1987/350i hesitation with foot to floor :(

[tcpc]

hi

i seem to get a kind of hesitation / reluctantcy to rev under full load between 4/5 thousand rpm, it does get there under protest so far i have put recommended plugs leads,dis cap and arm and have just put on a new coil today and it still does the same bloody thing , but what i did notice was when accelarating with graduale pressure it pulls to 5000 rpm more cleanly but again if i floor it it goes back to struggling to reach 5000 rpm or more.

has anyone got any ideas as to what could be causing this problem ie could it be the air flow meter as i am thinking along the lines of taking it to bits , but it is a sealed unit.

below 4tho rpm the car runs lovly and sounds great,

thank

tony

[shpub]

Could be almost anything in the ignition or injection system. Throtle pot, ignition module, dizzy electrics, injectors, ECU, throttle pot and so on. Air or fuel filter, fuel pump on its way out, air leaks in the intake system, vaccuum advance duff or pipe blocked to name but a few. Then there are wiring problems and duff connectors.

Might be worth getting some professional help by putting th car on a rolling road. Cheaper than replacing the engine bay bit by bit by trial and error. You can do some testing but it is very limited and does not confirm that the bit is good but that it passes the test.

Steve
www.tvrbooks.co.uk

[montegogt]

I had similar problems with my '87 350i too! I put it in for a 48,000 service and it came back with new plugs etc, but still wasn't happy in top when floored. I sent it back, and is much better now. I think if you have this sort of problem, the only answer is to start from square one and work through the ignition, get plug gaps and timing right, then get the box above the passengers knee checked, then there is the air box! Mine had been opened and tinkered with at some time... You really need profession help if you don't want to get severe depression.

[350matt]

Sounds like lack of fuel to me, best way to check is either with a mixture analyser on a rolling road on full throttle. Or plumb in a pressure gauge so you can see it inside teh car and take it for a spin - getting someone else to look at the gauge.
Should maintain approx 2.5-3Bar on full load.

Matt

[danny hoffman]

Might be a worn camshaft, if it's done over 40,000 miles I would check it

Danny

[si350i]

I had the same thing with my 350. After doing the same things that you have tried I ended up backing the spring off a bit on the air flow meter. It solved all the problems and it pulls much better through whole rev range. That said I have no idea if mine was set up correctly before I bought it. If you mess with them to much I think it will effect your mixture, make it run to lean etc, and this in turn may cause other problems, may be worth a try though to see if it helps but mark the point you moved it from so you can put it back if it makes no difference.

Simon

[tcpc]

Thanks everyone for your input, it has given me some thing's to think about

thankyou


Tony