• Welcome, Guest! We hope you enjoy the excellent technical knowledge, event information and discussions that the BMW MOA forum provides. Some forum content will be hidden from you if you remain logged out. If you want to view all content, please click the 'Log in' button above and enter your BMW MOA username and password.

    If you are not an MOA member, why not take the time to join the club, so you can enjoy posting on the forum, the BMW Owners News magazine, and all of the discounts and benefits the BMW MOA offers?

'93 K75s/ABS - Stumbling under acceleration after spark plug change.

lanceharrison

New member
Greetings!

So, I changed out my spark plugs Bosch X5DC to Bosch X5DC last Saturday, and all seemed well: Fired up the engine and it sounded normal under stationary revving. Tried to meet my club for a ride the next morning, but had enough stumbling/halting issues under acceleration that I turned around and came home. No, I did not do a test ride post-maintenance, unfortunately, so I did not catch that issue earlier. :-/ The following are some notes regarding my thoughts on this issue.

Note 1: I did attempt to modify the gap on one plug, #1 cylinder: Did I damage it inadvertently? I used the coin-type gap tool I already had.

Note 2: I did -not- have my m/c cover on my bike during the rain late last week: The car port where I store my bike is open on two sides and it might have gotten wet while I was at work. Should I be thinking water in the gas tank, or stick with the plugs as the possible issue?

Note 3: I tightened the plugs down finger-tight, then gave a 1/4 turn with the plug tool. I tried to use my Pittsburgh PRO (Harbor Freight) inch-pound torque wrench, but I could not hear/feel the "click" like with my Kobalt (Lowe's) brand foot-pound torque wrench, so I backed it off and stuck with a 1/4 turn. Also, I did use copper anti-seize on the plug threads.

I am going to try swapping in the old spark plugs and see if that changes anything. If it does, then I assume it is plug related. If the issue persists, then I do have Iso-Heet on-hand to try if anyone thinks this might be water-in-the-tank related. I am concerned it might be an air leak in the system somewhere as mentioned in at least one other thread I was reading here in the forums (http://forums.bmwmoa.org/showthread...ut-am-I-looking-at-breather-issues-or-bad-HES)

Please offer any feedback. I look forward to hearing (reading) from you.

-Lance
 
UPDATE: "Original" plugs back in place

OK. Just replaced the "original" plugs that came with the bike. Bike fired up and revved "normally," i.e. like before I tinkered with it. Now for a test ride around the neighborhood.

-Lance
 
See if the screw on tips (wire end) of the plugs are tight.

Inspect the ceramic for any cracks.

Too much anti-seize?




:dance:dance:dance
 
My hunch is that one of the spark plug caps did not snap securely onto the plug - causing an erratic spark at one cylinder.
 
Plugs could be a red herring. Stumbling under acceleration also happens when you're low on gas and it moves away from the pump pick up as you goose it. Or a plugged gas filter.
 
UPDATE: Test ride successful!

OK. Just got back from the test ride. Neighborhood run was good, so I took it out to the freeway. Feels like it is running "normally," i.e. the same as it ran before I started tinkering. One thing I did differently was to tighten the plugs down finger tight with the spark plug wrench, then tighten it down with about a 1/2 turn using the lug-wrench over the plug wrench. I skipped the torque wrench this time. I believe the Clymer manual is the one that recommends to tighten down with that half-turn on the wrenches, then using a torque wrench for the final bit.

98lee: I checked the plug caps and they did not feel like they could be twisted off. I actually read a long thread regarding spark-plug caps that screw on at the "nipple" end of the plug (opposite the electrode-gap end, I assume) on Ted's www.k11og.org forum the last couple days (old thread). I did not know such a thing existed before reading that thread. The ceramic appears to be good on both the "old" and new plugs. I would have to use a good magnifying glass to see if I did anything damaging while trying to enlarge the electrode gap on the #1 cylinder new plug. I tried to make sure I kept the anti-seize on the threads only, and not on the electrodes. :)

PGlaves: I tried to ensure the wires were pushed back on tight when I reseated the wire caps: I used the pliers to hold onto the wire cap tabs when removing and reseating the caps. I did use "djverhult's" YouTube video here as a reference, along with the Clymer, Haynes & BMW K75 (c.1995) Owner's manuals during the work. It is still possible one wire was not fully reseated.

35634: I learned the gas issue the hard way last year riding to San Jose on Cinco De Mayo. :) (The flap in the gas cap was removed last year by my local BMW shop when they replaced the clutch and rear main seal.) I had a full tank of gas when I started out this past Sunday morning. Since there was no evidence of stumbling during this evening's ride, I am hopeful that the fuel filter will not be an issue anytime soon. *fingers-crossed*

Thank you all for your responses!

-Lance

P.S. I used just the BMW tool kit for tonight's wrenching.
 
Back
Top