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99 GTX Surges hard under medium throttle and randomly shuts off

V

VOChris

New member
Whats up fellas! ok this is my moms 99GTX (i wish it was mine and she had a wart on her........Nevermind) anyways ive been its sole mechanic for better than 10 years and its only thrown me for a couple of loops. Im fighting one now. it has 129000 give or take. Its the GTX w/RamAir SLP package. The previous owner raced it on the weekends only but that was 100000 miles ago. It has the autolite copper plugs, MSD 8.8 wires k&n cone in the air box. Plus an underdrivin pulley. What its doing now is when crusing normally and or when accelerating lightly it starts surging hard. I want to say it the tach goes up and down by 500 rpm or better. its enough of a change that it pulls u back in ur seat then lets u go then pulls on u agian & so on. Now if u goose it to a downshift it stops surging and takes off. it doesnt really do it at idel or at or near wot. I have cleaned the MAF sensor twice. I got a iac and a map from a junk yard & no change. Also randomly and less often it will die, just like someone shut it off. It will then start right back up. Oh i cleaned the TB. Im leaning to the MAF cause the first time i cleaned it, it seamed to go away for a minute but i decided it was a fluke cause its so random.


Any Ideas would help

THANK YOU
 


The random shutting off sounds like time to replace the Crankshaft Position Sensor. They are known to do this and throw no CEL. Do you happen to notice the RPM's dropping to 0 before the car shuts off? This is usually a tell-tale sign.

The surging sounds like the TC. Next time it starts doing this take your left foot and tap the brake. This will unlock the TC. If the surging stops then we can go from there.
 
OK thank you for ur reply - it did throw a tcc code - not disengaging about a month ago - i got it to go away & it hasent come back - I soooo didnt want to do that job - but it is what it is. Ill post when i can get the brake tap done
 
First rule of surging... when was the last tune up done. Being copper plugs they need to be changed a little more often than say stock iridiums. Coils..are they stock? I have come across surging that ended up being a bad coil pack and was impossible to find until I shotgunned parts at the issue.

With the TCC causing an issue in the past though, it is very possible that the TCC is giving you issues. Yet..the oscillation is typicaly not as bad as you make it sound
TCC rpm oscillation
 
Hey thank you for that one - i stay on top of the plugs and its the hardest on wires ive ever known - but i do have 2 extra coil packs i can swap around a bit - also ive not yet read the link u sent but it looks very interesting. thank you for usefull info.
 
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