1ZZ-FE troubleshooting, who's up for it?

[BigTDogg (MA)]

New thread, why not, everyone else does it!

LOL... yeah, I could search, and find a bazillion different things to check. But I've already searched, both here and the intarwebs, and I'm still coming up short.

Car:

• 2001 Corolla LE, 161K miles, standard 1ZZ-FE engine with 4-sp slushbox.

Situation:

• CEL is on, code is P0420 (Catalyst below efficiency)

Symptoms:

• Shit gas mileage: 24-25ish MPG combination, sometimes as low as 20mpg. Straight 300 mile highway trip I can eek out 31mpg.
• Slight pinging (detonation) under hard acceleration
• Faint exhaust smell when vents are open

What I've changed/performed:

• Oxygen Sensors (both front and rear with direct plug in Bosch units)
• Catalytic converter (with direct fit magnaflow unit)
• Spark plugs (OEM NGK units)
• Cleaned MAF and K&N filter every oil change
• Seafoamed vac line and crankcase about 6k miles ago

Mind you, the ONLY code I'm getting is P0420. I'm most concerned with the CEL, because I need to clear it (and have it clear in the ECU) for OBDII inspection testing. Then I'm concerned with the mileage, then the detonation.

I think the exhaust leak is most likely from the flex pipe from the header, as the new cat is welded to the downpipe and the flex pipe section may be over stressed.

My plan right now is to cut out the craptastic Magnaflow unit and get a generic 2" in/out converter from an auto parts place. I am not getting a new Toyota unit, that'll cost more than I paid for the car. If that solves everything, I'll be estatic, however I don't see that happening.

Any help or suggestions are greatly apprecaited. It's got to the point where I'm asking myself why I'm driving the car if I'm getting dick for mileage (which is the primary reason why I bought it).

Thanks
T

[Bdub215]

well... you've got an aftermarket cat so start there, then i'd move to replacing the gaskets/doughnuts for the exhaust, the flex pipe is just that a flexible pipe no wire mesh or anything (unless yours has been changed) so nothing should be wrong there. bump up your octane to premium and go from there. thats what i would do.

[Milky]

replace the gaskets like Bdub said. there are 2. one is a donut gasket located at the header to downpipe, the second is located at the downpipe to cat pipe, before the cat. if either has a leak they can cause all the symptoms you describe.

[BigTDogg (MA)]

Originally Posted by Milky

replace the gaskets like Bdub said. there are 2. one is a donut gasket located at the header to downpipe, the second is located at the downpipe to cat pipe, before the cat. if either has a leak they can cause all the symptoms you describe.

Hmmm... the donut gasket may be the culprit. There is no paper gasket with the clamp, that's been removed and it's just welded there now.

I think I may have to add some support to the pipe, maybe on the "chassis brace" which goes across near that OEM clamp. I think the weld is putting too much stress on that donut gasket.

Thanks for the heads up guys, def apprecaited!

Oh, and if you happen to have the part number for that donut gasket (I'll search now as well) and any associated parts I'll need to replace with it that'd be awesome

[Bdub215]

I don't have the part number but I have one sitting in my center console for months now cause I meant to change mine and never did. They're cheap.

[BigTDogg (MA)]

Originally Posted by Bdub215

I don't have the part number but I have one sitting in my center console for months now cause I meant to change mine and never did. They're cheap.

I think I found it, does it look like this:




I found a few different manufacturers, Bosal makes one, Ishino makes one (W0133-1637104). If that's the part I'll keep cross-referencing to find the Toyota OEM PN.

Thanks!

[teppista881]

That's the correct part, yes.

I know it would be expensive and a pain in the rear, but you might also try switching your O2 sensors to Denso. There are cheaper roads to try first, but it's always a possibility that the Bosch sensors are giving your ECU bad data and tripping the code.

[BigTDogg (MA)]

Originally Posted by teppista881

That's the correct part, yes.

I know it would be expensive and a pain in the rear, but you might also try switching your O2 sensors to Denso. There are cheaper roads to try first, but it's always a possibility that the Bosch sensors are giving your ECU bad data and tripping the code.

Thanks, I'm definitely going to change the gasket first, then see what happens. I'd be shocked if the O2s are bad. Bosch plugs = bad, but I've had good luck with Bosch sensors in other cars where they weren't OEM.

[Milky]

Originally Posted by BigTDogg (MA)

Thanks, I'm definitely going to change the gasket first, then see what happens. I'd be shocked if the O2s are bad. Bosch plugs = bad, but I've had good luck with Bosch sensors in other cars where they weren't OEM.

FYI, my AEM UEGO wideband in my miata uses a bosch sensor. bosch does make really damn good o2 sensors, spark plugs are another thing

[BigTDogg (MA)]

Originally Posted by Milky

FYI, my AEM UEGO wideband in my miata uses a bosch sensor. bosch does make really damn good o2 sensors, spark plugs are another thing

How is TN about non-toyota-related threads? I'd love to see some pics and build info on this Miata

[adamsautocare]

Bosch O2 sensors were my problem. I had a p0420. changed my o2 sensors to bosch. Code came back and car was not idling properly. (used a scope and the voltage was way off which has been a problem with our cars and aftermarket O2 sensors I guess). Switched to Denso and no problems since. Not saying that Bosch sensors are no good, but there have been many problems with them and our cars.

[moviestar]

p0420 = replace the cat and o2 sensors.


rockauto.com for oem o2 sensors.....and take off that shitty magnaflow


also, you shouldn't seafoam your car....its killed a few rolla's I've seen.

[BigTDogg (MA)]

Originally Posted by moviestar

also, you shouldn't seafoam your car....its killed a few rolla's I've seen.

What exactly did it kill?

No point replacing the O2 sensors, they aren't the problem.

[moviestar]

Originally Posted by BigTDogg (MA)

What exactly did it kill?

No point replacing the O2 sensors, they aren't the problem.

clogged one of them beyond repair. Corroded another.


oh wait you don't have a maf do you? jk you have an 01...yeah be careful with it.

[Milky]

Originally Posted by BigTDogg (MA)

How is TN about non-toyota-related threads? I'd love to see some pics and build info on this Miata

well i dont want to annoy a mod or get banned, but here is a link to my miata's pics on my photobucket. i have not done any recent photos since the install, its still quite messy, but come spring ill have it cleaned up and more pics.

http://s910.photobucket.com/albums/a.../Miata%20Pics/