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Blew my downpipe off last night...have a couple questions

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RMeadows

15+ Year Contributor
83
1
Jan 2, 2007
West Palm Beach, Florida
Last night playing around with a mustang I blew the downpipe off the 02 housing. Now whenever I go WOT I get knock. Is is possible since the car is so loud now this is simply phantom knock? Pretty much as soon as I enter boost the knock sum gauge lights up 3 clicks. Car was tuned to ZERO knock before this happened.

Other question is this. I have an 02 Eliminator housing and the 02 sensor is therefore plugged into my downpipe. Since the 02 sensor is now being completely bypassed is the ECU going to go into limp mode? Car seems to be running okay but I haven't really been doing much else than babying it around. Is it okay to leave it like this until the weekend when I can fix it? Anything I should be concerned about?
 
I agree. your downpipe should not have come off unless it was not bolted on correctly. and the first thing you should do is find out why it did not stay on and fix it and put it back on. Even though it really won't hurt your engine to run off the o2, you are losing power plus depending on where you live a hefty ticket! and your knocking is probably cause from too much pumping loss. you need a certain amount of back pressure for daily driving for your throttle response. just get your downpipe on as soon as you can.
 
your o2 not getting any exhaust gases to it would make your car not run right and it would almost definitely cause knock... your car uses the o2 sensor to keep the AF ratio where it should be...
 
maybe... but knock sensors are tuned to pick up a certain frequency of knock, nut just any sound... if it was phantom knock from the noise, then his knock values would be waaayyyy higher... he said its only getting a couple of counts of knock.. and it happens when the boost starts to kick in...
 
maybe... but knock sensors are tuned to pick up a certain frequency of knock, nut just any sound... if it was phantom knock from the noise, then his knock values would be waaayyyy higher... he said its only getting a couple of counts of knock.. and it happens when the boost starts to kick in...

I have the PK code on my chip so the only time I would show knock is when i'm under boost. I drove the car home from work this morning and it was fine under boost, no knock. so not sure what happened there.

Anyway. I'm going to hopefully hop under it right now and get the dp bolted back up. I have a set of brand new DP bolts that came with my turbo install kit I can use. YES it blew off the bolts and everything. Really not sure how that could have happened OMG
 
Oh yea. One other quick question. Why didn't I get a check engine light? The car is basically running without any 02 sensor. I drove it 15 miles to work last night and nothing and then on the 50 mile trip home today it came on for about 1 minute and then went off again????
 
your o2 not getting any exhaust gases to it would make your car not run right and it would almost definitely cause knock... your car uses the o2 sensor to keep the AF ratio where it should be...

feel free to stop circulating that misinformation. Your ECU only uses the 02 sensor input under cruising conditions, when it leans out for improved mileage while. All other conditions, the ecu has preprogrammed fuel and timing maps triggered with TPS signal and rpm then varies these based on pressure sensors, water temp sesnors and the like.
 
feel free to stop circulating that misinformation. Your ECU only uses the 02 sensor input under cruising conditions, when it leans out for improved mileage while. All other conditions, the ecu has preprogrammed fuel and timing maps triggered with TPS signal and rpm then varies these based on pressure sensors, water temp sesnors and the like.

Isn't the o2 sensor info was used under all conditions except wot? (where it disregards o2 for max performance?)
 
well if your downpipe came off. your o2 sensor is still there, cause its off the o2 housing thats connected onto the back off the turbine. and your downpipe just connects to the o2 housing. Unless you have a different turbo setup and have a custom downpipe. Just put on the DP and see how it runs
 
well if your downpipe came off. your o2 sensor is still there, cause its off the o2 housing thats connected onto the back off the turbine. and your downpipe just connects to the o2 housing. Unless you have a different turbo setup and have a custom downpipe. Just put on the DP and see how it runs

My 02 sensor is in my downpipe, not my 02 housing. Hence the problem.

Anyway. I bolted it back up and made sure I tightened the crap out of the bolts. Hopefully it'll hold this time. I know the last time I kind of had trouble tightening them down so maybe I just didn't do it ALL the way. This time i'm sure it's on there good. She's running good as new again :thumb:
 
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