RomRaider

What does it mean if LTFT is running lean at low g/s (+10 ) as Running rich at low g/s means a leak?
I have Stock airbox with stock maf table using 650cc injectors (stock latency)

Previously had an intake manifold and tmic leak that caused my car to run rich. Intake manifold was under torqued. There was also no oem gasket on top of the phenolic spacer. As I didnt know, I just went back to stock latency and adjusted a bit by leaning out maf table. The higher stock latency never worked for me as it was too rich. I always had to compensate with maf table when maf table should just be left as is and not compensate for other fueling issues.

Here's a pic of the intake manifold leak. Almost impossible to see if intake is not removed. Pic shows new oem gasket on top already. The black soot is oil that has been spewed for almost a year now since Phenolic as installed without oem gasket on top. Could also just be improper torque during installation.


AVO tmic leaked at bpv bolt(the bolts went thru the thread and into the end tank) and possibly on the 2 1/8 sensor bungs. One is npt type, one is not and was loose as well.

Thanks to airboy dyno graphs for showing the inconsistency of my power graphs. This led me to investigate and found all this.

After 4 days of trouble shooting, last problem was to see a correction of +10 when it was -5 before. Finding that I have no more leak, I increased latency to 15% over stock and now it lines up.

It depends on where the leak is.
In vacuum:
A leak after the MAF, before the turbo will make you run lean
A leak after the turbo, before the throttle body is a toss up (probably rich)
A leak after the throttle body will make you run lean

In boost:
A leak after the MAF, before the turbo will make you run lean
A leak after the turbo, before the throttle body will make you run rich
A leak after the throttle body will make you run rich


If you're running lean at low g/s, it means a leak between the MAF and turbo or after the throttle body. The behavior in boost would let you know which it is.

My maf sensor harness had a loose wire issue. This made things very hard to diagnose. Moving a part of the wire would cause car to go very rich and have smoke at the back. We fixed it already and hopefully stays that way. There were 2 zip ties that compress the maf harness from connector, another one where the gray insulated tape is.

With the maf harness working now, we checked for leaks again.
1, Previously there was an up pipe leak (accordion) and stock was reinstalled.
2. Leak at BPV connecting to avo tmic. OEM gasket does not go flat with the tmic. Also bolts have already pierced thru the endtanks. Its an old avo tmic version. I reinstalled stock tmic for now to have that repaired. There are also 2 bungs for probles that are questionable in its seal.
3. Leak in intake manifold, there was no oem gasket put on top of the phenolic spacer (pic in earlier post). If you install Phenolic spacers, OEM gasket should be at stock location and another set on top of it sandwiching the spacers.

Everything is tight now, we've checked for leaks but found none. Car runs fine as well. The +10 I see in low g/s was corrected by increaseing latency for 650 cc DW by 15%. Previously was using stock as higher latency was too rich. The too rich condition coming from the leaks stated. Ive been tuning with leaks for quite sometime now, bad use of time! haha

I now see a -3 correction at idling (ac off) with this latency. Increased tip in a bit over stock to make it run as it should and also stablilize ltft now at -1 (0to 10), 4(10 to 40), 2(40 to 80),(80 up) . Im fine tuning maf in close loop just to get it closer but Im basically done.

Thanks for the guide below, pretty much sums up the experience. I was running lean in vacuum and richer in boost.

After doing a sanity check, I stuck with 17% over stock latencies with my 650cc DW. Injector comp and el comp were zeroed out. At idle, I got a -.78 learned correction. That's the closest I can get.

Whenever I turned on the AC, afr would hunt up and down and just wouldnt settle. Problem with lean LTFT A has been seen in previous days. Im pretty sure that its a leak after the Maf based on the info here. Checking hose clamps, it was just right there. Maf afta hose clamp to Turbo inlet was not tightened. Problem fixed, no more hunting afr at low g/s

Question: If there is a leak from turbo inlet, how will it show up in logs?

Great! It's always satisfying when you fix a problem and it clears everything up.
A leak between the MAF and turbo (IE: turbo inlet) will make the car run lean across the board, at all throttle positions.