Cold Start Rumble

[ApexDriller]

O.K. so this is normal. I have changed the donouts 4 times on this machine and still dose it when there new. Its almost like one of the injectors is dirty and not running clean for the first 10secs of idle.

Thanks for the replies

when ur machine is running, go to rear exhaust and plug or cover tailpipes with your hand or rag or gloves or whatever. Engine should stall in 1 second. If engine continues to run you got exhaust leak somewhere. Make sense.

 

[black knight]

no exhaust leak.

 

[Bigvander]

07 Apex Rough Start

My Apex sometimes won't even stay running at startup. It runs very rough with the help of some throttle, warms up a bit after 30 seconds of rough idling, and then runs fine. 8k miles, new donuts, y-pipe, and CR10EK plugs at 6k miles. The dealer thinks it is a sensor but can't seem to get it to act up anymore (getting warmer outside). It seems that it isn't getting enough gas but the exhaust smells like the engine is loaded.

Any ideas out there?

 

[Irv]

Good to hear it's normal. I run OEM recommened plugs as well. 87 octane. Stabil Marine Formula every other tank.

I would run Sea Foam instead of Stabil, especially "during" the season.

Stabil does just that, it Stabilizes the fuel, nothing more but Sea Foam cleans and stabilizes, amongst other things.

 

[RTX]

add me to the list of guys that are experiencing an odd start up
mine always started and idled fine untill this year.
it seems that it starts fine and about 10 seconds after starting it idles extremely low around 900-1000 rpm, borderline stalling.
it runs like this for about 2 minutes or so then it just kinda fixes itself and returns to a normal 1800 rpm idle
weird.

 

[4strokerpms]

cold start

I wonder if this has to do with the iac valve? It has coolant lines running to it and from what i understand should that plunger mechanism move to let more fuel/air mixture in when it is cold. My 2006 apex gt with 8000 miles does this rough idle for about 2-3 minutes when it is cold and had sat for a few days. Once it is warmed up it idles quite nicely. I cleaned my iac through the black air hoses this spring but won't know it that helped until next winter.

 

[black knight]

this used to happen when it was only cold out and now its starting to do it in this nice weather.
The iac is definatly comming off and getting cleaned. right now it makes the most sence. will post back hopefully will have time this weekend.

cheers

 

[thor452]

i fixed mine the easy way. bought a new one no more rough iddle.

 

[SledFreak]

Re: 07 Apex Rough Start

My Apex sometimes won't even stay running at startup. It runs very rough with the help of some throttle, warms up a bit after 30 seconds of rough idling, and then runs fine. 8k miles, new donuts, y-pipe, and CR10EK plugs at 6k miles. The dealer thinks it is a sensor but can't seem to get it to act up anymore (getting warmer outside). It seems that it isn't getting enough gas but the exhaust smells like the engine is loaded.

Any ideas out there?

Its those plugs.. My Apex with those plugs would never start well in the cold. Put the stock ones in it. Not worth the 1 or 2 hp aggrevation.

 

[jaydaniels]

Re: cold start

I wonder if this has to do with the iac valve? It has coolant lines running to it and from what i understand should that plunger mechanism move to let more fuel/air mixture in when it is cold. My 2006 apex gt with 8000 miles does this rough idle for about 2-3 minutes when it is cold and had sat for a few days. Once it is warmed up it idles quite nicely. I cleaned my iac through the black air hoses this spring but won't know it that helped until next winter.

You might be on to something here. My sled runs/idles very rough for a bit also until its warmed up. Starts fine and then after about 5-10sec starts stumbling. Eventually it comes out of it. On one very cold day this winter we had 3 apexe's that all started up and then after about 5 seconds, started stumbling and then actually quit. None of them would restart. The only way to get them to restart was I had to pour hot water over the thermostat housing to warm the coolant some. Almost like we tricked the sled into thinking it was warmer. They all started right up. I think, for some reason, they are getting too much fuel when cold. Might be related to the coolant temperature and the IAC valve.

 

[actionjack]

My Attak now has a distinctive low pitch resonance when first started until warmed up. My first season with this sled I did not notice that although I had heard it on sleds I considered buying. I noticed it for the first time on first start up after numerous pre-season updates last fall which included replacing cracked Y-pipe, oil and filter change, and changing to 10EKs. I was thinking of checking the exhaust again but now am leaning toward the plugs.

Oh well I'll prob have it apart enough again before next season to check the exhaust anyway.

 

[yamaha1973]

maybe go to the 9ek for better starting in extreme cold?

 

[dubla92]

When someone with the stated issue comes to me for repair I first inspect the exhaust (donuts especially). If the exhaust is ok then I check the idle speed when at operating temp and then sync the throttlebodies. The IAC only passes extra air when the engine is cold (no fuel). The injectors inject extra fuel for the cold start. I agree this is some what normal and can be helped by a block or oil heater. Most Apexs never get the throttlebodies synced after they get some miles on them and are broke in. The sync will get the idle smooth and stable again. As for the CR10EK plugs I had my doubts too but on a cold start all heat range plugs are cold right? The heat range only affects the tip of the plugs heat disapation at operating temps.

 

[jaydaniels]

When someone with the stated issue comes to me for repair I first inspect the exhaust (donuts especially). If the exhaust is ok then I check the idle speed when at operating temp and then sync the throttlebodies. The IAC only passes extra air when the engine is cold (no fuel). The injectors inject extra fuel for the cold start. I agree this is some what normal and can be helped by a block or oil heater. Most Apexs never get the throttlebodies synced after they get some miles on them and are broke in. The sync will get the idle smooth and stable again. As for the CR10EK plugs I had my doubts too but on a cold start all heat range plugs are cold right? The heat range only affects the tip of the plugs heat disapation at operating temps.

Some good points here. As for the IAC, is this extra air to compenste for the extra fuel when cold. IS it possible the IAC is not passing enough air hence a rich condition and the stalling out. How does the OAC know how much extra air to add? Is the coolant temperature sensor reading used to adjust fuel or fule mixture. By warming the coolant just slightly my Apex went from not starting to starting right up. All I did was pour hot water on the thermostat housing while cranking the engine over (just what I did to get my sled going in a jam, not recommending everyone do this).

 

[dubla92]

The IAC unit uses a heat expanding thermal gel that when cold shrinks to open the idle air bypass plunger and allow more air to be drawn into the intake side of the throttlebodies. It expands a set amount depending on the temp and the ECU map is calibrated for this. But it is based on the idle speed setting. The ECU determines the amount of fuel by reading the engine and air temps as well as atmospheric pressure. The IAC is not controlled by the ECU. It works off of coolant temp. The warming coolant expands the thermal gel causing the plunger to block off the high idle air bypass. So then the idle air is fed to the throttlebodies through the sync screws syncing intake manifold vacuum. The master idle speed screw manually opens the idle air bypass raising or lowering the idle speed. The sync bypasses work each cylinder individually. It is important to set the idle speed at 1500 RPM so that the correct amount of air is drawn into the engine upon a cold start. I have seen a fair number of cold start issues caused by someone having their idle set too low. Also never apply any throttle when cold starting as this will inject more fuel and cause it to flood.