suspected miss at temperature, bad lifter?
suspected miss at temperature, bad lifter? a few months ago I did a 6 speed swap on my car, and at the same time I did long tubes, or-y, and NGK TR6 plugs. well ever since my car has not sounded the same. it sounds and feels kind of rough. when cold, the car responds crisply and exhaust sounds about like it used to. then up to temperature it changes. becomes slower to respond and has a rough idle and the overall sound of the engine changes. under load, if I accelerate I can feel a sharp "vibration" in the car, and through the shifter, and can hear it in the exhaust. could this all be from poor y pipe design and excessive back pressure (custom built Y that is oddly shaped)? I am afraid that with the temperature thing it may be a lifter not pumping up when the oil pressure drops down to normal operating pressure. compression checked out good, plugs all look good. can a badly designed Y pipe do all this, or am I dropping a cylinder? any ideas?
Indeed. That "y" pipe directs the gas straight into the wall of that other pipe. I'm sure that cause some horrible restrictions.
Looks like it would actually direct the exhaust the wrong way too, by the angle it enters the passenger side.
Looks like it would actually direct the exhaust the wrong way too, by the angle it enters the passenger side.
I was afraid of that. I knew things were going bad when the guy tried talking me into letting him weld everything solid, including welding the y pipe to the stainless headers. I told him not to touch my headers with his welder or we would have some major problems. I hope that's all it is
I was afraid of that. I knew things were going bad when the guy tried talking me into letting him weld everything solid, including welding the y pipe to the stainless headers. I told him not to touch my headers with his welder or we would have some major problems. I hope that's all it is
Ya, good thing you didn't let him weld it all together.
I'm no expert, but I think the angle of that connection is causing the exhaust pulses to interfere with each other causing excessive back pressure. I think that's where your vibration is coming from too.
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what still has me curious though is why it only does it at temperature. cold it's fine, sounds normal, responds good and everything. going to try doing an oil change and see if it helps it any, it's overdue for one. then I will look into re-engineering the y pipe. I'm going to get a vid today comparing the exhaust between cold and at temp
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Addressing your problem. When it's warm it goes into closed loop. Then the computer tries to closely controlle the air fu mixture. With the headers and new exhaust it prolly needs a tune to take some of the roughness out of it. It will not take it all out but a tune will help alot. Also I agree you need a new y and merge. Flowmaster has some merges you can use to make a custom y with. I got my merge from flowmaster for 35 dollars
did an oil change today, and while under the car I noticed that the passenger o2 sensor had come unplugged. plugged it back in and went for test drive and it felt better. still not 100%. I think the rest of what I am feeling is that y pipe. and my ses light is still on from the a4-m6 swap. haven't tuned it since. but I did pull codes today and only got ones I would expect to see from EGR, AIR and auto trans missing
One going bad or un plugged will cause problems in closed loop it doesn't need to be both. OP glad you are getting it figured out. Let us know what you do with the ypipe.
Last edited by ds98formula; Jan 3, 2012 at 10:50 PM.
yeah thanks for everyone's input. it is running much better now, and I think the y pipe will take care of the rest of the rough feeling. now I just gotta figure out what I broke under the car that's making it "wobble"... on to the suspension section!
