Need help with codes

pipecraze

Registered User
I took my car down for inspection and it failed nox just slightly.

I ran codes and got 33...egr valve not opening/insuficientf flow and 49...default spark error. Is it likely that the faulty egr is causing the default spark code? I've done some searches on here but I'm really not sure what to look into first or how. Plug, plug wires, and o2's are new. The cam sensor, dis, and crank sensor are not too old and seem to be working fine.

I'm not too familiar with egr so any explaination of that system would be great!

Sean
89 sc
 
The faulty EGR is likely the cause for you failing for slightly high NOx. All the system does is flow a small percent of the exhaust gas into the intake to help keep combustion chamber temperatures lower, thus as to redure NOx production since NOx is produced in the cylinder when nitrogen and oxygen are introduced to each other at temperatures above 2500*F. As for the default spark code, yes, it is probably the faulty EGR causing this. I'm not sure, but I do believe that the EGR Valve Position acts as one of the 7 inputs the DIS uses to calculate spark timing and if any one of those 7 inputs becomes unable to operate, it defaults the spark timing to 10* BTDC. That would likely explain the codes you have.

I'd go ahead and probably try replacing the EGR Valve and clear the codes and see if it throws a code 49 again before even taking the car to get smogged. The EGR is fairly easy to replace on these cars, it's on the passenger side connecting to the exhaust manifold and runs up to the intake side of the engine. Just make sure that when you buy a new valve that you buy the exact same valve that you had before that has the EXACT same flow-rate as your current one, otherwise it won't work properly.

Heh, not bad for a 19 year old college student. :p
 
Ok....I'm going to go ahead and replace the egr valve first. Can anyone else verify that a possible bad egr valve is setting the timing to 10 BTDC.
 
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