Dead gas pedal trying to drive when cold started and not warmed up

[rel3rd]

6.0 engine, rear mount 76mm turbo, 80# injectors, 3 bar OLSD tune

Once warmed up a few minutes, it still seems slightly LEAN, (at tip-in) but at cold start, and limited coolant temp, if trying to driveaway after just a minute or less, it acts as if the car is not getting fuel...it's that lean. Like it won't take any fuel...or there isn't anywhere to get it from.

Never really noticed it before, but I also (almost) always let it warm up a few minutes before attempting to drive off.

What parameters should I LOG to help diagnose this?

I attached a copy of tune, but wondering if I do a cold start log, then what specific parameters should I include, along with the basic stuff?

[cobaltssoverbooster]

coolant temp
manifold pressure
afr wideband
commanded afr
loop status (your current file should force you to constantly remain in open loop)
stit
ltit
actual running airflow
iac steps

basically you need to check the afr error for cold starts. if the wideband is not tracking the commanded afr then you need to revisit the fuel table and make sure its perfect under full temperature. VE table effects the open loop cold coolant performance so it must be as correct as you can get it.
if it is then your only other option is to go into the open loop table and command different enrichment ratios to target a new cold ect afr. its kind of fudging the cold start fueling but adjust it to see if you can get the stumble to fade away at cooler temps.

you dont really have a way to fine tune the cold start. afterstart enrichment is a post cranking enrichment that ends very quickly. those settings wont help you after any runtime over say a minute of run time. that event is like 68 rotations long then it decays a small amount every 11 or so rotations until the event is over. its a fairly fast decay rate so shouldnt be your issue.

the idle airflow channels are to make sure your not stepping out of boundary on the iac, or the idle trims. they can effect the afr mismatch in open loop as well. keep in mind your idle trims will not be updating until 176*f is reached (adaptive idle rpm Min ECT- Value 176*F) if you want to use idle trims at colder temps you will have to modify the thresholds.

[rel3rd]

Thanks for the reply.
What puzzles me the most is how good it actually starts (cold), but then is nearly un-driveable, without any hint of cold driveaway functionality.

I'll try to get a cold start log done and amend the post.

[cobaltssoverbooster]

I'm going to guess it's a raf and fueling correction. We will see soon.

[rel3rd]

OK...Finally got a cold start datalog and also attached copy of current tune

[cobaltssoverbooster]

according to the log the wideband at full temp reports back roughly 12 afr when the ecu is commanding 14.68. you cant expect the ecu to properly run cold start coolant enrichment correctly if your afr doesnt track correctly when its warm. is the wideband calibrated correctly in hptuners?

[lukearmstrong1990]

you can try adding some fuel in with the open loop F/A vs ECT vs MAP table for when its cold.

I find engines with decent camshafts require some extra fuel to behave when they're cold. 12.8-13.0 for idle and cruise when they're cold seems to get me out of trouble. once they're at about 40-50 degree c ECT I find stoich AFR for idle and cruise to work ok.

also your idle is quite low for the colder coolant temps, does it still stumble if its idling at 1100rpm cold?

in regards to your lean tip in warm I'm assuming your converter flashes to at least 3500rpm on a hit? I usually set the PE delay rpm to 0 for anything with a converter flash of less than 4000rpm.

[rel3rd]

Thanks for the replies guys. I appreciate it...

according to the log the wideband at full temp reports back roughly 12 afr when the ecu is commanding 14.68. you cant expect the ecu to properly run cold start coolant enrichment correctly if your afr doesnt track correctly when its warm. is the wideband calibrated correctly in hptuners?

I thought I had mentioned that the car was evidently tuned strictly for WOT (on a dyno), and I've slowly been trying to get it RIGHT, mainly to help drive-ability. It runs great at WOT, but I am trying to dial in everything else. It's been hard since the stupid weather is 70 degrees one day, and 40 the next, sunny one day, raining the next...Since I don't dabble with the HPTuners on a daily basis, there's still plenty of stuff I don't understand, or that doesn't make sense to me...especially on this car, my first turbo car.

I've never been able to figure out how to make the "commanded" number show up as an accurate number. I'm 100% not commanding 14.68 AFR at all times. The BOOST ENRICHMENT reads correctly, and is always within single digit % AFR ERROR. I can't figure out how to make the commanded AFR read properly in a datalog, except for when in PE/BE.

It actually is MUCH CLOSER today, after moving the wideband sensor to AFTER the TURBO, which isn't like most turbo setups, since my turbo is rear mounted.

you can try adding some fuel in with the open loop F/A vs ECT vs MAP table for when its cold.

I find engines with decent camshafts require some extra fuel to behave when they're cold. 12.8-13.0 for idle and cruise when they're cold seems to get me out of trouble. once they're at about 40-50 degree c ECT I find stoich AFR for idle and cruise to work ok.

also your idle is quite low for the colder coolant temps, does it still stumble if its idling at 1100rpm cold?

in regards to your lean tip in warm I'm assuming your converter flashes to at least 3500rpm on a hit? I usually set the PE delay rpm to 0 for anything with a converter flash of less than 4000rpm.

I actually added a small amount in that table, which definitely seemed to help. I just added some more and will see how it acts on next cold start. I keep the car at my workplace, and after work, or weekends is the only time I can tinker.

I raised the COLD idle up slightly as well, and will report back as soon as I have done another cold start.

I only raised the PE delay because the car seemed to not want to "come up" on the converter when trying to build boost. It definitely helped delaying enrichment, but can probably be fine tuned a little for on the street. With the 2 step, I was not able to build any boost, but now can get 5psi, which as you'd expect bypasses any lack of converter flash as a trade-off.

When engine is WARM, the tip-in lean-ness is MUCH better, but still "feels" like it needs more fuel...comparable to a carburetor car with slightly too small of an accelerator pump nozzle, or a slightly lean transition from idle to main fueling circuits...if that makes sense? When cold, the other day, it was like if your accelerator pump wasn't even pumping ANY gas at all...


FWIW, I spent today moving my wideband sensor to the "DOWNPIPE", after the turbo, which on this rear mounted turbo car, means extending the harness about 8 feet. Car is blocked in it's spot, so haven't driven it yet.

I also re-installed both (new) narrowband O2 sensors. Due to the rear mount turbo, I run factory manifolds and O2's are in stock location, so no issues with being too far away from the engine, like w/longtubes.

What I noticed is, that the car IDLE was a little rougher, and made less vacuum, in CLOSED LOOP Speed Density, than when in OPEN LOOP SPEED DENSITY...

The only 2 things I changed, after adding the narrowbands, was ENABLE IDLE PROPORTIONAL parameter, and changed ENABLE ECT vs. IAT down to 130 degrees, instead of the 285* it was set at to keep it in open loop.

Are there other parameters that need enabling, or whatever, to take advantage of the closed loop functions?

[cobaltssoverbooster]

you have to transform the wideband channel and adjust the offset value to fix its target.
have you watched a setup video yet? https://www.youtube.com/watch?v=jMalD15mOg4&t=3s

[rel3rd]

Yes. My AEM 30-4110 was already predefined in the HPTuners software.

[cobaltssoverbooster]

Doesn't mean you don't have to perform a sensor transform to make it track properly. Just about every vehicle I have tuned with it's own wideband has needed the sensor to be transformed to track afr in hot the same as the gauge does

[rel3rd]

Maybe I'm not being clear?

My wideband is setup, exactly how the video that you linked above, said to do so, in the 1st part of the video.
Attached 2 pics---
Added Channel
MPVI Input 1
Transform

In fact the video even uses my exact wideband sensor as the example of how to setup a predefined wideband sensor. There was no mention of adjusting offset when using one of the pre-defined sensor transformations, that I could see/hear. Did I miss something? I attached pics below.

My wideband and commanded Boost Enrichment match, unless the (progressive) methanol is spraying 100%, then it drops nearly a full point into the mid/high10's at WOT, and 10# or more of boost

I just cannot figure out why the commanded AFR is always dead on 14.68, even if under load...Is that how it should be?


FWIW, the original issue of cold start driveaway is 100X better by slightly raising the colder temp IDLE RPM, and adding fuel to the OPEN LOOP F/A vs ECT vs MAP table. I basically added fuel to everywhere under 130 degrees of ECT and it seems to be OK now...or was this morning when I started car and moved it around the building and parking lot.

As for the narrowband O2 sensors....
What I had hoped to do was use the narrowband O2 sensors for cleaner idling and dialing in VE for CRUISE RPM or probably anything lower than 100kPa (NO BOOST). Like I said above, with the narrowbands functioning and car going into CLOSED LOOP SPEED DENSITY, the IDLE was much WORSE quality than with it staying forced in OPEN LOOP.