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View Full Version : boggs down at 3k rpm or so -- both o2 sensors throwing code



henschman
05-07-2008, 01:32 PM
I just started having this problem a couple of weeks ago. It started after I went really fast on the highway driving home (i don't know how fast -- had the needle buried at 120). When I slowed back down and let out the clutch, the car died. It now either idles too low and tries to die, or idles very high (sometimes almost 2000 rpm). Also, it bogs down when trying to accelerate. It does OK until about 3000 rpm, but then it won't go any further and makes an extra loud whining noise from the intake/supercharger. It's acting like something is really constraining it. It is throwing the codes for both o2 sensors. I suspect it isn't the sensors themselves though, since I just replaced the right one after it threw a code a few weeks ago. I thought it might be clogged cats, so i chopped them and replaced them with downtubes (i was planning to do that anyway) -- it didn't fix a thing.

any ideas? I hesitate to replace both o2 sensors just on a whim, with them being over $40 a piece, and one of them is new.

David Neibert
05-07-2008, 02:04 PM
I just started having this problem a couple of weeks ago. It started after I went really fast on the highway driving home (i don't know how fast -- had the needle buried at 120). When I slowed back down and let out the clutch, the car died. It now either idles too low and tries to die, or idles very high (sometimes almost 2000 rpm). Also, it bogs down when trying to accelerate. It does OK until about 3000 rpm, but then it won't go any further and makes an extra loud whining noise from the intake/supercharger. It's acting like something is really constraining it. It is throwing the codes for both o2 sensors. I suspect it isn't the sensors themselves though, since I just replaced the right one after it threw a code a few weeks ago. I thought it might be clogged cats, so i chopped them and replaced them with downtubes (i was planning to do that anyway) -- it didn't fix a thing.

any ideas? I hesitate to replace both o2 sensors just on a whim, with them being over $40 a piece, and one of them is new.

Sounds like a big vacuum leak...look on the rear of the inlet and return plenums for a hose that may have blown off and if you don't see anything they spray the IC tube connections with carb cleaner while the motor is running. Something probably sprung a leak when you were going wide open throttle.

David

henschman
05-07-2008, 02:19 PM
ah crap, that same thing happened to me in my turbo buick last year... blew an ic hose off the turbo while going fast on the highway.

i thought about that possibility, but i figured with the metal piping on this car it wouldn't be an issue. I'll check, though. i hope that's it -- that's about the easiest fix you'll get.

94MustangSC
05-08-2008, 09:37 PM
Possibly the IAC? I had one go bad on the dyno last year. You'd start the car and it would idle at 2000 rpm. Maybe yours is intermittent. I picked one up from the dealer; it was about 80 bucks.

henschman
05-14-2008, 03:51 PM
it was indeed the intercooler hose... the big nut that fastens the line to the supercharger had backed itself all the way off, and was hand loose. I screwed it back on and tapped it into place with a screwdriver and hammer, and it is all good. thanks for reminding me of that possibility!