So my car (94 325i) has a misfire that seems to be keeping it from passing the scam that is smog testing (PA). My first thought is to test the coils (plugs are brand new a week ago). When resistance testing them they all turned up with 1.1 to 1.2 ohms on a multimeter. I know that there is no cheap way to accurately test them, but using this test, I've been informed by a local BMW mechanic that they should return 0.4-0.8. Since my readings are higher, I would believe that they are just as no good as if they read lower. Thoughts and input from someone who knows more than I would be appreciated.
Let's begin with abit more information, which new sparkplugs have you bought ? Are there any vacuum leaks ? Smoke test the intake!!!
C217 S63 AMG S Cabriolet ( Daily )
E87 116i with mild cams, headers, cold air intake making 136 bhp Lol (My Learning Track Car)
E36 328i Sport ( Project in making and future race/track car )
The fact that you're getting the same reading on all the coils indicates they're not your problem.
Why are you describing this as "a misfire"? Is the engine running on 5 cylinders?
What were the actual results of your emissions test?
Chris Powell
Racer and Instructor since, well. decades, ok?
Master Auto Tech, owner of German Motors of Aberdeen
BMWCCA 274412
German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471
Attachment 598952
Attachment 598953
The higher numbers are from a bad aftermarket cat the car came with. Low numbers from a car that passed emissions two months ago.
The plugs were BKR6EKs which I know people have reported problems with before. They're on my short list to switch.
My buddy who owns a shop did me a favor and said he smoke tested the car and it came up with no leaks. I didn't do the test nor was I there, so I can't vouch that there wasn't a leak somewhere.
There is a highly audible sound when each coil is disconnected while the car is running.
The "misfire" is a quiet but lowly audible pop/putt sound heard from the exhaust. Very similar to when I was working in a garage with older cars a couple years back and someone would bring in a car with plug wires mixed and cylinders firing out of order. Same sound as when a coil is disconnected but with a couple seconds in between (not consistent enough i thought to measure the time) rather than almost all the time (as with coil not connected).
Last edited by Jeffersonwillis; 04-30-2017 at 09:57 AM.
I should add that when starting the car this morning, it shakes and rattled strongly to the point i didnt think it was a good idea to leave it run. Felt shake/contact under my feet.
Edit: shake unrelated to issue. Pulled coils and plugs were damp. Must not have covered them well enough when i cleaned the engine bay. Dried them with compressed air, no shake.
Last edited by Jeffersonwillis; 04-30-2017 at 10:27 AM.
The attachments didn't work.
The NGK BKR6EK would be the only plug I'd use in your engine.
Chris Powell
Racer and Instructor since, well. decades, ok?
Master Auto Tech, owner of German Motors of Aberdeen
BMWCCA 274412
German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471
Test 1 (bad cat):
CO % x liters- test value 1.50 / limit 1.10 (Fail)
HC ppm x liters- test value 700 / limit 275 (Fail)
NO ppm x liters- test value 8715 / limit 3600 (F)
RPM- 1744
Dilution- 14.3%
Test 2 (good* cat):
CO% x liters- test 1.70 / limit 1.10 (f)
HC ppm x liters- test 642 / limit 275 (f)
NO ppm x liters- test 3870 / limit 3600 (f)
RPM- 1741
Dilution- 14.5%
*Good cat is used, but has passed PA inspection on a 95 325i two months prior.
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