Stumped with odd running issue

[Johnwesley]

Some of you will remember the engine build I did over the winter. Really mild simple build on a 2005 fxdi. It was your basics 95" with s&s 510 cam and mild port work. All machine work done by AMS. It was a real bugger to tune and had some issues I wasn't aware of at the time. Main problem with the whole fueling system needed to be replace from the pump to the injectors. Steve was great to work with on that and the tune.

Issue is that the power is sometimes not there. It's almost like the ignition is cutting out. Some time when off the throttle and gently opening it there is a lack of response and then all of a sudden it takes off. Sometime seems to back fire ever so slight just as it takes off. Even when on the dyno it showed up on the upper rpms. It's intermittent and does it about 30% of the time. Makes it hard to figure out.

Here's the dyno with no changes done between the lines.

[rigidthumper]

I've seen similar issues caused by the fuse panel connectors not gripping the blades properly, or corrosion on the blades. This can happen to the system relay blades as well.  Take a spare fuse, cut one leg off, to be used as a gauge.  Pull & clean each fuse and relay blade with a wire brush, and use the one legged fuse to check "grip" of each connector while the fuse/relay is out for cleaning. Replace any loose/defective connectors you find with the gauge. Reinstall all items and retest.

[doctorevil]

Had a similar problem also with the throttle position sensor. sweep test with an analog test meter revealed small inconsistent voltage drops. Have you tried another coil,possible heat soak?

[Boe Cole]

I had a similar build - 95" w/510G cams.  Loved it - a real arm stretcher over 3200+- rpms - relatively mild up to then.  Also had it cutting out due to the "system relay" having corroded contacts.  Replaced the relay (less than $10 at the time) and all was back to normal.  You should also check to see if it threw any codes - mine did.

[Johnwesley]

All the fuses look good and are not corroded, also the system relay looks good. I pulled these codes:

P1004 System Relay Contacts Closed
P1351 Front Ignition Coil Driver Open/Low
P1354 Rear Ignition Coil Driver Open/Low

So I will probably just change the relay for good measure. Looks like issues with the ignition system. I cleared the codes and will try it again and see.

[Johnwesley]

Did some more riding and still acting up but no codes this time. It's not unridable, just not right. Sometimes it screams and other times it feels like stock and is just flat.

[kd]

Check the ground wire that is fastened to the top of the frame backbone up under the rear of the fuel tank.  They come loose and cause all kinds of running issues.

[BVHOG]

First off put a fuel pressure gauge on that you can watch while riding, secondly from the dyno graph it looks a lot like sumping, doubtful it is but just a thought

[Boe Cole]

All the fuses look good and are not corroded, also the system relay looks good. I pulled these codes:

P1004 System Relay Contacts Closed
P1351 Front Ignition Coil Driver Open/Low
P1354 Rear Ignition Coil Driver Open/Low

So I will probably just change the relay for good measure. Looks like issues with the ignition system. I cleared the codes and will try it again and see.

Don't remember for sure but those look like the codes I got when the system relay was acting up.  turned out to be the contacts were corroded when i took it apart after replacement.  All my bike's problems (not my problems!!!) went away after replacement.

[Johnwesley]

First off put a fuel pressure gauge on that you can watch while riding, secondly from the dyno graph it looks a lot like sumping, doubtful it is but just a thought

Tks, Steve put a pressure gauge on it while on the dyno and determined the pressure was fluctuating. That when the whole system was replaced. Then started tuning again. That's when this anomaly showed up. All that said it still maybe a good idea to double check.

[kd]

Had a friend experience a similar issue on the dyno and it was the ground wire I described. It had been discussed here before so that's why we checked it and bingo.

[Johnwesley]

Had a friend experience a similar issue on the dyno and it was the ground wire I described. It had been discussed here before so that's why we checked it and bingo.

Had the tank off and couldn’t find the wire you were talking about. No ground wire that I can find that had ever been in that area. Got a picture? This is a 2005 I would ass/u/me it’s the same

[kd]

I just looked back and see it's an TD.  I don't know where that wire would be.  It's the smaller wire paired with the ground cable at the battery.  On the touring you can access it to tighten it without removing the tank.

[chaos901]

On the touring you can access it to tighten it without removing the tank.

In that space between the rear of the tank and the partition in front of the battery.  The one with all the wires.

[Johnwesley]

First off put a fuel pressure gauge on that you can watch while riding, secondly from the dyno graph it looks a lot like sumping, doubtful it is but just a thought

Run the fuel pressure and it held solid, also kept the pressure after being shut done and left for 5min.

[Johnwesley]

Had a friend experience a similar issue on the dyno and it was the ground wire I described. It had been discussed here before so that's why we checked it and bingo.

Found the grounds on this one. They are above the ground on the primary. All was clean and tight. I took them off and looked everything over well and put the back on. No corrosion and wires were in good shape.

[gordonr]

So is it safe to assume the issue is happening around the same rpm range as your dyno show's?

[Johnwesley]

So is it safe to assume the issue is happening around the same rpm range as your dyno show's?

It does it there for sure. Seems when you roll off and then get back on it's worse. Feels and acts like the ignition cuts out and picks up, but then when it picks up sometimes the power is just not there. Seems most prominent at full throttle but could be that it would just be more noticeable there. Fuels system has been replaced from the filter to the injectors.

It hasn't thrown any more codes.

[Hossamania]

Could it be a wonky battery or damaged / internally corroded battery cables?
A worn ignition switch? Heavy key ring hanging from ignition?

[Johnwesley]

Could it be a wonky battery or damaged / internally corroded battery cables?
A worn ignition switch? Heavy key ring hanging from ignition?

Had the battery tested and it good. Starts great as well. Battery terminals look goo with no corrosion. The key is just a key with normal split ring on it. I keep the other keys on a separate key chain.



I'm about to just put new coil and wires on it for giggles. Even though them seem ok.

[Johnwesley]

Went to Sturgis on it and while up there, I didn't  have any issues. On the way up it did have some of the standard cut out when throttle was applied. During the ride up I ran through a thunderstorm and was drenched. During that time it acted up worse than normal. Was it the moisture causing the issue to be worse or was it sucking in some water and that add to the issue? I don't really know for sure. I can say after the storm I haven't had any other issues. I'm taking it up to Missouri this weekend and I'll report back on if It has any other opportunities. I did replace the spark plug wires why I was at Sturgis, just because.

[K4FXD]

Check the crank sensor, actually replace it.

When they are intermittent they cause all kinds of hell.

[Johnwesley]

Since I can't describe the sound or exactly what it is I recorded my ride today until it messed up. Then trimmed the clip to just that section. I was running the twisty roads in north Arkansas on my way to Missouri. I did realize sometimes you can feel the miss but it doesn't really change the sound. Almost like it skips a tooth but not as violent.

https://youtu.be/oYtuyvIDQ0w

[BVHOG]

Check the pins at the injector connection, motor torques, pulls on the wiring? Possibility and easily checked

[Johnwesley]

Thanks for the help, I'll check the wiring for the injectors. It just started after the tune, but had to pull the fuel system and replace. So it's possible the wiring harness was damaged.