OnegreatGuy Posted March 18 Report Share Posted March 18 Hey all, I am starting to work on road tuning my 1991 toyota mr2 turbo with the Link g4x plug and play ECU. I have had issues with the ecu disconnecting from PCLink, and chalked it up to bad grounds. However, I have gone through and sanded down all ground contacts and have ensured that they make good connections, as well as making sure all of them are in place. I have also routed the USB cable away from the ignition coil as much as possible, but I have to use a USB extension cable to reach the chassis. I am able get the ecu to connect to the laptop easily, but while driving it will disconnect itself after 5 minutes. This is annoying, but the real issue is that when I try to use the autotune feature to get in the ballpark of where I want my fuel map to be, pclink crashes and goes unresponsive after maybe 30 seconds, and it frequently freezes even if it doesn't crash. It seems to bring itself back if I unplug and replug the USB cable connected to the ECU. Any help fixing this would be greatly appreciated, as I am unsure what more I can do. Quote Link to comment Share on other sites More sharing options...
Adamw Posted March 18 Report Share Posted March 18 Is it still using a distributor? Quote Link to comment Share on other sites More sharing options...
OnegreatGuy Posted March 18 Author Report Share Posted March 18 4 hours ago, Adamw said: Is it still using a distributor? Yes, it is still running the stock distributor. I am not coil on plug yet. I've also tried installing pclink on a different laptop, which resulted in the same issues. Quote Link to comment Share on other sites More sharing options...
Adamw Posted March 18 Report Share Posted March 18 MR2's with distributors seem to be a bit of a problem child, probably the most common car I see comms issues reported on by far. From the few users I have helped with the issue I havent yet seen a common trend. The first one I looked at closely I found his comms issues mostly occurred at idle or when coming down to idle, turning off idle ignition control solved it so I assumed the large swing in ign timing was more than the rotor phasing would allow so the spark was possibly jumping off the end of the rotor to something that had a more direct connection to the ecu. The 2nd one had similar symptoms but turning off idle ignition control didnt solve it in that case. I got him to double check rotor phasing and that looked ok. With most other common stuff like resistor spark plugs and leads etc checking out ok I asked him to look at the ignitor and how it was grounded etc, he found there was a lot of corrosion where the ignitor or bracket mounted and also found the factory noise suppressor was open circuit at the same time (possibly the bad ground fizzed the suppressor?). He fixed both those at the same time and they solved his issue so Im not sure which one was the main culprit. Then the 3rd one was a bit different, it would lose coms at high load and sometimes a trigger issue would occur at the same time, we checked through most common stuff as above and couldn't find anything obvious. I dont remember if we actually checked the suppressor in that car - or maybe he said it didnt have one. Anyhow he wanted to change to coil on plug anyway so rather than spend more time diagnosing he just did that and both the comms issue and trigger error disappeared. That was still using the dizzy for the trigger. So my first suggestion is if you have idle ign control enabled then try with idle ign off. Check the ignitor ground and suppressor (most multimeters have a capacitor test) and confirm the other common causes such as HT leads, distributor cap/button etc. Quote Link to comment Share on other sites More sharing options...
OnegreatGuy Posted March 19 Author Report Share Posted March 19 4 minutes ago, Adamw said: MR2's with distributors seem to be a bit of a problem child, probably the most common car I see comms issues reported on by far. From the few users I have helped with the issue I havent yet seen a common trend. The first one I looked at closely I found his comms issues mostly occurred at idle or when coming down to idle, turning off idle ignition control solved it so I assumed the large swing in ign timing was more than the rotor phasing would allow so the spark was possibly jumping off the end of the rotor to something that had a more direct connection to the ecu. The 2nd one had similar symptoms but turning off idle ignition control didnt solve it in that case. I got him to double check rotor phasing and that looked ok. With most other common stuff like resistor spark plugs and leads etc checking out ok I asked him to look at the ignitor and how it was grounded etc, he found there was a lot of corrosion where the ignitor or bracket mounted and also found the factory noise suppressor was open circuit at the same time (possibly the bad ground fizzed the suppressor?). He fixed both those at the same time and they solved his issue so Im not sure which one was the main culprit. Then the 3rd one was a bit different, it would lose coms at high load and sometimes a trigger issue would occur at the same time, we checked through most common stuff as above and couldn't find anything obvious. I dont remember if we actually checked the suppressor in that car - or maybe he said it didnt have one. Anyhow he wanted to change to coil on plug anyway so rather than spend more time diagnosing he just did that and both the comms issue and trigger error disappeared. That was still using the dizzy for the trigger. So my first suggestion is if you have idle ign control enabled then try with idle ign off. Check the ignitor ground and suppressor (most multimeters have a capacitor test) and confirm the other common causes such as HT leads, distributor cap/button etc. The disconnecting happens under constant load, I've been trying to hold a cell for autotune to get in the ballpark. This has been at 1500 - 3000 rpm, there is not much difference between the two in terms of disconnecting. The ignition coil, spark plugs and distributor (main assembly, rotor, and cap) are brand new and the leads are well within spec. I believe the Ignition coil is grounded using the same ground location as the ecu, which I think may cause some issues, but my knowledge of electrical interference is very low. I will make sure that I check my ignition coil to make sure it is in spec, though, and I will turn off the idle ign control to see if that helps. I am unfamiliar with an ignition suppressor, I can't find a reference to them in my electrical manual. Is it integrated into the ignition coil, or is it a separate unit? Also, what is my best way to make sure that I don't have any rotor phasing? Thanks in advance! Quote Link to comment Share on other sites More sharing options...
Adamw Posted March 19 Report Share Posted March 19 49 minutes ago, OnegreatGuy said: I believe the Ignition coil is grounded using the same ground location as the ecu, which I think may cause some issues, but my knowledge of electrical interference is very low. With an old school 2 wire coil the "secondary ground" is connected internally to the positive post of the coil, a "condenser" is needed to provide a path for the spark voltage that has just jumped the spark plug gap to return back to the coil. Without a filter (or with a not working filter) then the spark voltage has to travel through the whole electrical system to get back to the coil via the ignition switch to the positive post. Andy Wyatt explains the basic idea starting around 8:25 in this video: https://www.youtube.com/watch?v=M1HfbXyYzSM There are a couple of variations of suppressors on early toyota's, search part numbers 90980-05179 or 90980-04084 to get an idea what they look like. They connect between the coil positive and ground, usually very close to the coil. Quote Link to comment Share on other sites More sharing options...
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