Idle Adjustment Suz 70HP 4 stroke

Can anyone walk me through setting idle? Motor stalls when put in gear. I've tried idle set screw but need to increase idle (throttle linkage?) and then fine adjust idle screw?? once I can put engine in neutral and it stays running. For now, have to rev engine and bringing to neutral; engine stalls. Thanks

Re: Idle Adjustment Suz 70HP 4 stroke

Are you using the factory Service Manual? It is a bad idea to mess with that engine without one.

Does it have a faster idle when started cold until it reaches operating temp? You may have lost the cold start and idle enrichment part of the program or you may have lost the way in which it is implemented.

Is it making power on all four cylinders?

There are too many possibilities involved to shade-tree it.

Get the Manual.

Re: Idle Adjustment Suz 70HP 4 stroke

Idle speed on a Suzuki four stroke is controlled by the idle air controller so be sure you know what you are doing. A service manual provides the information you need. You adjust idle speed by disconnecting the idle air control hose. Pinch it shut to prevent air flow. Adjust the idle speed by turning the bypass air screw. Reconnect the hose. Idle speed and trolling speed (idle in gear) are the same since the IAC controller sets the engine speed. If going from off idle to idle does not result in the engine returning to idle speed you have an idle air controller issue.

Re: Idle Adjustment Suz 70HP 4 stroke

Supreme Commander, Thanks, I have Suzuki service manual, having difficulty understanding all its info. Will try again to set idle with hose disconnected. We have 2 auth Suz dealers of which I have little confidence. Re IAC valve, I assume if I can not set idle satisfactory (plan to set idle in drive then take boat in lake to fine tune idle set under load) if that fails I should buy IAC and try again? Unfortunately our local non Suz marine mechanics do not have Suz parts or access to Suz computer programs. Maybe this time it will work!!

Re: Idle Adjustment Suz 70HP 4 stroke

nodork said:

Supreme Commander, Thanks, I have Suzuki service manual, having difficulty understanding all its info. Will try again to set idle with hose disconnected. We have 2 auth Suz dealers of which I have little confidence. Re IAC valve, I assume if I can not set idle satisfactory (plan to set idle in drive then take boat in lake to fine tune idle set under load) if that fails I should buy IAC and try again? Unfortunately our local non Suz marine mechanics do not have Suz parts or access to Suz computer programs. Maybe this time it will work!!

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DO you have a Evinrude/Johnson dealer nearby? The Johnson 70hp 4stroke is the same engine as yours and built by Suzuki. 99% of the parts are the same, only difference is the control to engine wiring connector, computer, and paint color. Sound like an IAC problem to me too. The so called "Idle set screw" it just a throttle stop, it suppose to keep the throttle plate ever so slightly open so it doesn't "stick" in the throttle body.

Re: Idle Adjustment Suz 70HP 4 stroke

Don't be in a rush to buy an idle air controller. It may just be dirty and need cleaning. On the other hand, you may have ECU issue which you really don't want to think about. This is not a complex procedure if you have the service manual as it clearly states how to set the idle. It's only a couple of steps. Read them, study the engine, read them again, and study the engine until you do understand the process. Stumbling through the process will almost certainly result in failure. Just messing with adjustments and not understanding how they work or what they actually do in the electronics industry this is called "knob twiddling". The same thing holds true with mechanics.

Re: Idle Adjustment Suz 70HP 4 stroke

As of now, have service manual, have fast idle at start that drops when engine warms up, power all 4 cyls, this seems OK. With hose disconnected and pinched ide set to 1000 rpm in neutral. Reconnecting hose engine immediately stalls and shuts down. I expected rpm to drop to 750 and continue to run. How do I clean the IAC? I removed the IAC, sprayed choke cleaner thru both hose connections, small amt of black debris came out lower connection, top connector clear, blew thru rubber hose, unobstructed, I only wiped off the round olive drab (IAC valve?) electrical piece removed. Should I have done more? How? It appears one needs to connect a wiring harness to the black box to get error msgs and then have programs to reset computer to correct msgs. Correct? Did not realize a Suzuki & Rude similar. Will visit Rude dealer. Don't know what ECU is. Will read up on that. Apprecite everyone's help and ideas. Will measure twice and cut once. Thanks.