due to detonated piston by a crappy local tuner so im familiar with that noise it made) and its working perfectly as usual with no smoke etc.Later today when i get back home from work i will try a compression test just to check if i have a different readings than when it did about 5 weeks ago(using same gauge).I dont know if this helps but its the easiest thing to do compared with an engine dissesembling.What do you guys think?thanks in advance.

Just check the plugs & oil. If it was run like that for a long period of time then I would do a little service.

I see.I will take a look at the plugs as i will be doing the compression test and see if they have the electrode 'pitted'.The oil level is the same and oil temperature didnt go up to 95 degrees as i have an alarm on the gauge preset to 97 degrees.The oil was changed about 200miles ago.I dont think it was like that for a long period as last week it was fine though i went to the drag strip and did about 6 runs but no standing starts.

Plugs may be fouled & oil may have got contaminated with fuel?

Had a simlar lean running issue due to bad mapping & plugs were fried, plus oil was stinking of fuel!

Ok i will check the plugs and oil though the oil looks to be in perfect shape.thanks

Forgot to add that im running 20%methanol and 80% 90 octane local unleaded fuel.

You said with the vacuum pipe disconnected it was running an AFR of 13.2 which means it was running lean not rich, oil should be fine.

Yes that's what i thought but i checked everything up.I know the compression test would not give the full picture on what damages i have made(if any) but at least i get to know roughly if there's a difference regarding compression.

If you had low compression the engine would run rough or misfire. How does it drive now? is there excessive smoke coming out the exhaust?

No the car works perfectly as usual with no smoke etc.Im only worried for the sustained wot on 4th gear.I dont think i have made any damage but i dont trust my luck lol.

:thumb:

Theres nothing wrong with your car stop worrying lol, your being over critical.

I have just completed the compression test,3 cylinders are the same as they were 5 weeks ago but 1 cylinder has decreased by 6psi.All readings were made when the engine was cold and there is only about 4% tolerance between the highest and the lowest cylinder .Is it something to worry about?thanks