I've searched, on here and all over my engine bay looking for anything abnormal. I cant find anything.

Newly rebuilt, streetported S4, check sig for mods. The car starts, idles and runs just fine, it simply wont accelerate while boosting. It makes boost, Im seeing normal boost levels (10-11psi) on my boost gauge, it just falls flat on its face while doing so and goes nowhere. I dont hear any boost leaks at all, everything is plugged in.

Two days ago I was driving to a buddies house and the coolant buzzer came on, I was down the street from his house and stopped it there. I popped the hood and a line had been cut by the hose clamp where I teed into it for a sensor bung. It didn't overheat, it didnt even get a chance to fully warm up. I didnt get a chance to fix it for a couple of days; after I did, this happened.

The line I teed into for the sensor bung is a custom one, I'm using N/A housings in this motor so I ran a line from the outlet at the rear iron directly to the water pump, teed into it and ran a line to the turbo from there. The sensor bung was before the tee to the turbo, so the line was cut before that as well. Is the turbo screwed now? I wasnt boosting it at all, the motor wasnt even warm when i stopped it and its still making boost..... I dunno, I thought I would fill y'all in to what has occured recently just in case it helps.

I've been all over the engine bay and cant find crap. So where should I start re-examining?

 

Other than a stuffed catalytic converter.........I've no other ideas why you see boost but the car still sits on its ***. I had that problem with a stuffed catalytic converter yrs ago. R squared same.

 

^ +1

Just loosen the bolts from the turbo to the first cat. you'll likely boost creep tho.

 

Hmmmm, ok ill check it out. All I've got it is a downpipe to an aftermarket cat. No air to the cat, so I guess after 3000 miles the thing cooked itself solid? We shall see, thanks for the input fellas.

 

Ok, well after "de-clogging" the cat, I am throwing 5' flames (sometimes inadvertantly) but still cant boost. I have no luck. The car drives around while not boosting, it will cut out every once in a while while driving, but other than that it drives fine. I just cant floor it. Anything above 50% throttle bogs it down, at any rpm range. It sounds like it is running on one rotor when it does this and hits a wall as far as acceleration goes. Doesnt. Go. Anywhere.

I'm stumped. Tomorrow morning Im gonna bust out the multimeter and start investigating sensors... My top 3 targets are the TPS (which I adjusted to no avail...) the AFM, and the Pressure Sensor. Any ideas, suggestions?

 

Hmmmm... Sound familiar.
I swapped my issue sensor, it didn't help.
I guess I should check the tps next, but it seems to read fine. (I adjusted it to 20% before setting idle -our thing to at least)
AFM has never been a problem before, guess I'll research how to check that.

 

check out your grounds bad grounds can cause hesitations search the 3500 or 3800 hesitation, almost sounds like your secondaries aren't engaging, I would also check out your boost sensor and your knock control all could possibly cause this

 

Its not hesitation, its a wall, it simply wont accelerate. I'm thinking its the harness to the secondaries atm. Time to pull out Mr. Multimeter...

 

I almost want to make a video so people will stop suggesting these "hesitation solutions". Only I doubt it would help since it wouldn't convey the vibrations and it would be tough to get all the gauges in the frame while driving.

1st mod on every fc should be a new wiring harness, because even when u replace more than half the connectors and run new wires they are still ****; apparently.

 

Haha, I definitely agree with you. I just tried swapping the vac source for my pressure sensor to no avail, hoping for the quick fix first.... grrr... at least the thing still drives around. Thursday ill have time to inspect the harness.

 

No such luck, not w/the wiring in these things. I'm hoping there is a secondary specific ground that was misplaced when I got my clutch/flywheel. I'm not de looming this shitty harness. I'll just get a new one from corksport before I do that.

 

Ouch, thats a hefty price tag.... may as well just go with a standalone EMS at that point. But tempting still.... I'm hoping that while replacing the coolant lines I simply put the harness under some stress that caused some solders to break in the injector harness, this wasn't happening until I pulled my UIM off last week.

But... I'm definitely saving for a Haltech. Get the 25 year old, backasswards engineered wiring the hell out of the whole equation.

 

Well If I went that route (new harness) I'd eventually get a power fc, gotta love a/c. If rtek ever comes through w/the afm delete I wouldn't even get that.

There shouldn't be any solder in the injector harness to break. what kind of idiot engineer would use solder on a harness that snakes around the engine bay and has no solid mounting points. Even in 86' that would have been a bad idea.

 

Eh, wishful thinking I guess. Its possible that one of the wires has corroded to nothing, or snapped, or is grounding somewhere....etc....

We shall see..... we shall see...

 

Is your timing correct? Almost sounds like heavily retarded timing.

 

It was when I set it months back.... I haven't done anything to change it since. I will check it out.

 

Fixed it!

After removing the UIM, and taking a closer look at things I saw that one of the pins had barely popped out of the #2 Secondary injector clip....... doh! Must have been wiggled out of there the last time I had the thing off. New clip, and it runs just fine, pulls harder than ever.

Thanks for the input fellas.

 

And the crowd roars. ROAR!

 

Good job.