Help!! Hanging Idle. Out of Ideas?

[blksvtCOBRA714]

Basically I am having issue with my idle hanging anywhere from 1500 to 1250 or so and it fluctuates sometimes in that range. This all started happening after I blew my FRPS. I've researched and tried most options just looking for anymore feedback.

Before the incident, my idle was find and sat around 850. Now it wont settle past 1200 most of the time. I know its not tune related because my car was running fine before the FRPS went up. This happened about a week ago and aside from the idle itself, I have no driveability issues.

Here's what I've already tried.
Replaced the FRPS twice.
Cleaned MAF sensor
Cleaned throttle body
Cleaned IAC sensor
Checked for vacuum leaks visually and w/ carb cleaner
Adjusted my Throttle position but no change at all.
Changed the plugs
Changed oil
Changed to new battery

Car still ran after unplugging the IAC valve, MAF, and TPS sensor independently.

I'm leaning towards a vacuum leak because on my boost gauge my vacuum is reading b/t 14-15 where I could of sworn it was closer to 18.

I tried the carb trick but still no luck. I pulled some datalog to see if some of my stuff compared to others is off.

Vpwr 13.5
ect 186
rpmsd 800.00
fpdc 0.17-0.18
iacdu 0.524
frp 40.000
iat 106
load 0.240
longft 0.810
longft 0.790
mafct210
rpm 1500
shrtft 1.000
spark 35.000
tp-v 170.00

This is all at idle and at this point my boost gauge was showing a vacuum just shy of 16 psi


Any ideas? This has me extremely frustrated at this point.

 

[Blueline]

Your vac at idle with stock cams should be around 20. It sounds like its def. vac related. Check vac lines again, there has to be a leak. Maybe the fuel that passed through them when the FRPS went was enough to damage a line that was almost completly dry rotted. Check the big vac line for the PCV and the one that comes from the bottom of the intake back to the blower inlet. Good luck, how are those wheels doing?

 

[blksvtCOBRA714]

Your vac at idle with stock cams should be around 20. It sounds like its def. vac related. Check vac lines again, there has to be a leak. Maybe the fuel that passed through them when the FRPS went was enough to damage a line that was almost completly dry rotted. Check the big vac line for the PCV and the one that comes from the bottom of the intake back to the blower inlet. Good luck, how are those wheels doing?

Thanks I'll just have to try again and see if I can find a leak cause I agree that it sounds vac related. I'm enjoying the wheels just haven't had to much of a chance to show them off much as I've corrected alot of things over the winter to get my car running right. But they really set off te look of my car and look sinister.

 

[V6&V8SHO]

I had the hanging idle and put in a new IAC. Problem solved.

 

[03SB cobra]

for vac leaks usually u can spray Carb clean in certain areas while your car is idling and see if it changes then u can narrow it down to that area

 

[03SB cobra]

Had that issue on a 98gt and ended up being a cracked intake manifold in the back

 

[blksvtCOBRA714]

for vac leaks usually u can spray Carb clean in certain areas while your car is idling and see if it changes then u can narrow it down to that area

Tried that but no luck in finding anything.

Had that issue on a 98gt and ended up being a cracked intake manifold in the back

I don't think it would be that though that would be really unfortunate.

I pulled some datalog to see if some of my stuff compared to others is off.

Vpwr 13.5
ect 186
rpmsd 800.00
fpdc 0.17-0.18
iacdu 0.524
frp 40.000
iat 106
load 0.240
longft 0.810
longft 0.790
mafct210
rpm 1500
shrtft 1.000
spark 35.000
tp-v 170.00

This is all at idle and at this point my boost gauge was showing a vacuum just shy of 16 psi

 

[blksvtCOBRA714]

When I was testing my vacuum lines, I did cap the vacuum line off of the boost bypass valve and the vacuum went back up to 20. At full throttle I noticed I was also only showing 13lbs of boost vs the expected 17. Has anyone heard of the boost bypass valve breaking particularly w/ an frps incident and could that be causing my vac and idle issues?

 

[TRBO VNM]

It definitely can cause your issues. I haven't seen the FRPS pop and then cause those issues, but then again, I haven't seen one be as extreme as yours was. Depending on why it happened and how you were driving it, the fuel spike going through the valve can't be a good thing and fuel does have the potential to damage the inside of the valve.

 

[SVT_Troy]

dont forget about the vacuum line under the blower......if its leaking you wont know unless you remove the blower.....