Check Engine Light.

115

Asked by Nov 03, 2013 at 02:33 PM about the 1989 BMW 3 Series 325i Sedan RWD

Question type: Maintenance & Repair

My 1989 325i convertible runs great but idles a little rough. I am planning to replace the injectors; I've been looking at newer Bosch injectors for Mustangs. Is that a good idea?

More to the point though; today I topped off the oil and forgot to put the filler cap back on.  When I stopped at a light the Check Engine light came on and it idle rougher than normal. When I stopped I was lucky enough to find the oil cap. I put it back on and the light never came back on.

Can anyone explain why it would act like that, and can I use that information to improve the idle in normal situations rather than replacing injectors?

4 Answers

263,975

With the oil cap off you created a vacuum leak. No need for new injectors, clean the throttle body, and MAF first. http://forums.bimmerforums.com/forum/showthread.php?875657-The-Full-throttle-body-cleaning-write-up

1 of 1 people found this helpful.
Best Answer Mark helpful
115

I cleaned the throttle body and MAF sensor. That didn't work. I replaced the injectors... no help. Mechanic checked ignition on a scope and everything is good. It runs very strong and very smooth. It just has a tiny miss when it's idling that his sensor doesn't even register, but that he and I are both feeling (more so when it's in gear). Any ideas?

115

I cleaned the MAF, and throttle body and tested the idle control valve. My mechanic smoke tested the vacuum lines, and I have no leaks; he tested the MAF, the fuel pressure regulator, and heat sensor and re-tested the ICV. He said the hoses are new and the injection components all fall within a very acceptable range. I did go ahead and replace the injectors with mustang 19# injectors because I read that you could do that without changing the chip. It runs great! But it still misses at idle exactly like it did before. Not a lot; it doesn't even move the tach needle. It's just doesn't fire every once in a while and then the next revolution the cylinder's flooded and it kind of thumps. When you give it gas it feels a little sluggish, but if you put your foot in it, it kind of clears out. Do you think I need an advanced chip with the new injectors? I don't really want to start down the road to custom fuel injection... I was trying to just get the idle smoothed out.

115

bump... ?

Your Answer

3 Series

Looking for a Used 3 Series in your area?

CarGurus has 32,629 nationwide 3 Series listings starting at $1,200.

ZIP:

BMW 3 Series Experts

  • #1
    Tom Demyan
    Reputation
    5,190
  • #2
    Robert Charlson
    Reputation
    1,670
  • #3
    grolyate
    Reputation
    1,270
View All

Related Models For Sale

Used BMW 5 Series
553 Great Deals out of 15,617 listings starting at $1,650
Used BMW M3
37 Great Deals out of 2,082 listings starting at $5,495
Used Ford Mustang
596 Great Deals out of 39,148 listings starting at $1,895
Used BMW 7 Series
133 Great Deals out of 5,148 listings starting at $1,750
Used BMW 6 Series
73 Great Deals out of 2,447 listings starting at $5,995
Used Honda Accord
1,101 Great Deals out of 73,054 listings starting at $1,100
Used Chevrolet Camaro
450 Great Deals out of 31,410 listings starting at $1,450

Used Cars For Sale

2018 BMW 3 Series For Sale
7 Great Deals out of 5,589 listings starting at $31,895
2017 BMW 3 Series For Sale
155 Great Deals out of 4,463 listings starting at $23,900
2016 BMW 3 Series For Sale
49 Great Deals out of 1,331 listings starting at $14,991
2015 BMW 3 Series For Sale
97 Great Deals out of 2,587 listings starting at $13,995
2014 BMW 3 Series For Sale
297 Great Deals out of 4,725 listings starting at $11,979

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.