Mr.Redface

How does misfire info from the diagonstice port work?

I had an event the other night where I started my car rode for about 1/4 mile made a turn an the car just died. It restarted after a couple of cranks but when started it acted like it was flooded. So since I had an interceptor gauge I went thru the readings. I found that I had 3 misfires. but as i drove the misfires went back to 0. It did count 1 misfire a mile later but cleared again as I sped up. I haven seen any other counts and I checked the codes nothing was thrown.

So my question is Does the interceptor gauge clear/interfer the misfire data or is the misfire info only temperary read once and gone?

Thanks

One other note with the radio up and the electrical steering it was hard to realize that the car had even stalled.

JeramieJJ

Did you check your battery connections? With a turn-stall, check its secured. Otherwise could have a harness issue, where grounding is occuring with inappropriate touching!

Mr.Redface

Thanks Checked the connections everything seemed OK. I set my gauge to Misfires for constant readout. And I found that I get 1 or 2 when traveling at low speed every 10-20 mins of driving. then my readout go to zero about 3 mins after the count. Maybe this is normal i never focused on this info before?

Mr.Redface

I did find this in the Aeroforce forum about Misfires. it looks like they are normal up to a certain amount and then it sets a code.

Another issue I have discovered if I put the Gauge in the Misfire screen (the one which shows which cyclinder has the misfire. After about 30 mins in this setting the gauge locks up - the red lights come on and the screen goes blank. This has happened both times I have put it in this setting. The first time I unplugged the gauge let the car sit. I then reconnected started the car and the gauge powered back up. The second time i just did it and i hope it comes back.

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keviiinn wrote:
2007 Chevrolet Impala SS.

one of the parameters I have my gauge set to in cyclic scan is misfires. I've noticed recently that I will get 1 or 2 misfires during normal light acceleration, or up to 8 when I'm backing up into a parking spot.

I then left the gauge on the misfires menu, where it shows which cylinders are misfiring. each of the cylinders will misfire at any given time.

however, I don't get any DTCs, CELs, or trouble codes or error messages of any kind. and also, the misfires will disappear from the misfire list, or go back down to zero in scan mode, in just a matter of 10 seconds or so after it says that there was a misfire. what could be going on?


Misfires are normal, especially when the engine is cold. It's only an issue when the number for a given cylinder gets above a factory determined limit indicating that something abormal is happening. This could be 50 per 200 engine revolutions for example.

The misfire counter resets after a predetermined period of time. I don't recall off of the top of me head what GM has set this value for your car, but it will will count misfires for a certain length of time then reset back to zero and start again.

Todd
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Aeroforce Technology

JeramieJJ

Good find.

But your car dying after a 1/4 mile is still a mystery in itself.