316 misfire at 4500rpm

[TomCropp]

hi there, ive had my e30 for a few weeks now and ive got a really bad missfire when i hit 4500rpm, this is around 85mph in 5th and my car will not go any faster,

im pretty sure my car is over fueling as i have rubbish fuel econemy black exhaust pipes and genral smell of fuel under the bonnet, i have recently changed ... air filter fuel filter plugs and oil this has made no difference to the missfire or the lumpyness at idle,

i think i may have a problem with my airflow meter? as i think at 4500 rpm the cars being starved of air and this is causing it to lose power and over fuel....?

has anyone had this problem before??

any help would be very much appriciated

Thanks Tom

[daimlerman]

Whip the cam cover off and have a look at the cammshaft lobes.If any wear is visible this is your problem.For the fuel smell,ckeck all the flexi fuel lines,including the two that are cleverly hidden under the inlet manifold.

[stitch-626]

as above^^
sounds like the cam is fooked, for the idle spray some wd40 on the inlet mannifold where it joins the throttle bodie and the 2 halves of the manifold join , the gaskets might be knackered aswell.

if you have the time/money/skill/tools get hold of another head and refurb it with new eveything, get it skimmed/cleaned whilst its stripped and when you fit it change the water pump and cam belt and it should feel like a brand new engine.


but will still go like a 1.6 m40.

if you want a simplar option find an m42 and fit that.
£250 inc fitting for m42
£500+ to do the head

your choice though, i did mine on my old 316i but that was all done on mates rates for parts and skimming.


went like sh1t of a shovval with a fast road cam and chip

[TomCropp]

im pretty sure the cams fine, if it was worn it wouldnt give those symptoms,

what benifit would spraying wd40 on the inlet manifold give?? would it more likely be the idle control valve sticking or something like that???

[Bullys_special]

Sounds a bit like my problem excetpt mines idleing at 2000rpm and over revving and popping like a bitch. Wish I knoew what was wrong with it.

[E30BeemerLad]

Lumpyness at idle and a juddering when cruising along on a small throttle opening is often the sign of an air leak in the induction system somewhere. This is often due to the rubber elbow which goes from the air flow meter to the throttle body being split. Take it off and examine for cracks as often difficult to spot when it is fitted.

The spraying of WD40 on it when the car is ticking over can cause a temporary seal of any cracks or splits for a few seconds and normal idle will be restored for a few seconds. Other things to check are that all vacum hoses are in good fettle and well sealed.

It could be an air flow meter playing up.

it could be the blue temp sensor which could be naffed, when these go on the blink they often tell the ECU the engine is cold when it is not, so the result is the ECU chucks more fuel in than is necessary (like running with the choke on) Sooty tail pipes would suggest a rich mixture.

Also, check the car has not been fitted with one of those nasty Ebay chips which simply fool the ECU into thinking the car is cold and again junk too much fuel in.

There are many possibilities but the above are where I would start looking

[TomCropp]

it could be the blue temp sensor which could be naffed, when these go on the blink they often tell the ECU the engine is cold when it is not, so the result is the ECU chucks more fuel in than is necessary (like running with the choke on) Sooty tail pipes would suggest a rich mixture.

There are many possibilities but the above are where I would start looking

i have a plug coming off the airflow meter that isnt plugged into a temp sensor??? i cant find a sensor anywhere for it to plug into, is this normal or am i missing something, i borrowed an air temp sensor off another car and plugged it in but it made no difference...

[eamo]

probably worn cam all right. can you redline it in 1st and 2nd?? if you cant its the cam

[TomCropp]

its definatly not the cam, it wouldnt cause symptoms that bad i had the cam cover off not long ago and the lobes on the cam are fine... im thinking more airflow/ fueling problems, im gonna put it on the scanner tomorrow see if i get any fault codes and then think about trying a new airflow meter.

[sharp3r]

ive just bought a 318i with the same fault, only revs to 4500rpm, pulling my hair out about it! have u sorted yours yet?

[TomCropp]

not yet mate, im sure its the airflow meter, im going to plug my car in to a scanner lunch time today, ill pm you my results and if i cure the problem

[Brianmoooore]

its definatly not the cam, it wouldnt cause symptoms that bad i had the cam cover off not long ago and the lobes on the cam are fine... im thinking more airflow/ fueling problems, im gonna put it on the scanner tomorrow see if i get any fault codes and then think about trying a new airflow meter.

A worn cam on a M40 causes symptoms exactly that bad - exactly like a rev limiter cutting in far to early!
There are other possible reasons for your problem of course, but reading off fault codes produced by an ECU so primitive as a M40 one, will confuse more than help!

[sharp3r]

i had mine on diagnostic equipment, didnt find a fault! spoke to someone at bmw and they seem to recon its a bypass valve inside the inlet manifold? when the engine reaches 4500rpm the valve opens to allow air threw, if your intake pipe for the airflow to the t/body has been split it will make this valve stick, is this true? its defantly not your cam! not prone for ware! and it wont be your airflow meter, i tryed one on mine! sam

[Brianmoooore]

Someone at BMW hasn't got a clue what they're talking about!

[TomCropp]

A worn cam on a M40 causes symptoms exactly that bad - exactly like a rev limiter cutting in far to early!

pretty sure your right i pulled the cam cover off last night and my cams pretty worn,

ive decided im going to build another head on the bench and swap them over once im done....

any advice on what cam to put in it???? schrick? bearing in mind id like a bit more power as its only a 316i

[Rizla_kid]

mine is like this bogs down and misfires as soon as i hit 3000rpm , if i hold my foot on the accel flat down p, the car runs smooth, but when driving the car normally it must look like i cannot drive becasue of the stutters, i tried everything and i got bored and its now in the hands of some very capable bmw specialists as of yesterday. i hope it gets fixed.

Ive noted so many things so ill put my notes to them tomorrrow.

This site has a wealth of information.

cheers

[Chris00]

My 323i did the same thing and it was the distributer rotor..