Throttle Body Replacement 1990
06-27-2013, 10:22 AM
#1
Racer
Thread Starter
Throttle Body Replacement 1990
Good Evening All,
My car has the dreaded sticking throttle due to a worn butterfly shaft. I have replaced the IAC, cleaned the throttle body (which was quite clean to start off with) and ensured the cable and linkages are all free and not binding. Tell tale is when I start and the engine races (high idle but not rough, when I wiggle the linkage on its stop it will drop down in revs.
Anyways my query is what path shall I go down since stock re-built or new 48mm twin tb's do not exist. My engine is stock and worried going to a 52mm will compromise my smooth progressive throttle off idle and cruising and introduce lean conditions. I would like a tb to accept the stock intake pipe rather than going extra for the bigger ones.
The aftermarket brands like BBK seem to have a larger opening requiring one of those smooth intake pipes instead of the OEM. I also heard the throttle springs are stiff on the BBK's so off lidle progression is compromised. I actually drove a friends 86 C4 with this issue and it was a hard car to drive smooth.
http://www.ebay.com/itm/BBK-POWER-PL...630fbd&vxp=mtr
Has anyone used this throttle body from Professional Products? If so what was it like, as smooth as the OEM and did the stock intake pipe fit?
http://www.ebay.com/itm/1985-92-TPI-...77d557&vxp=mtr
Lastly there is this mob who refurbishes stock units but bores them out to 52mm (seems to be a trend) and appears to be the cheapest. http://www.ebay.com/itm/TPI-52mm-bored-port-throttle-body-85-92-Z28-TA-Corvette-/230426189214?pt=Motors_Car_Truck_Parts_Accessories&hash=item35a6789d9e&vxp=mtr
Value everyone's input, the good, the bad and the ugly who has replaced their throttle body on a stock 1990.
Cheers,
Gary.
My car has the dreaded sticking throttle due to a worn butterfly shaft. I have replaced the IAC, cleaned the throttle body (which was quite clean to start off with) and ensured the cable and linkages are all free and not binding. Tell tale is when I start and the engine races (high idle but not rough, when I wiggle the linkage on its stop it will drop down in revs.
Anyways my query is what path shall I go down since stock re-built or new 48mm twin tb's do not exist. My engine is stock and worried going to a 52mm will compromise my smooth progressive throttle off idle and cruising and introduce lean conditions. I would like a tb to accept the stock intake pipe rather than going extra for the bigger ones.
The aftermarket brands like BBK seem to have a larger opening requiring one of those smooth intake pipes instead of the OEM. I also heard the throttle springs are stiff on the BBK's so off lidle progression is compromised. I actually drove a friends 86 C4 with this issue and it was a hard car to drive smooth.
http://www.ebay.com/itm/BBK-POWER-PL...630fbd&vxp=mtr
Has anyone used this throttle body from Professional Products? If so what was it like, as smooth as the OEM and did the stock intake pipe fit?
http://www.ebay.com/itm/1985-92-TPI-...77d557&vxp=mtr
Lastly there is this mob who refurbishes stock units but bores them out to 52mm (seems to be a trend) and appears to be the cheapest. http://www.ebay.com/itm/TPI-52mm-bored-port-throttle-body-85-92-Z28-TA-Corvette-/230426189214?pt=Motors_Car_Truck_Parts_Accessories&hash=item35a6789d9e&vxp=mtr
Value everyone's input, the good, the bad and the ugly who has replaced their throttle body on a stock 1990.
Cheers,
Gary.
06-27-2013, 01:29 PM
#2
Race Director
I would be concerned about the need for reprogramming a SD car when changing TB size. If not a problem (for you), the rebored stock unit is probably fine.
Otherwise, you ought to be able to find a good, functioning OEM TB somewhere. There are tons of them.
Maybe you could contact the ebayer and ask about rebuild w/o boring to 52mm.
Otherwise, you ought to be able to find a good, functioning OEM TB somewhere. There are tons of them.
Maybe you could contact the ebayer and ask about rebuild w/o boring to 52mm.
06-27-2013, 08:18 PM
#3
Racer
Thread Starter
Good point GreggPenn,
Speed density is definitely more sensitive than the maf set up L98's. Looks like the hunt continues for a refurbed or original working 48mm unit.
Cheers,
Gary.
Speed density is definitely more sensitive than the maf set up L98's. Looks like the hunt continues for a refurbed or original working 48mm unit.
Cheers,
Gary.
07-28-2013, 08:20 AM
#4
Racer
Thread Starter
Well I have a 52mm rebushed throttle body arriving. I am hoping I do not need any reprogramming on my 1990 for it to work properly.
As mentioned, I cannot find a stock rebuilt 48mm unit. Seems all of them are rebored to a minimum of 52mm. Anyone have a 1990-1991 running a 52mm with the stock ECM?
What are your experiences, was drivability compromised or no noticable difference?
As mentioned, I cannot find a stock rebuilt 48mm unit. Seems all of them are rebored to a minimum of 52mm. Anyone have a 1990-1991 running a 52mm with the stock ECM?
What are your experiences, was drivability compromised or no noticable difference?
08-01-2013, 04:05 AM
#5
Racer
Thread Starter
Hmmm this refurbished 52mm throttle body did not go as planned.
Once fitted, the idle was fine but it was sticking open and reluctant to go back to the throttle stop. Sticking as in the throttle hangs at 2000rpm or higher from the word go. I can physically move the throttle with my hand to go back to the stop. Not ideal to drive. Ironic how a new refurbed unit can be worse than the one I have.
Checked all linkages, nothing is binding. On closer inspection it seems the tang where all the cables connect to the tb is bent at an angle and compared to the stock unit its clear as day to see. I will admit the throttle body looks nice all bead blasted up.
I had to grind down the excess plastic shaft of the throttle position sensor and use washers and a new smaller screw set. The refurbishment place used an allen key screw instead of a flat screw so it fouls the TPS assembly. Not happy with make shift modification this either.
For the moment the old one is back on and is running as sweet as a nut. I wound the butter fly spring to make it tighter, carefully checked tightness of butter fly valves using the correct size torx bit. I can feel the throttle is a touch heavier to push and this should give a little more force upon backing of the throttle to go back to the stop. So far after testing I am getting no throttle hang.
Just food for thought for anyone else intending to do this.
Once fitted, the idle was fine but it was sticking open and reluctant to go back to the throttle stop. Sticking as in the throttle hangs at 2000rpm or higher from the word go. I can physically move the throttle with my hand to go back to the stop. Not ideal to drive. Ironic how a new refurbed unit can be worse than the one I have.
Checked all linkages, nothing is binding. On closer inspection it seems the tang where all the cables connect to the tb is bent at an angle and compared to the stock unit its clear as day to see. I will admit the throttle body looks nice all bead blasted up.
I had to grind down the excess plastic shaft of the throttle position sensor and use washers and a new smaller screw set. The refurbishment place used an allen key screw instead of a flat screw so it fouls the TPS assembly. Not happy with make shift modification this either.
For the moment the old one is back on and is running as sweet as a nut. I wound the butter fly spring to make it tighter, carefully checked tightness of butter fly valves using the correct size torx bit. I can feel the throttle is a touch heavier to push and this should give a little more force upon backing of the throttle to go back to the stop. So far after testing I am getting no throttle hang.
Just food for thought for anyone else intending to do this.
Last edited by XR_Strider_GuY; 08-01-2013 at 04:09 AM.