Mystery again

[McLin]

Hi,

after I replaced the EGR valve we didn't have the failure again. But now ist coming back in shorter periods.
But this time we had luck and we had connect to our obd2 Interface. What I seen there was not possible. RPM was from 200 to 9000 and we are in park Position the vehicle Speed goes up to 134kmh and down to 0 then again up to 64 and down.

Then there was a lot of missfires and a lot fuel avg. I Thing it was about 31 Liters per hour.

Is it possible that the ECU Unit is fault? Or the vehicle Speed sensor? There was no Trouble codes set.

Out old Posts to this failure are:

http://www.automotiveforums.com/vbul....php?t=1061010

http://www.automotiveforums.com/vbul...d.php?t=974088

http://www.automotiveforums.com/vbul...d.php?t=942927

I don't know what the failure is. But we replace TPS, EGR, spark plugs, spark plug wires, lower intake gasket upper intake plenum, pcv valve.

Videos about the problem:
http://youtu.be/KRF2dll2qbE
http://youtu.be/GJjDMIgB9ms
http://youtu.be/VDvNZ9s7G10

Scan Mystery:
http://youtu.be/A-gZEzmD4f8

[GTP Dad]

You stated that this is a 3.8. Try unplugging the Mass airflow sensor and see if the issue improves. This is a common issue and if the MAF sensor is the problem the car should smooth right out when you start it. Make sure to unplug the sensor with the engine and ignition turned off.

[McLin]

Ok did it. Failure is gone, but it comes and go when it want. Now after plug off the maf sensor my mil is on. How long should I test it? What can happend if I drive without it?

[maxwedge]

Power and accleration will be limited as you are running in " limp mode". It won't hurt anything and try it for maybe 50 miles of driving.

[McLin]

I think the lumina has problem to hold the rpm without the maf sensor. On red light the rpm stop on 1100 rpm after 5 sec it goes under 1000 and 1 sec after it hold it on 1000 rpm ( not computer rpm )

Is this normal condition without maf sensor?

Edit:

He did the same again. I hate it.

[GTP Dad]

It is normal and the MIL light is normal too. You will need to replace the MAF sensor and the car should run more smoothly after that. Make sure you check for vacuum leaks everywhere also have the computer scanned for additional codes. I recommend you purchase a MAF that is not remanufactured by Cardone. They are junk!

[McLin]

I think it was just loosen nuts. After I replaced the egr the failure was gone. So I wanted a look to the new egr valve. After I set the ratchet on the nuts I feel they where very loosen. So I fasten they up and the failure is gone the last three days.

Funny thing. I sprayed the whole engine with leak detector and no rpm changing was there. I think the egr did work with pressure and not with vacuum?

[McLin]

It was not the egr.

First the second upper plenum was melt. I did not replaced the egr tube in the lower intake for egr.

Second, and it was luck that I saw it: Ignition coil was blown. But the spark was jumping from cylinder 1 to 4 and not outside. It was dark and I saw something flashing. When the engine was warm engine run fine.