Rough idle. Feels like misfiring or running on only two cylinders.

9783 Views 13 Replies 7 Participants Last post by Mindful Lava, 28 d ago

MadCapsule

Discussion Starter · Sep 20, 2019

TL; DR version: new spark plugs, new coils, reconnected breather hose on air box, cleaned and oiled air filter, removed one-way valve from tank breather hose, replaced fuel filter, made sure small hoses to throttle body were still attached. Bike still runs like crap.

Here's a rundown of what's been going on with my bike.

While riding home from work, my bike started having an intermittent loss of power. The exhaust note sounded like like the engine was only running on two cylinders and it needed more throttle to maintain speed. It seemed to sort itself out a couple of times but would then revert to running on two cylinders.

My initial thought was that a spark plug or an ignition coil was going bad. I didn't know how many miles were on the plugs that were already in there, so I figured it would be good to have a set of fresh ones (CR8EIX). I also found a set of low mileage (just over 7k miles) ignition coils from a 2014 Speed for $60 on eBay, so I pulled the trigger on those as well.

While waiting for my orders to arrive, I took the fuel tank off and I noticed that the breather hose underneath the air box on the left side had popped off. Made a note to make sure it was connected when I put everything back together.

The new plugs arrived before the coils, so installed those first, put everything back together and fired up the bike. It immediately idled poorly and died. Before the plug change, it would idle fine from cold and then start running poorly after it warmed up.

I did some searching here and found that it's recommended that you remove the one-way valve from the breather hose underneath the gas tank (especially if the fuel tank is making a sucking sound when the fuel filler cap is opened, which mine was doing), so I did that. Also installed the new coils, since they had arrived, and made sure they were fully seated.

Same thing, rough idle immediately.

Yesterday I cleaned and oiled the K&N air filter, even though it didn't look particularly dirty (OEM paper filter is next on the to-buy list). I also replaced the fuel filter with a unit from NAPA (service manual calls for replacement at 24k miles, bike has 22k miles on the clock.

Same thing.

Tune ECU shows no fault codes and I have shut off the O2 sensor, since that was giving me a CEL a while back.

What should I check for next? Throttle body balance? Bad fuel injector?

Any advice would be greatly appreciated.

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crashmasterd

· #2 · Sep 20, 2019

I think there's really only two more easy things to check. Look for disconnected or deteriorated (cracked or split) vacuum hoses on the throttle bodies going to the MAP sensor on top of the airbox. If those are all good, then it's time to check compression.

If that's all good, the only other suggestion I have is it may be a defective or even just a plugged fuel injector.

If the compression test shows a leaky cylinder, then it could just be a tight valve somewhere. When was your last valve adjust? These bikes are also known to carbon foul compression rings, so a little sea-foam directly in the cylinder might do the trick as well.

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MadCapsule

Discussion Starter · #3 · Sep 20, 2019

I'll check the vacuum hoses and compression and report back.

I don't have prior service records, so I don't know when (or if) the last valve adjustment was done.

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crashmasterd

· #4 · Sep 20, 2019

This bike tends to get quieter when the valves get out of adjustment. This is because wear tends to tighten them up rather than loosen. When properly adjusted the valve train should sound like a sewing machine full of marbles. If it starts getting quiet that's a sign your valves may need new shims.

That said, these bikes don't generally go out of speck quickly. My bike when I sold it had never needed shims at 40k, although the factory manual says to check them every 12k miles. Most people I know didn't even check them until 30k or more.

Another unlikely possibility is the cam chain tensioner may have gone bad. I seem to remember someone having that problem once.

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AA

· #5 · Sep 20, 2019

Did the plugs all look the same?
Get a mate to check your header temperatures with an infra red thermo sensor while you hold the bike in the “rough” range.
That could tell you which cylinder is having problems.
Then you could swap injectors, repeat and see if the the problem follows the injector.

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AA

· #6 · Sep 20, 2019

Oh, if you are using Tune ecu, have you reloaded your map?
A mate was having huge problems on his Scrambler and they didn’t go away until we charged his(new) battery overnight and had his laptop on a charger while loading the tune.
Before that he was just part loading a then corrupted tune.

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dr_gallup

· #7 · Sep 21, 2019

If you get it narrowed down to where you are pretty sure it's a fuel injector I offer free injector testing to all S3 owners. I designed the older SAGEM injectors and still have access to the factory master flow rig. These days I only work on LNG and H2 injectors. PM me if interested.

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MadCapsule

Discussion Starter · #8 · Sep 21, 2019 (Edited)

crashmasterd said:
This bike tends to get quieter when the valves get out of adjustment. This is because wear tends to tighten them up rather than loosen. When properly adjusted the valve train should sound like a sewing machine full of marbles. If it starts getting quiet that's a sign your valves may need new shims.

That said, these bikes don't generally go out of speck quickly. My bike when I sold it had never needed shims at 40k, although the factory manual says to check them every 12k miles. Most people I know didn't even check them until 30k or more.

Another unlikely possibility is the cam chain tensioner may have gone bad. I seem to remember someone having that problem once.

Clappy valves are happy valves. My old Suzuki is the same way when the valves are within spec. I can hear the S3's valves clattering away when it's running, but I'll check the clearances if none of your other suggestions change anything.

Not exactly jazzed about having to pull the cams if the valves are out of spec, but I have an assortment of shims on deck if I need them.

Is the valve cover gasket reusable, or should I get a new one just in case?

AA said:
Did the plugs all look the same?
Get a mate to check your header temperatures with an infra red thermo sensor while you hold the bike in the “rough” range.
That could tell you which cylinder is having problems.
Then you could swap injectors, repeat and see if the the problem follows the injector.

I think all the plugs looked pretty similar, but I'll check them again and I know which ones went to which cylinder.

Will look into getting an infrared thermal gun this weekend. I'll finally have a use for the cruise control bar end knob that came with the bike!

AA said:
Oh, if you are using Tune ecu, have you reloaded your map?
A mate was having huge problems on his Scrambler and they didn’t go away until we charged his(new) battery overnight and had his laptop on a charger while loading the tune.
Before that he was just part loading a then corrupted tune.

I installed the updated Triumph factory map for my VIN quite some time ago and it ran fine for several months, until the current issues started.

dr_gallup said:
If you get it narrowed down to where you are pretty sure it's a fuel injector I offer free injector testing to all S3 owners. I designed the older SAGEM injectors and still have access to the factory master flow rig. These days I only work on LNG and H2 injectors. PM me if interested.

I appreciate the offer. I'll certainly take you up on that if I suspect a fuel injector is at fault.

Thanks for all the suggestions, everyone! I didn't have time to dig into it after work tonight, but I should have some time tomorrow night.

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MadCapsule

Discussion Starter · #9 · Sep 23, 2019

Quick update and some questions.

The vacuum hoses from the throttle bodies to the MAP sensor were all attached and show no signs of cracking.

The spark plugs all have a pretty uniform color.

With the air box off, I twisted the throttle open and looked at the intake valves. One of the intake valves in cylinder 3 has a small amount of carbon build up. Could this indicate that the valve isn't closing completely and some exhaust gases are leaking past it? The rest of the intake valves were all very clean.

I have a couple questions regarding doing a compression test.

First, I came across a post here where a member was saying that he had an issue where he had to give his Speed a fair bit of throttle while cranking the engine in order to get it to start. Another member stated that twisting the throttle while cranking the motor can throw off the TPS readings.

So I need to disable the TPS before doing a compression test with wide-open throttle? If so, will disconnecting the #6 engine management fuse take care of that.

Also, will removing the #6 fuse disable the ignition system (which is what I want to do while performing a compression test) ?

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dr_gallup

· #10 · Sep 23, 2019

Carbon buildup on the back of the intake valve probably has more to to with injector spray pattern than intake valve leakage.

I don't think you need to disable the TPS to do the compression check but I've never done it. I always start the bike with a completely closed throttle.

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MadCapsule

Discussion Starter · #11 · Oct 17, 2019 (Edited)

Okay, I have another quick update.

I just did a compression test and the numbers all came out good.

Cylinder #1: 145psi

Cylinder # 2: 148 psi

Cylinder # 3: 145 psi

I warmed up the engine first and had to hold the throttle open to keep it from stalling (I set the cruise control knob to hold the revs around 1800 rpm).

As the engine got hot enough to cause the radiator fan to turn on, the revs would periodically drop about 1000 rpm for a moment and then rebound.

I waited for the cooling fan to shut off and released the throttle. The revs dropped to about 800 rpm and then the engine stalled.

The engine was being run on 1 gallon of 90 octane, ethanol - free gasoline with 2 oz of Seafoam and I made sure the Shorai battery was fully charged.

I also checked the voltage of the battery while the motor was running and it was charging at around 14.2 volts.

I think the last easy thing I can do is to run some Seafoam directly into the intake while the engine is running.

I'm guessing I would just gradually squirt some down the rubber hose that runs into the throttle bodies? Or is there a better method?

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1050 James

· #12 · 1 mo ago

Hey madcapsule. Longshot but came across your post on the speed triple forum. Rough running and idle issues. You'd done everything I have do far (not done the seafoam though).

Did you resolve the problem in the end? If so, really like to know. Had this 05 bike since new, 60k mls and still enjoying it. Apart from this. Any help would be really great.

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TripleWill

· #13 · 29 d ago

Hey James,
I have a similar issue with my 2005. I had it at a dealer where they eventually diagnosed it. Check my thread for more details.

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Mindful Lava

· #14 · 28 d ago

While waiting for my orders to arrive, I took the fuel tank off and I noticed that the breather hose underneath the air box on the left side had popped off. Made a note to make sure it was connected when I put everything back together.

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