Suzuki DF115 surges at idle

[Panama Tom]

The fuel system had bad gas so I
changed all filters and fuel lines,
cleaned the VCM HP fuel pump, Pressure regulator, filter screen
checked all sensors all have correct voltage/ohms.
The Closed Throttle Position SWITCH is not responding to voltage ( Open circuit ) and I can't find a replacement.

The motor starts and immediately starts surging from 1K to 2.5k and while doing so it also backfires randomly. I ran a fuel pressure test both static and running, Static pressure when key on goes to around 38-40 then drops to 0. when the engine is running it stays around the same 38-40.

I have not checked the timing because it won't stay at a constant RPM
The engine also throws a Code 2-2 which is the CTP switch. Could the CTP switch cause the problem ?

Question What else can I check or adjust to get the proper idle?

Any help would be greatly appreciated,
Panama Tom

[Moonlighter]

Sounds very much like a faulty IAC valve to me. Suggest you do not start it again until its fixed, there have been a few that this caused the ecu to fry.

What year is this engine? If its a 2013 or thereabouts the IAC valve issue I mentioned is a known issue and was covered by warranty.

re the NTS if you go to the Buy Suzuki Parts link on this forum you can enter your engine details and find parts.

[Moonlighter]

2-2 is an air intake system fault.

See the list in the sticky at the top of this forum.

[Panama Tom]

Thank you moonlighter, The motor is a 2004 Df 115
I downloaded the 2 pdf files from the sticky but the manual I looked at ( from manualslib ) shows that code 2-2 as CMP sensor failure See attached PDF. I wonder if I am looking at the right manual?
I will test the IAC valve and post results.

Thanks again,
Panama Tom

DF 115 code 2-2.pdf

[Moonlighter]

Regardless of the code, the symptoms you reported sound typical of an IAC valve that is stuck or otherwise failed.

The Suzuki IAC valves are made by Mitsubishi and if you google the part number you should be able to find the Mitsubishi equivalent part number and get one of then at far cheaper cost than the one that Suzuki marine sells. Some people use aftermarket copies with mixed results but if you can find the Mitsubishi one its identical.

[briscoe]

Did you check the fuel injectors? I should have posted the other day... You could be getting the IAC code because the air can't adjust for the fuel. I had an issue with fuel years ago and it mucked up the injectors. Real easy to check. Just sayin,
Briscoe