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View Full Version : S14 Sr20 Ran Beautiful after retune. Now runs LEAN!

ghudson
03-17-2013, 02:13 PM
Let me start out with the info.

I just rebuilt my s14 sr20 and went to crank it up and a crazy amount of fuel would dump into the combustion cambers and flood my sr out immidiatly. The ecu was "said to be tuned" for this setup (550cc's, z32 maf, gt2860rs, fmic exhaust...) My setup consists of:

550cc's
z32 maf
gt2860rs
fmic
3'' exhaust
wiseco pistons
cosworth hg
arp's

So I wittled it down to the tune after checking all voltages(maf,tps) both at the sensors and the ecu (checked ect resistance at the sensor and ecu also)

I then proceeded to get Jason at e-mance to retune this bogus ecu and got the ecu back at WALA! The car started and ran AWESOME. AFR's were 14.5-15.0 idle, and 12.5 wot for the whole night. It was doing perfect! (I did overheat that day because my fan stopped working on my drive but i fixed it immidiatly and then went on to cruise the rest of the night with great AFR's)

Next day slowly the idle AFR's becae more lean (17.0-18.0) and the same with wot. I barley got into boost and let off due to the dangerously lean fuel mixtures.

Went on to check everything again timing, maf, tps, ect... And found out my pcv valve was allowing manifold vacuum to suck from the valve cover. That explained the lower and bouncing vacuum reading on my vac/boost gauge. The AFR turned to 14.7 now and it idles AWESOME. My problem is now the thing leans out horribly during wot (16.0-17.0) I dont have the pcv valve yet but i have blocked off the pcv valve hose off the manifold and I am just letting the valve cover breath to atmoshpere with no pcv valve.

I have looked at fuel pressure static and wot (45psi/55psi). I have looked at fuel pump volatge(12.6v). I have looked for exhaust leaks before the wideband o2 sensor. I checked the plugs and you can tell they were rich for a while but now they are slowly turning white (typical for running lean). I am so lost right now, I want to make myself believe that the fuel injector pulsewidth is off right now during wot-aka bad tune :( Its almost like the computer adapted/learned horribly and changed the injector pulsewidth within a day or so of running the car which seems IMPOSSIBLE!!!!

Any advice/questions will be appricated.
Tom N
03-17-2013, 02:22 PM
What fuel pump? Is fuel pressure rising with boost pressure at a 1:1 ratio?
Also if you rewire the fuel pump you will see around 13.5 volts at the pump with is much better than 12.x
ghudson
03-17-2013, 02:30 PM
Walbro 255. I have a new one coming in tommorow. I believe I will wire it with a relay since other guys have had great sucsses doing that. Still if that were the problem why would I have had such a nice ride the first night and now this. Also I feel like if the voltage at the pump were the problem I wouldnt be seeing 55psi at wot.

At this point ill try anything. Ill get back to you after i try it...
ghudson
03-17-2013, 02:55 PM
Well I be damned all the pump needed was charging system voltage (used fused jumper wires right off my battery). I just floored it in 1st and i was at 14.0 ish wayyyy better still not right but way better. I assume my new pump and some wiring will treat this. Thanks Tom N, I guess walbros do not like low voltage... Hope my sr20 is okay from all this nonsense of running lean :picardfp:
OrangeVirus1
03-17-2013, 02:57 PM
Well I be damned all the pump needed was charging system voltage (used fused jumper wires right off my battery). I just floored it in 1st and i was at 14.0 ish wayyyy better still not right but way better. I assume my new pump and some wiring will treat this. Thanks Tom N, I guess walbros do not like low voltage... Hope my sr20 is okay from all this nonsense of running lean :picardfp:

I'd still be careful and not go boosting around until it's fixed. 14.0 in boost is big time bad unless you are running E85/98
ghudson
03-17-2013, 03:03 PM
I know its still way lean. I was going to go putt it around and see what happens at full operating temp. Its way better and safer than 17.0 like it was though. I floored it up to 4k in my shop parking lot. Its still a fresh build so I cant rev it out of the sky. If it remains at that afr on my first test drive ill drive right back to the shop and wait for the new pump to come in...
Tom N
03-17-2013, 04:18 PM
The added voltage making a difference would tell me there's a problem with your pump.
ghudson
03-17-2013, 04:21 PM
I just went on a cruise (with the pump jumper wired) and the afr is around 15.0 average (during boost). Its the pump for sure. Good thing I ordered one on speculation. It will be here tommorow so Ill let everyone know.