Hey guys,
Once again I have a 98 lexus es300 with 163k miles on it which just failed emmisions. First I was getting po446 codes and po401 for egr flow codes. I spend some time, changed some vaccum hoses, cleaned out egr since the valve was sticking and the vsv's for egr and charcoal canister. After resetting and driving for a while, no more codes and all the I/M status were complete.

Basically car failed because at 25mph the HC and CO was too high. They were good at 15mph. I am attatching picture of my emmisions results here. What do you guys think is the cause of this and possible tips and solutions. Honestly I love the car but have already spent lots of money on it and thats why I am turning to you guys to see what some possible problems could be.



Thanks!!!

 

looks like your going to need a cat to me.. but not too sure..
i'd try seafoam too if anything.. my smog guy usually hooks it up though.. so not sure..
the smog tech didn't tell you anything?

 

This was a test only station. The smog guy was sort of grumpy and said he couldn't tell me anything. One thing I did notice when I got the car back was that the over drive was turned off. Is this a normal procedure for smog. Does having over drive off create alot more emmisions?

A new cat sounds expensive, and I have already spent soo much money on that car. The only reason I am hesitant to seafoam the car is that it has alot of miles and sometimes old seals are just held in place by the carbon deposits.

Any other ideas/ suggestions?

 

That makes no sense to me. What do you have to lose?

 

cheapest cat option would be some hi flow magnaflow or something

i would try the seafoam but idk.. my last resource would be the shop hookup :P

 

From what I have been warned about, if you seafoam engines that have around 130k+ miles, usually the seals held by carbon deposit **** and people have problems such as blue smoke out of the exghaust and stuff. But since the CO and HC was normal at 15mph and really high at 25mph does that necessairly mean the Cat Converter?

I am thinking about adding some of that guranteed to pass smog formula and probably seafoaming it and taking it in. Also one stupid thing I did is clean the egr with plent of carb cleaner, reset the computer and drove the car for about 25 miles. Could that have messed up the fuel ratio bad enough to cause such high pollution

 

Can anyone think of a reason tho as too why the hc and CO concentrations were good at 15mph but really bad at 25mph?

 

My guess is on the EGR system. The way it operates is that it recycles exhaust gases at higher speeds to reduce emissions. Get it checked out by a mechanic.

 

Does your tech let your car idle for at least 5 minuets before testing? cause I had a tech drive my car right up before idling and it failed on the same day went to another tech, he let my car idle and it was fine. This was before any mods

 

Actually i took of the EGR system that day and cleaned it very well. That is why the Nox readings were so low. I basically cleaned the EGR with Carb Cleaner, and then some of the carb cleaner was sprayed into intake. Then after resetting ecu i drove about 25 miles before taking it in. and my smog readings according to an online calculator mean by computer detected it running lean and over corrected. So could the Carb Cleaner in the intake have caused the ecu to think the car is running lean and made it run rich?

Also the smog tech let the car probably idle for about 5 minutes before sticking the pipe in , but he already had the OBD tests running at this time which all passed.

 

50% of people with 2000 year and older car's CAN"T pass emissions in CA....

 

Try cleaning your MAF sensor with a special MAF sensor cleaner from CRC. It may improve your air/fuel ratio response.

 

Also some "dry gas" the alcohol type has been known to clean up the emissions a bit for the test. A buddy passed IM-240 with his TurboCoupe with no cat back in the day with a couple bottles of the stuff...

Sucks to have the dyno, MA has gone to "OBD-II" check no dyno, as long as the computer says OK you can roll your cat free 500 hp tuned OBD-II car right on through heh.

 

Hey guys so this car failed smog a 2nd time with basically the same results. I had replaced the egr vsv, some vaccum lines, spark plugs, etc. What I noticed is car runs great with no codes. When I take it in for smog and he puts the front end of the car on a ramp for the rollers, the ecu detects a lean and starts running too rich. As soon as I leave the smog shop po171 code pops up but a few days later it will go away. I am amazed about why the lean condition only happens when he has the front of the car raised slightly on the rollers.

Thanks

 

EGR won't cause that, it only reduces NOX. It's quite possible that it's the cat. It's possible you might have a lean misfire as well. You need to scan for other codes. Check the air intake boot for cracks. Check for a possible intake manifold leak as well.