Mouse

I haven't seen this topic anywhere yet. I currently have a Megan Racing racing header installed on my 06 tC. I have heard after the fact that due to the increased airflow, if the valves and such are stock that it causes the cylinders to combust hotter. therefore over time, possibly damaging the valves, head, etc. Anyone out there in the community that is a seasoned mechanic, would love the input.

captainlaziness

I don't see how that would be possible, but I'm by no means an expert.

xdejablu3x

bump

speedelement

here's a relevant article
http://www.uucmotorwerks.com/html_pr...torquemyth.htm

its even more unlikely to occur on MAF cars since the "actual" airflow is measured to estimate how much fuel to inject.

engifineer

Given the MAF sensor and the O2 sensor, the car will keep itself within its parameters unless you shove more air in than the ECU can handle. You arent increasing pressure in the cylinder (like boost does) and are still pulling in the same air from outside, so there should be no issue with running lean.

Even cars with a MAP sensor instead of MAF, you still calculate airflow and mixture and the ECU compensates. Of course, cars with MAP sensors will run a little off if you change altitude greatly during one drive (no shutdown), like driving up pikes peak, but they would even be fine and actually should run richer, not leaner than normal in that case anyway. MAP equipped cars re-measure the static atmospheric pressure at startup, which "Resets" that issue so to speak.

Older carburated cars would have the larger impact, since thier fuel mix is in a sense set from the start.

Geigle

Quick question I have the DC 4 two 1 header and the Check engine light came on even with the defouler trick. So I had the codes ran and it came up a P0171. So from that I am thinking it is the O2 sensor. How ever it is going to suck to buy a new one like $200 ____in a man. How can I fix this I am doing the ecu reset right now. Any ideas? Can you fix an O2 sensor. And please dont lay into me if this is a question most know the answer to.

speedelement

P0171 means the front sensor is saying the engine is running lean, the defouler trick is for the rear o2 sensor, so it should be a different problem. you did put the defouler on the second/bottom sensor?
maybe check for vacuum leaks or cleaning the MAF sensor is pretty easy too.

Geigle

Ya the defoulers are on the s pipe and I already cleaned the MAF thinking it was the prob but the cel came back on after about ten min of driving. I hope it is not that sensor . I am geting rough starts and the car is idleing at 750 rpm. Could it just be runing leen and need a tune? I also checked the gas cap and it was not that.

Mouse

I have a race header on too.. as I started this thread... what you need to fix the cel is called an o2 sensor simulator. they sell them on the web. basically the ecu reads the measurements from the front and rear o2 sensors, and if they dont match within specs it trips the light for you to check things like mixture, clogged cat (because it doesnt know you removed it). that should fix the problem.

engifineer

They actually dont match. The ECU expects a different reading from the 2nd sensor, since the CAT that was there stock should be doing its job. If it isnt, it sets the code for a bad cat. That wont throw a lean code. The anti-fouler simply pulls the second sensor out of the flow a bit, so it skews its readings. Works sometimes, doesnt others. O2 sims are usually a bit overpriced from what I have seen and some of them dont work all the time either.

To set a lean code, the car is either running lean to a point that the ECU cant compensate, or the sensor is bad. But NEVER start off assuming it is a bad sensor. While many dealerships part swap to solve issues, it is the most expensive and least accurate way to work. Do the troubleshooting to see if there is a lean condition before just blaming the sensor. If not, you run the risk of replacing an expensive sensor and still having an issue.

Geigle

OK well I give up. I have read everything on SL that could be a problem with that code and cant get the CEL to stay off. I am just going to put every thing back to stock and take it in. Man what a pain!

engifineer

Well.. there is about a billion times more info than what you will find here.

The car thinks it is running lean and cant compensate. So if you dont have the equipment or the experience to troubleshoot that directly, then you can go back stock, reset the ecu and see if it goes away. If it does, you have then isolated the issue to your mods.

Geigle

OK will do. Realy the only option I have right now. I will also let you guys know what the issue is/was for any others that find its not the maf and the reset will not work.

OuterHeaven

If the car is running lean it could be because the car is sucking in air after the MAF sensor. This happened to me when the pcv vacuum hose disconnected from the intake manifold. The car ran like complete crap but still was able to barely idle (also it was lean). Lean means the car is either getting more air then it thinks it is getting OR it is putting less fuel into the engine then the ecu thinks it is putting in. I would look for vacuum leaks first especially after the MAF sensor.

Geigle

Thanks for the help I will double check it before I go through all the work.

Geigle

Oh man I hope you guys are in for a good laugh........ I can believe I didn’t notice this in the first place. So I take off my engine cover from Scion Pro. Great looking peace but blocks the view of the throttle body. The f-ing clamp bolt rattled out and the hose were the CAI connects to the throttle body came off. Thank god it was only that and a $.75 fix but man do I feel like a moron

engifineer

ouch... hope you didnt suck too much trash into your TB!!!! That is unfiltered air.

Geigle

I know man. I am a little worried about it. But the TB was still coverd by about 75% of the hose so hopfully very little crap got sucked in there. I figure it was only off for about 100 miles or so.