jlee29

iTrader: (5)

My 240sx Ls1/t-56 is getting horrible gas mileage 15mpg on the highway, seems slightly underpowered (but runs strong, no misfiring or backfiring), at the DMV my HC (emissions hydrocarbons) reading was through the roof limit 200 and mine was 2,000. There is no smoke during acceleration or start up.

The car runs the "Painless Perfect Engine Management (Speed Density)," and wiring harness with all new sensors.

The motor has 70k on it (only mods are Lt's and LS6 intake) and runs like nothing is wrong, perfect idle. (although it does seem to have less power than my other 240sx Lsx when it was stock)

I have tried: New Plugs, Oil change, Sea Foam intake and fuel, PCV.

What I think may be wrong: Injector malfunction , 02 sensor malfunction, tuning issue...

85MikeTPI

iTrader: (9)

Tune or something non-stock in the engine that the tune can't deal with.

arthropraxis

Vacuum leaks, how does it idle?

jlee29

iTrader: (5)

I am very skeptical on the Painless System as the culprit, but the motor is bone stock
It idles normal, with an occasional 100 rpm fluctuation, it has all new vacuum lines and all appear sealed, unless the manifold has a leak.

85MikeTPI

iTrader: (9)

Were you the orig owner of the 70k LS donor motor? How do you know it's all stock? Cam, injectors, ported heads, etc. can all be done by a previous owner. A speed density tune is only as good as the data used to create it. Put a scanner on it and monitor you trims and all the other sensors.

LS6 used larger injectors, did you use injectors that came with the intake or inform painless you were putting the intake and injectors on when they were creating the tune?

arthropraxis

My engine has a LS6 intake, it had leaks at the gaskets and PCV hoses. It got better mileage after sealing that up and ran noticeably smoother, I thought it was good before.

jlee29

iTrader: (5)

Thanks guys, I did not own the motor originally, but the previous owner said it was stock, so technically I can not say its stock for sure 100%. It does has the crummy 853 heads. I may take the intake off and injectors and put on the one I have ran on my other motor that I know.are good, working, and correct size.
The problem with Painless computer I have to buy there scan software/cable to check anything (I own Hptuners FML and I can't use it)
I own both size ls1 and ls6 injectors painless is tuned for both with simply connecting an extra ground wire to switch between.
If all else fails I am going to make my own stand alone harness go back to stock ecu and wiring.

Efi69cam

running lean will cause the HCs to go up. What were the CO readings?

I dealt with this on a home tuned vette- needed to fatten it up to reduce HCs. Seemed counter-intuative.

jlee29

iTrader: (5)

The exact emissions numbers are
HC(PPM) 1982 (Limit 220)
CO(%) 0.91% (Limit 1.20%)

I double checked the part numbers on the intake and injectors it does infact have ls1 injectors and an Ls6 intake manifold. It's possible that when painless tuned them for the two different size injectors that they had the Ls1 injectors with the Ls1 manifold and the Ls6 injectors with the ls6 manifold and maybe that is my issue? I'm going to swap to the Ls6 manifold and injectors and remove the (Alternate fuel ground) to change the injector map for the 29lb Ls6 injectors.

jlee29

iTrader: (5)

I also have a Wideband on my other 240 if I can't get it straight, that is an option to take it off and get some A/F readings.

redtan

iTrader: (5)

That should be the first option. You need to figure out exactly what sort of fueling your car is seeing, so between that the the O2 trims you should be able to get an idea.

jlee29

iTrader: (5)

Thanks guys, Ls1tech never lets me down. I'll pull my wideband gauge out of my other car and get some readings to post up.

jlee29

iTrader: (5)

I swapped to the clean Ls6 injectors today and found that the stock ls1's and rail was very gunked up. It seems to run slightly smoother but still has some power left on the table i think. No MPG results yet. I may need to clean my corvetter filter/regulator or get a fuel pressure gauge on the rail to see if its funtioning properly.

Rail
http://www.flickr.com/photos/55665137@N05/8212147316/
Ls1 injector
http://www.flickr.com/photos/55665137@N05/8211062335/

BuffJoeyD

iTrader: (2)

I would be lookin at cleanin up all that setup. Id be interested in how the tank looks as well- high HC, id be lookin at plug gap ( and plug type )

Its not a tuning issue. Its most likely lack of proper tuning. As well as that nasty situation you got going there.