jameson_g

Okay i'm sorry if this thread topic has been talked about, but i have read tons of h-t links and googled it a lot. The car has had an idle surge for 8k miles. I rebuilt the engine and swapped it out with the worn out gsr that was in there. The gsr ran fine with no major problems, but after the swap i have not been able to figure out the idle surge problem. In the cold mornings the car doesnt surge, only idles at 2500 rpm. after a few minutes of idling, it surges from 1K-3K.

Set up:
81.5mm b16, eagle h beams, 9:1 cp pistons, gsr cams, blox IM, BBK 70mm TB, walbro 255, stock injectors, rail, regulator, chipped P06, also surged with a stock P72.

Current attemps to fix it:
adjusted valves, timing is correct, deleted FITV, cleaned IACV and replaced with known good one, adjusted idle screw, coolant is bled.
I'm almost positive that theres no vacuum leaks. now that i put the BBK 70mm TB on, if i plug the FITV hole with my finger, the engine will bog and die. no codes are present.

Originally, i had the stock TB installed, researched that excessive vacuum through the FITV hole indicated either a bad FITV or some problem with the FITV. I actually used a piece of aluminum and gasket maker to seal the hole shut, because this was a temporary fix for the idle surge issue. I drove it for 6K miles and it ran fine, but it bothered me because im sure eventually it would have sucked the aluminum into the engine. I replaced the TB with a BBK 70mm, because thats the TB im planning to run with my turbo. I put a piece of gasket to block off the FITV and correctly bypassed the coolant lines that ran through it.
Even with the gasket in there, im still getting excessive vacuum through the FITV.
I'm wondering if this hunting idle issue could possibly be corrected through HONDATA s300 (the program i plan to use with my turbo). I would assume it probably be better to correct the problem before boosting the car, but i'm stumped on this. ANY HELP WOULD BE GREATLY APPRECIATED. if there is any details i have left out that would help anybody please let me know. thank you

jameson_g

bump... anybody?

Skunk2Brian

When you installed the BBK TB did you calibrate the Throttle Position Sensor (TPS)?

In a few rare cases I have seen those TPS sensors so far out of spec that the idle surged like that.

jameson_g

Thanks for the reply, but yes I calibrated the TPS on the stock TB when I swapped it as well as on the BBK. I even switched them out to make sure it was a good TPS.

ninor

Check for air in your coolant, just re-bleed it to rule it out.

Check for vacuum leak:
Take the intake off, start the car, put palm of your hand across TB. Does the car idle? Does it shut off? If it idles, you got vacuum leak (somewhere other then TB plate, anywhere from TB gasket to head intake manifold gasket), if it shuts off, go start it again, How many holes on the side of your TB (OBD1 or OBD2) FITV is Fast Idle Thermo Valve and is OBD1 idle control used for cold starts only and also there is IACV Idle Air Control Valve that both Obd1 and obd2 cars have. Only OBD1 TB has both valves.

If you have Obd2 type TB with IACV only, go full tight on idle adjusting screw and plug the hole to IACV, Does the car shut off? does it idle? If it shuts off, you have defective IACV, if it idles, your TB plate doesn't seal properly and it is letting air past it.

Good luck,

Nino