catnaround

Just purchased a 10 GS with Melrose long tube headers,high flow cats and a Air Raid air intake,check engine light is on and the mechanic tells me that the light is on because the original cats were removed and need to be returned or it needs to be taken to a dyno shop to have the computer fix the problem......any suggestions short of reverting back to OEM

JABCAT

88redconvert

Long tube headers almost always throw the check engine light. If there are any tuners in your area they can just turn the rear O2 sensors off. Mine did the same thing.

TorchRedFred

I would assume the previous owner had a tune done with the mods, but if not, like JabCat and others stated, you definitely need one to tune out the rear 02 sensors and to get the full performance benefits of the mods.

buckmeister2

If he has rear cats, doesn't he have rear sensor bungs? Wouldn't the rear sensors be in place? And, if the tune is'was done right, wouldn't he be good to go without having to turn off the rear sensors? Sounds more to me like either the sensors were cut, or there was never a tune done after LT install.

OP, please be sure to let us know what the fix is.

Batman75

[QUOTE=buckmeister2;1598332001]

Sent PM Jim, would like the name of the two instructors.

JABCAT

z06clif

Headers=tune.....everytime

Clif

buckmeister2

Thanks for the clarification, Jab. I have seen LT's with bungs, and without, and header mid-pipes with cats with bungs for rear sensors. Didn't know what the OP had,but figured he at least needs a tune. So, if your headers have bungs for the fore sensors, and you have cats behind them with bungs for the rear, wouldn't you just plug in all the sensors and get a tune?

Orion2011

Just turn the rear O2's off with a tuner.

JABCAT

I'm far from technically fluent on this, mostly what I've researched when I installed my longtubes & exhaust. My understanding is it has to do with the placement of the sensors & the increased exhaust output not being funneled through 4 cats. I'm trying to remember when I removed the stock exhaust, I believe the front O2s were right up next to the manifolds & the rears were just past the first set of cats (don't quote me on that). With the longtubes the fronts get moved way down to the end of the headers where they meet the x-pipe/cats (if you have them) and the rears get moved to after the 2nd set of cats, at least that's where my bungs are on the LG's. I believe, again not an expert, that change in location and the removal of the two front cats causes the rear O2s to foul pretty quick causing the check engine light, and they aren't needed. So most x-pipes come with bolts to close off the rear bungs or you could install the O2s but just have them turned off by your tuner.

Ahrmike

I put a 90 extension on my uncatted headers and it throws a CEL once in a while. Heard the same thing happens even if you run a HFC so I guess they work?

MYCoupe

Just to clarify this for everybody. The front O2 sensors are the ones actually used to measure and adjust the A/F ratio. The rear ones are used to measure the efficiency of the catalytic converters. When switching to LT headers, even with cats in the x-pipe their efficiency is not the same as the OEM ones hence the check engine light comes on. As others have said the solution is to turn them off as they are basically useless.

itomh

Either buy a tuner and tune car or get a proper dyno tune that is required after adding headers, not cheap, probably $500+. Another option, the cheapest, would be to pull your PCM located behind front passenger wheel under the wheel fender. I went this route when I installed my headers myself. From shipping to return to me was about 5 days $149 plus shipping. Cost effective and not as aggressive as a dyno tune, but you will leave a coupe ponies on the table.

https://www.eastcoastsupercharging.c...er-tuning-faqs

S.C. vette

mrk1957

Ditto

catnaround

want to thank everyone for the information,i did take the car to a tuner in tampa and everything is well thanks again

mrk1957

Glad all worked out.

0Tampa Tuning

Thanks for stopping by yesterday and it was a pleasure to calibrate your beautiful GS Corvette. There was several rookie mistakes made to your Corvettes computer which I enjoyed correcting. Im glad your back up and running with some extra power !

Home of the $295 Calibration with HP Tuners and wideband for stock to bolt ons Corvettes and Camaros to be street race tuned.

Tampa Tuning's in-depth computer process includes low end parking lot driving, cruising at highway speed and WOT.

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Reach us at : Tuning@TampaTuning.com


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Corvette Camaro Truck Tuner in Tampa Orlando

Complete Street

Get it tuned. We could possibly help via mail order if no one local can work with you. Info is in the sig. Thanks!