Hanging Idle Help! 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.

 

[Wiseguy]

Get it Smoke tested for a vacuum leak. If the frps blew badly enough, alot of fuel could have gotten into the intake and damaged the vacuum lines and made them swell.

 

[Snakesvt04]

Change your plugs, but dont think that would much but you never know since you blew frps..if you think theres a leak, spray some carb cleaner around the area. It should suck it and idle funny.

 

[blksvtCOBRA714]

Get it Smoke tested for a vacuum leak. If the frps blew badly enough, alot of fuel could have gotten into the intake and damaged the vacuum lines and made them swell.

Where could I go to get it tested? It was badly flooded when it blew so I'm thinking it has to be leaking somewhere I just haven't found any spot yet.

Change your plugs, but dont think that would much but you never know since you blew frps..if you think theres a leak, spray some carb cleaner around the area. It should suck it and idle funny.

I'll give that trick a try. Oh and I did replace my plugs as well they were pretty fouled too but it didn't cure anything either.

 

[Wiseguy]

Any shop with diagnosic abilities should have it. Change your oil too, if you haven't already. The carb trick works but is flammable...

 

[blksvtCOBRA714]

Any shop with diagnosic abilities should have it. Change your oil too, if you haven't already. The carb trick works but is flammable...

Changed my oil too. Called a few local shops around here and can't get in in a decent time frame. 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

 

[Wiseguy]

Your fp looks high at idle, check that connection. Should be 30psi at idle with normal 18in/20in of vacuum. Also, if large vacuum leak/high idle you would get a po171 or174. You should be able to hear that kind of a leak. Its idling at 1500rpm?

 

[blksvtCOBRA714]

Your fp looks high at idle, check that connection. Should be 30psi at idle with normal 18in/20in of vacuum. Also, if large vacuum leak/high idle you would get a po171 or174. You should be able to hear that kind of a leak. Its idling at 1500rpm?

I do have a fuel pressure gauge and it shows about 30 psi at idle and can't really hear any audible leaks aside from the engine noises. And yes its idling around 1500 right now. After I initially turn it on its close to 800 but after i hit the gas once, it settles at 1500 and doesn't drop back down usually.

 

[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 particullarly w/ an frps incident and could that be causing my vac and idle issues?

 

[itSSlow98]

What are your MAF counts doing at idle, it sounds like either a vacuum leak or IAC issue to me.

 

[blksvtCOBRA714]

What are your MAF counts doing at idle, it sounds like either a vacuum leak or IAC issue to me.

Mac count stays around 210. I don't think its the IAC, I really think its vacuum related, particularly my boost bypass actuator on the back of my blower. Trying to get ahold of kenne bell today to get their take on it.

 

[TRBO VNM]

Something you can look at in regards to the bypass, maybe have someone start the car while you watch it or look at it before you start it to see the lever/stop position. when you start it, it should open up. If it is sucking air through the bypass (showing a leak), then I would agree, it is probably the bypass. At idle that line is at vac and should be pulling the bypass open and then once boost is applied it forces it closed. So if there is a leak and the vac isn't pulling it open, then that would also be an indicator of a bypass issue.

With the car off it should just be in the closed position. If you can get your hand in there to move the lever/stop, there should be some resistance. I would think if there is a leak, then with car off you probably don't have a lot of resistance.

 

[blksvtCOBRA714]

Something you can look at in regards to the bypass, maybe have someone start the car while you watch it or look at it before you start it to see the lever/stop position. when you start it, it should open up. If it is sucking air through the bypass (showing a leak), then I would agree, it is probably the bypass. At idle that line is at vac and should be pulling the bypass open and then once boost is applied it forces it closed. So if there is a leak and the vac isn't pulling it open, then that would also be an indicator of a bypass issue.

With the car off it should just be in the closed position. If you can get your hand in there to move the lever/stop, there should be some resistance. I would think if there is a leak, then with car off you probably don't have a lot of resistance.

When I was looking at it yesterday, the lever was pretty easy to move and didn't have much resistance. No one is around really today to help me look at it in that respect. I did get a hold of Matt at Kenne Bell and he thinks that the bypass could be bad. Just like you said earlier if fuel gets in there it can erode the diaphragm pretty quickly and being how bad my frps went and how much fuel were in all my lines, I think its quite possible that it blew on me. So I just ordered a new one, so hopefully that fixes my issue. If not, I'll let you know and might have to bring it back down to you so we can get this sorted out.

 

[TTRIMSVT]

We have had it happen several times. the fuel will get in the vac line and eat the inside of the bypass the thing is sometimes it will still work but slowly because of the vacuum leak.