LT5 hesitation...
 

... which Marc says ALL LT5's have...

I still have a small amount of water in my tank - hardly noticeable, and it will all be out after a few more drives.

But something came to me here this morning, related to the residual water. When backing uphill, up my driveway, she struggles. Warmed up, it's not noticeable even.

But backing uphill cold, RPM's are probably right about 1.6% throttle. Which is where DataMaster showed the hesitation, and LOPE - from 1.6 - 2.4% TO. LIKE a vacuum leak, if throttle linkage is HELD at that throttle position... Like the pulsewidth / gas isn't sufficiently calibrated @ that throttle position... http://www.zr1.net/forum/images/icons/icon5.gif

Now I have a little water still mixed in. Even LESS gas, exacerbating the problem.

The water isn't the issue, because it will shortly be spent.

The issue is the pulsewidth calibration at that TO %.

Any thoughts here on increasing the pulsewidth at the 1.6 - 2.4% TO position???

Re: LT5 hesitation...
 

Good question huh guys...

Anyway here, the water is gone. Took a ride, backed up the driveway, smooth as silk again - except for that light 'bump' at 1.6% - same as usual, that Marc says every one of 'em has...........................

http://www.zr1.net/forum/images/icons/icon5.gif

With a stick, you're well over 2.4% TO, when you let in the clutch. This automatic has no choice. A stick won't see it unless you're in the garage.

Re: LT5 hesitation...
 

What torque converter are you running?

Re: LT5 hesitation...
 

It's a Precision Industries piece there Hog - pretty stout piece (for $9C, it oughtta' be).

2300 stall...

Re: LT5 hesitation...
 

Very nice, the Vigilante is a high quality piece.

Since this occurs when the car is cold, sonds like you'd need to do some Open Loop tuning.

Does the A/C compressor loading affect this issue at all. Better with A/C On vs. Off?

Whats your timing advance doing at the 1.6-2.4 TP opening?

Re: LT5 hesitation...
 

Does it Closed Loop too there Hog.

Only the left-over water in the gas tank exacerbated the glitch, because fuel calibration I think is not correct for that TO % range.

DM log (CL) showed SA @ about 16' as it hit 1.6 TO, and then when it exceeded 1.6%, up to 2.4% TO, it bumped up to 25', then up and down, until TO % exceeded 2.4%.

DM video is here, lope starts at 2:53, as TO hits 1.6%

Marc looked at it when we talked about it, AT LENGTH, and he said they'll all do it. I can't argue with him on it - he knows better than I do.

I'm not satisfied tho'...

Re: LT5 hesitation...
 

The C/L Threshold for Idle is 1.95% TPS, right in between your 1.6-2.4%. So the ECM is straddling idle and open throttle operation. That means its also jumping between C/L idle spark advance and open throttle tables. In addition, it sounds like a bit of a lean surge which the BLM look like at idle. A log or spreadsheet would be better to review.

Re: LT5 hesitation...
 

What's up Dom...

I haven't figured out how to plot / grid values in Windows; much less Linux; still reading there.

Just needs a little more thought here, and my CPU stays pegged ;)

Re: LT5 hesitation...
 

DM must have a way of creating a .txt file from the scan.

Re: LT5 hesitation...
 

Like i suggested before- if it has a lean stall tendency stock, definitely program in some 'pump shot' in the low rpm range to see how it affects your auto equipped car.