91 240 ka24de running weird.

[91240coupe]

I got a 91 s13 with a ka24de with 149k miles. I just recently put in a new injen air intake and it ran perfect. Car has an exhaust leak right now from the cat and im going to get it welded soon.

Now when i park and let the car idle it would rev up to 1400-1900 rpm for about 30sec to maybe a minute then it would drop down to normal idle. Not sure if maf has a small leak somewhere or something else.

But i do know i have a bmc vacuum leak idk if its because of that leak my car is idling high then back to normal.

i hope i explained it good. thank you. [emoji5]

[TheMechanic]

check engine light when this happens? if so pull codes when it does it.. could be IAC tripping out... as far as the reason... could be dirty... could have an electrical problem

[OnTheChip]

A bmc vacuum leak will definitely cause idle problems.

[TheMechanic]

is that the egr modulator? ive heard the elbow likes to crack

[91240coupe]

check engine light when this happens? if so pull codes when it does it.. could be IAC tripping out... as far as the reason... could be dirty... could have an electrical problem
No check engine light.

[91240coupe]

A bmc vacuum leak will definitely cause idle problems.
Ive checked the hoses and not sure if the hoses are bad. Hoses looked pretty good

[frankies1390]

try unplugging sensors first.. such as coolant temp sensor, maf, but id focus on idle air control valve pull it, check it, clean it

[jza80king]

Just recently bought and replaced all the vacuum hoses on my car. Take a spray bottle and add dish soap and water. Go around spraying carefully and you should be able to pinpoint any vacuum leaks with bubbles. Once that is done I would look into the IACV and clean as mentioned above.

[kruked]

Start w/ the obvious and fix the BMC leak first. Any vacuum leak will cause various problems.
Leave the IACV as the second thing to check once you fix/replace the BMC.

[91240coupe]

Thanks guys!!!!

[trikk]

did you ever fix the problem?

[91240coupe]

did you ever fix the problem?
Havent had time to check it out.

[91240coupe]

Ok update guys!! So i tried unplugging the iac and all of a sudden idle goes back to normal.... i would start it and bam it normal at idle 800-900