sXeVegan

My car has so little power in the upper range that I'm not even sure if i could bring my car to redline in 2nd gear. It just kinda sits around 7-7500 rpm. Can this be as simple as a clogged cat? The only codes I run are O2 and pressure sensor. Since my O2 is bad, isn't there a better chance i have a clogged cat? The car has new plugs in it and i checked them today. They were black but i cleaned them up. They looked a lot better than the old plugs that were in last week when i changed them.

sXeVegan

My other question is how much louder would the car be if I just just bent a new pipe to replace the cat. With my current cat back, its already a little too loud for my taste. Does the cat do a lot to quiet it down?

Next question....im surei can search and find the answer to this because ive seen a post about it before, but since im on a role ill throw it out.... I plan on switching to an RB header and pre silencer right in the begining of April. I've heard a dispute on whether or not they use an O2 sensor. I'd just replace mine now but im cheap and if i won't be using one in 3 weeks then i won't waste my money. Does the RB header use the same O2 sensor as the stock header? If it doesn't have an O2 sensor, won't it always run rich? Won't it also always be throwing a code? Does the ecu have a safe mode kinda deal where if the O2 sensor is unhooked ithe car will run poorly? Thanks for the help

bingoboy

rb header and presilencer will make your car much much louder. with a decent muffler setup it won't be intolerable. with N1 style mufflers, i hope you've got earplugs.

the racing beat street header has a bung for o2 sensor, but you will have to extend the wire on the sensor. the o2 sensor is used only for low/constant throttle cruising, mainly highway driving. after low load, low/constant throttle cruising for a bit, the ecu will check the o2 sensor to see if it should run leaner. i've heard this will get you maybe 3mpg highway driving. the rest of the time the o2 sensor isn't used.

if your power is lacking that much up high, maybe your 5th/6th ports and or vdi are not working. you may want to check those.

sXeVegan

Im a noob so this could sound VERY stupid but I thought that the 5th/6th port problem was more of an S4 issue. Does it happen in the S5 too? I didn't mention before that i have an s5 vert.

ok...after doing some searching i proved myself wrong. I guess its all the n/a things. I will try the grease test. I also found this. ". Lube the shaft and work it in and out." My dream girl is now an RX-7 mechanic.

I will also try regrounding since it appears as though that fits my symtpoms as well.

trainwreck517

iTrader: (1)

Yes S5 engine still has 5th 6th port, so if they are stuck closed your uper power will suck..

seach.. aaroncake has a write up on how to clean and check if they are working.

sXeVegan

Just to add another little piece of info, the car idles fine and in neutral it gets to redline VERY quickly. In first it still accelerates at high rpm but my belief is it SHOULD do it better. The car throws out a VERY loud backfire when shifted above 6000 rpms. I'm not sure if thats related or not.

WAYNE88N/A

If your secondary injectors are not coming on line when they should, and your 5/6 ports are opening, you'll get that boost sensor code...There is nothing wrong with the sensor, it's giving the code 'cause you don't have the extra fuel to go with the extra air that's coming in, the ECU sees that something's wrong, and throws that code (this is all from experience w/ an '88, I presume the S5 is the same boost sensor setup). Check your secondaries per the Haynes or FSM

sXeVegan

Thanks wayne. Ill check them out this weekend. My question about that is, wouldn't that make the car run lean instead of rich? I'm actually not sure if the car is even running rich or not, but the way my plugs were blackened so quickly and the backfires, i assumed i was.

WAYNE88N/A

yeah, it would make sense that it might run lean, although I think the primaries would work a little harder to try to get the preset A/F back on the map, that's why I'm not ******* mine too much till I get those secondaries running good again. They're getting power & signal from the ECU at the 3500 rpm point, but they 'aint squirting the gas, man...If your injectors are so shot they're squirtin' a stream instead of a "fog", that may give you the rich visual symptoms, not all the gas is gettin' combusted when it should...just a guess...BTW, if you've got the ECU codes pulled up while your driving along, you can see exactly when that boost sensor code hits- mine does it at the point the secondaries should be online, my ports are already open by then, about 4000 rpm or so...

sXeVegan

sooo.....i hook up the wire like i normally do to read the codes. Normally youd read the codes with one click of the key. I can do this with the car running? Will the check engine light just come on steady (by steady i mean not flashing) right when the boost sensor fails? I'll have to change the O2 sensor first I guess so i don't confuse the two.

on a side note this is so difficult. After tons of searching i realized that it could be one of a million different things. (ground, secondaries, cats, 5th/6th ports, fuel filter, the list goeso n forever). I guess I'll just start with the cheap stuff and mosey on down the list.