Idle problems with blower

[Desert Stallion]

Well, just picked up an '89 GT with what I think is a killer setup already installed, but the damn thing won't idle!

-Sportsman block
-NOVI 1000 w/ 8lbs pulley
-AFR 185 heads
-TFS Track Heat intake
-190lph fuel pump
-24lbs injectors
-equal length shorty headers
-Bassani X-pipe
-Flowmasters

The problem is that if you keep your foot on the pedal, it runs fine at 1500 RPM, but as soon as you let off it starts reving up and down wanting to die until it does, or it will just quit all together. If by some miracle it is idling, and you turn the steering wheel, it dies. If you're coming up to a stop light and push in on the clutch, it dies.

Basically, it won't idle.

Here's what I see as being possible causes...

-bad/dirty IAC
-bad TPS or set incorrectly
-I read something about when a power pipe is used, it could actually cause air to backflow over the MAF because of BOV location??

When you're driving it though, the thing pulls like no other car I've driven. It's friggin' awesome! It just can't be driven right now because I live in the ocean of stop lights.

This is my first supercharged car, and I'd like to make it as driveable as possible, ya' know? If it ain't gonna idle at a stop light for me, then it's not worth a whole lot.

 

[D347643]

maybe vacuum leak? hook up a vaccum gauge on your shrader valve and check how many in merc it has at idle. yeah the tps may be the cause, same with the iac. but the surging you are describing sounds like a vac leak or unmetered air. hope you find it.

good luck,

Drew

 

[jason89gt]

won't idle

are you using the stock mass air flow? odds are it's the maf with the back flow problem. can you take the power pipe off and see how it idles?

 

[JenkinsBS]

my guess is its the stock Mass air sensor, calibrated for the 19lbers it had on there before the 24's, so you might want to check out PRO-M sensors, much better than any other brand (C&L) AND...

get a bigger TB, that little stock one is deffitly not enough for the heads you have, and the blower

b.j.

 

[88stangmangt]

had the same problem untill i sprayed some throttle body and dumped in some fuel injectors cleaner.solved my problem maybe it just went away for a few months but the engine is pulled now so i guess i wont know till it goes back in. but i also wasnt happy about the putty i found on the back of the lower intake to seal a vacum leak.

 

[cavallonero]

IF its dying when you put the clutch in its very possibly a bad IAC.
Mine did exactly the same thing when it died (actually I accidently killed it)
Disconnect it while its somewhat ideling and if the car doesnt respond - its likely bad. You can get em at autozone for about $40.
FIY, many supercharged systems have trouble ideling but I havent heard of any dying when you clutch. So what Im saying is even if you do replace the IAC, you may have another problem. Try one of those kits on ebay that let you adjust the throttle bypass manually.

 

[TheUser]

I had the EXACT same problem! Sorry I can't tell you what fixed it...blew head gaskets and just now getting it back going again and i'm pulling the blower. I think the surging idle on mine was because of the B303 cam and the reason it was probably dying was because I didn't have a Bypass valve, so the blower was pushing air in and it wasn't being used. But yeah, i'd clean the TB and Idle Air-Bypass Hope you get it fixed man...I know what that's like and it blows.

 

[Desert Stallion]

Cleaned the IAC and it seems to have fixed it. The motor starts and idles fine now, go figure.

Anyway, the car has a 80mm MAF calibrated to the 24lbs injectors and a 75mm throttlebody, so that's not an issue.

 

[Azul93GT]

Cleaned the IAC and it seems to have fixed it. The motor starts and idles fine now, go figure. ...Anyway, the car has a 80mm MAF calibrated to the 24lbs injectors and a 75mm throttlebody, so that's not an issue.

Did this problem stay fixed? I'm having similar but not quite as bad idling issues as the ones that you described. Cleaning the IAC didn't seem to do much.

I starting to think that my cam (TFS STG 1) may be ill-suited to blower use since it has a lopey idle, which causes vacuum fluctuation, which in turn cause the FMU to enrichen the fuel too much at idle. Does this sound plausible?

 

[BlackFox5.0]

My car is doing the same EXACT thing, but only when the blower is hooked up.. I asked a fellow mustanger who knows his stuff on superchargers, and he said that it's because i don't have a Bypass hooked up, He also said that one of those air bypass plates for your IAC will help with idle problems.

A friend of mine made a good point. He said that the IAC is made for stock airflow through the intake. If your engine is demanding more air to stay running, then letting in the same amount of air through the bypass for a stock engine is not going to cut it. I am going to try one of those bypass plates. www.50resto.com has them for like $17 +shipping. I have also seen quite a few supercharged mustangs with this plate too, so I think it's common place on a blower car....

 

[Azul93GT]

I'll give the bypass plate a try as well. My idling issues only occured post blower installation.

 

[BlackFox5.0]

Today I just bumped the idle by turning the idle screw in a little bit, and my car idles! And doesn't stall when I stop anymore. The idle is higher than I want it, but it's fine till I get the air bypass.

 

[noslow5_0]

hey blackfox you making more boost now??? hows it runnin???

 

[RydeOn]

Mine did the same thing when I didnt have a bypass valve. When I installed that it idles like stock.

 

[Azul93GT]

Mine did the same thing when I didnt have a bypass valve. When I installed that it idles like stock.

Do you mean the IAC bypass adjuster(Idle air control adjuster) or a blower bypass valve (BOV)?

 

[BlackFox5.0]

Im making boost now yes, turns out the vacuum line plugs on the bottom of the intake were cracked up, so air was coming out, but when that boost comes on, all I can say is, wow....

 

[BlackFox5.0]

Do you mean the IAC bypass plate or the blower bypass valve (BOV)?

I'm pretty sure he means the bypass for the blower.

Doesn't it stay open when at idle, allowing air being forced in to go back into the front of the blower?

 

[Azul93GT]

I've been doing a little looking into the bypass valve, and it seems like the way to go. Did you fellas assemble your own bypass set-ups, or did buy pre-packaged kits like this?

 

[Ranchero5.0]

Just buy the dang valve and fab your own fittings. The kits are for catalog heros, not hot rodders.

Jamie

 

[RydeOn]

Well, I guess I am a true hot rodder!

Yes, the blower bypass valve is what made my car run 100x better. I reccomend you purchase one if you buy an entry level kit that doesnt include them. Black fox, nice to see you found it.