1998 Ultra, 55k miles. Replaced CPS with Standard Motor Products. Decided to reset TPS, .275. Cold idle .650. Unplugged battery + for 2 hrs.. Hooked + battery back up. Did on-off for 30 seconds to synch ECM and ICS.

. Fired right up, cold idle good. Warmed it up some and took 10 mile hwy. run at 60-75mph. Pulled in at rest stop turnaround and left it running in neutral to light a cig. Idle started fluctuating from 1000- 1600 rpm. Left it running when I got home and felt ICS for movement and could not feel a thing.

Replaced CPS because of goo and I had an almost-die situation on the road when stopping and had to work the throttle a few seconds to keep it going and it cleared up.

Video shows what's happening now. Over-rich on back cylinder when it fluctuates and "sounds" like valve clatter at exhaust, mostly on back cylinder it seems.

All I can think of at this point is a new head temp sensor. Replaced it about 12k miles ago. Damn video will not upload, say NPR not aaccepted...

Ideas appreciated . Ken

 

Meant to say mp4 not accepted.

 

Have you checked the temp sensor? The temp sensor goes bad the idle will fluctuate between cold and warm idle

 

You also can check the TPS sensor and Idle Speed Control Motor but to me it sounds like the classic faulty temp sensor

 

Yeah. Kinda what I'm leaning toward.....head temp sensor. Plus new idle -throttle cables. Maxed out on adjustment, but not my current problem.

Ken

 

In order to help others understand:
CPS-Crank Position Sensor..The original factory unit melts a beige/tan sealant goo.
TPS-Throttle Position Sensor
ECM-Computer
ICS-Idle Speed Control

Suggestion:
Have you removed the access panel for fuel tank and looked inside the tank?
REASON: When adjusting/altering parameters it is important to insure that everything is working correctly.
The tank liner is known to release a piece of liner and that piece can hinder fuel flow at filter sock.
Have you changed the two intake manifold seals?
REASON: Original seals should have failed by now and there could be unmeasured air entering the system.
Have you reviewed the ONE nut by throttle actuator arm? Have you tried to clean the actuator motor shaft?
REASON: That one nut can get loose and cause arm to be loose and it is part of actuator speed control that could be dirty.
Are you running the original factory fuel lines under the tank?
REASON: Those lines can leak at swivel and are not serviceable. A leak could cause fuel issues.

The engine head temperature sensor causes run away throttle.
Throttle ramps UP for no reason and then flips immediately back DOWN for no reason.

*you can test the head temp sensor with a simple ohm meter: It is just a thermistor.

 

You should NOT be maxed out on adjustment unless you have incorrect cables or ends are bad.
Bad cables can also lead to incorrect readings at throttle body.

 

Don't start replacing FI components without first checking to see if you have a fault code stored. The head temp sensor code is 14.

I don't think you have a bad head temp sensor. You need to very carefully check your throttle cables. The idle fluctuation could be a loose cable causing the butterfly to flap. The clatter you're talking about at the rear cylinder could be something else entirely.

carl

 

Well, Carl, you may have hit the nail on the head. Neither the idle or throttle cables completely tightened the cables back ...there is a little slack in both. Think I will try new cables first. Pretty sure they are both the originals. Everything I've looked at/replaced have all been original. Plus, both cables are slightly less cost than the ETS and they have been on my soon to do list.

IM, I''ll check that nut again, could have loosened a bit since last time I checked. I did notice when I reset the TPS it was a little higher than last time I set it? It's been running real good with no problems for 12k with the exception of no cold idle, so thought I'd give the settings another shot. One thing at a time. I'll be real happy if it's the cables causing the slight (500rpm) idle fluctuation.

Thanks to all for chiming in, guys. Your answers. are highly valued. Will check back in after new cables are installed to see if that fixed the problem.Still learnin' something new every day. Ken

 

BTW, IM, cleaned the actuator arm and the butterfly shaft at all points. Tank liner looks like new. I am not running factory fuel lines, I posted a thread where I changed everything out to barb fittings and plain fuel line from the tank down. Cost was about $35+ my labor. Not a leak anywhere. Orings at swivels on injectors have no leaks, and are the only orings on the fuel lines left. Ken