Mi16 Inlet Diaphraghms Woes
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  1. #1
    Fellow Frogger! WRCPUG's Avatar
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    Default Mi16 Inlet Diaphraghms Woes

    Ive been driving my dads Mi16 the past few days and theres something seriously wrong with its power delivery. It really struggles down low in the rev range and just wont rev cleanly.

    Once over 5000rpm it pulls quite nicely but before then its not happy at all and torque is wayyyy down.

    The car is a 1995 model with 185,000Kms. Its got the same motor as the S16 and ive read on these forums that theres a problem with the inlet diaphrahgm or something like that which causes this problem.

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    Can anyone shed any light on this problem and any possible solutions to fix it.

    Thanks

    Alex
    PEUGEOT 306 GTi6 (1997-1999 HYBRID)
    105.4kw (141HP) ATW
    2:09 Phillip Island (Toyo Street Tyres)

    2001 YAMAHA YZF-R6
    119HP

    1993 MITSUBISHI 3000GT Twin Turbo
    300BHP
    STOCK-14.006 @97.4mph HEATHCOTE
    STOCK-1:15 CALDER Long Circuit (Stock Street Tyres + Stock Pads :banghead )
    (For Sale)

  2. #2
    Fellow Frogger! Wintermute's Avatar
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    Quote Originally Posted by WRCPUG
    Ive been driving my dads Mi16 the past few days and theres something seriously wrong with its power delivery. It really struggles down low in the rev range and just wont rev cleanly.

    Once over 5000rpm it pulls quite nicely but before then its not happy at all and torque is wayyyy down.

    The car is a 1995 model with 185,000Kms. Its got the same motor as the S16 and ive read on these forums that theres a problem with the inlet diaphrahgm or something like that which causes this problem.

    Can anyone shed any light on this problem and any possible solutions to fix it.

    Thanks

    Alex
    If it is indeed the same as the S16, then there are six things (That I know of) to look at, but first a simple test will tell you if it is the vacuum pots that are the problem....

    with the Engine idling have a look at the vaccum pots on the inlet manifold, they should be in the down position. now rev the engine slightly and they should pull up. If they do not then you know the problem is somewhere in the vacuum pot system.

    Mine had three faults!!!

    1. check to make sure none of the pipes have completely collapsed and restricting the air flow. Mine did this.

    2. check that the solenoid is actually working. They tend to fail due to heat. It might be fine when the engine is cool, but stop working when it heats up. The solenoid is (I think..... I moved mine) on the passenger side, mounted to the head, probably near the thermostat housing.

    3. the vaccum pots themselves may be faulty. if you can get the hose off at the t junction, suck on each one (to the vacuum pots) individually, to see if the pot works.

    4. you could have a perrished hose. if in doubt replace all of the hoses. I actually used watering system pipes to replace mine. worked a treat and haven't had any problems since.

    5. there is a plastic multiway junction that connects to the engine vacuum, brake booster, brake booster auxilary pump, and the solenoid that controls the maninfold vacuum pots. Mine broke at the junction where the pipe that runs to where the solenoid fits in. I fixed it by drilling out the hole a little bit, and screwing in one of the home irrigation junctions..... I did this a temporary fix about two years ago whilst waiting for the part.... the part is still sitting in the glove box

    6. Make sure that the wire hasn't fallen off the solenoid!!!!

    Regards,

    Tony.

    edit: and yes what you have described sounds like the symptoms of the manifold being stuck in short fat mode, which is only normally used above about 4.5 to 5K RPM.

    When mine was dead I did an experiment, and tied the butterfly in the up position, the low end power/tourque improved dramatically, but the car completely ran out of steam above about 4.5K RPM. I think mine actually transitions at about 5KRPM I have often thought it would be a good tweak, to get the ECU changed to do the transition earlier, say about 4.2K RPM.
    Last edited by Wintermute; 11th April 2005 at 12:12 PM.
    306 S16 1995 black
    Morris 1100 1965 green

  3. #3
    Fellow Frogger! WRCPUG's Avatar
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    Thanks heaps for your help wintermute...i checked the vacuum pots and im pretty sure they are working as the lil bit is pulling up when you rev it.

    Ill have to check the other things you mentioned when i get a chance
    PEUGEOT 306 GTi6 (1997-1999 HYBRID)
    105.4kw (141HP) ATW
    2:09 Phillip Island (Toyo Street Tyres)

    2001 YAMAHA YZF-R6
    119HP

    1993 MITSUBISHI 3000GT Twin Turbo
    300BHP
    STOCK-14.006 @97.4mph HEATHCOTE
    STOCK-1:15 CALDER Long Circuit (Stock Street Tyres + Stock Pads :banghead )
    (For Sale)

  4. #4
    Fellow Frogger! Wintermute's Avatar
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    Quote Originally Posted by WRCPUG
    Thanks heaps for your help wintermute...i checked the vacuum pots and im pretty sure they are working as the lil bit is pulling up when you rev it.

    Ill have to check the other things you mentioned when i get a chance
    Hi Alex, If they are pulling up when you rev it then you probably don't have any of the other problems I mentioned. The pots are connected to little cams which turn butterfly valves in the manifold, which should move quite a distance (probably 2cm or more from memory). I should have said if this happens then don't worry about the other stuff as it is working properly. If they are operating like this then I suspect the problem with no power down low is elsewhere.

    Another thing it could be is an exhaust restriction (though there are many other possibilities no doubt). I had a wire fall off which killed the ignition but the injectors kept running (was travelling at 100KM/H at the time), resulting in a whole pile of fuel being dumped into the exhaust. It blew my cat and the car ran like a dog till I got a new one.... the other thing was the induction noise was ferrocious (I have a pod filter) I think that it was partially exhausting through the inlet due to the pressure build up in the exhaust.

    Tony.
    306 S16 1995 black
    Morris 1100 1965 green

  5. #5
    Fellow Frogger! WRCPUG's Avatar
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    Another thing it could be is an exhaust restriction (though there are many other possibilities no doubt). I had a wire fall off which killed the ignition but the injectors kept running (was travelling at 100KM/H at the time), resulting in a whole pile of fuel being dumped into the exhaust. It blew my cat and the car ran like a dog till I got a new one.... the other thing was the induction noise was ferrocious (I have a pod filter) I think that it was partially exhausting through the inlet due to the pressure build up in the exhaust
    Mmmmm interesting. Before my father had the car it was owned by my uncle and the honeycombs in the cat had callapsed seriously choking the cars performance. This was fixed a few years ago by gutting the cat and the car ran great again.

    I think i will have to check the inlet pipes and air filter to see if there maybe is a restriction there.

    Just another thing....the car was struggling to pull up hills the other day on the ECCA cruise. I had to keep it above 5000rpm for it to go anywhere and had to shift down for overtaking alot (like a stupid non torque producing VTEC) its quite frustrating when you are used to having a nice spread of torque.

    Thanks again for your help
    PEUGEOT 306 GTi6 (1997-1999 HYBRID)
    105.4kw (141HP) ATW
    2:09 Phillip Island (Toyo Street Tyres)

    2001 YAMAHA YZF-R6
    119HP

    1993 MITSUBISHI 3000GT Twin Turbo
    300BHP
    STOCK-14.006 @97.4mph HEATHCOTE
    STOCK-1:15 CALDER Long Circuit (Stock Street Tyres + Stock Pads :banghead )
    (For Sale)

  6. #6
    Fellow Frogger! Wintermute's Avatar
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    Quote Originally Posted by WRCPUG
    Mmmmm interesting. Before my father had the car it was owned by my uncle and the honeycombs in the cat had callapsed seriously choking the cars performance. This was fixed a few years ago by gutting the cat and the car ran great again.

    I think i will have to check the inlet pipes and air filter to see if there maybe is a restriction there.

    Just another thing....the car was struggling to pull up hills the other day on the ECCA cruise. I had to keep it above 5000rpm for it to go anywhere and had to shift down for overtaking alot (like a stupid non torque producing VTEC) its quite frustrating when you are used to having a nice spread of torque.

    Thanks again for your help
    no worries. It certainly sounds like the problem is with the variable intake.... If you had a restriction then I would think that high revs would be affected more than low.

    Did you check the pots when the car was cold or when it was hot? my solenoid (valve) stopped working when the car got up to temp, but was fine when cold.

    I've uploaded a short video of the vacuum pot on my car working just to make sure we are talking about the same thing since it is possible there are differences between the S16 and Mi16. It is 2.9MB so might be a bit slow depending on your internet connection. There should be one of these on each side of the mainifold both should work as in this video. They drop back down again somewhere around 5K rpm (or at idle), though I wouldn't recommend reving the engine to that to see if they do!

    check it out here http://home.people.net.au/~tonywww/s16/inlet_vacuum.avi

    Tony.
    306 S16 1995 black
    Morris 1100 1965 green

  7. #7
    Tadpole :Jear:'s Avatar
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    Hey guys this all great info, the exact same thing has been happening on 93 Mi16 which has only just gone through 90,000km, it is the same problem with the motor sort of hesitating as the revs rise, but it only really seems to happen once the motors warmed up, not when it a little cold in the morning, after looking at the video I dont think the little arms on my diaphrams stay up like the ones in the video, im going to check right away

  8. #8
    Fellow Frogger! WRCPUG's Avatar
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    hey wintermute- i checked when the car was cold. I fiddled with all the plugs and wires.

    I checked the pots and yes they were working however in your video they seem to be opening alot futher than mine.

    However i did something really stupid...i tried to take off the vacuum hose off the pot itself....and i ended up breaking the plastic tube bit. Im going to have to glue it back on. so now only one vacumme pot is working (I always end up breaking something when trying to fix something . god i hate cars)

    Anyways this morning driving to work the car actually felt great down low in the rev range..it didn't sputter and feel like it was gasping for air. I didnt get a chance to take it above 5000rpm to see if the top end had suffered however.

    thanks again for your detailed help and video
    PEUGEOT 306 GTi6 (1997-1999 HYBRID)
    105.4kw (141HP) ATW
    2:09 Phillip Island (Toyo Street Tyres)

    2001 YAMAHA YZF-R6
    119HP

    1993 MITSUBISHI 3000GT Twin Turbo
    300BHP
    STOCK-14.006 @97.4mph HEATHCOTE
    STOCK-1:15 CALDER Long Circuit (Stock Street Tyres + Stock Pads :banghead )
    (For Sale)

  9. #9
    Fellow Frogger! Wintermute's Avatar
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    Quote Originally Posted by WRCPUG
    hey wintermute- i checked when the car was cold. I fiddled with all the plugs and wires.

    I checked the pots and yes they were working however in your video they seem to be opening alot futher than mine.

    However i did something really stupid...i tried to take off the vacuum hose off the pot itself....and i ended up breaking the plastic tube bit. Im going to have to glue it back on. so now only one vacumme pot is working (I always end up breaking something when trying to fix something . god i hate cars)

    Anyways this morning driving to work the car actually felt great down low in the rev range..it didn't sputter and feel like it was gasping for air. I didnt get a chance to take it above 5000rpm to see if the top end had suffered however.

    thanks again for your detailed help and video
    No probs a bit of 5 min araldite will probably fix it but make sure you put something in the hole through the tube and turn it while the araldite is setting I think I used a pop rivet, or drill bit, can't remember. that happened to one of mine (though not while I was pulling it off), and at the time you couldn't just buy the vaccum pot, you had to buy the entire inlet manifold at something like $800!!!!

    You should be able to buy the vacuum pots for about $90 now (that was the last price I paid about 2 years ago).

    I ended up cutting one end off an irrigation joiner and aralditing that to the pot, I couldn't get the original bit that broke off to glue back on successfully. note though that it did break after some time (probably about 12 months) and I just glued another one on .

    With repect to them opening further in my video, it is possible you have a very slight leak in one of the hoses, and they are only half opening as the vacuum isn't strong enough to fully open them up..... either that or the Mi16 has a different manifold????. once you have fixed the pot, id be searching for leaks

    the other thing you can try is manually moving the cams on the end of the pot. If they will go further than the pots are pulling up then I suspect your vaccum is leaky.

    Actually re-reading your post, I'd be almost certain that the butterfly is only half opening. If the pots are in the down position the performace should be ordinary, but if they are half open (I tried that by tying them in that position when I was trying to work out what they did) it is positivly woefull. If you think the low end is good now, wait till you get them working properly!!!!! I think you will be plesantly surprised!!!!

    Tony.
    Last edited by Wintermute; 13th April 2005 at 12:00 AM.
    306 S16 1995 black
    Morris 1100 1965 green

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