Quad throttle bodies

**MiC** · 27-04-2006, 04:47 PM

So I've put 20v silvertop throttles onto a 1991? sw20 3sge .. However there's just one wierd problem..

When throttle is opened just under 5%, the engine just revs a little and bogs back down and then repeats (so it revs up, bogs down, revs up, bogs down)... It's not according to rpm either as I can rev it up, and then hold throttle at that 'bad' position and it'll still do it. Makes it hard to hold speed if I'm driving at 60 or 80km/h.

This problem however goes away when the tps is unplugged. And it has been tested with another tps (to see if the tps is the problem) but it still does the same thing.

Anyone have any ideas?

**mullett** · 27-04-2006, 05:13 PM

Are you still running factory managment?

RM

**MiC** · 27-04-2006, 05:29 PM

Almost.. I'm running it off an safc. With the tps unplugged tho everything works fine and the safc seems to read the tps fine too.

**limbo** · 27-04-2006, 08:50 PM

I think it has to do with the quad throttles not closing properly? Did you check the butterflies line up correctly when putting it on?

**oldcorollas** · 27-04-2006, 08:55 PM

are the throttles balanced at small throttle openings?? i would (also

) suggest they are not balancd properly... it is just as important to balance ITB's as it is to balance twin carbs.
what is the O2 sensor reading during this rev and bog? perhaps the fueling is also way off for that region? but i would start with the balance.

with TPS unplugged? what does the ECU use the TPS for? accel and idle position...

what happens if you rotate the TPS so that it registers as a larger throttle opening?? does it still do it then?

what if TPS is attached to lo, but not to the throttles??

**slide86** · 27-04-2006, 08:56 PM

is the TPS setup in teh correct position?

is it the 20v TPS or the 3sge TPS? maybe they send a different signal to the ECU and the 20v type doesnt send the right voltage that the 3sge ECU recognises for the % that the throttle is open.......maybe, i dunno tho

**Norbie** · 27-04-2006, 10:44 PM

This is a classic symptom of a misaligned TPS. If the throttle is open but the TPS says it's closed, you get the situation where the ECU goes into decel mode and shuts off the injectors above ~1400rpm (or thereabouts). Then the engine speed drops below 1400 and the injectors come back online, the engine speed increases, then the ECU goes back into decel mode - and it goes back and forth just as you described.

Grab a multimeter and check the TPS output, I'll bet it's not opening the IDL circuit until you hit 5% throttle!

**MiC** · 28-04-2006, 12:32 AM

Cool Norbie that sounds right on the ball.

Will have to call the tuner up now as I've left it with him

I know the 20v tps does send the signals in a different wiring configuration to the the 3sge one but I thought I had already switched it around to the right order. Pretty sure the balance is correct too.. I forgot aligning the tps but didn't think it would have this effect anyways.

Hopefully all goes well and I'll maybe be able to post up clips

**Ben Wilson** · 28-04-2006, 07:48 AM

I agree 100% with Norbie, I had a similar problem with my car which resulted in the motor not running above 1800 RPM unless I had more than about 20% throttle on. Lucky ZE are torquey little beasts and you can short shift them at 1500...