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Discussion Starter #1
Well, figured it should be asked anyways, even though i'm reasonably sure it's a VAF issue.

Here are the symptoms:

1) If the car is running in neutral, and you tap the gas more than 25% throttle, the throttle response is dead awful. The worst i've ever seen. I hear the throttle body open, then literally a second and a half later, then the motor finally lazily revs up, stuttering a slight bit.

2) Upon takeoff, if you aren't smooth with your go pedal application, the car bucks and bogs like crazy, then smooths out after a couple seconds.

3) On a 1-2 shift, if you shift quickly, don't slip the clutch much, and give it some go juice, it bucks and bogs like crazy. (No, it's not motor mounts) In order to make this shift smoothly, it involves more clutch slippage than should be, and very light throttle.

4) The car STILL hauls ass once it's moving, throttle response is unaffected in the higher rpms.

5) From time to time, particularly after it bogs, it will blow some big nasty black clouds of unburnt fuel.




I used some CRC MAF cleaner on the VAF, and that seems to have helped some, so did i just answer my own question? Need a new VAF? Time for an RX7 VAF?
 

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Discussion Starter #3
BOSS302man said:
Is your rubber air tube in good shape?
Yeah, it's a brand new dealer part with less than 1000 miles on it.

It's all connected well, no leaks in the intake system anywhere.

I was almost thinking a vaccuum leak, but it idles well, and once it's cruising, it's getting over 30mpg combined still.

I'm leaning towards VAF since the cleaner helped a little.
 

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On a cold start, my 91gt would bog real hard in 2nd gear, just like you're explaining, but once I got the cai on, it seems to have fixed it. If you have the haynes/chiltons it should you how to ohm out the pins on the vaf to make sure it's working properly or not.
 

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Discussion Starter #5
I don't have either of those, sadly... :(

It's not just a cold start occurrence. To be honest, i don't notice it much because of the way that i drive. But my gf has only been driving stick for about a month and it bugs her, because she will experience it more often. It's not just a case of her driving badly, i've been able to easily duplicate it myself, and the huge delay revving in neutral happens whether the car is hot or cold.

I guess i'll try to find a chilton's.
 

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When was the last time you did a tune up on it?
 

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Discussion Starter #7
Maybe 2000 miles ago. It hasn't been driven a ton since i bought it. First thing i did was a tune up.

Plugs, wires, cap and rotor, oil change, new air filter, etc
 

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Discussion Starter #9
therieldeal said:
i had wierd symptoms like this when i first got my 91 and it was a bad clt temp sensor
CLT? Acronym for....

Sorry, lost here. :(
 

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I'll assume it's short for coolant. I have a spare, but only because mine is broken. Still need to swap it out, probably do that today.
 

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Discussion Starter #11
That would cause a stumble and to run rich from time to time?

I mean... that might make sense.... our radiator needs replacing, i just haven't gotten around to it, but the temp gauge shows fine.....

Elaborate? Might be on to something here....
 

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It's a sensor in the thermostat housing. It only sends a signal to the ECU. the temp gauge uses a totally different sender. It's a single pin connector, should be black plastic on it.

This one:
 

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I bought a chiltons today, 6.50 at half priced books. sweet deal. anyway, it says that to test the VAF.... I'll upload pics, baha. gimme a few.
 

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Discussion Starter #15
Thanks a lot man. Definitely got something to do this weekend now. :)
 

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whoa there

there are 3 different coolant temp sensors:

the one pictured above doesnt go to the gauge or the ecu, it essentially connects directly to the fan relay. its just a thermoswitch that grounds out at 200 something degrees.

there is a teeny tiny 1 wire one on the front corner of the head, that feeds the dash gauge

on the side of the head there is a green 2 wire plug (rectangular), this is the coolant sensor that feeds the ecu. this is the one that went bad on my car.
 

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Discussion Starter #17
^You talking about the one on the waterneck, right?

Basically, if that's bad, it's screwing up what the ECU wants to do, maybe jumping between hot/cold maps? (grossly simplified, yes)
 

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ciento44 said:
^You talking about the one on the waterneck, right?

Basically, if that's bad, it's screwing up what the ECU wants to do, maybe jumping between hot/cold maps? (grossly simplified, yes)
No! The one in the side of the head on the drivers side below the valve cover breather tube.
The one in the water neck as you call it is the tempature fan switch.
 

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therieldeal said:
whoa there

there are 3 different coolant temp sensors:
If you have an auto gt, there is a 4th senser. A fan temp switch in the radiator for the high speed in case the other temp swich fails.
 

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So the one I pictured is for the fan only? I replaced it with the good one I had yesterday, when I pulled it out, it was just the pin stuffed into the backside of the sensor, it's no wonder my fans were sketchy, damn used cars...
 
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