Jmsomm

Just got the car running with long tubes, and a BTr stage 3 NA cam. Car has +28 short term fuel trims at idle, seem to drop down to around +7 with some rpm. Had the car tuned through mailordertuner. If I’m correct, that’s way to high isn’t it? Car runs ok, just smells really bad and burns my eyes. Worried about hurting the engine.

aaronc7

Yes that quite high. Possibly running a little lean at idle if it's hitting the STFT limit. The smell and burning is just more a normal result of the cam though IMO.

Need to have a tuner look at it to fix the airflow and/or fuel models to get things back in check. Wideband highly desired to dial in the PE (high load) operation as well.

Jmsomm

Alright, I’m surprised it’s not throwing any codes, should it be? The trims seem to drop to about +1.9- -3.6 when I give it some throttle.

aaronc7

I forget exactly the limits for the "system too lean" or too rich codes. But if the tune disables Long Term Fuel trims this may in effect disable that feature/diag trouble code from functioning right.

If it's a MAF or speed density tune, it's entirely possible for it to be really lean in one spot and fueling fine in another. Lot of guessing/speculating until we get some logs or read the PCM and see what's on it--> all goes back to taking it to a trusted tuner.

benflynn

Your tuner didn’t finish the tune, tho most turn off short term cause they are usually wrong at idle with big cams. Mine runs better with them off, once tune is right.

jfigus

Can you log using HP Tuners? What are the STIT and LTIT values? (Long/short term idle trims) These will be in grams/second. It's an adjustment to the idle base running airflow value. If the net value of STIT + LTIT is a large number, you'll need to adjust your idle base running airflow.

What is the MAP reading during warm idle? You'll need to dial in the VE table. There are only a couple of cells in the VE table that will be in use once the engine is warm and idling. You can raise the VE value in those cells to bring the fuel trims down.

Finally, I would disable EVAP purge while tuning idle. This can be disabled in the special functions dialog under HP Tuners while the engine is running. When EVAP purges, it adds fuel to the intake and this affects this fuel trims. It's hard to get a good read on fuel trims when the EVAP purge is cycling on/off.

Jmsomm

I do not have HP tuners at the moment. Removed the MAF and cleaned it really good, pulled the plugs to look at them. All 8 have quite a bit of carbon built up and smell a little like gas. They all looked the exact same . Car has been running on jackstands so primarily at idle. Could that cause it?

phils C5 vette

You may have an unmeasured air leak. The car thinks its lean, and adding fuel.
if you changed injector, the data may not have been entered correctly

are the long term fuel trims on ?

Jmsomm

long term fuel trims are off. Used a smoke machine and found zero vacuum leaks. Car is still on stock injectors. Got it out for a drive today and it runs great. Just rich at idle.

benflynn

My idle trims are wrong with tsunami cam, runs perfect in open loop

tblu92

I would be more concerned with the "long term fuel trims" and not the STFT's
At training we were taught not to look at the STFT's at all
+28 is a lean condition but you will only get a LEAN code if the LTFT's go beyond either plus or minus 25%
Agree I would check for a vacuum leak or a post MAF airbridge leak