2014 ST Surging on Start-Up - Could it be a bad MAP Sensor?

[TONYO]

OK Folks.... This oldtimer finally got the new vacuum lines installed. Please overlook my slow pace. I am not what I used to be. And.... I will say this. That back hose is very hard to get to on a 2014! Also checked the other side PCV and it's blocked off tight. SO...... It is still the same. It will start but surges and cuts off if I don't give it a bit of throttle. No codes.
Any advice would be very much appreciated. TYIA Tony

[TONYO]

OK....Ima try this here. My 2014 ST is surging at startup. I have replaced the map vacuum lines and it is the same. SO.... I'm thinking it could be a bad map sensor? What do you guys think? I can't thank you folks enough for the input. TYIA Tony

[Snowbelt Spyder]

Why do you think that? Do you have a code? Do you have any codes?

[TONYO]

No codes. I don't really know what to think at this point. That's why I'm asking here. It is my hope that someone will see this and say.... Yeah, mine was doing that and it was........... Thanks, Tony

[Bfromla]

Surging how big a gap of RPM’s. Mine will 500-700 until it's warm (longer if just sitting - telling me it wants to MOVE) you’ve done the map hoses, pcv - what about fuel & air filters, fresh gas, maybe some system cleaner (at least 1 tank of gas run through) & phone con with dealer? They will want you bring it in, but you can try for an over the phone diagnosis.

[Snowbelt Spyder]

No codes. I dont really know what to think at this point. Thats why im asking here. It is my hope that someone will see this and say....Yea mine was doing that and it was........... Thanks Tony

I understand, Tony. But there usually isn't just one thing. The ECM is pretty good at telling you if there is a bad sensor. They all have signal too Hi/Lo fault codes.

So, Here’s your To Do List. Fuel, Air, and Spark. There are a number of things to check. All can be done in one day and relatively inexpensive.

Fuel:

- As was said, bad fuel can happen anytime. Or, weird weather that results in condensation in the tank. Is this old fuel that’s been in there since last fall? You may have to siphon out the tank and refill. Be sure to get the hose all the way to the bottom. That’s where the water is.

- There are dozens, maybe hundreds of posts on here over the years attesting to, that the 998 needs the occasional dose of Seafoam. Get some in the tank and run it. If, after a few minutes it begins to improve, keep it running and try to ride it up and down the driveway and around the block. Stay close to home.

- How old is the fuel filter? How many miles? The one that’s on there could be 10 years in service. Right side by where the canister used to be. You already know where it is. Replace. Piece of cake.

Air - Not Enough:

- It’s spring. Critters are on the move, building nests, and procreating. Open up your intake at the air filter and check things out…including the condition of the air filter.

Air - Too Much:

- Back to vacuum leaks. I see by your profile that you have an SM5. Then, you have another vacuum system over there on the right-hand side of the machine that provides the vacuum assist for the clutch. It starts at the throttle body for the front cylinder, goes through a check valve, to the solenoid valve and then down to the clutch. Inspect the length of hose for cracks and holes. Make sure that it is still connected to the throttle body. You will notice that the solenoid valve has an open port. That is to relieve the vacuum from the clutch when you release the clutch handle. It should NOT be sucking air all of the time. If it is, replace. Refer to pic.

- Also, another source of vacuum leaks is the rubber boot that the throttle bodies mount into with the rest of the engine. You’ll see those hose clamps and rubber boots. Check for tightness of the clamps and inspect the rubber boots for cracks and leakage. There are those that have tried an in-place repair with silicon sealant. Doesn’t work. A full replacement is called for.

Spark:

- While you’re crawling around in there, check out those wires that you put on to see if there’s a rub that damaged the insulation, and that you put them on the plugs completely.

Heat under the bodywork is the enemy of the 998’s rubber components.

By the way folks - It’s not a PCV valve. It is a Purge valve. Two completely different emission control systems. Neither the 998 nor the 1330 have PCV valves, only Purge valves.

[TONYO]

OK TY! I just spent the last two hours looking and feeling for cracks etc. Everything seems ok. The fuel filter was changed approx. 25000 miles ago. The gas was 2 weeks old when I first posted this. It is ethanol free gas. I always switch to that the first of Nov. & run it till about this time. I had run over 100 miles on that tank of gas with no issues b/4 it started this. And it's always in the garage. No critters in there. SO.... My plan was to see what you guys said today and call the dealership in the morning. They are closed today. I can't say how much I dread taking it to the dealership!!!!! I have always done my own work/maintenance and it has saved me thousands of dollars in the 9 years I have owned it. BUT I'm not what I used to be to say the least. I found a used map sensor on ebay for 30 bucks shipped. I emailed the seller and he said he guaranteed it to be good. And that if it doesn't work for me, I can send it back for free. After this post, I figure that's not the issue. BUT I am tempted to get it & see. Nothing lost seems like to me. I'd do dang near anything to avoid that dealership! I also checked to see if there were any hidden codes. Pushing the buttons. The screen came up clear. SO.... The plan for now is to call them in the morning. I'd bet that he will know what's wrong with it. I don't expect him to tell me. Will see come morning. I will update then. Cannot thank you guys enough for the help/info/advice. Tony

[2dogs]

TONYO I can't find where you explain the RPM range(s) for your surges or the duration of the surge. Could you advise please?

[TONYO]

TONYO I can't find where you explain the RPM range(s) for your surges or the duration of the surge. Could you advise please?

OK... Sorry. I know how this one does when it's first started. I always for the last 9 years allow it to slow down rpms b/4 I put it in gear, so it don't clunk so hard. I am very easy on this machine. This goes from approx. 2000 rpms and 4000rpms.... As long as I hold the throttle at 2000 rpms. If I allow it to idle..... it shuts down. Thank you very much for the input/thoughts, REALLY! Tony

[Bfromla]

Head scratcher. Sorry beyond my experience

[TONYO]

OK Guys. Just talked to the service manager. I'm takin it in on Sat. WISH ME LUCK! IMA NEED IT! TY ALL.... I will update when they get done with me. IF I don't die of a heart attack when they show me the bill. GEZZZZZZZZZZZ

[TONYO]

OK.... Two weeks at the stealership and it is fixed! Part#270600040 Pressure Sensor is what they said was wrong. It's running good now. SO.................. It was painful, BUT I am happy it's fixed. THANKS Everybody. Tony

[Scottncol]

OK.... Two weeks at the stealership and it is fixed! Part#270600040 Pressure Sensor is what they said was wrong. It's running good now. SO.................. It was painful, BUT I am happy it's fixed. THANKS Everybody. Tony

Is that the Map Sensor that you were referring to?

[TONYO]

NO. You can google the number n find out which one it was. AND....I dont trust them. Charged me 135 bucks to replace my air filter