Contour Enthusiasts Group Archives Forums Modifications 3.0L Duratec The 3L is up and running!

Its not the injectors. Still seeing about 13.2:1 afr at WOT. The issue is at idle and decel. Maybe it is in the tuning down low, just need to add some fuel and mess with the idle values as Keyser mentioned.

That may be contributing but I wouldnt think that was the whole problem.

Misfiring at idle can be ignition, or O2 sensor bad (which you can watch them both and compare banks together at idle and cruise for diagnosis), vacuum leaks, wrong sized pcv, air leaking in after the MAF but between the throttlebody, and a few others or any combination.

I found that the basic idle and airflow stuff didn't need to be touched much if at all for a smooth idle to develop.
I ran mine at 750 or 800rpm idle all the time, can't remember which one I settled for.

Just don't forget to sit down with a program and watch those upstream O2s and compare them with the downstream O2s and cross-bank. That tells you a tremendous amount.

If you pulled your downstream O2s ( ) then you will have to compare cross bank but it is less effective.

The last 3L I built and finished on Sunday has a Brnespeed Xcal2 tune on it. It has SVT cams, 19# injectors, no EGR, No lower O2's, and gutted precats, stock SVT exhaust.

It idled like stock - EXACTLY and pullled very nicely indeed.

Yeah, good. Just what I'd expect. You don't need those other things for it to run good.

However;
Only bones I have to pick is pulling the downstream O2s when they don't NEED to be pulled, AND can be used as a backup diagnostic tool. They also don't set codes when you solder in the resistor and Capacitor from the MIL circuit....making them perfect backup sensors for tuning. Believe me, I used them a lot to diagnose/compare upstream downstream performance and bank to bank performance.
And pulling EGR when it has no effect on performance but if kept installed can help reduce Nox emissions.

I keep anything that doesn't hurt my automotive goals. Namely my priorities are set as such:
safety->performance->environment->OEM driveability->fuel economy

Well I've been fiddling with fuel and timing and I seem to have gotten the car running quite a bit better (stronger and smoother). I'm still having a problem with idle, though. I tried adding 2.5% more fuel (on top of the 10% I added before) through the MAF transfer function (#MASS/TIC at MAF counts <265) but the car started idling around 1400 RPMs, albeit smoothly. I changed the values back to original and the idle went back to the way it was (<750RPM and oscillating). I tried playing with the values in the isc_Neutral_idle_air table but it doesnt seem to be doing much to cure the idle problems. I guess I'll try to make greater changes on it.


BTW, can anyone give me some reference numbers on how much timing they've been able to add below and above the IMRC point? I keep adding timing and I don't hear any detonation, but I want to know how much I should expect to be able to add.

IMRC adds like 10-14 degrees above the base timing curve.

Without it you can probably add at least 5% top the base timing below IMRC and smoothly transitioning to upwards of 15% increase as you go above 4000rpm. That would be my guess for a car with no secondaries, NA on 10:1 compression. You of course have to adjust that based on your own compression ratio and/or boost/nitrous if applicable.

As far as adding fuel with your MAF, that is not the best way unless you have a MAF with an unknown MAF transfer function, i.e. you are trying to tune in the MAF.
If you want more fuel then add it to the base tables.

In your case, you may want to add a little bit then just drive it around an hour and let it learn. THen examine the fuel trims throughout the 'cruising' rpm range in 500 rpm increments. If you have anything outside +-5% in long term fuel trim then you can start guessing what the airflow was at that rpm and throttle positions, then add +-5% to your MAF in that area, then of course smoothly transition it to the areas where you didn't need to add any fuel.

Yeah I figured that changing the MAF transfer function wasn't the best way to deal with the idle issues I'm having, but the base fuel table only goes down to 1000 RPM. The long term trims were originally off by roughly 10-20% in low MAF counts so I adjusted the MAF transfer function to get them closer to 1. The car seemed to run a lot better after this.

Update on the idle issue:
I multiplied my original values in the isc_Neutral_idle_air table (from 1392 RPM and below) by 1.2 to see if the surging would stop, and it did seem to get quite better, but now at least half of the time I decelerate to idle, the idle hangs around 1300-1400 RPM. Sometimes it stays there until I accelerate again, and sometimes it will eventually drop back to my set idle of 750 RPM. When it goes to 750 RPM, it has never jumped back up to 1300-1400 RPM, though. Is there any other possible settings that could be making the RPMs hang, or did I probably just multiply by too much? The idle_speed_RPM_adder_for_ACT (inlet air temp) table is all set to zero, so it couldn't be that. However, the idle_speed_RPM_adder_for_ECT (coolant temp) table has different values in it, but the max value of 504 for added RPM is only when coolant temp is at -256 and -20, which seem to be impossible values to come across when the engine is running.

Here's what my isc_Neutral_idle_air table looks like after the 1.2 multiplication:

DSDRPM --- AIR_#/M
4095.9375 --- 2.0000
4080.0000 --- 2.0000
1792.0000 --- 0.9399
1392.0000 --- 0.9116
720.0000 --- 0.4922
520.0000 --- 0.3599
0.0000 --- 0.3242
0.0000 --- 0.3242
0.0000 --- 0.3242

Now this may be a stupid question, but I see that my target idle RPM of 750 is not listed in the left of the table, so would changing one of the zeros on the left to 750 and finding an AIR_#/M value for it possibly make the car idle stable at 750 RPM?

we should meet up and figure out this problem cuz I am in the exact same boat. I figure datalog at idle an see just how much airflow you are getting and then use some function to equate a new percentage of airflow at idle.

You guys shouldn't have to make changes to those tables to get it to run and idle.

I can't really help diagnose a problem like that without exact info like injector size (and what they were stock) TB size and what it was stock, MAF and if it is stock or not, type of manifold setup, 3L or 2.5L.

Just FYI, the basic 3L will run just fine on an SVT base tune, injectors and MAF. NO changes would be needed to get it to run.

If you took a non SVT 2.5L and converted to a 3L, I'd suggest you start there and use the values from someones stock SVT code and put them in over your base code. THEN change those things that are 3L related like engine displacement, injector size if not 19#/hr, and MAF transfer function if not an SVT MAF.

Above all, you must make sure you have no mechanical problem or vacuum leaks first. You must not have an atmospheric vent PCV system either. PCV air is metered into the engine and counted through the MAF so it must draw air after it has been measured by the MAF. THis air affects idle and cruise, only Full throttle it isn't used.