05 4 Tec Surging.

[boater30]

I have a 2005 GTX 4 Tec No Blower it has 78 actual hours on it and has been adult driven since new. When you run it about 30 MPH at about 4500 RPM it will surge up and down varying about 350 rpm, run it faster or slower it runs fine, I changed the plugs but no difference, it isn't an ignition issue, more like a fuel or throttle issue, possible vacum leak ?? Any suggestions appreciated Thanks Terry.

 

[neophyte]

I have the exact same issue on my 2012 Challenger 180 4-etc.

please post if you get it sorted. Spark plugs didn’t do it for me. I just had my SC rebuilt, I’m going to do a test run this weekend.

 

[boater30]

Plugs did nothing, I don't have a SC on mine, I am going to try sea foam in the fuel and The sea foam spray in the throttle body to see if I have an exhaust leak, which I doubt because It runs up around 7000 RPM or better. I would think an issue like this with such low hours you wouldn't have a fuel problem or dirty injectors ? should be easy to figure out. ??,

 

[neophyte]

I wish it were easy. I don't mind forking over some dough to fix a problem. I HATE forking over my hard earned cash to fish for a solution.

I ran 1 can off seafoam through 25L (8gal) of fuel (so high concentration relatively) and it made no difference. Perhaps I need more?

It's weird because at low and high power settings the boat runs beautifully. Run it mid range and the rpms start to fluctuate. It reminds me of an overspeed governor kicking in.

Under 100 hrs on a 8 year old boat. I expected better quality from BRP

 

[skiasylum]

The cam on the TPS could cause the RPM fluctuation mid range, sending bad info to the ECM and it then doesn’t know what to do and starts searching. Fairly cheap to replace.

 

[neophyte]

The cam on the TPS could cause the RPM fluctuation mid range, sending bad info to the ECM and it then doesn’t know what to do and starts searching. Fairly cheap to replace.

thanks for the tip, so are you suggesting to replace entire TPS or the cam on the TPS.

THANKS again, I’m not a gear head, got to dumb it down for me lol

 

[skiasylum]

Don’t think just the cam is available.

 

[neophyte]

Update...

took the boat out for a rip on the weekend, still surging 5400-6000 rpm. The sound is annoying

oh well, at least my SC got rebuilt and I have fresh plugs

Gonna touch base with the technician tomorrow and ask about the TPS. Perhaps this is something I can do my own. Does anyone have tips on where to get a shop manual or engine schematic?

cheers

 

[skiasylum]

They all pretty much work the same.

A dealer can also test your TPS with a BUDS reader, pretty simple.

 

[neophyte]

I just got word from the shop that while accessing the TPS to do a bench test, the technician noticed that the intercooler was cracked. He hooked it up to water and verified the leak.

new IC on the way. They are very confident that this is the cause of my issue.

I will post an update after the job is done and I take her out for a rip.

 

[neophyte]

Got the boat onto the water on the weekend, the new intercooler fixed the surging. The boat is purring again!

thx for the tips and support