Lean Running, Low Power
 

My UK 2000 Turbo is running very lean (see pics) and I've changed the MAF to a new genuine one and reset the ECU but it doesn't seem to have solved it. The car also sometimes has a slight misfire around 2k rpm on very slight throttle. Nobody can currently suggest much, and possible fuel pump suggested by one garage dismissed by another as being unlikely.

Car is standard bar a cat back Afterburner Vortex, was advised this wouldn't need a tune to be fitted and car ran fine for month or so with it before now. Battery was changed about a month ago, after fitting a large pothole blew the battery cable off, could this have damaged it?

https://cimg1.ibsrv.net/gimg/www.sco...5fe56d0888.jpg

https://cimg2.ibsrv.net/gimg/www.sco...7c552a547e.jpg

There is either too much air (air leak) or not enough fuel (fuel pump/injectors).

Air leaks should be easy to check. For fuel, you'd need to get some data logs taken. I presume that the garage just does dyno runs and not mapping? Would have thought that any decent mapper would be able to identify the cause quickly but I guess you don't have an ESL daughter board with which to map the car?

In which case maybe first replace the exhaust with standard if that is the only part you have changed (at least you can rule it out then).

Well they said on their website they did Ecutek remaps, so possibly. Its in with someone else now, but if not could always take it back for mapping/logs.

Thanks for your response.

If its not been mapped then its not down on power at all, they are 215 stock.

Guy who dynoed it said it was "very weak low down", and was surprised it made 240, he used to tune almost exclusively subarus.

But yes, it's not low on power except low down. AFR is my main concern by far.

If he's saying that take it elsewhere. Scoobs don't make bhp low down the rev range.

Anyway that's a bit by the by, the afr's are def a problem. Fuel pump could be a possible cause.

What ever you do don't drive it hard and keep it off boost till it's sorted, bad afr's will kill your engine. Unfortunately I'm not sure who's your way who's any good. Sure someone can advise.

I've already taken it elsewhere, as he didn't seem particularly interested in me being a customer, and I had said I just wanted it fixed, I'll spend whats necessary.

I've driven it to a new place which came recommended by my friendly local garage. My main issue is where I live, when I was at uni in Nottingham I was spoilt for choice.

Thanks for your reply though.

yeah plenty up here. fingers crossed they can sort it, failing that may be worth traveling

I'm not sure your down on power, looks identical to my graph from 10 years ago.

Also are you sure AFR was a measured correctly with calibrated sensor? Reason I ask is not many cars would run at all 23:1. That's past the lean burn limit of a lean burn engine. So I'd say the readings are out.

If my99/my00, hesitation/misfire at circa 2000 is common as they tend to run on the O2 sensor quite heavily at low rpm. Mine is bad about a minute after startup and goes away. They start using O2 sensor too early imo.

Just read all the thread, yes it is a bit low on the mid-range. I was just looking at max bhp.

Unfortunately no boost graph, so can't see if it's boost related or indeed AFR. It could also be something like cambelt out one tooth on one side (easy to do). Cam timing can have quite an impact on torque curve. It's very unusual to see torque so flat and power continously increasing

AFR doesn't look an awful lot different to mine but I'm no expert.

https://farm5.staticflickr.com/4457/...2765d283_b.jpg

The OPs AFR, are higher than they should be, but shape of AFR graph reasonable. Should be about 14 off boost going to 11.5 as boost comes on, and near 10.5 at the red line.

Higher than 12:1 at max load is a cause for concern, however..
I was just questioning if measurements were valid because 23:1 probably would be too lean to fire at all. Trouble is a misfire or leaking exhaust etc can all affect validity of results.

Thanks, looks like mines spot on then, UK 2000 with green panel Filter, PPP Intercooler Pipework, PPP ECU and Decat downpipe with the centre cat still fitted. Charlie at SRR did say it was fine.

Hey all, thanks for your inputs. Turns out another diagnostics place have just discovered low compression cylinder 3, around 80psi, although all of them are low and after testing suggest that the AFR is fine and probably a bad reading.

He recommended if I get heads done this will only increase pressure on the bottom end and that will go too :(

Time to start looking for a new motor

Thats a shame, although now you mention it, not the first time I've seen an engine down on compression not make the mid-range power, but make power ok at redline. I suppose you don't know if its rings/bores/headgasket or valvetrain related. At least you've found it before it gives up when you're driving it. If you're able to do it yourself a cheap ebay USB borescope might help you find out if the cause is bore/piston related or not. If its valve related it might drive fine for years...

Shane: Indeed your AFR looks bang on the money for Subaru/PPP (un-remapped) ECU.

If it wasn't a Horizontal engine you can stick a bit of oil down the bore and see if the readings come up (probably rings if so), but no idea if it works on these.

The guy at the workshop said unfortunately the MAF slowly getting dirty (even though it was brand new in March :( ) will likely be the reason for it to begin running lean and the high temps most likely unseated one of the valves or something similar. Even though he could do a leakdown test he didn't want to waste my money because he was certain its valve related. It will run perfectly fine as long as I don't cane it (never did really) but it will run without going pop, sounds awful though.

If anyone knows where is good for a rebuild or who sells decent engines let me know!

What air filter are you using out of interest?

Please don't shoot me but for a while it had K&N. I know now why people don't rate them... :(

I'm saying nothing :thumb:

I've known for a while that it isn't good for it, and should have acted earlier. I had promised to replace it with a cosworth dry filter come next oil change, which coincidentally is about a month away and is definitely not at the top of my to do list anymore.....

A paper filter from ICP is less than a fiver. And cleaning the MAF takes a matter of minutes.

I had cleaned the MAF following instructions on here. And yes, I think the soon to be 4 figure bill is enough of a reminder I f***ed up..