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Mid RPM Stumble.

444 views 5 replies 5 participants last post by  tksmr2 
#1 ·
I have a reocurring mid RPM stumble that really annoys the heck out of me.

I have now narrowed down its onset to getting wet. It first occured when I washed my engine for the first time ever. Everytime it gets really wet and soggy, or especially when I drive through a big puddle, it comes back.

For some reason it coincides with the TVIS switchover at high 3000 to mid 4000 rpm.

THis is a really pronounced, and VERY annoying flat spot that is very akin to turbo lag. Once, I even broke traction (on snow) while making a left turn at an intersection. I was trying to accelerate normally from a standstill, but as soon as I hit 3600, the car just very nearly bogged. I then instinctively apply more gas. As soon as the RPM hit above four grand, the power came on and next thing I know I was opposite lock trying to save it.

Thinking it might be the TVIS being really gummed up, I tried unplugging all the vacuum hoses related to it and started going at it with some carb cleaner. Didn't really help.
My next troubleshoot was the ignition - I think it's severely retarding the timing during the TVIS switchover. How? I don't know.
But then again, all ignition related components and connectors that I could see never really get wet either. So I'm right out of ideas...


But one thing is this: It gets ELIMINATED everytime I disconnect my battery and reset the ECU.

So I only have one working hypothesis: One sensor is screwed up and that the ECU is getting wonky signals. So much so that it's adjusting timing on the fly to compensate for whatever it thinks is wrong.

Trouble is, which sensor?

And any other ideas?
 
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#5 ·
check the tvis sillnoid under the intake manifold. sounds like you might have water in the conector, or in the check valve system might have a lose vac line.

unplug the tvis electrical conector, Drive the car, does it go away?

Check your cap and rotor for water as well and you spark plug wires at the spark plug ends.
 
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