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> The MPS puzzle?, Lean mid range
DJsRepS
post Dec 18 2005, 08:31 AM
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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.


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Posts in this topic
DJsRepS   The MPS puzzle?   Dec 18 2005, 08:31 AM
MecGen   Hey Sound like your on the right track... I woul...   Dec 18 2005, 08:57 AM
DJsRepS   Real stable reading and steady idle!   Dec 18 2005, 09:02 AM
Bleyseng   Send it to me as I have probably 25 good control s...   Dec 18 2005, 10:02 AM
r_towle   The mid range is in my experience a bad mps. I fo...   Dec 19 2005, 08:35 PM
DJsRepS   Yea Im about a year into it myself. What I dont ge...   Dec 20 2005, 07:36 AM
Bleyseng   To answer you question as to why the "doesn't ...   Dec 20 2005, 08:08 AM
bd1308   my car did the same thing (D-jet 2.0) it really s...   Dec 20 2005, 08:23 AM
Bleyseng   Install a set of new plugs and see what color they...   Dec 20 2005, 08:31 AM
DJsRepS   Thanks Bleyseng for the reply. The oil in my OEM ...   Dec 20 2005, 08:49 AM
bd1308   thats the oddest thing ive ever heard of.... its ...   Dec 20 2005, 09:26 AM
DJsRepS   Its old and used to leak but I resealed it and tes...   Dec 20 2005, 09:40 AM
Bleyseng   The oil in the MPS is from it being run in a worn ...   Dec 20 2005, 09:43 AM
DJsRepS   I did have all plugs off the harness to inspect th...   Dec 20 2005, 09:55 AM
Bleyseng   usually a bad CHT means too rich waay too rich. T...   Dec 20 2005, 10:07 AM
r_towle   The settings are on panders site for each specific...   Dec 20 2005, 10:22 AM
Bleyseng   <...   Dec 20 2005, 01:17 PM
r_towle   Im thinking of the one that has no diaphram...I go...   Dec 20 2005, 06:38 PM
Jeff Bowlsby   These are the early MPS: http://www.914world.com/...   Dec 20 2005, 07:08 PM
MecGen   Hey Rich Fuck this is a bitch...

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