Help my petrol runs like a diesel

[keen 6]

I'm stuck I changed the engine mounts on my 88 e30 318 but now have a problem. this could be co-incidental as the was a hint of a problem before starting. The car runs rough and at idle it surges from around 200rpm to between 1200 to 1500 then drops back again after running for a while it will try to run at this very slow idle (200) and can do so for about 30 seconds at normal road speed (100) it has a fine miss intermittent very similar to a plug breaking down (only way to describe it) then as you approach a stop it snuffs out. if you try to rev it to keep it running it struggles, again its like a race cam has been fitted and its hunting then if you give it small revs it struggles to get going but eventually gets there.What have I done? jacked the car up lifted the motor about 40mm and fitted new engine mounts and lowered the motor back down I have tried another idle valve and another AFM and new plugs I have checked the earth strap and cleaned both sides of the strap. When the motor was on the jack I double checked to see if any wires or hose or anything else was stretched but everything seemed OK.As I have said earlier this could be coincidental and it does appear to be worsening. Is it likely to be something like a crank sensor going or a sticking injector or the ECU some help here I would be very grateful thanks Ken some more info the car is manual and nz new no A/C just basic model any more info needed just ask

Edited January 4, 2009 by keen

[Jamez 2147483647]

are you getting spark to all cylinders? sounds like 2 of them only fire every so often causeing a wierd inbalnce

my 318i when wet would do this because it was prone to having water get in the spark plug holes but thats a completely different thing

and go get it tuned, since you got a new AFM.

im sure someone else on the forum will know whats wrong

[keen 6]

are you getting spark to all cylinders? sounds like 2 of them only fire every so often causing a weird unbalanced

my 318i when wet would do this because it was prone to having water get in the spark plug holes but thats a completely different thing

and go get it tuned, since you got a new AFM.

I'm sure someone else on the forum will know whats wrong

Thanks for that the AFM is off another car that is working OK and made no difference so returned everything to the way it was The plugs that I took out all looked the same and again I used the ones from another car and that made no difference

[Jamez 2147483647]

no i ment if you take all the leads of then put a sparkplug in one then ground it on top of the block do you get a decent spark? sometimes if the lead is getting grounded befor the sparkplug you will get a weak/no spark.

i find if i got a problem its either spark,fuel or compression.

[Silver Fox 43]

Does sound a bit like timing Ken, so could be crank sender, when did you do the cambelt last? May have lost a tooth or 2? Also check the ECU, I had one die on me, similar symptons. Good luck.

[keen 6]

The cam belt is not a problem its not that long ago I replaced it about 20000kms but if its that I can manage putting in a new one now that you have taught how to David, but the ECU is another story how do you check that and also how would I check a crank sensor? would a static ohms test pick it up and how would I check the timing ? I have a strobe light where am I checking the marks?

[Silver Fox 43]

Not sure how to check them, I just changed mine.

The timing marks are on the harmonic balancer on the front of the engine, and the ali housing either on the oil filter housing or the cover next to it?

[keen 6]

Timing marks found and that looks OK so must be down to crank sensor or ECU anyone got either of those two at a reasonable price?

[pureboiracer 0]

sounds like a possible air leak to me

[320guy 0]

You checked all the main engine grounds?

[keen 6]

If it is an air leak, and I remove the oil dip stick should the revs stay the same or should they drop the revs, the same as when running normally?

[keen 6]

I would like to thank everybody who tried to help me with this problem.I have found the culprit and completed a temporary repair till tomorrow.There was a crack in the rubber intake pipe after the AFM on the underside. just taking the pipe off and checking it for cracks did not show up the first time till I bent it hard into a "u" shape and found a perished crack in the pipe.This looked normal till it was stretched onto its mounts which opened it when the engine ran and caused the fault .All is running normally now so thank you all again.Keep up the good work .Ken