Stupid jerking @ 1800 again

[talonmike]

It is really intermittent. If the cat is clogged it is always clogged. Sometimes it is running fine, sometimes it jerks.


I will try to disconnect the EGR to see.

[needsaboat]

Subscribed.

[eq1]

Originally Posted by talonmike

It is really intermittent. If the cat is clogged it is always clogged. Sometimes it is running fine, sometimes it jerks....

If the symptoms were being caused by a direct mechanical cat failure of some sort, like being clogged, then yeah, seems like the symptoms wouldn't be intermittent. But if a cat malfunction somehow caused a change in the O2 sensor, or O2 sensor reading, or some other sensor reading, that might be intermittent...

[talonmike]

But the first o2 sensor, the one that is mainly used for mixture adjustment, is before the 2 cats.

[eq1]

It is? I thought the first O2 sensor is screwed into the first cat...

[talonmike]

Yes, before the grid inside the cat

[biododge1]

I would disregard most sensors like the o2-by default the ecm will run the car just fine even if they are all bad-the sensors just "fine tune" it all for economy and emissions. Without a real good code reader (one that can turn off things like egr, purge valve, etc) i would first unplug the o2 sensors, egr, etc(pull it off and make sure its closed), drive the car and see if you get any change for the better. If yes, plug 1 sensor in at a time-clear codes, drive, repeat this process until the bucking issue starts-that will show you the bad (if any) sensor.
Another thing to look at is the valves. Are they within adjustment, is the vtech valve bleeding psi and engaging just a few valves (when they should be off)
Another thing to try is shut off the ima via switch. My car was bucking real bad, I had thought it was the egr, I went through everything, sensors, egr, cats, fuel system, only to find that the "new" bcm i had didnt play nice with my original ecm and mcm( my ecm is a first version, no re-flash, mcm is a # 10) It was causing the ima to kick on and off fast without showing it on the dash at certain speeds.

(oh, as for if a cat can be bad at 100k, yes, mine seem to last about that long and then i get codes. Ive replaced 2 on mine so far, and have the code now-just in time for 300k. But im going to try cleaning it this time lol)

[eq1]

This all sounds like good advice to me, especially just flipping the IMA switch, since it's easy, to see if that changes things...

[talonmike]

I check this morning again. It is not jerking in lean mode. When it start, the bar graph was at 6l/100km. It is really intermittent. Always when engine is warm. I will to some test next weekend.