2000 firehawk wont downshift properly
02-14-2014, 08:31 PM
#1
2000 firehawk wont downshift properly hello all, i just picked up a 2000 firehawk as my 4th ls1 for a steal and couldnt resist, car was very clean and runs fine, all options work and is a true firehawk in great shape. it does have one issue and i decided to purchase despite it feeling confident i can fix it. ok so drives fine cruising around, however if you go to WOT the car only downshifts once or sometimes doesnt downshift at all, from previous cars i know its supposed to drop 2 gears at WOT, and this car doesnt and as result dosent really get up to speed or go as fast as a normal ls1, engine is running through rpm just fine, just the gear ist proper. now i will add that it does seem to idle low, around 500 and have noticed 400 at some times however have had no issues with stumbling or rough idle. the other thing i noticed is when i first looked at it with the seller it had this extra spring attached to the throttle body arm, the part the throttle cable is wrapped into. it stretched to a bolt on the air lid, and as result made the pedal much stiffer. i removed it never have seeing this on an f body and the pedal is back to its normal feel however car still doesnt downshift right at WOT. any thoughts on wether this is an aging transmission or something else? car is stock with 92k miles except for an slp lid, bbk long tubes, and SLP loudmouth ll exhaust. any input is appreciated. this car was bought to be my replacement daily trans am so im not trying to mod the crap out of it but i do want it to downshift correctly so i can play with it when needed.
right now my current thoughts are that the extra spring on the throttle cable was there from a previous owner for a reason, and that the suspect to this problem is the cable. car shifts fine when cruising
right now my current thoughts are that the extra spring on the throttle cable was there from a previous owner for a reason, and that the suspect to this problem is the cable. car shifts fine when cruising
Last edited by usnfenix; 02-14-2014 at 08:36 PM.
02-15-2014, 10:56 AM
#3
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What you mean by "right" is not clear. But the stock
part throttle shift tables are craptastic for the 2-1
kickdown, only downshift at >96% pedal below 38MPH
(for my original gearing) and there are many 4th gens
out there that don't draw to 96% (at the blade or at
the TPS, indicated) because the pedal travel is too
short.
Start with a cinder block on the pedal and measure
blade across the TB face; if not dead center, then
bump-stop inspection, cable-snugging and bending
the pedal arm for more draw are your next steps.
You should measure idle and matted TPS voltage
too, and sanity-check.
part throttle shift tables are craptastic for the 2-1
kickdown, only downshift at >96% pedal below 38MPH
(for my original gearing) and there are many 4th gens
out there that don't draw to 96% (at the blade or at
the TPS, indicated) because the pedal travel is too
short.
Start with a cinder block on the pedal and measure
blade across the TB face; if not dead center, then
bump-stop inspection, cable-snugging and bending
the pedal arm for more draw are your next steps.
You should measure idle and matted TPS voltage
too, and sanity-check.
02-15-2014, 11:48 AM
#4
ok so updates, today i replaced the TPS and no joy everything same as before. i did however pull everything off to see if the TB blade was dead center at WOT and its not, not even close really. ill post pictures below. i got some live data from a code reader ill post as well in case it has some relevance. i took it for a spin and did notice some things i didnt add in the first post. i put it in first manually and went to WOT, and from having 3 auto ls1's before i know that did not feel at all like 1rst gear WOT. felt the exact same as it does cruising at 40-50 and going to WOT, it just accellerates in its current gear and upshifts from there. HOWEVER, at WOT, and manually in first gear when i shifted to 2nd the car remained in current gear, i shifted to 3rd as i was a second away from redline now and it still didnt shift at all, only placing it in overdrive did it finally react and shift. in OD it will shift on its own however no kickdown to a lower gear at WOT. ill post my pictures below and my live data i got. idle is definitely low.
this is my TB with gas pedal fully depressed. gas pedal does sort of feel like it has a shorter travel than my previous f bodys.
and heres my live data, first image is in PARK, second image is in DRIVE but still sitting at idle. and the third image is the tps and maf readings which had no change in either park or drive.
this is my TB with gas pedal fully depressed. gas pedal does sort of feel like it has a shorter travel than my previous f bodys.
and heres my live data, first image is in PARK, second image is in DRIVE but still sitting at idle. and the third image is the tps and maf readings which had no change in either park or drive.
02-17-2014, 10:39 AM
#10
Well theres your problem... its not going to downshift correctly if its not at WOT. That's probably in the 70% range. Looks like you need to adjust the throttle cable. Theres a block about a foot or so up the cable that you can make some adjustments at. When your done, with the ignition on and engine off, hook up your scan tool, hit the pedal and see what your TPS is at just to verify its at or near 100%.
02-18-2014, 03:44 PM
#11
Well theres your problem... its not going to downshift correctly if its not at WOT. That's probably in the 70% range. Looks like you need to adjust the throttle cable. Theres a block about a foot or so up the cable that you can make some adjustments at. When your done, with the ignition on and engine off, hook up your scan tool, hit the pedal and see what your TPS is at just to verify its at or near 100%.
