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98 gt running odd lately.

905 views 3 replies 4 participants last post by  Most Unclean 
#1 ·
98 gt running odd lately. extremely high idle, loss of power..

Okay so I've had the idling problem since I've had the car basically. Today I finally decided to take a look at it and the IAC is bad. I'm planning on fixing that tomorrow.

I think it's been bad for a good minute (since the previous owners) because I looked at the hose connecting the intake to the IAC and there was a lug nut stuffed in it to prevent the air flow. I took the lug nut out and re-attached the hose and now it idles at 2k and the hose makes this terrible humming noise.

But I'm still wondering if this is going to fix the rest of the problems. I feel a huge loss of power until I hit about 4k RPMs. Really the only way I can describe it is it feels like it has VTEC or something. Kinda sluggish until it hits 4k and then it jerks and gains its power back. It's been doing this for about a month now.

When I have the AC or the heat on, it will occasionally jerk a little bit if I'm driving at a constant speed.

It's throwing two codes. It's saying that the catalyst system is below threshold (bank 2) and the other one was about the IAC.

Could the cats and the IAC be the cause of all of these problems? Or could there be something else wrong with it?

In terms of mods it has:
X-pipe
Magnaflows
CAI
Aftermarket coil packs
70mm bbk throttle body
 
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#2 ·
#3 ·
Diagnose and confirm the Idle Air control valve is bad and replace if needed. I would start there first. Then clear the codes and test drive to see what comes back after the drive cycles are complete.
 
#4 ·
The IAC for this car was a constant problem for me, I had many of the same problems you described. But no catalytic problems or nut it hose ... WTF! ... find the previous owner and beat his ass.

After replacing the IAC most of my problems went away. First time I used an aftermarket IAC and still had troubles. After putting in a new OEM IAC she purred like kitten. GET THE OEM, NOT AFTER MARKET.

I had the the hum , it was the IAC inducing harmonics back into the cold air intake, crazy loud. Had lots of troubles near idle speeds and little hick-ups at higher RPMs. Also had a vacuum leak but those tend to be more evident.
 
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