I've been trying to diagnose a 5th gear, WOT hesitation, and naturally after touching anything on my 87 TII there are now 50,000 new problems. I should just learn to never touch it if it works at all.

One of the things I did was try to swap my variable resistor. The first time I did this something got all fucked up and my boost gauge decided to pin itself to the maximum, while I'm sitting there at idle. So that scared me, I quit for the night, and then all kinds of **** happened at home that have been preventing me from working on the car.

Today I try it with the new (well, used, but still with the factory JB weld on it) variable resistor again. But I don't start it, I put it in the ON position. And I hear this rapid-*** clicking that sounds like the injectors. I go under the hood and touch the rail, sure enough it's the injectors firing like little bitches. So I turn off the car, put the old resistor back on, put the key to ON and no clicking. Good. So I change the resistor again, put the key to ON, and no clicking this time.

Can anyone take a wild guess as to what the hell is going on with this thing? Is my ECU going haywire? I have nice new grounds all over the place so that's definitely not it.

 

the clicking should be normal. mine does it too

 

It's not the fuel injectors.
It's the BAC valve.


-Ted

 

LOL, it's your BAC valve, not the injectors.

 

I just noticed these replies... it was NOT my BAC valve. I know it's real simple to say, oh, clicking with key at ON = BAC. But no, no I tell you. I know what the BAC sounds like, I know where it is, etc. This clicking was NOTHING like it. And from feeling around, it really was very obvious that it emanated right from the fuel rail. And some of this was happening with the intercooler off, and sure enough things smelled more like fuel in the throttle body afterwards. The question was not WHAT was happening, but why... and I found out why:

I since noticed that I had knocked the vacuum line off my boost sensor while changing the variable resistor (I still can't believe I missed that, it's always something real simple.. to my credit at least it was dark out). That vacuum line being off seemed to make the whole system absolutely crazy and erratic... it was real finicky, like if you nudged the boost sensor (with the vacuum line off) you would hear a relay or something click and the BAC (yes, I mean the BAC this time) would stop clicking like it had been shorted out... Then I discover the unhooked line, reattach it, and everything is stable again.

Whatever, I have brake problems now taking priority anyway. Just wanted to say that it wasn't my BAC.

 

sounds like you have a plethora of grounding issues. the ECU may be going into cold start ECU pulse width modulation because it thinks the car is cranking.


hey, it sounded good didn't it?

 

It may not have been the BAC valve, but it certainly wasn't the injectors. Injection and ignition timing is a result of input from the CAS. If the engine isn't spinning, then the CAS isn't spinning, so there is no trigger for the ECU to operate either the injectors or coils.

Disconnecting the vac line off the MAP sensor would cause a vac leak that will upset idle. The effect on the actual sensor would simply be a constant atmospheric pressure signal being sent to the ECU, which would result in overly-retarded ignition timing at low-load.

If the clicking you heard wasn't the BAC valve, then it may have been one of the emission solenoids. These can chatter sometimes if the TPS adjustment is a bit out.

 

A vacuum line off a boost sensor with the engine not running does not effect anything.

If the engine was not running and the key was to ON, and you KNOW the clicking was coming from the fuel rail, then that would mean the fuel pump was running (when it should not be) and the clicking is from the pulsation damper as the fuel is flowing thru the rail back to the tank.

If the pump is running as described then the fuel pump check connector is jumpered OR the fuel pump's Circuit Opening Relay is having a ground put on it by the vane in the afm. I'm saying the fuel switch in the afm MIGHT be *made* when it should not be *made*.

PARTING SHOT: Did you pull the BAC plug off and the clicking sound continued?

 

Lesse...BAC valve bolted to the intake manifold...
Intake manifold bolted to the engine...
Fuel rails bolted to the engine...

Nah, it can't be the clicking could travel to the fuel rail.

How about you UNPLUG the BAC valve and tell us if the clicking went away or not???


-Ted

 

OR, if he has an s5 t2, his boost control solenoid could have been clicking too, they tend to do so wildly when the key is on for some reason.

 

ik its a bit of an understatement to say im late but it definitely can be the injectors firing, im dealing with it right now and i have proof. I have a guage on yhe feed line and i can watch the pressure drop with the clicks and when i open the afm so the fuel pump kicks on the pitch changes, because they are actually spraying fuel. No idea what im gonna do with this information but figured id at least share it.

 

the pressure will change when the AFM is opened, that doesn't indicate it is the injectors turning on though. i have heard the S5 TII boost control solenoid clacking away when turning the key on before but it never caused any drivability concerns.