Need some help on a couple of things to get my car running perfect. Ive read and reread injuneers write up and others and some good friends came by today to show me a couple of things but I still need a little help with some issues.
First, when the car is cold (in open loop) it runs rich at part throttle, around 11.8-12.4 according to the air to fuel ratio gauge I have. Once warmed up and goes into closed loop it does ok at staying around 14.7 +-3. What adjustments can I make to fix this since in open loop it runs on set tables and isnt adjusted using the o2 sensors.
Second during deceleration after WOT the car shoots flames out the back. I believe this has something to do with the DFCO table. What should I adjust or do to fix that?
Third, During the hot weather days I get constant knock retard no higher than 5.0 WOT and around 0.1-4.3 at part throttle. Pulling some timing should help correct? I'm pretty sure it's only a degree or 2 is false knock and the rest is real. How much knock is acceptable or can be tolerable?
And sometimes after getting on it a little the car for .5 secondond wont do anything if I hit the throttle again. Is this a tip in issue and how can this be fixed?

Thanks

Ray

 

My "scanner" writeup was never intended as a primer on PCM tuning. There are some "simplifications" in there to make it useable as a scanning guide for the average reader, and those simplifications might confuse with regard to tuning.

Why is it a problem that the PCM sets a richer A/F ratio on cold start? That's generally required to keep it running smoothly when its cold - identical to the choke on a carbed setup. There has got to be cold start enrichment table in there somewhere, tied to the coolant temp.

 

The only reason it's a issue is because it's painfull to drive like that, mostly in low rpm's. Every now and then the car will cut off because of it. It's not really that big of a deal but if it's normal then it's cool.
Also another question. If it was hot outside all day and the car was driven alot during that time then I park the car and drive it 8 hours later after the temp has changed dramatically will the computer have to re learn which intern will make the a/f ratio a little off till it's learned?

 

is the screen out of your MAF ???? if so put it back in.

 

Good question. I'm pretty sure it's in but i'll check.

 

I agree with injuneer--the engine requires more fuel to run smooth until it is warmed up to normal operating temperature. You said it's reading 11.8-12.4 AFR during these "warming up" conditions...it is not uncommon to need AFR much richer than that (10:1 or even more fuel) on a cold start. I've read a couple books on EFI and both have pointed to this fact. If I were you, I would reset the tables that deal with cold start to factory specs...

My problem is, I've read these books about what the computer needs to do, but the tables they use have different names and parameters than the tables in TunerCat, so I am spending ALOT of time just trying to figure out which tables do what.

 

Update

The screen is still in. Also my last issue I think clears up alot for me. My o2 sensors where bad. I had been using ALOT of Torco fuel addatives in the past couple of weeks and I belive that was the death of my o2 sensors and spark plugs. That was the reason it was taking me so long to go into closed loop. Now with new sensors and plugs I warm up in 3 minutes +-45 seconds.
Also I pulled 2 degrees of timing and I'm still getting knock. I dont really want to pull anymore till I get the LT4 KM and see if it actually helps as much as everyone says.

 

The PCM does not need to "learn" anything based on ambient air temp changes. Ambient air temp affects the density of the air, and hence the mass flow rate. The MAF sensor is directly measuring the mass air flow rate. Even in cases where the PCM makes a VE based speed-density calculation, the PCM effectively calculates the air density using the IAT - so it still doesn't matter what the air temp is, as long as the sensor is working. The PCM knows the actual mass air flow rate.

When you start the cold engine, the PCM sets an enriched cold start A/F ratio, based on coolant temp. It then divides the MAF mass air flow rate by the A/F ratio to get the mass fuel flow rate. It corrects that mass fuel flow rate calculation, based on the learned long term corrections in Cell 16 for the idle condition, and in Cell 18 for the "load" condition. Then it sets the injector pulse width required to flow that mass rate of fuel.

Once the coolant warms up enough to allow the PCM to go into closed loop, the only significant changes are 1) the shift to the hard-coded 14.7:1 A/F ratio for everything except power enrichment (PE) mode (lets simplify and say PE = WOT), and 2) the use of the Cell 1-15 learned long term corrections. None of this is going to be affected by changing inlet air temps, unless your MAF sensor is miscalibrated.

 

Awesome. Makes sence. I thought it was the change in air that was making my car drive bad and throwing off the a/f but in the end it was the bad a/f sensors. Is there a write up anywhere explaining the cells in more detail and thier function in corilation to the rpm youre in etc? Couldve used it earlier when I was cruising at p/t doing 65mph in cell 18.

 

There is a table in my scanner writeup showing the stock cell RPM and MAP boundaries.

 

This is Open Loop AFR vs. Coolant Temp vs. MAF in tunercat.

 

If you can tune your car you get the same effect as the LT4 KM by alterning the knock sensitivity.

Increase the numbers in Knock Retard Recovery Rate vs. RPM and decrease the numbers in Knock Fast Attack Rate vs. RPM.

 

Good info. I have the LT4 KM but I'm still seeing knock on the scanmaster. My big question now is when trying to remove timing from WOT is there a special table or just remove as I would any other time?

 

What would be the optimal setings for both these tables?

 

Its actually Open Loop AFR vs Coolant Temp vs MAP. I took the first few rows (Cold Temp) and made them so that none of the AFR's went below 11.5. There were some stock settings that were as low as 7.5. My car would run pig rich at cold temperatures to the point where it would miss until it warmed up. This solved my cold richness problems.