I took my car into a local tuner shop to pull some fuel as my AFRs were running in the 10s even at idle and cruising. Naturally my mileage is **** and I wanted to get some fuel pulled at idle, and other non-boost conditions.

They tuned it and when I picked the car up the idle was 15-16 AFR and cruising was around 14.4. After the car warmed up though, everything went back just the way it was before the tune. PIG RICH. Also after warming up, my IDLE went up to 1600rpm (from 1000). For two days, the idle was 1600 and my AFRs were still rich, so I took the car back in.

The tuner readjusts everything while I'm driving and the car is hot. We pull some more fuel, play with idle until it settles at 950 stable. At this point, idle is 15AFR and cruising is good too. Later that day, after some boosting, everything goes pig rich again.

It has been a week and when I start the car cold, idle is nice and lean, cruising is lean, until the car warms up and then everything is back to 10 AFR.

I think it is something to do with coolant temp, I notice when it hits 180 or 190 (even with the oil still low) that is when the change in AFR occurs.

Any ideas?

Car:
mild port
PFC
stock twins at 13psi
hks twinpower
Stock FUEL
no emissions stuff
etc.

 

The FD should run pig rich when it detects something wrong with your intake air sensor. It's like a fail-safe. I've had this happen with the stock ecu, but I don't know if that happens with the PFC. I would suspect that is your problem if the PFC knows to richen the car with a faulty intake air sensor.

 

K I'll look into that.

Anyone know if that can happen with the PFC?

 

If the IAT fails, the PFC may dump fuel.

It should be pretty easy to detect - your Commander IAT reading should be '--' or something like '-45C'.

I would do a full sensor check. Did your tuner disable O2 feedback? If not, you may have a faulty oxygen sensor.

 

I don't have the commander. I'm thinking about just replacing the IAT and O2 sensor. They are old, it can't hurt.

 

you can probably get a commander for the price of those two items and eliminate the guess work.

 

Or you could get the datalogit software and really see and understand what everything is doing. . .as well as learn (it's not too difficult) to make all those adjustments yourself

 

If the water temp and fuel temp sensors connectors were swapped, it would go richer.

 

Could it we O2/FB?

 

Yeah that is a thought. Just plug in my own laptop and save a lot of money on tuning, lol.

Anyway - I missunderstood my tuner and he actually knew what was causing the rich condition. There are 3 maps on a PFC tune and the "Coolant Temp Compensation" map was still set rich so after the temps warmed up, that map would overide the base fuel map.

Should be an easy adjustment, I just have to find a couple days to leave the car, becuase they need it cold and hot, then cold, etc.

 

You can change those settings yourself with a commander, easy fix. The highest temp on that table is 80C = 192F, and the standard setting is 1.0 (no change). Not sure why the previous tuner did that unless it was to protect the motor under warmer engine temps. That would be one way to richen fuel across the entire map on a hot day, on the track, etc.

I sure hope your tuner is NOT charging you for multiple visits In my experience, that particular map does need some fudging to cover the engine operating temps, but that's why I think you should get a commander so you don't have to keep going back to someone to fix something simple like that

 

No, I paid for 1 tune and it was like $300. No more charges as I bring it back.

I don't mind some added buffer for hot days and track events, but it is at 10 AFR even at idle. Sometimes, when already hot, the car won't even start easily because it is too rich (starts then dies immediately).