Cant get Tunerpro RT to connect once engine starts

[EagleMark]

I haven't used serial cables in so long I forget how to check them. With USB if you plug in even a pass through cable (not device) it will show under Printers and devices in windows 7.

Since it is when running and you found electrical noise... Is this a conversion? Look at EFI harness. Is it anywhere near spark plug wires, coil or distributor cap? Or a arc from ignition somewhere? I think you found the issue. 40,000 volts near an EFI 5 volt signal does cause interrference.

[Fastmax32168]

I am having extreme frustration with this issue. My car has been together for over a month and I cannot datalog it so I can tune it. I have checked all of my grounds and made sure nothing is running parallel to ECM wires, arcing, etc. I have purchased a new usb cable and gotten rid of the serial port setup. I have even purchased a new laptop as my other one was long overdue for upgrade. I still have the exact same problem with the new laptop and usb as I had with the old laptop and serial port cable. Tunerpro works fine on my other car tuning $A1. It will connect and monitor this car using $42 until I start the car. As soon as I start the car Tunerpro begins connecting and disconnecting about every second or so. I am up for any and all suggestions at this point.
Thanks
Roy

[EagleMark]

I had an epiphany this morning. I noticed I have a little ignition static coming through the speakers when the radio is off. I am thinking this could be creating interference and causing my problem. I am currently using a serial port connection. If I went to USB is it possible it would take care of this issue?
Roy

Since it is when running and you found electrical noise... Is this a conversion? Look at EFI harness. Is it anywhere near spark plug wires, coil or distributor cap? Or a arc from ignition somewhere? I think you found the issue. 40,000 volts near an EFI 5 volt signal does cause interrference.

Sounds like you found the issue earlier! Since you have data, key on engine off, the data wire must be correct.

[Fastmax32168]

Yes but I cannot find any source for the noise and do not know where else to look. I made certain everything was clear of the plug wires and double checked all of the grounds. All of my wiring is neat and organized, So much so that I dont know what to re-do to try to fix the problem. The car is a Malibu wagon running a TBI out of an 89 C1500. I used the original ignition wiring to power the ignition, and the original ECM wiring to power the ECM. Any suggestion on what wires to start with?
Tonight I downloaded winaldl to see if I could datalog with it and I cannot. It acts the same as tunerpro. However my old Autoxray scanner will connect and stay hooked up no problem. I just cannot datalog with it so it is pretty useless other than to see generally rich or lean.

[Fastmax32168]

Mark, One thing I could look at is that I had to move the coil off of the motor and on to the firewall for clearance purposes. Does the coil ground through its bracket to whatever it is mounted on? If so I could rubber mount it and run a ground wire back to the motor so it was not grounding on the firewall but other than that I am having trouble finding something to look at. If the coil does not ground through its bracket then this idea probably holds no promise.
Roy

[EagleMark]

I could spot an issue fairly quick if you had some pictures? Osiliscope can find anything is how I learned to spot them. Coil seems a likely suspect but probably not ground, should be isolated in bracket. More like voltage EMI/RFI from coil or coil wire to body... and not sure that is the issue, just a hunch. You had all the clues, happened many of times.

What kind of altenator do you have? Voltage when running? Grounds from body to block, block to frame. Should have been 2 main grounds off harness to engine? Nothing from EFI grounded to body? Check the data wire from ALDL port to ECM? Ha! Runs right behind the firewall where coil is to ECM right?

I'm really at a loss why data would stop when engine starts? Maybe some ECM but I do that all the time with 1227747. Can you connect after running?

[Fastmax32168]

Looking at the plug wires I used on the car, I do not see them marked as resistor anywhere. Is it possible that nothing is actually hooked up wrong and the plug wires themselves, even though they are not closer than 3 or 4 inches to any ECM wiring are creating a signal that is causing this problem?
Roy

[PJG1173]

Ha! Runs right behind the firewall where coil is to ECM right?

The TBI conversion in my toyota I have the coil mounted to the firewall on a piece of angle iron. No issues with the 7427.

have you tried dataloging with an eval copy of datamaster?

[Fastmax32168]

I dont think Datamaster is available for a 7747. Those wires from the ALDL connector run along the front of the dash. There has to be at least a foot between them and the coil.
Roy

[phonedawgz]

Disconnect the alternator and see if the problem goes away.

[Six_Shooter]

Disconnect the alternator and see if the problem goes away.

I just read through the thread and this was going to be my first suggestion as well.

If you have another ECM to swap in, that could also help eliminate some possible areas of issue.

[EagleMark]

What kind of altenator do you have? Voltage when running?

I should have added try and disconnect after checking charging...

[Fastmax32168]

I think I have this fixed. I Changed out the plug wires this morning for a set of Mallory suppression core wires and it stays connected now when I start it. I will try some datalogging later today.
Roy