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MAF & EGR Problems related to Plugged Catalytic Converte

 
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Ollie2003LS
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2003 Chevrolet Impala


PostPosted: Mon Mar 12, 2012 5:55 pm    Post subject:  MAF & EGR Problems related to Plugged Catalytic Converte Reply with quote

'03 3.8 101k

I had written previously here about rough start and sluggish acceleration issues that I had attributed to a bad MAF (Though there was no code present at the time and performance seemed to improve when unplugged).

I am now showing a P0102 (MAF) and P0404 (EGR) code. I was all set to purchase a MAF from Morad when both of these codes showed up and made me suspicious that maybe the problem was elsewhere. I was wondering if a clogged catalytic converter could not only mess with the EGR but also throw off MAF readings.

We took the car to a muffler shop to be tested for excessive backpressure. He read the codes and said that my problem was all intake related and that if the cat where plugged the car wouldn't be able to get up to highway speed at all. We are now smelling exhaust in the cabin at stops and low speed when the air is not on recirculate (Could this be a bad EGR?)

When I pulled the EGR valve and inspected it there was light carbon marks(heat marks?) but nothing really to be cleaned. The car wouldn't start with the EGR off (supposedly this shows that the EGR passages are clear) I plan on testing it more with a DMM this weekend.

Should I go ahead and buy a new EGR and MAF or is it possible they are just operating incorrectly due to plugged cat. I'll try to get cat tested next week if you think that's wise. I had thought the problems with the converter were limited to the '01 and '02 models Confused

Thanks as always!
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98ss
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2002 Chevrolet Impala
2011 Chevrolet Silverado


PostPosted: Mon Mar 12, 2012 8:25 pm    Post subject:   Reply with quote

If the shop did a backpressure test, they took out one of your 02 sensors to plug the guage in. It is possible the 02 bung could have gotten cracked. If they just read the codes the problem may not be related to the trip to the shop. Check out easyautodiagnostics.com for how to further check out your situation. Personally, I haven't had real good luck cleaning egr valves. I usually spring for a new one, they aren't that expensive. But, it is worth a try.
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Ollie2003LS
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2003 Chevrolet Impala


PostPosted: Mon Mar 12, 2012 9:14 pm    Post subject:   Reply with quote

98ss wrote:
If the shop did a backpressure test, they took out one of your 02 sensors to plug the guage in. It is possible the 02 bung could have gotten cracked.


Sorry I wasn't too clear... The codes were already present when I took the car to the shop and the car was never tested for backpressure. The shop essentially said that it would be a waste of time to test it and that if it were indeed a plugged cat that the car would barely able to drive. I took it to the shop thinking that maybe exhaust gasses where backing up and influencing the operation of the EGR valve and or the MAF's readings. Is this possible?

Thanks for the link... that's how I was planning to test EGR this weekend. I already cleaned what I could with some carb cleaner, but it just wasn''t that dirty to begin with.
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