Tranz Zam

Heres a question that's been asked a thousand times, but I still seem to get different answers. I need a straight answer, the car isn't much fun driving right now and I want to put some miles on it!

Heres the run down on the car:

69 Camaro
02 LQ4
TH350W/2800 stall
3:08 rear gear
27" tall rear tire

Heres the issue:

During deceleration the car acts like its searching for an idle. It never dies, but searches hard for a second before it'll catch itself. I don't have a VSS. I've read multiple threads where people don't use them and are fine.

Now....

I've contacted a sponsor on here about getting my car dyno tuned. I've called twice with no answer, so I sent an email with my phone number and my info. I got a 2 sentence response saying that I need a VSS. Nothing more in depth, no phone call, nothing. Keep in mind these are people I'm trying to spend my money on. I contacted another local dyno shop and they said they can tune it but they cant get to it until late August.

Now the million dollar question: Can you dyno tune this symptom out or is it truly the result of not having a VSS?

Would a mail order tune from one of our sponsors get it done?

Thanks guys

redline2k

iTrader: (9)

Are you using electric throttle or cable throttle?

Tranz Zam

Cable throttle.

I've read that DBW setups can have issues without a VSS. On my T/A I'll be running one.

ls13ater

iTrader: (3)

89-95 truck 2wd 700r4 tail section and speed sensor, 4l60 reluctor wheel swap it out with the plastic gear, wire the sensor up bolt the tail section on and call it a day!

Tranz Zam

Right, but many people seem to run without one and seem ok. I'm wondering if its something in the tune itself that's causing the problem?

I didn't build this standalone harness and I don't think they left the pin for the VSS at all. I could pin it back in I guess.

ls13ater

iTrader: (3)

The timing map will never be right, it will think it's in park, plus gas milage will suck, hell over all performance will be down, it's alot easyer to tune with a speed sensor

Tranz Zam

Oddly enough the car runs amazingly well, it just acts up during deceleration. Gas mileage is great.

I'll check tomorrow and see if they removed the pin for VSS. IIRC its pin 50 on Red.

If I was to re-pin the VSS back in, could I use the Dakota Digital VSS they offer that installs between the speedo cable and trans? Its an 8k pulse generator.

garys 68

iTrader: (1)

I'm using the inline Dakota Digital with a manual trans. Works fine. They also offer a short cable not on their website if you have clearance problems with a direct bolt on.

Tranz Zam

I guess I'll end up wiring the VSS back in. I still don't get how someone with the exact same setup wont experience any issues, but I do.

BoostedLT5

iTrader: (1)

I ran the Dakota Digital VSS generator on my 87 swap and it worked fine. You have to tune the pcm with the correct signal and put in the correct pulses per mile so the pcm see's the actual speed the vehicle is traveling.

gofastwclass

iTrader: (2)

First, everyone has different versions of "fine." I wouldn't take someone's word that their car "works fine" without a VSS, they may simply have a higher tolerance for things like that. I have very little.

The root of the problem is the PCM needs to know the vehicle is or isn't moving. If the vehicle is moving, execute this, if it's coming to a stop or stopped, do that. The "this" and "that" have to do with idle speed and how the PCM adjusts for and predicts what the engine needs to keep it from stalling coming back to idle. Depending on your setup (cam, heads, etc.) this may be more or less exaggerated than a totally stock engine.

Since you now understand why this happens, the solution is to install a VSS sensor to vehicle detect movement. It does NOT have to be speed accurate since you aren't using it for shift points, it only needs to work for the idle routines. The simplest is probably a Dakota Digital SEN-01-4160 (or similar) pass through speed sensor. This will allow you to keep your mechanical speedometer in your 1969 Camaro and send a signal to the PCM that you're moving or not. Best part, the sensor is less than $45 from Summit.

Tranz Zam

I know what the VSS does, but most seem to not have any issues with the idle hunting around without one. I have no issue pinning it back in, was just confirming that the issue is in fact not having a VSS.

I still don't know why Slohawk never called me. I guess they have some serious cash flow coming in, they don't need mine.

redline2k

iTrader: (9)

No vss on a cable throttle might give you some issues when letting off the throttle and slowing down.

garys 68

iTrader: (1)

The result of no VSS is hit or miss. I've been told by others that theirs ran perfect without a VSS with manual trans. But on both my 02 and 05 I could reproduce the stalling issue almost every time when depressing the clutch and coasting to a stop.

Tranz Zam

Thanks for the info guys. I'll just run it and see what happens.