S4 shooting ducks from rear cylinder.

Been suffering from deteriorating part throttle performance and poor idle quality and stalling for a little while now. Now it's not rideable.

Runs OK immediately on startup, but a minute or two of running and it starts missing on the back cylinder, backfiring out the intake. It will get worse until the engine stalls.

I synced the throttle bodies best I could with the intermittent running.
Runs just as crappy with the filler open, so there's no tank vent issues.
New spark plugs, still bad.
Snugged up hose clamps on the manifolds.
PCIII removed.
Swapped coils front to rear, rear cylinder stays bad.
If I unhook the coolant temp sensor, the fans will come on. So I think the coolant sensor is OK.

Battery is good, reads 13V on a good multimeter.

Both injectors read 13 ohms.
Little filter screens on the injectors are clean.

Can't check fuel pressure tonight, but I'll have that capability tomorrow.
Next is swapping injectors to see if the problem follows those.

Anybody got any bright ideas? or BTDT?
-----------UPDATE------------------
Valve train:
Belts tension is OK.
Cam timing marks line up like they should.
Nothing obviously wrong with the valve gear and cams, haven't removed any of 'em for close inspection.
Intake opener clearance .004".
Exhaust opener clearance .005" & .006.
Closers have clearance, no measurements as that's a real PITA.
Closer springs are not broken.

Turns out I can't check leakdown at the moment, I don't have an adapter that'll fit the small plug threads.

Inspected the near-new plugs.
Front cylinder spark plug looks fine, like it's been running.
Rear still is very new looking and still white.

I'm beginning to suspect there's a fuel delivery problem....


Modified by Speeddog830 at 8:45 AM 4/2/2005


Modified by Speeddog830 at 7:39 AM 4/14/2005

Check the throttle POT? Also, you can easily check internal ground of ECU by grounding the black wire on the data port. If the bike behaves, then there is an internal ECU problem.

Hmmm...I'll have to try grounding that black wire on the data port.

I swapped injectors front to rear, rear cylinder still misfiring bad.
Swapped injector wiring front to rear, runs worse.

I borrowed a complete known good ECU/gauges/keyswitch, and my bike runs fine with it. Runs like crap with my suspect ECU. Did several back to back to back to back tests.

99% sure my ECU is shagged.

Suggest you leave off the PC when you get your new ECU.

bcm,

Granted, leaving off the PCIII would be safer, although I have no idea if it contributed to the demise of my current ECU.

Unfortunately, with no PCIII I'm forced to live with the OEM map, which isn't all that good.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Speeddog830 &raquo;</TD></TR><TR><TD CLASS="quote">bcm,
Unfortunately, with no PCIII I'm forced to live with the OEM map, which isn't all that good.</TD></TR></TABLE>

Not really Nick, send Bruce about $700 for a shiny new FIM ECU You know you want one

Come on Ducman..For the last time....there is no one here to tune them. $700 and hoping it works right.

while i agree that the U59 is a better overall solution than the PCIII, i don't see how there's any risk to the ECU in running a PCIII. electrically, all it does is intercept the signal and then send a different signal further down the data path. from what i understand, the PCIII doesn't send any signal back up to the ECU so where's the risk? it's a pretty simply device electronically.

Mine worked great. I expect it to be fine when it comes back with the 800 map in it. Who knows I may just pony up and get the software and use mine as a guinnea pig. I know of a dyno I can get use of.

So far I'm quite happy with the FIM unit.

Runs great, possibly better than it did with a PCIII/dynotune setup. I think my OEM ECU had been sick for a while, so the A-B test is a little fuzzy. Mileage is still good, and the low rpm and small throttle performance are very smooth.

Only gripe is that it won't run with the sidestand down any more, apparently it's thinking it's still 2001
I'm going to ping FIM to see if that issue can be addressed easily.
------------------------------------------
Sure wish I could change the title of this thread...

Speedog:

So you went with an FIM unit? Do you order it with whatever equipment you have? In other words, you said stock S4, cherry bomb exhausts, stock headers, and they sent you a pre mapped unit? If so, did you tweak it at all, and if you did, did you do it yourself?

Sounds better than running a stock ECU with even a dyno tuned PCIII! Or even a DP ecu with pcIII!

Rideon

Rideon,

Yes, I went with the FIM unit, ordered it from BCM.
I told 'em I had an S4 with cans, otherwise stock.
I don't know what map they actually put in it...

I don't currently have access to the hardware necessary to tweak the map.
I'm pursuing this on an ongoing basis, I would really like to be able to tweak it a bit.
It's a good map, but it could be better.

I'm convinced it's technically a better solution than a PCIII on any Duc ECU, but the current lack of local support is a serious issue.

Addendum:

It is absolutely annoying as hell how the FIM unit deals with the safety switches.

With the sidestand down, the engine will crank, but will not run, nor start. It will crank, even if the engine is in gear. Same if it's in gear and the clutch is pulled.

I can bypass/eliminate the sidestand switch, but it'll still crank when in gear.

I'll have to frankenstein my wiring to even get it close to the way it was originally.

Why couldn't FIM just keep it the way it was stock? AFAIK, it's even worse than the way the '01 bikes were.

I had a similar problem with my carbureted 2000 750 Monster. I went nuts trying to figure it out! I spent many hours and $ to resolve it. My problem was electrical. Turns out there was a grounding probem with the wiring harness. You have to put a meter on every wire and if you've done any rewiring (removed the kickstand safety for example) check all those places. A good shop should be able to go through it for you. Good Luck and I hope this helps.
Frankie

Thanks, frankie.

The replacement FIM ECU did the trick, so all is pretty much as good as can be expected.

I'm slowly making progress on getting some local support for the FIM.