500EFI Whipple idle problems
 

ok guys i need some help here, ive got a problem getting a 500 efi with older side mount whipple to idle! when i first start the boat it will idle with NO issuses, but as soon as i give it some throttle and then back to idle it will act like its goin to stall and then idle high (1200-1500 rpms). if i shut it off and restart it, it will idle fine till i touch the throttles again.........its got me stumped ive tried a new iac valve.........i really need some help.......thanks, ted

Vacuum leak of any kind? Perhaps something being opened as it comes from pos pressure to vacuum and sticking open? Just some general ideas. Is the TB closing all the way back up?

one thing i did notice is someone had drilled a 3/8 hole in the brass filter that goes with the IAC valve! i swapped the one off the port motor and the engine idle bounced between 800-1200 rpms. i will have to check for vacuum leaks

iac sensor maybe no good,,,staying open,,, the brass filter just clean it out with break clean or take it off and see if it helps

make sure you secondary throttle plate is closed all the way

thanks for the input guys, i should proly get a merc scan tool as well, we just had both engines completly apart for blown head gaskets

could this be a TPS issue?

maybe a tps issue.


I have a side mounted blower with a bunch of pulleys if your looking for a spare blower..

You should run a seperate oil line to the blower to keep the oil cooler.

is the TPS adjustible on a side mount whipple TB?

Well guys both throttle blades are closing, I checked the voltage on the TPS its at .6v closed and 4.5v at wot, I pulled the iac off the port motor (port motor idles and runs fine). And I still can't figure out why this thing idles high. It starts and will idle until I give it some throttle and back out, then it stubles like it's goin to stall and then picks back up and idles at 1200-1300 rpms and will not idle back down. Help!!!:lolhit:

ttt

A couple things, sounds like the engine hits the stall saver mode in the computer and cranks a bunch of iac counts into it. It won't count back down because it's out of its programmed rpm limit for iac correction. Chances are it tries to stall because the throttle blade isn't open enough. Use your scanner and open the throttle blade till iac count is hovering 5 or less in neutral, this will allow maximum iac correction when in gear. This may require a few restarts as tps position will increase and go to another idle speed table, I usually adjust the secondary blade instead, quicker and no worries of affecting tps range. It takes an 1/8" allen.
Another thing to watch is to see what % your tps reads after you return to idle and it's idling high. If it reads higher than 0 %, you are in a different commanded idle speed table and it will try to maintain that commanded rpm instead of the commanded rpm of 0 % throttle.

Thanks for the input, I don't have a scan tool. But I did check the voltage at the tps with it high idling and the throttle closed and it was reading .52 volts

Cool, doesn't sound like a tps prob. You'll need a scanner to set the iac correctly, you can do it by ear. Keep opening the secondary blade till the idle is too high, then back it down a 1/4 turn and you should be fine.

Well the high idle is gone, But now it's surging after I give it some throttle, it idles fine till I give it some throttle and back out, now it's surging between 800 and 1300 rpms. WTF this thing is driving me crazy

Try swapping the computers between engines. That will tell you if its a mechanical engine issue or a computer tuning issue. My sidemounts run great.....

ive swapped the iac, tps, computer, im starting to think ive got a intake or vacuum leak......

check under the upper intake there are a few capped vacuum ports that may have fallen off...... the other thing maybe the fuel injectors are bad,,, one or two that stick would cause the symptoms you are seeing,,, i would take them out and test them

Get a smoke test on there u got a leak

yea im pretty sure its a leak, i talked to dustin and hes thinking the same thing

dustin also said to check the bypass valve, does anyone have any experience?

has anyone ever had a bypass valve go bad?

jpzaluski, i think you might be on to something here, it definitely starts happening when i comes from neg to pos, maybe the bypass valve........:kiss:

Re-check base timing. Improper timing will cause surging.

I'm not well versed in how the bypass valve is plumbed on the Whipples, however if it bypasses to atmosphere, or even before the throttle body you now have a source. It's allowing boost out under positive pressure, but as soon as the motor returns to vacuum you are allowing in unmetered air, thus the higher idle.

well i switched bypass valves and still no luck, for the hell of it i got a new iac valve, is it possible this is an IAC problem? i traced the wires back to the computer and it look like one of the plugs might have been hot (looks brown colored around the wires). oh and i just ordered a rinda scan tool, so hopefully i get this mess worked out very soon........ted

Yes for sure could be a iac problem that is its job is to stabilize idle under different loads.Ohm out them wires make sure all are ok. Keep head up u will get it. Scan tool will be the key!!!

Good luck Skydog

thanks skydog, i sure hope soo, this thing is driving me nuts!!!!

Man buddy been there more times than I care to say....aaaahhhhh sucks I can not even sleep it kills me and I am mean to every one hahahaha
And yes u will get it!!!!!

hahaha funny you should say that, my wife said she is going to kill me if i dont get if fixed! (think ive been kinda short with her).........:lolhit:

Hahahah yea my wife told me that many times hahahah

Ok hooked the scanner up lastnite and showed a map sensor low code, also checked the iac position and it was at 0, tried to adjust it to 40 and the motor just revs to the moon and iac position goes to like 120+. The weird thing is with it revving high like 1300 with the throttle closed the tps said 1.75 volts till I shut the motor down

Sounds like vacuum leak, low map. Make sure map is not pluged with crap. Or intake not pluged and look at all plugs in to sensors make sure one of the little male prongs are not getting bend to the side and not going in female part of the plug.

Look real close at wires on tps too. U are close to it buddy.

One other thing.... U said after u rev it up it stays high right. If u get the idle down manually is the idle smooth and right or does it want to stall until u turn key off and restart?

That tps volts is not right buddy. U need to check to see if the tps is going all the way back or its in the tps. What does motor do if u Unhook tps from intake I mean unscrew the tps.(keep it pluged in) start motor and rev up does it idle back down right if u don't show the ecu any tps volts over idle?

yes it just stays high, yes it wants to stall until i turn off and restart

Ok so I don't think its a vacuum problem if it was it would do it on start up and all the time.

when i shut the key off with it revving high and the tps v at 1.75 it goes back to .5-.6 volts at the tps, im thinking a vacuum leak and the computer trying to make up for it, ive check the volts and position of the tps a few times with the key on and the motor not running and its at .6v closed and very smooth to 4.75v

Well buddy u know anyone with a smoke machine? They are sweet u will find if u have a leak. Why better than just spray with carb cleaner.