ECMlink Bad Idle and misfire

[jmbond47]

I have a 1996 Mitsubishi Eclipse GST was running fine a few month ago but has been sitting due to body work being done on it. Started it up to get everything circulating again and to run some fresh 93 through it but when I went to start it up you could tell it was not running right and the dash was showing that is was idling at 250rpm and the AFR gauge was out of range sitting on the lean side so I turned it off and connected to my ECMlink v3 lite and it was showing that my idle was fluctuating around 900rpm yet my dash was saying 250rpm still also got a DTC for a unknown misfire.

I suspect a bad O2 sensor due to it not fluctuating at all during idle and being stuck in open loop. I will add a picture of my log as well. Just looking for any help or suggestions due to my inexperience with this platform thanks!

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[jdxnc]

Make sure it didn't loose the tune, V3 is not supposed to when battery power is lost/low but I've personally had it happen.

 

[Sirius1995]

Random misfire can occur when you have bad gas, did you purge the system or just add new gas in the tank? I just got customer today who got some bad gas at gas station before coming to service their car and it has random misfires due 5% water in the gas and low quality fuel with 10% ethanol according to the fuel test I did

 

[curt-s]

If it's stuck in open loop at idle because of a noncycling o2, it's not an o2 issue. Your engine should still idle well even in open loop if your fuel/air mix is correct. Seems like it does better without but still not there due to your WB reading.

The dash/ECU incongruity is really very odd. Your wideband shows pig rich and I don't see a MAP sensor. Can you attach a log for us to look at?

While you're at it, check your wiring harness and connector to your PTU. If you have a spare, swap it in.

 

[Sirius1995]

If it's stuck in open loop at idle because of a noncycling o2, it's not an o2 issue. Your engine should still idle well even in open loop if your fuel/air mix is correct. Seems like it does better without but still not there due to your WB reading.

The dash/ECU incongruity is really very odd. Your wideband shows pig rich and I don't see a MAP sensor. Can you attach a log for us to look at?

While you're at it, check your wiring harness and connector to your PTU. If you have a spare, swap it in.

Maybe AFR is correct but maybe fuel trim is off? That can be O2 related, adjusting too rich or lean, and vacuum leak also is a possibility (not O2 related)

 

[curt-s]

Maybe AFR is correct but maybe fuel trim is off? That can be O2 related, adjusting too rich or lean, and vacuum leak also is a possibility (not O2 related)

If they've disabled closed loop, trims don't get calculated into the pulse width or updated.
That's why combinedft is 5.1% and openloop is 1. STFT and LTFT are closed loop adjustments only.

Since it's running openloop, the ECU is using only the fuel adjustment value, deadtimes, and sliders (or VE if SD) to determine the pulse width according to RPM (and MAP if SD). Presuming the wideband is reading correctly, the system is injecting a lot more fuel than it needs to. Idle at 9:1 would also run noticeably more poor than 14.7:1.

One of the things to focus on here is why does the ECU and the tach show two wildly different values suddenly. The PTU provides signal for the tach and goes to pin 58 on the ECU I believe.

 

[Sirius1995]

If they've disabled closed loop, trims don't get calculated into the pulse width or updated.
That's why combinedft is 5.1% and openloop is 1. STFT and LTFT are closed loop adjustments only.

Since it's running openloop, the ECU is using only the fuel adjustment value, deadtimes, and sliders (or VE if SD) to determine the pulse width according to RPM (and MAP if SD). Presuming the wideband is reading correctly, the system is injecting a lot more fuel than it needs to. Idle at 9:1 would also run noticeably more poor than 14.7:1.

One of the things to focus on here is why does the ECU and the tach show two wildly different values suddenly. The PTU provides signal for the tach and goes to pin 58 on the ECU I believe.

Oh I just noticed that he has closed loop at false 0 and open at true 1

Yea you're right

 

[jmbond47]

ok so I don't currently have access to the car right now and my laptop is with the car as well with the logs in a shop but I can get some more pictures on Monday as well as pull up more values for the logs if it is helpful. I will add photos of the two other pictures I have of the stream. I did not purge the system I just added 17L of 93 primed the fuel pump and started it.

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additional information one thing I did fix when the car was sitting was the main battery ground it was grounded through paint so i sanded down the paint to ground it properly as well as properly crimped new connectors on the ground wire due to the old ones just sliding off the ground wire could this have changed anything?

 

[curt-s]

If you were able to start the car with a pissy ground then likely no.

So I'm also seeing your AEM WB is always 9.1. I thought it was just a point in time reading but additional pictures show either you're well below 9.1 and bottomed out or the voltage from your WB isnt right. Check your settings for it when you can.

Meanwhile your front o2 is pegged rich at 0.8v so in closed loop it's trying to remove fuel (hence your majorly negative combinedft at 70+ seconds)

Check your fuel injector settings to ensure youre still adjusting for your injector sizes and deadtime is right or at least appropriate for your injectors.

 

[jmbond47]

That is the one thing I did. I calculated for my size injectors and made the change and I did not notice any changes when I did so.

 

[Sirius1995]

If you were able to start the car with a pissy ground then likely no.

So I'm also seeing your AEM WB is always 9.1. I thought it was just a point in time reading but additional pictures show either you're well below 9.1 and bottomed out or the voltage from your WB isnt right. Check your settings for it when you can.

Meanwhile your front o2 is pegged rich at 0.8v so in closed loop it's trying to remove fuel (hence your majorly negative combinedft at 70+ seconds)

Check your fuel injector settings to ensure youre still adjusting for your injector sizes and deadtime is right or at least appropriate for your injectors.

would that be failsafe by any change?

 

[jmbond47]

Update pulled the plugs this morning and cylinders 1,4 are wet and look to be rich and cylinders 2,3 look dry and lean.

 

[evil_eagletalon]

It could very well be leaky injectors. You can remove them and get them tested and cleaned. Also pull the vacuum line off the regulator and inspect for fuel there shall be no fuel if there is the engine is sucking in fuel through there.

 

[jmbond47]

No fuel in the regulator or vac line. I will pull the injectors and take them to get cleaned and tested!

 

[evil_eagletalon]

Try starting the engine and removing them soon after and inspect for any wet leaking tips

 

[steve]

And please don't post pictures of your logs, post the actual log (*.elg) file. That way people can see exactly how you're configured, what other things you might want to log, and the result.

 

[dwb]

This has to be a bad power transistor. Half the RPM on the tach, pig rich, and no spark on two cylinders.

 

[jmbond47]

This has to be a bad power transistor. Half the RPM on the tach, pig rich, and no spark on two cylinders.

sounds like that is it from the two seconds of looking I just did, I have a friend that has one that I can borrow and put on tomorrow and see if it fixes the issue!

 

[steve]

Make sure your connector has the locking clip too. Those has been known to go missing and cause the connector to come loose.

 

[jmbond47]

Make sure your connector has the locking clip too. Those has been known to go missing and cause the connector to come loose.

will do!

 

[jmbond47]

it's fixed! thanks for the help everyone! it was the PTU the connection was corroded on a few pins cleaned it up and ran perfectly!

 

[curt-s]

*cough* I suggested to check your connector and potentially swap PTUs last week (post #4)
Always have a spare coil and PTU with you, that's my motto. Any time there's ignition breakup I suggest to check the connectors. I had broken pins on my harness PTU connector many years ago. They were still in there but certain vibrations caused intermittent contact and she kicked like a mule when it went out.