S4 with poor hot idle

[s4_icyau]

I have an S4 with a similar issue.

It used to idle at about 1000rpm, but I got the bike's TB resynced and it idled better at 1300rpm.   But after a while, when the bike got warmer, 180 degree and up, the idle would start to get rough and it feels like it wants to die.   I haven't changed the sparks or the battery lately. 

And this problem just appeared one day a couple months ago.   I'm probably going to take it back to the shop, but am hoping for a cheaper DIY fix. 

[Speeddog]

I have an S4 with a similar issue.

It used to idle at about 1000rpm, but I got the bike's TB resynced and it idled better at 1300rpm.   But after a while, when the bike got warmer, 180 degree and up, the idle would start to get rough and it feels like it wants to die.   I haven't changed the sparks or the battery lately. 

And this problem just appeared one day a couple months ago.   I'm probably going to take it back to the shop, but am hoping for a cheaper DIY fix. 

How many miles on your bike?

When were the valves adjusted last?

How many miles from the TB sync until the hot idle issue started?

[johnster]

My s4 will stall frequently until fully warmed up, and idles really really low (~900 rpm).....I always just attrubited it to the cams I am running (DP SPS cams)....The idle is very rough + slow-sounding compared to other monsters I've been around....An s4rs I saw the other day idled like mine does when the fast-idle lever is on all the way!!

-Upping the TPS for a higher idle would help I think....Nothing really to add, just lettin you know that you're not the only one with an s4 that doesn't like to idle.... 

[s4_icyau]

My S4 has about 11k miles on it.  I dont know when it values were last adjusted.  I bought the bike used. 

The hot idle issue came up just after a couple hundred miles after the TB sync.  I had it looked at in the first place cause the idle was rough all the time.  Now after the sync, the idle run smooth until it gets to over 180degrees.  It hasn't been too bad of an issue, but one i would like to figure out.

[Speeddog]

I split this off from the other topic, it was getting a bit confusing...

[scott_araujo]

The spark advance drops way off under around 1000 RPM.  This puts less strain on the starter and makes the bike easy to start but it runs like crap if it gets down that low while idling.  I'm not sure if that's affecting you. 

Look for any obvious vacuum leaks like a charcoal canister hose that popped off.  You may also want to check the valve clearances.  If your valves are out the TB synch can have limited benefit.  Check/change the plugs and air filter but if that doesn't do it you should take it back to the shop.  It shouldn't be dropping out of tune a few hundred miles after the synch.  Take it back to the shop and explain the problem and how it happens once it is warmed up.

Also, you shouldn't be monkeying with the TPS to get it to idle properly.  The TPS gets set and left alone.  If it's not idling smoothly there's some other problem.

Scott

[5lv]

My S4 has the same problem. Runs perfectly until it gets hot. Very unstable idle and one cylinder cuts out untill about 2 grand under light throttle. Give it more gas and it's OK. It was just serviced, valves, plugs, TPS, CO adjust, and TB sync. It was ok for a few hundered miles, but is pretty bad now. Just over 7000 miles.

[rule62]

This idle behavior is very much like what I am experiencing with my 620 "Stumble at Idle" thread.

[Rameses]

My old S4 was doing the exact same thing.  Started happening at 180 degrees and everything.

Nothing I ever tried made any difference, nor was I able to find any other S4 owners who'd found a solution to the problem.

I'll be watching to see if you get it figured out.

[5lv]

My problem turned out to be a coil. I bought a set on Ebay last fall for $50 and decided to give them a try. Now it runs smoother and idles perfectly, even when stuck in traffic. As Mr. Spock would say, Random chance has operated in my favor.

[rule62]

Do you recall if it was the coil on your H or V cyl?  When my bike starts this stumble beavior, I can take the plug wire off of the H cyl and the bike starts to idle lower (obviously), then by placing the plug wire back on and taking it off again and then back on, I can immitate the stumble.  If I take the plug wire off of the V cyl the bike stalls.  I'm thinking that the H cyl coil is going bad.  Not firing properly when it gets hot.   

[scott_araujo]

Good analysis.  Swap parts between the cylinders and repeat the experiment: coils, wires, ignition packs if you ahve them.  When you find the part that makes the bike stall when you remove the H plug wire but only idles lower when you remove the V (opposite behavior of now) that's the part that's flaky.

Scott

[rule62]

Changed the coil and the spark plug wires.  Still stumbles.  Damn!  Gonna reset the TPS tomorrow.

[Rameses]

Anybody ever make any headway with this?

[jerryz]

TPS must be spot on 15omv its really critical a low revs  and the balance as well.....also tickover must be 1100-1150 minimum any less and it will run bad , also fuel filter must be clean and Iridium plugs help.The S4 does get hot in traffic .