random idle drop

91beatuphatch · Post by **91beatuphatch** » Fri May 27, 2011 9:09 pm

okay the basics...

91 integra ls b18a1 205k, aem short ram, 4-2-1 header is the only engine mods.

after hitting operating temp, my car will just randomly drop idle down to roughly 250 +- rpm. sometimes it will sometimes it wont. but i cant seem to figure it out.

the only code its throwing is a fuel system malfunction. ive checked all injectors, replaced fuel filter and checked pressure.

all vacuum lines are uncracked and correct.

any ideas. if im leaving any needed info out let me know ill fill in the blanks.

Phate · Post by **Phate** » Fri May 27, 2011 9:11 pm

Do a compression test. I'd be willing to bet you have bad compression in cylinder #3.

JustRob · Post by **JustRob** » Fri May 27, 2011 9:24 pm

What number is that code?

91beatuphatch · Post by **91beatuphatch** » Mon May 30, 2011 2:01 am

okay drove it around today... when the idle drops itll be random. not a consistant thing. lets say ill pull to a stop light, engine will idle down to about 900 for a few seconds then drop. it doesent always drop to 250 sometimes itll only go to about 500 or so. it doesnt surge like a iac.

as far as codes go...

i checked again today and its throwing 2 codes. #1 and #43

1 is o2 sensor 43 is fuel supply system.

91beatuphatch · Post by **91beatuphatch** » Mon May 30, 2011 2:06 am

well after researching i figured out that both codes are associated with each other. but would the idle problem have anything to do with the o2 sensor? never had a bad o2 do this before.

JustRob · Post by **JustRob** » Mon May 30, 2011 3:32 am

91beatuphatch;265876 wrote:well after researching i figured out that both codes are associated with each other. but would the idle problem have anything to do with the o2 sensor? never had a bad o2 do this before.

It's possible that it could be the issue and is the best place to start.

The O2 sensor could be bad, there could be a poor connection or a loose wire, or the ECU could be bad. The most likely of these being that the O2 sensor is bad.

If it were my car, I would replace the O2 sensor, reset the ECU and see what the car does from there.

gcef89 · Post by **gcef89** » Mon May 30, 2011 7:24 pm

i swapped a b18a1 into my ef and it did this when i thought i had my vacuum lines right but didn't. recheck all of that!

91beatuphatch · Post by **91beatuphatch** » Fri Jun 10, 2011 1:07 am

Okay today I installed a new o2 sensor, I cleared all codes and I'm still getting the same #1 and # 43 codes. Which are o2 and fuel system. Any ideas?

JustRob · Post by **JustRob** » Fri Jun 10, 2011 4:04 am

Here's the service manual excerpt on how to diagnosis the issue.

91beatuphatch · Post by **91beatuphatch** » Fri Jun 10, 2011 11:05 am

hay thanks for the scematic but where is picture indicating? its not very detailed