intermitt engine wierdness

[bmwrp8]

first of all i would like to say that this forum is a very big help to me thankyou all...Going back, at first i was having problems with my idle at morning the idle was rough and sometime dies, when warm it only idles at 500rpm sometimes 400...I changed the ICV now it idles better than ever at 750rpm even at mornings.But now my problem is when i'm at the stoplight or stopped for a long time at idle when I put it in D and step on the gas the engine hiccups then accelerates fine...sometimes hiccups then dies but idles fine has power...what could be the cause?thanks in advance oh yeah its a m20 525ia has 257,000kms

[neil_004]

check the ignition system.

[bmwrp8]

check the ignition system.

what should i check for?i just replaced the crank S.sensor & sparkplugs

[DaveVoorhis]

I had the same problem with my M20, but only within a fairly narrow temperature range -- about 0 - 10 degrees C, and only when the engine was warming up, not cold but after five minutes or so running. It was fine when fully cold or warmed up. Someone on this forum suggested cleaning the connections to the coolant temp. sensor, which I did. That seemed to improve it, but didn't entirely cure it. I traded that car for my current E34 before I had a chance to investigate further.

I'd also suspect a sticky AFM or an intake vacuum leak.

[bmwrp8]

I had the same problem with my M20, but only within a fairly narrow temperature range -- about 0 - 10 degrees C, and only when the engine was warming up, not cold but after five minutes or so running. It was fine when fully cold or warmed up. Someone on this forum suggested cleaning the connections to the coolant temp. sensor, which I did. That seemed to improve it, but didn't entirely cure it. I traded that car for my current E34 before I had a chance to investigate further.

I'd also suspect a sticky AFM or an intake vacuum leak.

I checked for vacuum leak theres none AFM is fine coolant temp sensor cleaned with contact cleaner... happens when engine is fully warmed up...any idea? Takers anyone???

[e34musician]

Assuming you can reset your CEL, Disconnect your MAF sensor harness (you will get CEL) and see if the problem goes away. If yes, replace your MAF. The car will be running in safemode without MAF sensor connected.

This fixed my problem (similar to yours) on the M60 couple weeks back.

[bmwrp8]

Assuming you can reset your CEL, Disconnect your MAF sensor harness (you will get CEL) and see if the problem goes away. If yes, replace your MAF. The car will be running in safemode without MAF sensor connected.

This fixed my problem (similar to yours) on the M60 couple weeks back.

i don't have check engine light... but I checked the computer for codes by carsoft but all is fine the DME isn't throwing any codes. checked AFM its fine...

[DaveVoorhis]

How do you know the AFM is good?

Might be worth checking the fuel pressure, too. Maybe a failing fuel pressure regulator?

[bmwrp8]

How do you know the AFM is good?

Might be worth checking the fuel pressure, too. Maybe a failing fuel pressure regulator?

I borrowed three AFM from the yard still the same just replaced my fuel pump last sept. fuel pressure regulator?how to check?

[bmwrp8]

forgot to mention i need to adjust my valves its a little noisy do you think its one of the causes?

[bmwrp8]

anymore takers?/suggestions?

[Ross]

Check the cap, rotor and wires.

[bmwrp8]

ok just now here's what I did, First checked the ignition just changed the plugs,check the wires rotor is fine I just cleaned it,then I cleaned every contacts of the engine,Temp.sensor , AFM , and every contacts in the engine that I see with contact cleaner...now idles better but still there,checked again for vacumm leaks coudn't find any...but heres one thing whenever I disconect the vacumm hose of the fuel pressure regulator hiccup is gone and it idles better esp.during warmup...any comments?suggestions?

[bmwrp8]

ok just now here's what I did, First checked the ignition just changed the plugs,check the wires rotor is fine I just cleaned it,then I cleaned every contacts of the engine, Temp.sensor , AFM , and every contacts in the engine that I see with contact cleaner...now idles better but still there,checked again for vacumm leaks coudn't find any...but heres one thing whenever I disconect the vacumm hose of the fuel pressure regulator hiccup is gone and it idles better esp.during warmup...any comments?suggestions?

[DaveVoorhis]

Change the fuel pressure regulator. See if that fixes it.

[bmwrp8]

Change the fuel pressure regulator. See if that fixes it.

will do tom.or sat. do you think for the meantime is it ok to disconnect the vacumm hose that runs to the fuel regulator?it runs better when disconnected

[DaveVoorhis]

Should be okay, because it sounds like your fuel pressure is too low, possibly due to a weak spring in the regulator. Removing the vacuum hose will raise the fuel pressure. Be sure to plug the vacuum line.

[bmwrp8]

Should be okay, because it sounds like your fuel pressure is too low, possibly due to a weak spring in the regulator. Removing the vacuum hose will raise the fuel pressure. Be sure to plug the vacuum line.

thanks for the reply DaveVoorhis & others that replied will leave it disconnected til I buy a new regulator till sat. then ill know if the hiccup is gone...will keep posted again thanks:D