xodaraP

Ok I went through the TeamFC3S tutorial on adjusting my TPS to get my idle down, my TPS was in fact off hovering around the 1.7-2.0 mark on the DMM, I unscrewed the adjustment screw until I got it down to about 1.1-1.2, however it seems loose like it's going to literally come out of it's socket. Doesn't seem normal.

Also now it idles a bit lower, but still too high, around 12-1400 and now it's no longer a smooth idle, it shudders occasionally while idling which doesn't seem right.

I'm presuming a vaccuum leak on this one unless someone has a different idea. I did find one vaccuum leak but I'm assuming that's been there since day 1 - the hose going to the stock boost sensor has been snapped off. Presumably so the original owner could install an A/M boost gauge.

I'm guessing I shouldn't have tried screwing around with this. But too late now methinks, just need to try and fix the problem. The vaccuum leak in the form of the boost hose I will fix tommorow. But that's definitely not causing the shuddering which means something else is. Do I need to screw the TPS screw in a bit maybe? Or is there probably another vaccuum leak somewhere? Maybe I knocked something out but it looked fine.

Any help appreciated here guys. Really don't like my engine making those sounds since it doesn't sound like a good thing...

Thanks,
Sean

xodaraP

Update:

I have fixed the vaccuum leak, however this didn't seem to do anything. It's still running at 1500RPM smoothly and when I rev it a bit it drops down and bounces between 12-1400rpm, then after about 5 seconds it changes and goes straight back to a 1500rpm smooth idle. This is driving me mental.

Any ideas guys? I have looked everywhere and can't see a vaccuum leak but there may still be one, if it's without a doubt a vaccuum leak I'll go even further looking for one.

TPS is sitting now at 1.1kohm. So I don't think it's that. ECU problem maybe?

Thanks,
Sean

RotaryRocket88

iTrader: (7)

S4 or S5? Set the TPS by voltage rather than resistance. Every time I've tried to measure resistance on the TPS, I get hit and miss readings or no readings at all.

That being said, you want to see 1.0V between the top wire on a S4 TPS and the negative battery terminal. You also need the motor to be warmed up completely so the thermowax moves the throttle plates to their normal resting position.

On a side note, are you sure your thermowax is doing anything? If the piston never moves, it'll never bring the motor down to the ~750rpm range when hot.

xodaraP

I have been completely warming up the engine (10mins or so) before testing

It's an S4 - true JDM.

Top wire? There's 2 I would say are on "top" of the other one - which colour were you referring to?

And I haven't had a big look at the thermowax I'll have to do that. Was checking everything else first as the thermowax does seem to be working.

Thanks for the tip about voltage though I'll have to do that on Sunday (next day off)

If you could let me know the colour though - that'd be awesome.

Thanks,
Sean

Chuck

iTrader: (2)

Some additional things to consider....
- Is the throttle cable too tight?
- Have you, or a previous owner, adjusted the throttle plate gap? It should be very small and if it has been opened, it will increase idle speed to the point that it can't be adjusted back by the air mixture screw and TPS.

xodaraP

1 - It didn't seem so but I'll have a look
2 - I haven't touched it but the previous owner may have. I have no idea. I shall check that too..

Thanks

xodaraP

Update:

Everything looks fine on throttle side but I will have to adjust the TPS again by voltage this time. After fixing the vaccuum leak I'm not smelling fuel anymore, and the car is running so much better especially turbo spool etc. - what a difference!

I have seen a few threads and things regarding air pumps. Mine has been completely removed and blocked off by a previous owner. Is this something I should replace or has that been done for a good reason? I know on an S5 it causes all sorts of problems including loss of 40hp and no bottom end (which my car is terrible at, until it hits boost it has nothing whatsoever down the bottom)

Is this the same case with an S4? Or am I just imagining a horrible bottom end. Could that also be causing the running rich and high idle?

Also - The BAC valve. The FC3SPro website mentions you can use it to adjust idle but doesn't show you how at all. I know when I turn the AC on it drops from 1500rpm to about 1200, it is a noticeable shift in RPM when it is turned on, so I'm assuming the BAC valve is in fact working, but maybe there's a problem there.

Thanks

Edit: Does the stock boost sensor not being connected cause problems such as these? As the connector on mine has been snapped off. I have blocked the line to prevent vaccuum leak, but if this is causing the problem I'd better track down a boost sensor and get it reconnected. Also it has an FCD connected, HKS. Wasn't done by me. As well as a turbo timer that strangely enough reads about half the RPM of the proper tach when it is in tach mode. I presume it's just a shitty turbo timer.

HAILERS

Remove your intercooler. Lift upwards on the Fast Idle Cam Screw. I attach two jpg showing where it is and colored the arrow to it in GREEN. Watch the linkage and see if the gap b/t the throttle stop screw and linkage closes/get nearer to each other.

In other words see if the throttle plates close more by watching the gap b/t the throttle stop screw and linkage. If it does get closer, then there's your problem. The water thermowax is not shoving the cam off the rollpin to fully close the throttle plates.

This would explain why your having problems with the TPS adjustment screw about to fall out from adjusting it.

It would help if you had some PVC pipe to replace the intercooler temporarily so you could run the engine while making adjustments.

I'm just repeating what someone said above about the throttle plates being open a little too much. The waterthermowax will do that if the cam and roll pin do not seperate.

And once seperated, you need to adust the TPS again, because the throttle linkage has moved to where it should have been in the first place. The throttle plates/linkage must be fully closed to set the TPS right.

HAILERS

.

1990TurboII-75K

I have a question regarding the Throttle Stop Screw and the Gap show in your picture. Does the gap go to zero if the engine is warmed up (fast idle cam not engaged) or is there a minimum clearance that should be present for a warm engine?

Should this gap be zero with the fast idle cam defeated (as with the screwdriver in your other photo) and a cold (room temperature) engine?

Do you ever adjust that set screw for the Throttle Stop Screw?

wargoblin

I had the same issue, and this was causing it. The throttle body needed to be lubricated. I just cleaned off the throttle springs and re-lubed them and my idle was perfect.

xodaraP

Thanks HAILERS much appreciated

As I was saying before the boost sensor nipple has been snapped off so I am assuming the ECU is adjusting for not having anything from the boost sensor by running uber rich, maybe it's causing the high idle as well.

Either way I have organised another boost sensor, should be here in a couple of days, as should my tuneup parts. I'll get the new boost sensor on, reset the ECU by taking the battery terminals off for a while etc. then adjust everything else as necessary if I'm still having problems once I get the new boost sensor in there. Don't want to touch anything else now I've found the boost sensor problem as chances are if the ECU knows there is a turbo there but isn't getting anything from it it's compensating by running uber rich.

Thank you to everyone who's helped out - I'll update once I get the new boost sensor installed.

vrracing

iTrader: (1)

Here's a trick I use for this problem. Get a drip irrigation head like this one.



Get a dremel and grind out the innards. Then just epoxy it on to the bottom of the boost sensor and walla, you're good to go!

xodaraP

Yeah I've looked into doing things like this but it seemed like a temporary fix so I'd rather replace it. I've bought a new one regardless but I'd like to see if fixing it temporarily fixes any of the problems I'm having. Since I imagine a turbo ECU not seeing a turbo is not really the best thing in the world

arghx

iTrader: (3)

You need to read the FSM idle set procedure for turbo cars. Jumper the initial set coupler and try adjusting the BAC valve screw, after you get your pressure sensor installed and verify your fast idle system works properly. You could adjust the stop screw as a last resort--I have never used it to set idle on a car that still had a BAC valve.

HAILERS

I'm not suggesting messing with the stop screw or adjusting the stop screw. I'm suggesting the water thermowax/fast idle cam/rollpin are NOT disengaging and thereby holding the throttle linkage open.

Simply get a mirror and flashlight and look at the fast idle cam and roll pin and assure yourself they are seperated from each other. IF they are, then no action needs to be taken to readjust or fix the water thermowax/fast idle cam. BUT the water themperature needs to be HOT when checking it. IF you turn the engine off for a period of time, then piston on the water thermowax retreats and in turn the rollpin and fast idle cam once more engage and drive the throttle shaft open.

IF someone has been messing with the throttle stop screw, then you'd have to set the amount the throttle plates are open per the FSM and then readjust the stop screw.

You look at the GAP in the jpgs. Lift up on the screw with your fingers. If the gap gets smaller, then the waterthermowax is holding the throttle plates open. There should be little if any gap when the engine is hot and everything is where it should be.

If you don't have both water lines on the throttle body, then that could be a good part of the problem.

I'm also not saying it can't be something else causing your problem.

1990TurboII-75K

Don't want to confuse the info regarding the OP. I just wanted to clearify that the pictures with the Throttle Stop Screw and the gap are on cold engines or with the Wax Motor engaging the Fast Idle Cam to the Throttle Cam Roller.

I checked the FSM and there is no mention of the Throttle Stop Screw or method to adjust or check it either on the engine or the bench.

Should the gap go to zero with the Fast Idle Cam disengaged, whether or not the engine is warm? If the gap does not close, does it indicate a diry throttle body or a misadjustment of the Throttle Stop Screw?

arghx

iTrader: (3)

I have given up on trying to set those screws up on a bench. It's very difficult to accurate measurements on the TB bore clearance, even with a set of feeler gauges. I followed the procedure very carefully one time and it still didn't idle right. It might work ok on a relatively stock car though.

I think the best way to do it is just seat-of-the-pants. On a car without a BAC valve, you pretty much adjust the stop screw (with the fast idle cam disengaged and car fully hot, if you have not done the TB mod) until it gets right around where you want it to be. If you still have the BAC valve, jumper the initial set coupler and adjust the BAC screw first per FSM instructions. As a last resort adjust the stop screw if you have to (loosening it lowers idle, tightening raises idle). I wouldn't be so concerned about how the stop screw is "supposed" to look, just focus on whether the idle speed is where you want it to be. Remember that these procedures in the FSM are for completely stock engines idling at 750.

This is all way easier if you have a FMIC or a custom test pipe to delete the intercooler.

xodaraP

UPDATE:

I have managed to get the pressure sensor going, and it is telling me something interesting. When idling, I'm sitting at ~-100mm/Hg. Under boost, it goes up to 0 but I am not getting any positive manifold pressure. Must be a massive vaccuum leak somewhere. Think I need to find that and fix it before I do anything else.

Will chase that fast idle cam though - could definitely be a contributing factor if the ECU is trying to compensate for the obviously huge vaccuum leak somewhere.

Thanks,
Sean

xodaraP

UPDATE:

Pressure sensor is fixed and stock boost gauge is now acting as it should be. Car seems to be running a little bit less rich already. Exhaust is still popping like the cat is burning unburnt fuel though. So I'm going to readjust TPS and look at the cold start cam to nut this out as soon as I get a day off (Friday)


Thanks all,
Sean