guys i keep failing the emissions test. im good on everything but my NOx. Ive been told time and time again that its my EGR or cat.

i am running two cats one on the stock mani and one new one down below. i got fed emissions.

i am also throwning a CEL # 25, lean air/fuel ratio. does the EGR have any relation to this code. if my VSV or temp sensor for the EGR failed wouldnt i be throwing a code for the EGR. i applied vacuum to the valve itself and the engine stumbled and died like it should. i cleaned the injectors and filter too but im still getting the code and failing.

id imagine that if the egr valve were stuck open, then that would be 'sort' of like a vacuum leak and thus cause a lean condition.

but if that were the case it should throw a code metioning ur egr... im not sure but thats my 2 cents

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No it wouldn't. Air contains 20% oxygen. Exhaust contains 1-2% oxygen.

The symptoms could be related. A lean mixture often produces excessive NOx. Could be EGR problem, but not likely. Does it fail at idle or part throttle?

Is it running closed loop? Any other symptoms? How does it drive?

yes, it will cause running problems if the egr is leaking one of which will be a slightly lean mix but not that much, more of an issue with the computer not knowing the egr is open and not making needed adjustments. at idle the vac is the strongest so it'll pull in more exhaust than it should and begin to run rough and stumble.


i agree that high nox can be caused by running lean, lean burns hotter, burning hotter can raise nox. but higher compression can also raise nox, it could be a carbon buildup issue or ignition timing issue.

well i know i have no carbon. i just put the motor in and started driving it not too long ago. pistons were clean when i put it in, took out my plugs the other day and shined a light down there and they are still clean as can be.

it drives fine, no knocks or pings. doesnt buck or stumble. drives like it should. im not too sure about my ign. timing. i dont have a timing light. i have retarded it a bit awhile ago to see if that could help me pass, but still no go. should i reset the ecm? warm it up, unfuse for 1 min, start it and run it for 10?

check the base timing for sure! short E1 to TE1 and start engine, it should be already warmed to temp. check timing and set to 10d btdc.

is there a way to check the timing without a timing light. i do not have one, and if i did i am unsure how to hook it up. and when you say base timing do you mean distributor, ignition timing, or crank and cam timing? and how would that make it run lean

There is no sure fire way to check with out a timing light. But hooking one up is a piece of cake. There should be three wires coming off the timing light. the red and black go to the battery, for positive and negative. And then there will be a wire with the shape of an o on it. Open it up and put it around #1 spark plug wire. then aim away.

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Did you make sure the cam timing is absolutely dead-on when you rebuilt it, or was this a used motor in unknown condition?

im am 100% sure it was dead on as far as i can remember. i guess i can take a look though.