Misfiring 40% of the time

[e34_spangler]

At idle I'd say 40% of the time the car mis fires but when it doesn't it runs amazing what causes this engine to misfire?

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[dnguyen1963]

Two things you can check, ignition wires and loose elbows connecting to the throttle body.

[e34_spangler]

And those are the only things?

[jlevie]

Replace the ignition wires, distributor rotor, cap, and O2 sensor. Then have a shop run a smoke test to check for intake leaks and fix them.

[IAmGary]

Start at the ends of the ignition system: Crank Position Sensor (if it's dirty you will get misfires, worse when cold and will degrade over time as it gets dirtier. If it has a short you'll also get misfires) and then check the other end (plugs, plug wires, cap, rotor and ignition coil).

Yes, it could be the ECU. Yes it could be a bad injector. But start with the electrical system first.

[e34_spangler]

Ok so didn't have much time to check much but I made sure my plugs and everything where In there correctly etc. But I forget to mention the car hesitates at time so i idk if that helps narrow down what it is? I was think cap and rotor but I don't wanna just spend massive amounts of money and just start replacing everything

[dnguyen1963]

Do a smoke test before you throw money at your car.

[e34_spangler]

Do a smoke test before you throw money at your car.

Ok

[sweet6e30]

i had this kind of happen to a clients car, i found that believe it or not it was missing at low rpms and idle due to injector connector corrosion. under full load in various gears it would run on all 6. this was due to incorrect voltage being supplied to the injectors. When driven hard voltage squeeked through. it seemed to be just enough. but at Idle it farted!

If the ignition system all checks out good and you have spark on all 6, i would check the 6 connectors to each injectors and clean up the contacts. if its still missing, then check the injector harness plug under the intake plenum and clean up those contacts. if its still, you might have a bad coil thats on its way out providing inconsitent voltage at inconsistant times under varios conditions. if still missing, check your injectors. Usually this shit happens due to corrosion in connectors. pull the cap and inspect it and the rotor. when was the last time you replaced those components?
hope that helps

[e34_spangler]

Ok so I actually thought ahead and made sure all connections are good! Cap and rotor looked fairly new and Yeah so I'm thinking I'm just over exaggerating and its just a rough idle but I'm trying to narrow stuff down like ignition wires cap and rotor plugs are all new air filer new ,afm readjustment , icv working kne but used

[IAmGary]

It takes 2 minutes to check the CPS for dirt... at least do that much if you can't test it with a meter or replace it with a known good one. It's as important to your ignition system as anything else.

[e34_spangler]

It takes 2 minutes to check the CPS for dirt... at least do that much if you can't test it with a meter or replace it with a known good one. It's as important to your ignition system as anything else.

Already cleaned the bad boy

[e34_spangler]

Ok did a check for vacum leaks and there's none now what I think is happeining is collant is running throufh the engine not allowing the spark plugs to work and not combust right? But there's no signs other then loss of collant that a head gasket eould be bad and the guy had bmw put a new one in so is there any other way collant would be running through the engine? Hope all that jumbo made sense

[jlevie]

The cooling system won't be the cause of this.

[e34_spangler]

The cooling system won't be the cause of this.

Ok coukd valce adjustment be a problem?