Hey guys,

Problem is simple: stock 94 prelude S - sohc everything stock. its failing georgia emissions for (barely) high CO. I've changed s.plugs, s.plug wires, oil changed, fuel filter, valve adjustment, pcv valve, O2 sensor, Cat. I'm out of ideas. Well, there's the MAP and EGR but its not throwing any codes and those two parts are mighty expensive, so why replace them? No vacuum leak I can find and it runs great. I appreciate any help that anyone can offer.

 

What brand of catalytic converter did you put on?
You might have to bite the bulllet and get the diognostic done.

 

i got the high flow cat from magnaflow - loved putting it in stupid triangle bolt pattern!

Let me ask this: is it possible for the MAP or EGR to fail without throwing a code?

 

It's certainly possible for your EGR ports on the intake manifold to be plugged up enough that you are failing emissions, but not so bad that it is throwing a code. If you haven't done it yet, I would suggest cleaning them. Check around for threads on doing this; you can do it yourself with a drill and get replacement plugs for less than $5.

 

Yes, pre 96 Preludes only check to make sure the EGR valve is opening and closing. Unlike OBD2 which actually monitors flow. Its very common for the EGR ports on the Prelude intake manifolds to clog up with carbon. So most likely your valve is still opening properly but isn't flowing the proper amount to lower emissions to passing levels.

 

Thanks guys, I'll clean the EGR and take it one more time to get it checked, I was being lazy and didn't check it since NOx was fine. - but I guess if it fails again, it's the MAP? Can something on this thing be cleaned like the EGR or is this a replace only part?

 

High carbon monoxide (CO) indicates rich fuel mixture. Leaky injectors, excessive fuel pressure and sluggish or contaminated O2 sensors are all possibilities to investigate.

Make sure your timing is on par with your motor specs as well.

 

do u smell gas coming off the motor?u not throwin codes,i would try different shop.

 

ccoungo - thanks for giving me a few more things to check out. i plan on cleaning the EGR valves because it will probably help but i am not convinced thats the problem since its fine with NOx and if i am not mistaken, EGR really affects NOx more than CO2 but whatever, I plan on cleaning it. i will check the timing again, i did check it when i adjusted the valves but that will go quick. thanks for the suggestion

KillB - there is no gas smell coming out of the motor. everything seems fine. maybe after i do the egr and injectors etc as suggested, i will take it somewhere else. thanks

 

Forgot about this post: issue resolved - cleaned EGR ports and EVERYTHING emission related dropped, not just NOx or CO2. Took ten minutes, wasn't hard at all - had to drill, tap and plug with a screw but no big deal, seriously if I can do it anyone can.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jeff13m &raquo;</TD></TR><TR><TD CLASS="quote">Forgot about this post: issue resolved - cleaned EGR ports and EVERYTHING emission related dropped, not just NOx or CO2. Took ten minutes, wasn't hard at all - had to drill, tap and plug with a screw but no big deal, seriously if I can do it anyone can.</TD></TR></TABLE>

Good info

 

instead of a high-flow cat you should get a normal one and you'll see a drop in emissions!!!!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jeff13m &raquo;</TD></TR><TR><TD CLASS="quote">Forgot about this post: issue resolved - cleaned EGR ports and EVERYTHING emission related dropped, not just NOx or CO2. Took ten minutes, wasn't hard at all - had to drill, tap and plug with a screw but no big deal, seriously if I can do it anyone can.</TD></TR></TABLE>

Did you do this with the IM on the car?

 

puts some gallon of ethanol in with a full tank gas and you will pass.