emissions problem

[Hotrod705]

I went to dmv today to get tested and this is the results.
carbon monoxide acceptable is 15.00 mine is 35.35
hydrocarbons acceptabe is 1.60 mine is 2.93

I took out the front cat and put on a down pipe. would putting the cat on make the difference with these numbers? I've done a complete rebuild so I was surprised to see these numbers. Everything is to spec. I put in new pistons,rings,mains, hg, arps. waterpump, starter, plugs, wires, cold air intake, remaned head, all new gaskets and seals, car runs nice. Any suggestions would be appreciated.

 

[jetjock]

I'm not familar with AZ's test method (I'll have to check it on their website) but from your numbers it appears the engine is running rich. HC can be high for other reasons but along with the high CO it's an indication of a rich mixture. The best rebuild in the world won't do squat for emisisons if your EFI and especially the lambda trim system isn't working right so I'd start there. Check the O2 sensor and Vf signals. Airfilter clean? The front cat isn't going to be a help or hindrance but if the engine has been running like this for a while (and it would run fine with those numbers) it's not doing your main cat any good.

Edit: OK, you're in PHX so you're stuck with the IM 147 test. That explains the readings in grams per mile. Check what I said.

 

[Hotrod705]

What are the lambda trim system and vf signals? Thanks

 

[Nick M]

Is your car stock?

 

[jetjock]

What are the lambda trim system and vf signals? Thanks

In simple terms the lambda trim sysem refers to the O2 sensor feedback loop while Vf is a signal that represents what the engine's computer is doing to keep the engine running at lowest emissions. Both signals are available at the diagnostic connector near the battery. Do you have a service manual? And as Nick asked, is the car stock? Emissions problems can be difficult to diagnose so if this doesn't make any sense you'll probably need to bring the car to a shop.

 

[bowsercake]

I was a gross polluter. I checked my timing and it was at 15* BTDC and I changed it back to 10* which is stock. Also, i changed out my spark plugs and changed my valve cover gasket to prevent oil from getting into the valleys again. Oh yeah, i also ran the car at 3000+ rpm for about 3 minutes before i got smogged. It takes alot to get my 16 year old cats running well.

 

[koulee]

I thought that the pre-cat was only for cold starts in the morning and have no effect on a hot engine...

 

[Hotrod705]

car is stock and I do have a service manuel

 

[jetjock]

Use the EFI portion of the service manual to check the O2 sensor and Vf signals. Check to see if the sensor is cross counting.

Koulee: You're right.

 

[Hotrod705]

I've never dealt with the emissions before. What do you mean by cross counting? I'll check it out. Thanks

 

[jetjock]

Cross counting is what the O2 sensor does as it switches from lean to rich in response to the ecu adjusting the injector duration. It indicates the lambda loop is working and the ecu is controlling the mixture. You said you have a service manual right? Read the EFI troubleshooting section and do what it says about checking the oxygen sensor.

 

[Nick M]

I thought that the pre-cat was only for cold starts in the morning and have no effect on a hot engine...

No. It is a NOx reducer. You need CO to reduce the NOx, so they are first. The Supra isnt the only car with a reducer.

Since your car is stock, pull the plugs and see how much oil if any is on the plugs.

When you check that oxygen sensor voltage, it should average 450 millivolts as it switches. If you notice it below this and you have no part throttle driveability problem, than this could be it. If the ECU thinks the car is lean, it will richen your mixture.

 

[jetjock]

No. It is a NOx reducer. You need CO to reduce the NOx, so they are first. The Supra isnt the only car with a reducer.

Since your car is stock, pull the plugs and see how much oil if any is on the plugs.

When you check that oxygen sensor voltage, it should average 450 millivolts as it switches. If you notice it below this and you have no part throttle driveability problem, than this could be it. If the ECU thinks the car is lean, it will richen your mixture.

Well, the pre cat is a TWC, not only a reduction bed. It's not used only for NOx. And while it's true CO is required on the rich switching side of the loop the main cat will handle everything just fine and if his plugs were oil fouled he'd be having much bigger problems. I don't think his loop is shifted lean but it's good that he check it all the same. Btw, did you get that stethoscope link I posted?

 

[3p141592654]

Jetjock, have you passed ASM5015/5025 without the precat? I've got one coming up and would rather not put the stock DP back in. The Supra seems to be classified as a high emitter in CA these days, so I expect more scrutiny than normal.

 

[jetjock]

Jetjock, have you passed ASM5015/5025 without the precat? I've got one coming up and would rather not put the stock DP back in. The Supra seems to be classified as a high emitter in CA these days, so I expect more scrutiny than normal.

Hey there 3p. Yeah, the records show the MKIII comes up bad in Cali. Not sure why that is except for maybe it's age and bad maintenence but lots of them get tagged as Test Only. From what I've heard failures tend to be mainly for HC. I tell ya, Enhanced has been nothing but a headache for everyone since it began.

I've always passed ASM5015/5025 without the precat except for one time but that was for another issue and before I owned a 5 gas. I know several others who routinely pass it without the precat also. As long as the engine is hot, in tune, main cat lit off, all the usual stuff, it shouldn't be a problem. They've never got me on a visual either, seems they either don't know or don't care about the precat. They'll for sure look for the main one though.

Btw, thanks again for your previous thoughts on that loop I had shifted lean. I never did get a chance to look at it again and as far as I know the owner is still driving it like that. Still bugs me though.