Free Auto advice from a certified mechanic !

[scap99]

Sorta. It's a combination of different parameters that will help get you your throttle response.

I have zero experience with HP Tuners, only drove the truck while Charlie tuned my Silverado.

On the other hand, I have a pretty strong grasp of SCT and Ford tuning concepts. I didn't do my own tuning, but I did hundreds of logs and revisions with Erick over at Leading Edge Tuning on my F-150.

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[Savage20]

The backdoor tuning simply dials up the throttle position with artificial advance. It works and you can roast your tires at a whim but it's hell on fuel economy and transmissions, especially if you dial back the TM also. If only it were as simple as "Throttle Delay: Off" but it's not.

Black Bear is still a good recommendation. Even his mail-order tunes. On a stock 6.2 it's worth it IMO. It doesn't need to be any faster but damn that throttle delay is turrible.

 

[scap99]

The backdoor tuning simply dials up the throttle position with artificial advance. It works and you can roast your tires at a whim but it's hell on fuel economy and transmissions, especially if you dial back the TM also. If only it were as simple as "Throttle Delay: Off" but it's not.

Black Bear is still a good recommendation. Even his mail-order tunes. On a stock 6.2 it's worth it IMO. It doesn't need to be any faster but damn that throttle delay is turrible.

I think we're talking about the same thing just from the perspective of two uniquely different platforms. GM/HP Tuners vs Ford/SCT.

 

[Savage20]

These get good reviews also:

 

[TexMex247]

TM247 this is one of the best threads I have seen in a long time. Thank you.

Thanks for the kudos Sugar Land. I enjoy the problem solving challenges. It honestly helps me as much as the people in need. I learn a lot through this kind of interface, real world problems instead of hypothetical BS they teach in tech classes.

 

[UberDuper]

2001 Honda s2000

After driving the car for 30 minutes or so, I start getting very strong gas fumes from the under/rear of the car. I suspect evap canister is leaking but haven't been able to find any drips or wet spots or areas that look like fuel has run down them.

Also after 30 minutes or so of driving, especially in stop and go traffic, the car bogs in first gear under ~2500rpm. This has progressively gotten worse over the past two years. Now when this starts happening, coming to a stop idle will dip too low and become very rough. Usually recovers within a second or two. Recently it's started doing this and not recovering until I give it throttle. Sometimes it's fine after that, sometimes it dips right back down and does it again. The bogging has started to happen in second gear as well now and sometimes during 1 - 2 shifts, it feels like the motor stalls before I release the clutch and then it's like push start / popping the clutch. This is all, I hope, due to heat soak at the aftercooler (it's supercharged) and I'd just replaced the water pump with a larger bosch unit from a mustang cobra and flushed the system.

I haven't driven it yet and probably wont until I figure out the source of the gas fumes. It's bad enough that I'm concerned an open flame would ignite. I'm going to see if I can pull the canister off tonight to find out if it's full of gas.
I've been trying to figure this out for a long time. s2000 specific forums haven't been much help and every dealer/mechanic I talk to wants to bill me 1.5 hours to smoke test the evap lines and doesn't even want to talk about testing purge valves, etc. Car has never thrown a code so I'm highly skeptical that it's a leak in the lines.

Any thoughts would be greatly appreciated.

 

[Savage20]

Sounds like a faulty evap could cause both your problems - gas fumes and poor idle. Try disconnecting and plugging the evap vacuum lines. See if that fixes your idle performance.

When you remove the gas cap to get gas, have you noticed excess pressure venting? Or perhaps no pressure venting at all?

 

[UberDuper]

No pressure venting at all. My previous s2000 used to hiss nearly every time I removed the cap. This one, I can't recall it ever doing it. However, I've only filled the tank 5 or 6 times since I got it.

 

[Savage20]

Sounds like you definitely have an evap issue. No check engine light?

Your tank is venting to atmosphere right now, which isn't exactly the worst thing in the world. And it's not particularly dangerous either, IMO. Remember, up until a few decades ago, no cars had sealed gas tanks. They all vented to atmosphere.

 

[orbitup]

2006 GMC 5.3 211k miles. P0030 and P0053.

I replaced the upstream O2 sensor but the codes are still there. From what I've read it could be an ECM or wiring problem?

 

[UberDuper]

Sounds like a faulty evap could cause both your problems - gas fumes and poor idle. Try disconnecting and plugging the evap vacuum lines. See if that fixes your idle performance.

Would I just disconnect/cap the vac line to the purge valve? That's under the hood in a frustratingly difficult to find and reach place. Or the line at the canister?

 

[Savage20]

Their is a fault in your evap which is creating a vacuum leak to the motor, and venting your tank to atmosphere. If you don't have a CEL, I would just completely bypass the evap canister. Plug any vacuum lines to motor and vent the tank to atmosphere with a length of fuel line and a $5 inline fuel filter from VatoZone. With the extra length of fuel line you can place it in a spot where the fumes do not work their way back into the car. The bottom-rear of the engine bay is a great place to start, not the rear of the car as you might guess.

 

[Savage20]

Would I just disconnect/cap the vac line to the purge valve? That's under the hood in a frustratingly difficult to find and reach place. Or the line at the canister?

No I would not disconnect the purge valve. I would disconnect and plug after it. If you disconnect the purge valve you may trip a CEL.

Just make sure you know any existing lines are gtg. The vent line from canister to intake manifold may be what's leaking. The canister may not be bad at all, but a hole in the hose will cause a vacuum leak and fuel vapor leak.

 

[Savage20]

2006 GMC 5.3 211k miles. P0030 and P0053.

I replaced the upstream O2 sensor but the codes are still there. From what I've read it could be an ECM or wiring problem?

How long ago did you replace the O2S? Have you cleared the codes and they came back? Or they just never went away? You need to go through a few drive cycles for the computer to run the test a few times. It needs to pass a couple times before it clears the code.

I would disconnect the battery for 15min to clear the stored codes. If the codes don't come back, it's fixed.

 

[UberDuper]

The canister is at the rear under the tank. Plenty of s2k owners have to cap/delete the evap system when they run a standalone ecu. I'll go see if I can figure out which lines they're capping. I haven't been able to find a good description of which lines are which.

 

[Savage20]

Disconnect everything and plug it. Find the vent line that feeds the canister and vent it to atmosphere.

I used to have an S2000 but thankfully never had evap issues. Can't stand the damn things though...

 

[Savage20]

Just don't disconnect the fuel lines lol. Only the vacuum lines.

 

[orbitup]

How long ago did you replace the O2S? Have you cleared the codes and they came back? Or they just never went away? You need to go through a few drive cycles for the computer to run the test a few times. It needs to pass a couple times before it clears the code.

I would disconnect the battery for 15min to clear the stored codes. If the codes don't come back, it's fixed.

I did it months ago and cleared the codes. I don't think I disconnected the battery though.

 

[Savage20]

If you cleared the codes and they came back, then there's definitely still an issue. Disconnecting the battery is just an easy way to clear all codes.

 

[orbitup]

If you cleared the codes and they came back, then there's definitely still an issue.

That's why I'm asking the experts. I know how to turn a wrench but I suck at diagnosing.