Car drives lean under 4k

[gofer]

I just looked at your mods list and can tell you exactly what the problem is, your injectors are too big for the SAFC without running a chipped ECU. Your looking at a correction of around -40% from stock to make up for those injectors which can be done using the SAFC but the problem lies with the timing advance. When you compensate that much airflow with an SAFC it leads to VERY aggressive timing advance that will kill your performance because you'll start to knock.

 

[Chicken Patty]

I believe I stated here somewhere and sorry if I didn't and causing you hell.

However, I'm on the stock 450's, AFC removed. Did that to troubleshoot.

 

[delta448]

Corey, he said he is currently on stock injectors and a chipped Eprom...

I am on stock injectors and fuel pressure is 42-43psi.

I am currently on stock injectors, so don't go by my profile.

Also, I can't get the logger to connect to my car with the EPROM, so I can't even see the TPS voltage or to see if anything funny would show. I tried changing the baudrate and all of that like it says on the DSM Chips website.

...my first thoughts are that the SAFC or the chip is set incorrectly, but like we both already mentioned, a log would be pretty valuable for diagnosing the issues here.

Edit: Posted at the same time. Since the SAFC is removed and the MAF has been swapped with no change, I'm leaning towards a problem with the chip tune or an ignition / spark timing issue.

 

[Chicken Patty]

It did it with my old ECU as well. So chip and afc are out of the question. I will do my best to get you a log as soon as I can. I'll have to swap ECU's again.

 

[Chicken Patty]

Could a boost leak around the TB or intake manifold area cause something like this?

If not, then I'd say spark or timing. I'm going to try and do a boost leak test today.

 

[delta448]

Possibly. That would be a good thing to check anyway.

Obviously, when you lose metered air you'll run rich and when you gain unmetered air you'll run lean. Do you only run lean under vacuum? Do you run really rich under boost?

I doubt that any post TB leak would be substantial enough to cause these symptoms without also causing a high idle, the ISC would have to be almost at it's full closed position. IIRC, I think EvoScan has the ability to log ISC steps?

 

[Chicken Patty]

Well since replacing the o2 the car doesn't drive lean anymore, just does what I described in the last few posts.

When I give it gas it does dip rich though as it enters open loop.

 

[Chicken Patty]

Just to, I'll dl a boost leak test today, then if problem persists I will swap ECU's to log The car and post the log.

 

[Chicken Patty]

Try to get your logger going again ASAP, it will help immensely in diagnosing your problems.

Things you could look into:
Double check that your Eprom chip is for stock injectors.
Check the knock sensor for any leaking goo.
How fresh are your plugs, are they 6's gapped to 0.028"?
Check battery health, also remember to reset your ECU after installing the O2 sensor.
Replace the fuel filter if you haven't ever.
Check plug wires.
Remember, misfires will read as a lean condition on a wideband.


How's the car act when you first start it and let it idle?
Fire right up or crank for 5+ seconds?
Purr like a kitten at idle or cough and sputter?
Does idle quality change with engine temp?
Stab the throttle at idle in neutral, what happens?

Sorry just saw this post, the only thing I would have to check is plugs/cables, and fuel filter.

The car takes about a second or so to start up an idle fines. The idle does not change when warm, just starts to dial the idle down as temp goes up till it's at about 750-800 RPM once fully warmed up.

 

[cookmeup272]

How long were you running lean for? Seeing as how they are cheap anyways, I would get a new set of spark plugs. Maybe run some 7's

 

[Chicken Patty]

Plugs have about 2k miles on them, they are 7's gapped at .025.

I have also tried a different set of plug cables, no change. I think it's timing related. Kinda does feel like if the car retarded timing, advanced, retarded, advanced and so on. Just doesn't feel like a smooth climb through the lower RPM's. I can tell it's not a misfire, it's like a quick loss of power then gain etc. Feels like timing being pulled/added.

 

[BIRDCLAWTSi]

Not unless you get the CEL on and the DTC code thrown for it on your logger or code reader.

The downstream O2 sensor is only there to make sure the catalytic converter is doing it's job. It's voltage signal is directly compared by the ECU against the front O2 sensor voltage to determine if the converter is functioning.

I would'nt say the downstream O2 is ONLY there to monitor the catalyst efficiancy, It also has an effect on LTFT. It will make subtle adjustments to ensure the catalyst is performing properly.

 

[gofer]

Sorry about the earlier post, I guess I missed the stock injectors and removed SAFC post but those 750's are too big to run with that SAFC when you put everything back.

Now that I know you've removed your SAFC are you sure the wires you reconnected at the ECU are making a good connection? More specifically the BLUE/YELLOW wire going into pin 90 better know as the volume airflow sensor signal? You must ENSURE that thing is making good contact since thats the only signal your ECU receives from the MAF to monitor the amount of air coming into your motor.

By all means do a BLT, thats basically a given whenever your DSM starts acting up, it should be done as frequently as oil changes if you DD your car.

I would'nt say the downstream O2 is ONLY there to monitor the catalyst efficiancy, It also has an effect on LTFT. It will make subtle adjustments to ensure the catalyst is performing properly.

I'm not trying to start a "he said she said" argument but guess what, the rear o2 sensor really is only there to check that the catalytic converter is functioning. The reason why people emulate it, and the only reason, is so the CEL goes out so you can see if you actually do throw an important CEL later on down the road. There are 3 different LTFT values (lo, mid, hi) and are only updated based on MAF sensor frequency.

 

[delta448]

Now that I know you've removed your SAFC are you sure the wires you reconnected at the ECU are making a good connection? More specifically the BLUE/YELLOW wire going into pin 90 better know as the volume airflow sensor signal?

Good call. I thought about that as well, I actually mentioned that same thing (although quite a bit less specific) in another former SAFC user's thread earlier today.

OP, use solder and heat shrink if you do find an issue there.

 

[Chicken Patty]

Well I found the issue, and did it stump me! It was the ECU!

When I swapped ECU's I didn't feel any difference, but I had the bad o2 sensor at the time so maybe that is why. The person I swapped ECU's with was having the same issue and he just told me today! The moment he told me that it hit me! I swapped back to my Original non eprom ECU and the car is perfect and so is my buddies car who had the eprom.

Any ideas? The eprom is socketed, but has the factory chip still in it. Car drives amazing!!!!!!!!!!!!!!!!!!!!!!!!!! I'll update the first post with the o2 sensor information and that it was the fix.


REALLY WANT TO THANK EVERYONE FOR THE HELP!