F.I. engine idle goes up and down.. up and down.. up and..

squarebackagain · Post by **squarebackagain** » Wed Jan 14, 2009 9:07 pm

I bought MAP SENSOR CLEANER and cleaned all the washers/gaskets in the MPS and reassembled them using the RTV. I put the gasket in first, then the metal ring, then the diapragm, then the stopblock. I looked it over and can't see why the metal ring would go anywhere other than between the gasket and the diaphragm- and that was how it was laid out before so I assembled it that way. I used a miniscule amount of permatex, but I used enough.
Still no vacuum!
Now I am getting worried...

raygreenwood · Post by **raygreenwood** » Thu Jan 15, 2009 5:14 am

Did you RTV the main body gasket as well? Also look carefully for debris around the main o-ring and for proper fit of the body halves.

A final check that could confirm ugliness....is to put a temporary dap of RTV to cover the vent holes in the rear...and put the plug back in the back. If it holds vacuum then....then you most likely have a crack around tehrim of the copper diaphram. Ray

squarebackagain · Post by **squarebackagain** » Fri Jan 16, 2009 7:37 am

Yes, I did RTV all mating surfaces after a thorough cleaning. When that didn't work I plugged the air holes but still no vacuum. I don't know what you mean by putting the plug back in the back, I didn't remove any plug. Unless you are referring to the epoxy that was removed before I got it?
By the way, I inspected the diaphragm very closely and could find no cracks. After cleaning it looked to be in great shape. Any chance there is something I am overlooking?

raygreenwood · Post by **raygreenwood** » Fri Jan 16, 2009 2:52 pm

There are only a few places it can leak. (a) between the coppert plate and the back part of the body. (b) because of a cracked copper plate (c) from the main o-ring on the two body halves.

Oh...Wait.....try this:

Put a dab of grease on both the center adjusting screw and the outer hex adjusting acrew to block the threads just to see if it plugs the leak. Its possible that the cleaner you used may have screwed up the fine o-rings that are in the threads of the two adjusting screws inside.
you can only reach these areas properly by taking the epoxied plug out of the back....remembering where it started because its an adjustment.

My bet is that the body o-ring is still leaking. Smear grease or oil on one area at a time until it quits leaking and you will know where to look.
Lastly...just to see....this is insanely rare....but dribble some oil into the plug socket and around the base of where the four pin plastic plug meets teh body...and vacuum it down again.

But...bear this in mind. If you have the original screw plug still epoxied in...in the back.....and you pluged the two vent holes and its still leaking....thene there are only two other places it could be leaking from....the main body o-ring or the plastic electrical plug.

Ok....do you or do you not...have the screw in aluminum plug that goes into the back of teh unit...where the epoxy was?
The epoxy...only blocks the threads...I don't care about that....but the plug MUST be there...or this thing will never run correctly. The plug is not a plug at all. Its a large fat adjuster screw.

What I was getting at...is that if you have the screw in plug for the back...and you temporarily seal up the vent holes and put the plug back in with a little sealer as well......temporarily....and you vacuum the unit down....and it holds vacuum now.....then that means the leak WAS between the copper plate and the body of the unit....or....the copper plate has a crack either around the edge or in the very center next to the boss.....or.....the two center adjustment screws in the center of the copper plate have bad o-rings.

To recap......if sealing up the aluminum plug and two vent holes .....aft of the copper plate does not seal things up.....then your main o-ring or electrical plug are the only culprits left. Ray

squarebackagain · Post by **squarebackagain** » Fri Jan 16, 2009 8:37 pm

I was messing with the sensor again tonight and noticed something: when I blocked the four air holes in the back (yes the epoxy is gone but the metal "plug" that looks like a flat-head screw with a hole in the middle is there still- I haven't touched that) and blew air through the vacuum inlet on the other side of the sensor, it remains as I said, like blowing through a straw. BUT when I cover the four holes on the back and try to blow air lightly into the "plug" I am unable to. It seems it is holding air from that side.
Based on this experiment, I agree that the air must be leaking through the body seal. The o-ring looks good, but just for measure I cleaned the surfaces again and the ring, applied a bit more RTV and closed it up. We will see what happes in the morning when it dries.
By the way, there is no wrong way to align the two halves of the sensor right? It seems to be symmetrical in terms of the mating surfaces.

...ok so I woke up this morning and tested the sensor... VACUUM!... but not indefinately. It drops about 0.5lbs per minute. Took me a second to see the needle drop.
How important is it that it holds indefinately? Would it be better to risk the adjustment by opening up the MPS and reapplying more RTV, or to allow the sensor to ALMOST hold vacuum indefinately?
I don't suppose anyone makes a rebuild kit for these anymore

tested again tonight and as long as I keep the vacuum under 15psi it holds. Once I increase the vacuum to 15psi it begins leaking at about 0.5psi per minute. What do you think?

raygreenwood · Post by **raygreenwood** » Sun Jan 18, 2009 1:03 pm

From your description...its not the o-ring leaking its the diaphram or the diaphram gasket or the orings on the adjusting screws.

Bear with me here:

You said.....you plugged the ...four holes?...thould should be two vent holes...butwhat the hay.....
You noted you plugged the four vent holes back near the big screw in plug and blew/sucked through the vacuum nipple.....and it held vacuum? But will NOT hold vacuum when you do not cover the vent holes?
......did I get that correct?

If so....then you have a problem with the diaphram or the orings on the adjuster screws or the diaphram gasket.

You need to take a look at the cross sectional diagram of the MPS. The copper diaphram that holds the adjuster screws....divides the unit in two parts. The area under the screw in, flat-blade screwdiver plug....where you access the adjuster screws....the part that has the vent holes.....is open to outside atmospheric pressure all of the time. It NEVER sees vaccum.
The only part that sees vacuum.....is anything on the other side of the copper diaphram moving forward toward the vacuum nipple.

If you blow through the nipple...and air escapes out of the vent holes in the very back of teh unit...you have either a cracked diaphram, leaking o-rings on the adjuster screws or a bad gasket between the copper diaphram and the body. My bet is that you have a cracked diaphram and just can't see it. Ray

squarebackagain · Post by **squarebackagain** » Sun Jan 18, 2009 1:38 pm

My MPS has four holes around the plug in the back, two facing out, and two facing down. I can post another picture if this sounds inacurate, or if it seems someone has tampered with it I would like to know...
When I stop up the four holes around the plug and blow air INTO the plug-hole (where the adjuster screw is-all four vents and plug on same side of diaphragm) it DOES hold.
The MPS does not hold when I apply vacuum to the vacuum nipple whether I stop up the vents or not. If I blocked up the vent holes and it DID affect the vacuum from across the diaphragm I would agree that the diaphragm is cracked. And while the adjuster-plug side of the MPS never sees vacuum, if you blow air into this side with the vent holes blocked, a cracked diaphragm would allow air to leak across and subsequently would not hold...Since the air holds, the diaphragm must not be leaking right? I know it sounds complicated, but in practice it made sence.
I applied more RTV to the outer ring, this time not just to the mating surfaces, but to the inside of the o-ring in case it had stretched a bit, and it seems to hold-- but not indefinately.
I put it back in the car and took it for a drive: warming it up still produced a rolling idle, but once the car was warm the roll subsided (same activity as before I worked with the MPS), and driving at slow speeds it feels the same, a little more pep but basically the same. Once I hit 4th gear however it feels great! No more tugging, I had to work to keep it under 70mph, and I was driving up and down the hills here in Reno!
I still think my TPS is off a bit, and I know the MPS leaks a little; but what change at higher speeds!
Do you think that I should spend some more time on the MPS trying to get an indefinite vacuum seal, or since the car drives well- is the seal important enough to worry about at this point? It IS important to me to do this job right, but I am worried about tuning the engine one-turn-too-tight if you know what I mean.

raygreenwood · Post by **raygreenwood** » Mon Jan 19, 2009 4:58 am

It appears that your diagnostics are spot on! So the main o-ring is leaking. I would also do the same diagnostcis around the plastic plug for the electronics to make sure that there is no leak there. You could use soap andwater and simply blow through the unit.
You should be able to get the main o-ring to seal by taking out the o-ring again and reapplying sealant. Make sure it drys a full 6-8 hours before putting vacuum or pressure on it. For right now this is preferable to trying to find an 0-ring to replace that one. Its shape is rather unique. A round cross section o-ring can be used...but it changes the adjutment of the unit.

Every MPS is worth saving especially if it has good resistance and a good copper diaphram

squarebackagain · Post by **squarebackagain** » Tue Jan 20, 2009 7:18 am

Thank you for the help so far, now I am wondering how to stop the surging idle altogether. It's actually more prevalent now than before. It surges during warmup as I said, but also now sometimes when I drop from high to low RPM like when exiting the freeway. Could it still be a vacuum leak? I really cant see where else to look.
I ordered a new set of gaskets from ebay and am planning on replacing the injector and intake runner gaskets once they arrive- but that was done already a few months back, all hoses are clamped even the one running under the plenum. I know you have given a list here of places to look, and I am attacking them one by one, but am running out of places to look. I was really hoping the MPS was the problem.
Again, my generator light is always on, and I have read on thesamba that a generator light can be indicative of a bigger problem causing rough idle, what do you think?

raygreenwood · Post by **raygreenwood** » Tue Jan 20, 2009 8:33 am

Don't adjust anything else until you fix teh MPS. That alone can cause surging idle. Not only is it simply a vacuum leak....which messes with idle....it is a fuel mixture change.

The issue with tthe generator light could be low system voltage...or voltage that is varying too highly. Ray

squarebackagain · Post by **squarebackagain** » Sun Jul 19, 2009 6:20 pm

Okay, it's been some time and the work is slow; but thanks to Tram I was able to get a good MPS. After installing it however I have not been able to get this thing working right. First off the idle surge is back worse than ever, same issue when cold it sounds great but once it warms up it searches and surges. Also, when I drive the car it has NO power. Tops out at 65mph and even the slightest uphill brings me almost to a halt.
I have adjusted the valves over and over, testing to see if it runs better at a TIGHT .006 or a loose .006. I have replaced all the hoses I could find (can't seem to find hoses to fit over the intake runners so I clamped them tight. They seem ok).
Reading back over some posts here and on thesamba I decided to pull the AAR and clean it. In order to pull it I had to remove the distributor which leads to a strange story:
1. the notch on my dizzy (0 231 166 001 aka 311 905 205 L) corresponding to TDC is located at about 7 o'clock not the 4 o'clock that I keep reading about. I have never thought much about it because I found TDC the first time using a long wooden stick inside cylinder 1 and it matches up with the marks on my crankshaft and the mark where the rotor meets the mark on the dizzy.
2. I have never been able to get a good reading as to the RPM's when setting the idle, it always reads 48rpm or -23rpm if I turn the sensor around on the tach.
3. the cap has never sat right on the dizzy body, always seems to teeter back and forth until I attach the two clips on ether side.
4. when removing the dizzy all I did was remove the 13mm nut and lift straight out so that it would set back in properly without having to adjust it again.
5. I removed the cap and rotor to clean the contacts when the dizzy was out.
6. After the AAR was clean and back in the car I installed the dizzy body, rotor, and cap... and now while the notch on the body of the dizzy still sits at 7 o'clock- the rotor points to 4 o'clock when the engine is set to TDC!
I have gone back over the procedure again and again and I can't figure what went wrong, now the car won't start. Now that the rotor is set on the dizzy the cap no longer teeters, but sits firmly where it should, could the previous owner have just set the rotor at TDC facing that little notch even though the rotor was not fully depressed and seated in its position? And if he did, would the car run... not well but at all?
My spark plug wires were set to correspond to the notch on the dizzy body-(the #1 plug was at 7 o'clock, #2 at 4 o'clock, #3 at 2 o'clock and #4 at 11 o'clock roughly) so I moved them all one position counter-clockwise but my car still won't start!
This rolling idle problem has really turned into a nightmare. I can't even drive my car. And what the heck is up with this distributor? My uncle told me they changed it out to get rid of the points and vacuum advance but I am beginning to think he does not have as firm a grasp on the mechanics of this car as I thought. I am not trying to take advantage of the forums; but all the mechanics I have met keep telling me they are happy to help then when I show up with FI they insist I exchange it for carbs before they will help. What do I do about this dizzy so that I can see if the MPS Tram sent me and cleaning out the AAR helps the idle issue?

raygreenwood · Post by **raygreenwood** » Mon Jul 20, 2009 8:23 am

All right....this is simpler than you think. Your distributor drive was installed 90* wrong.

Remove the dizzy. Turn the engine until the crank pulley lines up at "0". Check that both valves of # 1 cylinder are closed. If they are not both closed, you are not at TDC...turn it some more.

Now...with either a dizzy drive extractor...or a long bolt threaded into the drive....pull it straight up and out of the case. Mind that the shim washer underneath the drive either remains on its seat in the case or comes up with the drive.

Now....becasue of the helical gear....whevere you install the drive...it will move as its gear contacts the teeth on the crank....by an exact amount either backward or forward (can't remember which).

I take the shim....and cover the botton side with tacky wheel bearing grease. I use a long wooden dowel.....to slide it down into teh case so it sticks to its ledge. I put the grease on one side....so it does not come up each time you remove the drive while you are working on it.

Look in the haynes or bently manual at the section about the drive angle and the half-moon cut-out with reference to the case centerline. Orient yourself and the drive with the bolt still in the center.

mark the edge of the drive pinion...and the edge of the case hole with a sharpy marker. Slide the drive pionion into the case and watch it rotate with the helix as it engages. Look closely at it an determine how far off it is by the mark you made on it...with reference to the mark you made on the case. It is usually off by about 15* or so.
Now....pull the drive back out...make sure the shim is still in place.....move the drive so that the black mark you made on it...is not on teh other side of the mark you made on the case next to the drive bore.
Re-install the drive pinion. Are the marks lined up now?

If so....install the dizzy. Make sure the rotor is on correctly. The rotor should now pouint to the notch in the dizzy at about the 4;00 position.

Re-time everything. And...change your wire position.
Moving counterclockwise....the cylinder that the rotor points to when its pointing to the mark on the dizzy is #1, ....then....moving cunterclockwise...is #2, #3 then #4.

Wait....I keep forgetting. You are working on a type 3. 4 oclock position is correct for a type 4. I cannot remember if its right for a type 3. I will check on that tonight...or look in the bentley.

Also....what are teh specs for this enegine? Is it stock? is the compression and cam stock? Are the heads, the valves and the exhaust stock? This is very important. Ray

squarebackagain · Post by **squarebackagain** » Mon Jul 20, 2009 12:23 pm

I fixed the problem this morning. I don't know if 7 is the right position for type 3 or not, but when I pulled the dizzy, (I didn't notice the way the bottom of the dizzy lines up inside the engine before) lined it all up and replaced it... presto! Car runs better than ever! Idle still surges but I lowered the idle speed and that got rid of the surging until I drove it about 15 miles. I think I need to work on the idle speed at this point- hopefully it will solve the problem once and for all.
I think the fuel pressure was too low by the way. It registered 28lbs with a mechanic so I never tested it myself until yesterday. I finally made a pressure gauge of my own and it tested a solid 22lbs. I increased it to 28-29lbs and between that and the new MPS the car runs like a champ!
Now I just have to get my hands on a stock exhaust system to replace this silly thing my cousin put on the car (two sets of two chrome pipes sticking out the back...) Any recommendations?

raygreenwood · Post by **raygreenwood** » Mon Jul 20, 2009 1:36 pm

You never said anything about an odd exhaust. That alone can cause problems. Its ounds like a 2 into 2 you have...which is just about the worst money can buy.

Stock for type 3 in better than stock for a type 4.

It still sounds like you have a vacuum leak...and/or....electrical connector problems. Ray

Post by **Piledriver** » Mon Jul 20, 2009 2:29 pm

They make decent 4>1 headers for T3s, but don't go larger than 1 1/2" on a stocker.

A real "stock" muffler will probably last far longer than a header, unless you go SS.

Time to get out the propane torch... (unlit) and hunt the dreaded vacuum leek...