Suzuki DF60 2004 Won't go above 3000 rpms No error codes

[go2ski]

The IAC valve recently broke and I replaced it. When it broke it only let me run the engine about 2000-3000 rpms at first and then finally stopped running (I had to get to the dock) and would die when switching into gears (it would run out of water above 3000rpms but in water, it would die when switching into gear in water). When I installed the new IAC valve I messed with the bypass air-screw too and the error for the IAC valve went away. It now will go into gear but will only run at 2000-3000 rpms with no errors showing in water. I have replaced the oil pressure switch thinking that could be a culprit but nothing changed. Any help? I have a service data attached with it running out of water. Service Data.pdf (The errors shown in the service data are there from before I haven't gotten any more errors since I installed the IAC valve

[Moonlighter]

May be the neutral throttle switch on the engine - on the starboard side gear linkages.

This switch tells the ecu if the engine is in gear or not. If the switch is broken or misaligned the ecu wont see the “in gear” signal and will electronically limit revs to about 3000rpm.

[Murray]

To test Moonlighter’s theory you should be able, with the SDS hooked up, engine running in neutral change the gear to forward and the “Neutral Switch” should go from On to Off. Full disclosure: I’ve never used the SDS program so I could be wrong.

[go2ski]

Thanks for the advice I saw some other post say something about the neutral switch and was gonna try that next. I’m not sure if the sds shows it on and off I’ll look when I can and will post when I do.

[redlowrey]

Mate the iac valve has got absolutely nothing to do with the engine not running over 3000 RPM, something else is wrong, on the first page of the sds manifold absolute pressure is very low 12in, hg with the engine running, does the engine idle smooth or rough, on a good running engine there would be around 16 to 18 in, hg, that would make the signal voltage on the map sensor high and I see that the injection pulse width is around 4 ms that is what a four litre engine would run at idle.
Need more history on the engine, did it used to run good or did you buy it like this. With the neutral switch your sds will tell you on or off depending on the shifter, you would know if the neutral switch off in neutral the engine would have a distinct hunt in the rpm ounce you were over 2.500 rpm. pull the plugs and have a look at the colour of the porcelin near the electrodes.

[go2ski]

redlowrey the engine was sitting in a yard for years and then we bought it with the boat for 1500. It was tooken to a mechanic and was completely re done and ran fine. The engine has only had problems the past year but we’ve had it for about 5 years. I’m gonna test the neutral switch tomorrow if I can’t see it on the SDS I’ll use a multimeter.

[redlowrey]

It's on the bottom of the third page, neutral switch on. Run the engine on the muffs with the cowling off put it in to gear, be careful, and give it a squirt and see if it goes over three thousand rpm, that will test if it has a restriction in the cowl or exhaust gas is leaking out of the engine holder, also take the cover off the intake and make sure there is no restriction on the flame arrester at the throttle body, and pull the plugs to see whether the electrodes are black very important that you do that.

[go2ski]

redlowrey I just tested the neutral switch it works doesn’t go over 3000 rpms out of water and the electrodes were fine the engine doesn’t sound like it’s misfiring just won’t go over 3000 rpm.

[go2ski]

I definitely think something with the electronics is wrong given the symptoms. I don’t hear anything wrong with the engine and it doesn’t die. Something is limiting its rpm’s

[redlowrey]

Have you actually checked and made sure the throttle plate is in the wide open position when the shifter is all the way forward, because if the computer was limiting the fuel and the throttle was wide open you would hear the engine struggling with too much air and not enough fuel, for the engine to run ok at 3000 rpm with a supposed wide open throttle does not make sense. Put up a screen shot of the sds with the throttle wide open.
There is no way the engine can run fine at 3000 rpm unless the throttle plate opening and the amount of fuel were matched, if the computer was only injecting enough fuel for it to run fine at 3000rpm when the throttle is opened to the wide open position it would die. Your throttle plate is not going to the wide open position, pull the cover off and check it.

[go2ski]

redlowrey when I put it into full throttle it hit 3000 rpms and it was kinda bouncing between 2800-3000 rpms without me moving the throttle. I’ll check the throttle plate as soon as I can and put screen shots up.

[Moonlighter]

Just a reminder that if the engine is in neutral the ecu will limit rpm to about 3000rpm, it will be like a race car on the pit lane limiter, it will miss and fart and run bad if you push it to that limit.

[redlowrey]

The hunting coming from the engine is so obvious from a failed neutral switch when the rpm is over 2.500 you could not mistaken it surely. The impression I am getting that it runs to 3000rpm when the shifter is all the way forward and the engine runs okay, which is impossible if the throttle plate was in the wide open position and was only injecting enough fuel to run at 3000rpm, it would lean out back fire and stall.

I think his throttle plate is opening less than half way, unless he can't pick the hunting action from the computer switching the injectors on and off. I understand that you think he is in neutral while he has the throttle wide open I told him in post 7 to have it in gear when tying it.

[Moonlighter]

I guess I am still suspicious about the switch Red!

Im not aware of too many other conditions that dont throw a fault code that would be stored on ecu that would limit rpm to about 3000rpm? Especially if things like spark plugs have been changed and fuel flow/pressure verified to be OK. Not sure if he has addressed those issues though?

The only other thing I can offer apart from your suggestion re throttle not fully opening is a low voltage issue to the ecu - not long after I added NMEA2000 interface to my engine, we had the intermittent issue with no acceleration past 3000rpm on occasion, and it turned out to be a false low voltage signal somehow caused by the interface connection to the ecu that threw it into safe mode and limited rpm. It felt very doughy even below that rpm. Re-routed power supply for the interface cable to a different source as per the Service Bulletin they subsequently issued, problem solved.

So perhaps there could be a bad wiring connection to the ecu or something? Bad white wire?

[go2ski]

I have checked all fuel lines and the fuel definitely has pressure and spark plugs are new. The oil is fine I check that too and the oil pressure switch is new. The regulator & rectifier is fine I tested that and the IAC valve is new. Most of the stuff I replaced had lots of corrosion and/or it was giving errors. When I plugged the computer in the other day it showed the neutral switch going on and off I’m not sure if that completely means it’s working though. I will post the service data with it in gear today. The engine does not backfire when it runs in gear just bounces between 2800-3000 rpm like when you hit your rev limit on your car.