I recently had my upper intake off to block off the omp, i have a slight vacumm leak at the gasket flange but it ran fine for a few days and a roadtrip. Now when i start my car it idles rough and when i give it any gas it will stutter then jump to 2k and back to idle over and over at any throttle position. could the vacuum leak just have gotten worse? need help my cars stuck in my schools parking lot

 

It's possible. How bad did the gasket mess up when you removed the upper intake? But it's also likely you just forgot to reconnect a vacuum hose back up.

With the engine off and cold, have someone else look for a disconnected or loose hose. They don't have to know anything about cars. You'll be surprised how a different set of eyes sometimes catch something obvious that we'll miss cuz we've been staring at it for hours, lol.

 

Luckily i'm an auto engineering student at Ferris State and was able to push my car into our shop, had two professors and multiple students look at it, no one found anything disconnected or loose.

After playing around with our smoke machine i still cant find any leaks, however playing with every hose and wire i could find in the bay i somehow got it to be able to rev past 2k and make it some what drivable.

next step is take it all apart again, new gasket and new vac hoses i suppose

 

When you get the intake back off, verify you havent broken any of the injector wires in the injector clips. Had that happen when I removed the oil injectors from my setup.

 

well the weather finally cleared up and i went to start it..... started fine, revs fine, and drives fine.

idk if she was just on her period or if its a wet/humid weather issue, what could have gotten shorted or wet to cause something like this?

and ill take a look at all the injector wires when i trailer her back home, i can see how that could effect it.

 

Water and/or moisture in the engine bay is a no go for anything electronic... anything could've technically happened if you've had a wet connector.

 

the engine bay didn't get wet, from what I saw atleast, it just had been raining hard all day and was very humid.


after a few more start ups randomly, im back at square one, some days she starts fine others it barley stays alive. I cant decide if its a vacuum problem or if a sensor is tripping out.

Ill try and get a video if any one is interested, if I cant fix it within a couple weeks im probably gonna start an n/a Bridgeport build and replace every thing unless a t2 engine comes my way

 

You likely have faulty wiring/connections.

 

ive gone through all the wires I touched or disconnected and all seemed to be in tact.
Is the tps the sensor on the front part of the throttle body near the double throttle diaphram? i noticed it really only reads up to a certain throttle, is there a second tps or something?

but i cleaned everything up installed a new gasket, now i just have to tighten everything back down, hopefully she runs fine.

 

For an S4 the TPS reads up to 30% throttle or so before the throttle linkage separates from the TPS. When fully warmed the TPS reads from 1 volt at idle up to about 4.5 volts.

The primary injector plugs were probably not touched but if they are problematic then it could cause the issues you are describing such as hard to start and idling, driving issues when not under load.

 

air flow meter not pluged in or not working?

 

Still unsure about what is or was wrong, but after I put it all back together it worked perfectly fine, minus me breaking the delay valve for the double throttle.

But shes away for the winter now, time to replace everything for fun

 

Sounds like a wiring issue. It seems they just come and go for no rhyme or reason.