"The Problem," cont'd

[CJFusco]

Ok... a fuel filter is on its way, and I bought a bottle of injector cleaner for the next time i fill my tank.

That being said, I have some more specific information on my "problem" (sluggish accelleration, esp in high gears, with some hesitation from idle, and an occasional rough idle). To be more specific, accelleration is way worse than normal, with throttle imput having apparently no impact on accelleration in 4th and 5th... if i give it half throttle in 4th, and then floor it, there is no noticable change in accelleration rate.

When I rev it in neutral, it revs quickly and smoothly; if there is a change from when the car is running well, I can't see it.

Does this (ok revving in neutral) mean that it's probably not the fuel system? Or would revving still be ok with a fuel filter/injector problem due to the low amount of fuel needed to rev the engine in neutral?

This damn thing is driving me nuts.

[carsontc]

from the earlier thread

Originally posted by AFJuvat
How is throttle response in neutral?

Change fuel filter as described, check fuel pressure, look for injectors with leaky seals (you will hear them hiss and bubble)

AFJuvat

and

Originally posted by turbohead7
The throttle switch is what I truly think is ailing you. I've seen these little babies cause severe hesitation problems. Remember, it's a two position switch, not a throttle potentiometer. It only tells the DME two things: Wide open throttle, or off-idle. Therefore it should click when the throttle is just barely opened and when the throttle reaches wide open. Sometimes the throttle plate shaft seals leak, and reverted oil makes it's way into the switch drowning it in oil. Also check to make sure your floor mat isn't bunched up under the gas pedal----sounds stupid but it happens! PS is your master leaking?

don't think you answered Jurvy...

or whether you tested the TPS...

my TPS got wet and it ran like crap until I cleaned it

but your fuel filter is easy and needs to be changed regardless

[AFJuvat]

Something is still screaming to me

accellerator cable, vacuum hoses, throttle switch.

How does the car drive?

AFJuvat

[CJFusco]

1) The master isn't leaking

2) Accellerator cable: Seems fine, although I installed a Throttle Cam not too long ago and there is a little more slack than the stock cam. I drove fine with it for awhile without problem. I will reinstall stock Cam to see if this has anything to do with it.

3) How do I check fuel pressure?

4) How do I check throttle swich?

5) Floor mat is fine

6) How do I check to see if any of the injectors have leaky seals? I had the hood open with the engine running earlier, and I didn't hear any hissing or bubbling.

I'm gonna keep plugging away at it until i find the culprit!

PS Juvy - the car drives fine except for the aforementioned sluggish accelleration... why?

[CJFusco]

ok here's the deal.

I put the stock cam back onto the engine, and the problem was even worse. I had to push in the pedal a lot more than normal to even bring the car up from idle.

DOes this mean it has soemthing to do with the throttle cable or the throttle swich?

Throttle Swich: I think I know where it is - - it's underneath the housing that the cam is on top of, right? Ok, how do i get to it... and how do i know if it needs to be "cleaned"... and how do i "clean" it?

Throttle Cable: Where do I even start?

[AFJuvat]

Throttle switch - under the throttle body - if you are flexable, you can get it from the top - if you have long tools, from the bottom - otherwise, the throttle body is coming out.

Haynes has the testing procedure for the throttle switch - don't remember it off the top of my head.

Proper adjustment - the throttle switch should click the moment the throttle cam starts moving - you can make minute adjustments with the screw on the front of the throttle body, right under the cam.

Throttle cable - should be tight, not guitar string tight, but no slack at all. You adjust throttle cable tension at the firewall. It it is stretched past its limit, you disconnect it from the gas pedal and the throttle cam, then pull it through the firewall from the engine side.

Fuel Pressure check - need a gauge for that - you connec it to the big nut on the front of the fuel rail - procedure detailed in Haynes.

Throttle Body: brake cleaner in the throttle body You don't need to remove it to clean it out. Keep the butterfly closed and spray it down - after that is cleaned up, spray out\wipe up the inside.

You can soak a rag in the stuff and clean up the area where the butterfly seats in the throttle.

If you are feeling brave, remove the idle adjust screw and spray out the air bypass passages - otherwise, just spray out the passages the best you can with the screw in place.

After a good cleaning, you will have to reset your idle

AFJuvat

[Porsche944]

OK, since going back to the stock throttle cam made things worse, I'd wager we're looking at adjusting the TPS, throttle mechanical stop, and the throttle cable.

To start with, get yourself some carb cleaner, paper towels, a 13mm wrench, a 10mm wrench, an 8mm wrench, a 6mm Allen Wrench, flat and phillips screw drivers, and a pencil and paper.

Remove the throttle body(Don't loose the red O-ring). Use a flat blade screw driver to bottom out the idle by-pass screw. Count the number of turns (fractions are OK), and write that number down.

Remove the idle by-pass screw. Inspect the O-ring. Clean the screw and O-Ring (if it's in good shape).

Loosen both screws on the TPS. Use the 8mm wrench to loosen the jam nut on the throttle plate mechanical stop screw. Back the stop screw out until it does not touch the throttle stop arm. Clean the throttle body bore, throttle plate, idle by-pass port, and both vacuum ports. NOTE: If either vacuum port is plugged, use a small sewing needle to open the port. Make sure both ports are open.

Once the throttle body is clean, adjust the mechanical stop until it just touches the throttle plate stop arm, and then turn the screw an additional 1/2 turn. Tighten the lock nut.

Hold the throttle plate closed and adjust the TPS so the TPS makes a soft 'click' just as the throttle plate comes off of the seat.

Install the idle by-pass screw and set it for the appropriate number of turns open.

Install the throttle body.

To adjust the throttle cable, loosen the jam nut where the cable goes into the fire wall, and then install the cable onto the throttle cam. Using the adjuster, set the cable so that there is not too much slack, but enough to let the throttle plate close fully. Listen for the TPS to click each time the throttle closes. Once you have this set, tighten the jam nut.

Connect a tach to the coil primary wire (green), start the engine, and use the idle screw to set the idle to 950 +- 50 RPM.

Disconnect the tach and go for a ride....

BTW: I'd use the round throttle cam. The stock cam sucks.

[CJFusco]

ok, i tightened the throttle cable, and believe it or not, it did help quite a bit...

but the car is far from feeling "normal"

It still feels like there should be a lot more accelleration with the pedal floored than there is... i just know how my car usually "feels", and it just isn't normal now.

Should I still go ahead with the throttle body cleaning/throttle switch test? If so I will probably do this at the same time as my fuel filter + spark plug change next week.

[AFJuvat]

Couldn't hurt. Change cap and rotor while you are there (unless done within the last 30K miles)

Also check fuel pressure. - at least test the dampener and regulator to see if they are holding good vacuum.

AFJuvat