355 check engine light on

Do you have O2 sensor spacers?

Don't wrap the cats, that wont help. Do a search for the thread on Check engine lights and how to solve them on here, lots of great stuff there.

 

Yes you do need to heat them up pretty good before the smog. Less restrictive means less heat. Would I wrap them? No its more an internal thing.


Secondary air. I was thinking the other day about this. was going to put an external switch to turn them on just during a smog check to see if it lowers emissions or turn it on then turn it off right before testing. Of corse not for the actual test just to see the results for my own silly reasons

 

Its a really big core and its the core itself that stays hot. You could try wrapping them but they get so hot themselves I personally dont like to have them in contact with any material. This is coming from a person that runs high temp ovens daily and I would hate to see a fire from the wrap picking up any foreign matter and ignite it.

If your just trying to squeeze through smog...sure try it

My spider passes Pro Cats just barely but it does.

 

The CEL will come on every once and awhile if you have anything other than OEM cats on a 5.2 F355. The issue is the motronic is so fine tuned to not only individual 02 sensor readings, but the DIFFERENCE between the front and rear 02 sensors per bank. How fast the differences change, how much the differenc is, different changes per senerio, ect, ect, ect.... I had a detailed discussion with the head tech at FoS (Mark) during a tech session this past summer and he basically explained all what I just stated to me.

Every aftermarket cat has reported CEL issues, or at least I have read of issues for each here on Fchat.

Either get a 2.7 car, use stock cats, or.... live with the intermittnet CEL.

Edit: I choose to live with the CEL and use test pipes. If I ever need to pass smog or sell I will put the stock cats back on.

 

Grant - I've had HyperFlows on my 355 for 7+ years. They've never been wrapped, I've never failed CA smog, and I've had only one or two CELs since installing. My CELs typically showed up after laying heavily and abruptly into the throttle, usually to pass a car quickly. My OBDII read the fault as "rich fuel mixture in cats" or something to that effect. After re-setting, it's never re-appeared for any other reason than the one I describe above. Hope this helps...

Doug

 

No, you don't have to live w/ the problem. I have a 1998 5.2 Motronic w/ Hyperflows and the frequency of occurrence of the CELs went way down w/ regular O2 spacers but did not completely eliminate them until I replaced the regular O2 spacers with ones that have a tiny catalytic converter built in. See link here to "Mini CAT Mechanical Simulator"
O2 Spacer - Oxygen Sensor Spacer - CEL / MIL Fix - Oxygen O2 Sensor Adapter - O2 Sensor Extender

 

My car is a 1995 with a 2.7 Motronic with only 2 O2 sensors and it has no issues, but the later 5.2 cars have four O2 sensors, one set before the cats and one set after the cats. The 5.2 engine management system has been programmed to expect a specific set of temp and fuel mixture parameters from each set of sensors based on a normal set of cats and a stock exhaust. When you modify things its easy to get things out of the expected range and the computer says "Uh Oh, somethings not right, I better throw the light." Putting spacers in the "post cat" O2 sensors to remove them from the exhaust stream somewhat reduces these instances. I will try to find the thread, but I think there is at least one FChat sponsor vendor that sells these.

As far as why not to wrap, the reason is that cats operate at every high temps, and wrapping the outside will not really change the internal core temps very much. BUT wrapping them will restrict the metals ability to expand and contract some and more importantly a wrap tends to create a heat spike in the metal at both points where the wrap begins and ends. This will lead to fatigue and cracks for sure.

Hope that makes some sense!

 

Those are really cool I would love to try them, like others I dotn get any tossed codes with my cats so I have no valad way of testing them

Glad they work as they are really cool units

We do have some structrules regarding smog and every creative way to remedy them helps us out.

 

How long have you been running them that way? I would be very interested in finding a way to completely eliminate the CEL, but alas I have never had someone step up say they have a combination that works to fix the issue.

 

Only a month or so, but long enough w/ enough drives that I'm sure it would have come on again by now. There was another guy on F-Chat that said he was running regular spacers and had no problems but they were right angle ones. I was running straight tube spacers, so when I heard of these I just switched them out. So far so good, but I'm confident that it's a good fix, it just seems logical that it will fool the O2 sensors back to thinking the cats are good.

 

The rear 02's you can just make a little line voltage box and run 1.2-3v to them and the CEL will stay off. You wont have the functionality of the rears which is just to keep an eye on the cats.

I remember someone doing it a while back here on the forums.

 

It's a very common problem and one I've just learned to live with. Buy a OBDI tool that allows you to reset it. They are less than $30. I get CEL lights about once every three or four months. I make sure it's the cat code, reset and then off to the races again. The good news is that you will have no problem passing the smog test since the cats are very good. It's just an annoying issue. I have the spacers sitting in my garage cabinets and just need to get off my lazy rear to install them.

 

hi,

to my understanding even with 5.2 cars, high flow cats didnt throw CEL..?

I was also curious if the 5.2 355's have a manual sequence to read and delete codes.

on a previous car of mine there was a specific pushing of the pedal sequence with the key turned half way, that when done just right, the CEL would blink to read out the code, and then you could reset it..

seeing a CEL light is annoying even though you know its not a serious issue, but to my understanding a CEL is not the same as a "slow down light", which i believe kills the throttle..?

 

5.2 (96 onward) F355 will also throw CEL light if you install High Flow cats. The use of long O2 sensors spacers will reduce the frequency a great deal.

The 96 (almost every other 96+ cars sold in the US) comes with mandated OBD2 system which provides a standard connector under the dash where you can plug in a over the counter OBD2 scanner to read the error codes, and erase them.