Rich at idle lean at cruise

[Josho]

I'm currently trying to work the kinks out of my sr that just got tuned by Enthalpy. I have basic mods, cams, gt2871, z32, 850 inj. Ect.. I have a wideband and I recorded the reAdings to see what you guys think. FPR @ 32psi idle. A/F @ idle: 11.1-11.4 @ cruise: 14.5-15.0 @ wot: 12.5-13.1. The reading is constantly bouncing but it stays between those numbers. What are some things I could try to get the correct readings?

[Josho]

Could this be a maf problem?

[marks14]

The Cruising AFR looks okay. I was having a similar problem with it being rich at idle < 10 , then really lean in boost 15-16. It actually ended up being a faulty BOV, you could check the BOV out if you have one.

[Josho]

Bov is new. Ill check it out though. Any other suggestions

[Croustibat]

If it is not a double piston BOV then it leaks at idle, no matter what you do or how brand new it is. Recirc it and problem solved.

12.5:13 is too lean at WOT too. If you run high octane pump gas, better be in the low 11:1 If using e85 , 12:1(what a gauge set to work with regular fuel will display, it is not the actual AFR) is good. Maybe this could be caused by a faulty fuel pump, but if you have a newish one it should be ok, even if it is an ebay knockoff.

I am surprised your tuner did not see that problem coming though. Any MAF engine will have trouble with a non recirc BOV / non double piston BOV.

[Kingtal0n]

You have enormous injectors so even a slight miscalculation on the rom's part could cause a very rich idle. It also stands to reason that perhaps < 1ms (.001 seconds) of injector on-time is a problem for those injectors, so you might just be stuck at that air fuel, unless you raise the idle speed to give the injectors more head room.

You do need to examine extensively for a boost leak though, any tiny leak in the plumbing will cause the maf to read more air than the engine is actually ingesting which may cause that symptom.
It is common for blow-off valves to hang open at idle (in fact most are designed this way on purpose)- those types of BOV should be recirculated.

It is very difficult for a mail order rom tune to have a perfect idle A/F ratio with large injectors. You may need to try a piggy back just to attempt a correction-
If you notice as you lean the mixture out it begins to miss and stumble/pop/backfire then it may just be the injectors have reached their minimum on-time.

Also, of course, many other things can affect idle A/F displays, such as exhaust leaks, fuel puddling and engine "loading up"(due to cam timing)
If you cannot seem to correct the issue, check the plugs every 1500 miles, if they are always looking white/tan then I would not worry about it anymore.

And last if you are using 93 octane pump gas, you need to shoot for 11.5:1 air fuel ratio during WOT. With those injectors it should not be a problem, and you have no reason not to.
To avoid using a piggyback try raising your fuel pressure first. It may even help your injectors deliver consistent fuel at idle, it may improve your idle conditions.

[Croustibat]

These injectors are not that big, i have seen correct idling with 1600cc injectors on these engines. With correct A/F too.

boost Leak problem,
fuel pump problem,
tune error

my bet is on the first two, which did lead to the third. You cant/should not tune an engine if it is has boost leak/fueling problem.

And i sense the boost leak is from the BOV. Try blocking the bov hole and see if problem is still there.

[Josho]

Ill check everything out real well. I'm gonna try adjusting my idle and fuel pressure first. Thanks guys

[Josho]

Well the bov checkout ok. I checked for vac leaks, didn't find any. I even broke out the water bottle with dish soap and sprayed all ic piping and vac lines. A problem I did find was a fuel leak coming from the fuel pump fuel out line. I replaced it and its running a little better. Now if I'm driving and I come to a stop, my wideband will read 11.8, the it will creep up to around 14.6, then fall back down to around 12.0. I didn't have time to adjust the fp or idle since I replaced the fuel line. But something tells me that is not my main problem.

[Croustibat]

I still think it is a bov problem. As said before, all BOVs that are not with double piston design leak when there is a high vacuum (like at idle). This is not a problem when it is recirculated, but it is when it vents to atmosphere.

Either recirc it, remove it, or use a double piston design (expensive). Try removing it to see if the problem is solved (dont forget to block the hole ).

I would not change base fuel pressure too. If your fuel and timing maps where done on the current setting, dont change it.

edit: forgot about some things... it could be lambda related if still used, or ... weather related. If the engine temp is less than 80°C, the ECU will enrich (not to that point though)

Getting a 14.7 / 15:1 idle with a Z32 maf and big injectors is not easy though. The Z32 maf lacks low flow resolution, and your injectors may have a high latency... Do you know what it is ? If it goes higher than 1000µs, not sure you can do anything about it.

[anarchyperf]

What brand injectors are you running?

[Josho]

JECS 850cc inj