now pass for HC, failed worse for NO on emissions

When i first took my dodge spirit 2.5 3 cylinder for inspection, i passed for CO but failed for NO and HC. I changed plugs, going one step hotter, replaced my map sensor, my egr valve and tubes going to it and the map, my egr switch, and my gas filter (which may have been plugged as the white spark plugs indicated the car was running lean). I reinspected and now passed for HC but my NO reading went up significantly, so i now fail for a bigger spread. Previously i barely failed, very close to the max. Before i was in the 1200 range and now am in the 1900 range on NO reading. How should i attack this problem. please email snipped-for-privacy@hotmail.com

Reply to
john
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Check timing for too much advance. Make sure the EGR valve is actually operating when your depress the accelerator. NOx is caused by too high combustion temperature which is usually mitigated by EGR and aggravated by spark advance. You could also try different (colder) spark plugs. Maybe you did not need hotter plugs to address your HC problem. You could also still be running lean which would be the fault of the O2 sensor and/or injectors (assuming nominal pressure at the fuel rail), but you should see a lean mixture code for that.

Reply to
Ryan Underwood

High NO is caused by too much heat and is to be totally expected after changing to a hotter plug.....

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

john wrote:

Reply to
Mike Romain

First things first. Use the correct part number Champion plugs. Address your engine as a "four cylinder" and find that extra cylinder, it's there somewhere!

You are most likely running lean - low fuel pressure/volume, plugged injectors, O2 sensor stuck rich (not likely, but you never know), etc... You may also have a bad backpressure transducer that is not allowing the EGR valve to open.

Toyota MDT in MO

Reply to
Comboverfish

Oy, here we go again with "Chryslers only run properly with Champion plugs" bullcrap.

There is only one injector. Perhaps the extra injectors that don't exist ran off with the missing cylinder, and the lot of them eloped to Greenland.

Perfectly likely, given the age and condition of the car.

Reply to
Daniel J. Stern

Except for extreme circumstances involving pre-ignition, the heat range of a spark plug doesn't affect combustion chamber temperatures at all.

Reply to
invalid unparseable

Correct.

Reply to
Daniel J. Stern

Reply to
Shep

Well, if you want to elaborate on every possible plug the OP could use with pleasing results, go ahead. I would rather save time and tell an obvious shotgunner to use the factory original plug, specifically because it is exactly what was spec'd for the car. It's not like I endorse Champion; they have probably caused me more grief than any other brand - but not when used in Chryslers as the OE recommendation. We're dealing with a "spark plug re-engineer" here...

That is so true. I added an unnecessary "s" to injector. Throttle body injected it is!

Eloped = no wedding presents.

Toyota MDT in MO

Reply to
Comboverfish

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