engine dies just off idle

[leonpiper69]

So I have been fighting something. 2001 LS1 w/ 4l60e


I have played with the idle and no matter what when I put it in drive the idle drops a little like it should and then if I take off reaaaallly slow it will die and stall out. I have to two foot it to keep it running at really slow speed. If I am at a red light and take off normal with at least a bit of acceleration it runs fine.

I just installed a painless harness and there is a connection for "gear indicator switch". I have never hooked anything like that up. the old harness was a truck harness I modified. Never hooked up a gear indicator switch or a brake pedal switch for the TCC.

Could the gear indicator switch cause an issue with it dying just off idle?

Any help would greatly be appreciated.

Or does anyone see anything odd in the tune. This was tuned 15 plus years ago buy someone, no idea who back out in the midwest. The engine does have a decent cam but I don't know the exact specs and a 3600 stall converter. Stock injectors. Stock LS1 intake and throttle body.

5-7-21 tune no vats new idle.hpt

[SiriusC1024]

Probably that dip in the Low and High Octane base spark. Give it slight throttle and spark drops to 12*. That's dumb. See 800rpmx0.08g by 1400rpmx0.12g? Bring the spark back up inline.

The High Octane table definitely needs fixed. Since those two base tables are based on a 2002 Corvette A4 file go ahead and copy from one of those tunes on the repository. Note that the Fuel adder of the 2002 Corvette file give more spark with enrichment. For now leave that table zeroed anyway. Do bring over the adders and multipliers for IAT and ECT, though.

Knock settings are ok.

Tuning VE is a huge component of good drivability. Verify MAF.

PE needs that 1.179 copied across. Idk why it's set to lean out.

After you're sure fueling is correct go back to spark adjustments.

Yet another hacked MAF-only tune. So hacked that they forgot to force High RPM Disable in the Dynamic tab. Sorry about what that tuner did. Not all of us midwest guys are that way.

[leonpiper69]

Thank you I will look at those.

This thing was tuned by a shop back in around 2007 or so I think. Not making excuses for the shop (I don't even know who it was) but I imagine back then a lot of people were still figuring things out and some just opened shops winging it.

I bought this engine tuned and running in a car. Then helped remove it from said car when the friend that owned it went to a 408 with a glide.

Some of the things you mentioned are a little over my head but I grasp most of it. Luckily the car is in paint jail for another month or two plus so I have time to learn some more before making any changes. But I will now do a bunch of reading.

Thank you

[Alvin]

This sounds like a swap.

GEN 3's do not trim the idle past being pretty much completely stopped.

When you don't have a P/N switch with a swap.. The desired idle airflow (LTIT and STIT) removes airflow while idling in P/N. It's easier to idle in P/N, and doesn't require as much air to idle. Then when you put it into gear, it has no idea this happens, and has to learn back up. This takes a little bit of time. In that time you could have a low idle / stall condition like you describe. If the P/N switch is hooked up there will be two separate learns between park and neutral. There will also be an anticipated bump in airflow as you put it in gear.

Without a log this is just a guess.


Oh you'll need the brake pedal switch hooked up also or else you might encounter "brake torque management" which sucks all the power away as you try to leave. You will also not get a TCC lockup. This wire needs power while not on the brake. Kinda confusing.

[edcmat-l1]

A data log would tell more about what's going on than the tune file. And make sure to check your fuel pressure. That's the first thing you should do. Ideally you should have a fuel pressure gauge on it you can view while driving.

[bk2life]

I have played with the idle

have you started here?
https://forum.hptuners.com/showthrea...e-(w-pictures)

[leonpiper69]

This sounds like a swap.

GEN 3's do not trim the idle past being pretty much completely stopped.

When you don't have a P/N switch with a swap.. The desired idle airflow (LTIT and STIT) removes airflow while idling in P/N. It's easier to idle in P/N, and doesn't require as much air to idle. Then when you put it into gear, it has no idea this happens, and has to learn back up. This takes a little bit of time. In that time you could have a low idle / stall condition like you describe. If the P/N switch is hooked up there will be two separate learns between park and neutral. There will also be an anticipated bump in airflow as you put it in gear.

Without a log this is just a guess.


Oh you'll need the brake pedal switch hooked up also or else you might encounter "brake torque management" which sucks all the power away as you try to leave. You will also not get a TCC lockup. This wire needs power while not on the brake. Kinda confusing.

It is a swap into my 71 chevelle. I know I would need the brake switch for lock up. But I while I planned on hooking up the brake switch I will also hook up the gear indicator switch. I was told it wasn't needed as it only puts the display on the dash on a factory setup (which I was unsure of).

As far as torque management, it has no trouble leaving a few hundred feet of rubber at 30mph so I don't think that's an issue. But will still be hooking it up eventually.

[leonpiper69]

A data log would tell more about what's going on than the tune file. And make sure to check your fuel pressure. That's the first thing you should do. Ideally you should have a fuel pressure gauge on it you can view while driving.

can't log it until I get it back from paint in a couple months.

[leonpiper69]

have you started here?
https://forum.hptuners.com/showthrea...e-(w-pictures)

I will def check that out thanks. Don't know how I missed that one. I read most of the stickies before posting.