The MPS puzzle?, Lean mid range Options

[DJsRepS]

Ive delt with a bitchen miss thats driven me crazy for way too long. (about a year after a dropped valve repair) Ive read many posts and followed many suggestions and found many small fixes (some of I woudl have bet fixed it). Ive rebuilt the FI harness, soldered the relay board, ohmed every part and Tstat sensor. Cleaned and tested TPS and Triger Pts. Intake vac at 20" at idle. All new Ign OEM wires plugs etc.. No points (eletronic) all in distributer. Idles good reves good but crusing speed bucks. (the TPS tracks I bent arms slightly to start a new track then ohmed all). And the intake temp sensor is unplugged (runs way bad with it) MPS checks great both Vac and ohms. Sealed settings never touched.

Symptoms now idles good reves good but hold the throdle steady almost anywhere off idle and it sounds like massive ign failure.

I just pulled the plugs to check them and they look snow white. I turned the fuel pressuer up did not seem to help. I experimented on the MPS and made up a test I unplugged the hose from the MPS and stuck a vac gauge on it reading the intake, then used my new hand vacuum on the MPS.

Here is what I learned. (following all related to MPS controled by the hand Vacuum) If holding vacuum 15" w/n start right and starts fine at 0 vacuum as in normal cranking conditions. At 0 on the MPS barely idles, At 15" on MPS idles great. But at 20" on MPS idles bad (20" is my intake vacuum at Idle) Well then I went for crusing mid range rpm held the throdle missed like mad slowly pumped up the vacuum on the MPS from 0 and could tune out the miss totaly by adjusting vacuum to the MPS.

Helped eliminate my ign problem I thought I had. Running so lean and 90%RH in the air sounded like an ign breaking down. Problem alot less noticeable during dryer weather.

Seeing how I could tune out my miss using vacuume on the MPS I decided to open er up. My 72 has been stored longer than it was ever used. First thing I noticed was grease. Oil migrated and solidified in the control. I unsoldered the coil and cleaned it out. I removed the check valve like disk form the vacuum port and cleaned the grease from it. Mine had a smaller check plate and spring built into the disk and it was stuck! (first problem I found) I did not touch the sealed adjustments or the mystical sealed disk where all the adjustments rest as it vacuum test perfect. The next minor problem I found was the core stop arms had pad like things at the tips one missing and one falling off. I glued hard drive jumpers on the ends that touch the ever moving core. Reassembled and vac test perfect and tried it out exact same results no better and luckly no worse.

I am going to remove the glued on pads and try it on the car again, as they wrap all the way around the arms and add about 5 to 7 thousandths of an inch to the arms width. Im gona go with no pads and light touch on the shaft core with a touch of lube.

And as if to add to my confusion I tried an MPS in the car that has a terrible vacuum leak (wont hold for 10sec ) and is the wrong number all together for my system and my car runs great compaired to the OEM MPS. WHY??

Im leaving the bad MPS on for now. I would love to get this thing working right. Without spending alot on parts that dont cure my woes.

Should the MPS be sent off to a pro to be tested and set to specs on the bench or adjusted in the car with an exaust analyzer?

Pls HELP, advise me of any experinces (Good or Bad) any have you have had with the real brain to the Djet EFI system the Manifold Pressure Sensor the MPS.

[Bleyseng]

Yes, you can tune the MPS by removing the epoxy and then carefully remove the WOT stop and inside are the two screws.
Start the motor and have a friend hold it at 2500rpms running.....
then slowly adjust the inner screw till it runs smoothest possible.
Now you need to install the WOT stop to a calibrated setting using a Wavetek or a wide band.......or the diaphram will crack as it must be supported.

this whole operation is best done where you can use a wideband to read the A/F mix.
13.7 to 1 at partload
12.5 to 1 at WOT

[DJsRepS]

Bleysing is the wavetek or wideband an exhaust gas anilizer?

Ive been leary of peeling the seal and changing the factory setting of the MPS, I have read alot of neg posts about that. I was leary about opening it up and I did find a fix, solidified oil/grease inside and into my internal check valve had a retrun check disk stuck by the oil.

I think with an intake vacuum of 20" there are no leaks. All new hoses and new rubber plenum boots and injector seals. Just got done overhauling the heads, 1 new intake valve 1 new guide all new springs (one cracked and dropped the valve another cracked in two in my hands inspecting it) all valves and seats ground and lapped, all new seals every where inc front and rear mains all execpt oil cooler. The crankcase PCV system can cause vacuum leaks I paid attention even to that, right down to the seal in the cap of the dipstick its self. Oh and a new PVC valve and new Vacuum advance for the distributer (it was shot). Ive checked the valve clearance twice. When having driviability troubles sometimes starting at square A and work your way through a process of elemination gets the job done.

Im going to read the plugs again today after running great with a bad leaky MPS. I dont want to just give up and run the bad MPS as a crack or leak can only get worse changing the values my car seems to like now.

[Bleyseng]

A Wavetek in an inductance meter per Brad Anders
A wideband exhaust gas meter like the ones used at a dyno shop or other auto mechanic shops


maybe you should install a leaky AAR valve.... (IMG:http://www.914world.com/bbs2/html/emoticons/av-943.gif)

[DJsRepS]

My AAR valve is out of circut already. It idles low when cold and the equivalant of the choke injector is making it rich till it warms up. I live in Fla it warms up quick.