I'm tinkering with a new copy of TTS Datamaster in my '87 using a Moates ALDL/USB cable and Dell laptop powered from an inverter. I disabled every timeout and screen saver setting I could and set up a datalog of my morning commute (covering the screen with a towel so I wouldn't be distracted while driving). The capture stopped after 20 minutes & there are a bunch of "Having problems linking" messages in the log file. I just spoke with one of our IT guys (who is a serious car guy) & he verified I'd addressed all the computer timeouts.

While driving I'd noticed the MPG display wasn't functioning and toggled the display mode switch (instant, off, average) a few times. Could this have disrupted the scan/communication?

I'll try it again tonight, keeping my hands off the switches, and probably answer my question. In the meantime, have any of you seen this or have any other ideas why the communication may have been disrupted?

 

Now have recorded two complete commutes.

Toggling the mpg mode switch has no effect, so that theory's busted.

I noticed this morning the battery voltage drop during engine start was too much for my inverter causing the PC to switch to battery power & disrupt the com/usb port communication with Datamaster. Datamaster was unable to recover from this & had to be restarted before communication with the USB port could be reestablished.

So, at this point, I suspect yesterdays problem was either due to a battery voltage fluctuation or inverter related issue. I probably should have got the $80 inverter rather than the $30 one. The packaging on the cheap one claimed 160Watt but inside stated that was the peak power and the average was only 120W. The more expensive unit (sorry I don't have brand name info with me) clearly stated 150W average and 180W peak on the package. That should have been a clue, eh?

Bottom line, what I have is adequate, but I'll probably have to live with occasional drop-outs. I think I have enough computer battery life for a full commute so, with a few adjustments to my power settings, I may be able to skip the inverter entirely.

Thank you for your attention.

 

With the late 80s Vettes when you hook up to datamaster it disrupts the gas mileage and trip/ miles readings until datamaster is unhooked and the car is shut off and on a few times. Mine does this also , so its not just you..I don't understand why you can't just run your computer off the battery for the time you datalog. Most computers will run for at least 1 full hour off there regular batterys and with a larger battery you can get up to 2 hours run time..If yours doesn't last this long its time for a new battery.Adding the inverter is just putting something else into the system that may cause problems.....WW

 

Agreed.

My computer's new to me (gift from a friend) so I'm not too sure of it's usefull battery life & figured an inverter would reduce the number of things to worry about, d'oh!

I'm chasing down a code 32 that only seems to be triggered when I start the car for my commute home. Thus I need to scan in the evening and figured I'd datalog both commutes just for grins & to get a feel for how the car is operating.

The remaining fly in the ointment is Datamaster doesn't appear to report the EGR diagnostic switch state which is what I need to see!!! Well, that and the fact it seems to be impossible to actually buy a replacment EGR temperature/diagnostic switch.

 

Datalogging probably won't tell you anything other than there's a 32. Since it's at startup, suspect a grounded harness between the switch and ECM or a bum Switch which should be open until there's exhaust flowing by it (and if there was, it wouldn't start or it's going to run like crap). Verify there's 0 volts at the ECM pin meaning something is grounded - it will have the reference voltage if it's not. I'd then start by disconnecting the harness to see if the 32 goes away. If not, ohm the wire between the connector and the ECM pinout (you will have to disconnect the ECM side since it's a reference voltage). Post what you find out for further help.

 

The FSM says to use a scanner to find out what the ECM is detecting on circuit 9XX (I forget the number just now)---i.e. whether it thinks the switch is closed or there is a short. Unfortunately Datamaster doesn't report this.

But it does seem like it's the switch or a ground. It only seems to happen when the ambient temperature is warm (>50F) so I'm thinking it's the switch. The combination of weather and weekend business have kept me from popping the hood to investigate any further. I have been looking for a replacement switch, but after a few searches here and looking around on the web, they apparently went out of production in 2009 and I haven't found any.

The car runs (and idles) fine so I can take my time. I'd like to resolve it before my next smog check though.

 

You may want to look for the Tube too - I've never been able to get an old switch out without ruining the Tube (And then there's the insulation with the Replacements seemingly lasting less than the original - my original was shot before the warranty was up). I would check around the connector since it's plastic and rests up against the intake or if they get moved around they can hit the tube or end up in contact with the tube connector and melt which can cause the short to ground.

 

Thanks for the heads up. I'll pop the hood and give it all an inspection. If it looks like too much of a pain in the patooshka I'll just pay my mechanic to deal with it. He's checking his contacts now to see if he can find the switch. (Used to be a $20 item, d'oh!)

 

I enjoyed getting 60+ mpg on the way home last night... LOL

 

D'oh! I had to re-read my own post to understand why.

If you switch from average to instantaneous MPG and head down a good hill you might see 60+ MPG, I did coming down the Tehachapi pass driving the Vette to it's new home.

What I don't understand is when I reset the MPG it diplays 12.8MPG. I'm not sure if that's a default or maybe lifetime average.

 

I couldn't tell you on that one.

I plugged up the datamaster for the first time last night and noticed the instant MPG showing some crazy numbers, then I read your post.

 

12.8 is the default when your sitting still not moving and reset it. If your running down the road when you reset the mpg it could end up being anything...WW

 

Thanks, that's the answer I was hoping for. I was a bit alarmed when I first saw that number!!!

Having lived with the car a few months I'm getting 18.5 to 19+ mpg in mixed highway/street driving. I average 20+ commuting on the highway during the workweek, but the average takes a hit driving around town on the weekends.