dmyers

I recently replaced the TPS on my S5 N/A because the narrow range sensor was showing 3.8 Kohms when warm and would not adjust. Of course to do this I had to pull the throttle body off to get to that damn bottom screw for the TPS out. I put everything back on per the FSM and Haynes manual, adjusted the TPS etc. and rechecked it to verify everything was cool.

My problem now is that when I try to hold the RPMs steady at 3K or less the RPMs will drop about 500 RPMs in a fairly rhythmic manner. When I keep the RPMs up above 3-4K I don't see the problem. The behavior sounds like a vacuum leak to me but I am having no success finding it. I have now replaced all of the vacuum lines around the throttle body and checked from the AFM back with starting fluid for leaks and found nothing. I am considering pulling the TB back off this weekend and being double secret careful to make sure I haven't missed anything.

On a related note, I replaced the vacuum line running from the intake pressure sensor to the intake manifold (months before I replaced the TPS) and I did not find a pellet in the old one that I have heard mentioned before. Does anyone have one of these for sale (or know where I can get one) or should I not worry with it?

Thanks in advance for any and all help.

Pinfield357

did you try spraying carb cleaner (i would not use starting fluid as it is more likly to expload) around the TB area?

could a gasget be leaking nera the TB?

did you set the TPS when the car was hot?

dmyers

TPS was set when hot.

We sprayed around the TB, but the only area where we couldn't spray was on the bottom of the TB, that's why I'm considering pulling it off again and being double careful when I put it back on.

Thanks for the tip about the carb cleaner.

HAILERS

So...anyway, spray the starter fluid at the hoses front and back and around the periphery of the upper intake manifold mating surface. No leaks found? Ok, before removing the throttle body, take the airpumps intake hose off the air filter. Spray into the hose towards the airpump. Is there a noticable change in rpm? Yes: antiaftervburn valve inside the acv is bad.

Still no noticable leaks? Take off the throttle body. REmove and replace the two grommets on each of the fuel injectors. Maybe also the o'rings also if they have not been changed recently. The lower grommet gets hard as a rock and does not seal good in that condition. Leaks air. Unauthorized air leak.

Also make sure the brake booster hose is on good b/t the mainfold and the booster feed line.

HAILERS

Rythmic up and down? Make sure you reinstalled the two smaller hose on the front of the throttle body in the correct order. Only one is a source of vacuum. Swapping these two will cause an erratic idle. See and read the FSM, free at http://www.iluvmyrx7.com Fuel section.

dmyers

Just so I am clear, the you smaller hoses you are referring to are the one going from the Thermo Water Valve to the Double Throttle Diaphram and the one going to from the Thermo Water Valve to the Check Valve to the back of the intake (it's getting too dark to see exactly where it goes)?

If those are the ones you are referring to then they are correct and I have double checked that the Check Valve didn't get turned upside down as well.

Or

Are they the ones labeled number 6 on page F1-35 in the Fuel Section of the FSM? If those are the ones, then I haven't checked them and didn't intentionally disconnect them to begin with. I will look at those in the morning if it isn't f'n raining again.

Or

Am I smoking crack and totally not grasping what you are referring to?

In any case thanks for your help Hailers. You rock!

dmyers

Bump.

HAILERS

No. Even I don't know what I mean somethimes. But, on a series four, there are three vacuum hose on the front of the throttle body. One large for the oil injectors, and two smaller ones. One of the smaller ones is to supply a vacuum for the solenoid rack. The other small one is not a source of vacuum. It is for the fuel injector air bleeds. If they are swapped, the car idles irregular. If you did not take them off, then disregard.

No, not talking about the vacuum hose for the double throttle diaphram.

And disregard the fuel injector grommets if you did not take the fuel injectors out.

Its more of less a shotgun approach of mine when it comes to vacuum leaks on someones car that I can't see,hear, smell etc. About the only thing that can help is if some starter fluid is sprayed at the hoses, bac hoses, mating surfaces of the intake. Don't forget to spray around the back of the throttle body too. There should be a couple of hose back there too. Oh, I guess carb cleaner is alright instead of starter fluid. Got me. Never used it.

And neither of us is on crack. I don't need it. It just comes natural for me to appear to be on crack.

dmyers

It seems that I am in good company then.

Thanks for the suggestions, I'm going to load up on vacuum hose, carb cleaner, gasket sealer, etc. and tomorrow I am going to begin removing, replacing and cleaning everything around the throttle body as well as other things which can effect idle (bac, etc.) until I either fix it or am broken to the point where I am willing to pay someone to fix it for me.

Thanks again.