e36 m3 misfire when cold and under load

[leez]

hi gents

as the topic states my m3 is giving me some trouble and i cannot seem to find the problem. ive changed the ffg

1. compete vanos rebuild, solenoids tested
2. fuel pump changed
3. injectors serviced
4. serviced car
5. changed maf
6. tried another computer box and vanos control unit
7. checked for intake leaks
8. tested all sensors using multimeter. changed temp sensor
9. checked all earth cables
10. checked fuel pressure 3.5 bar on idle
11. tested coilpacks resistance and checked coilpack boots

diagnostics reveals nothing but low dme voltage. car misfires on inclines and worse with aircon on. also misfires when cold. when i turn my key on for the first time in the morning, my fuel pump relay chatters during the priming. i believe this is because of low voltage as i have also replaced the relay.the low voltage seems to be only on the engine harness. im not sure if i sure replace the harness. would a cracked head or blown headgasket cause the same issues> my car has 143k on the clock, does not overheat, no oil and water mixing and engine does not smoke.

Any input would be appreciated.

 

[444YYY]

You've really checked quite a bit!
You didn't mention checking if the alternator is healthy? 14.4V?
What about the condition of your battery?

Not sure.... But worth a check?

 

[danieljames]

My 2c...

You've done so much you might aswell go the full monty. Blown head gasket...can't say.(I'm no mechie tho).

I say pull the head off. Do a pressure test. Check for cracks and also valves/stem seals/valve springs etc. Soema check everything. Possibly a destroyed lifter? Just fishing here. Some ideas maybe. I mean....what have you got to lose?

Fuel pump.....uhm....I dunno

M50B25-L6

 

[leez]

You've really checked quite a bit!
You didn't mention checking if the alternator is healthy? 14.4V?
What about the condition of your battery?

Not sure.... But worth a check?

O yes, I forgot to mention I checked that as well. tested twice at 2 different places. Both turned out fine. Charging under load was fine

---

My 2c...

You've done so much you might aswell go the full monty. Blown head gasket...can't say.(I'm no mechie tho).

I say pull the head off. Do a pressure test. Check for cracks and also valves/stem seals/valve springs etc. Soema check everything. Possibly a destroyed lifter? Just fishing here. Some ideas maybe. I mean....what have you got to lose?

Fuel pump.....uhm....I dunno

M50B25-L6

I've changed fuel pump. My last resort will be to remove the head. Reason is because that's the most expensive to do.

 

[moranor@axis]

how does it run when warm?

 

[leez]

how does it run when warm?

Runs better than when it's cold. Its usually misfires around 2000rpm when driving in town but on the freeway on a incline in 5th gear it misfires no matter what the rpm. Also the diagnostics does not pick up any fault except low dme voltage. I can unplug a sensor and it wouldn't register a fault

 

[moranor@axis]

seems to me you should check the charging and battery system if its complaining about low voltage...

if that checks out you should do a wet and dry compression test to see what the general mechanical condition of the engine is

 

[hoosain]

check your wires going into your throttle sensor they become brittle with age and the plastic sheathing around the wires break off and then you could have a magnetic interferance
while your car is misfiring in the morning press on the boot thats going into your throttle sensor and see if it makes a differance

 

[Hubblyking]

The e36 m3 harness is :yuck:

 

[ClassicB]

Dont rule out head gasket. Use to happen to a friends e36 M3. Progressively got worse. The head gasket head a slight crack in it.

Skimmed the head, new gasket, etc, all was back to the way it should be.

 

[leez]

check your wires going into your throttle sensor they become brittle with age and the plastic sheathing around the wires break off and then you could have a magnetic interferance
while your car is misfiring in the morning press on the boot thats going into your throttle sensor and see if it makes a differance

ive checked the wires and changed the tps

---

Dont rule out head gasket. Use to happen to a friends e36 M3. Progressively got worse. The head gasket head a slight crack in it.

Skimmed the head, new gasket, etc, all was back to the way it should be.

if my fuel pump relay was not chattering during priming i would have definitely pulled the head off long ago. im going the get another ecu harness and try that first

 

[lambchop]

Spark plugs

 

[leez]

Spark plugs

New plugs 2000km ago

 

[calypso]

Spark plugs

New plugs 2000km ago

I had a brand new plug fail in around that time. OEM platinums for the E46. took the coil pack out with it. So worth a look.

 

[leez]

Spark plugs

New plugs 2000km ago

I had a brand new plug fail in around that time. OEM platinums for the E46. took the coil pack out with it. So worth a look.

I've heard stories of that happening. I bought these plugs from agents. Should I try ngk

 

[Peter@AEW]

Not plugs

do a compression test whilst hot.
should read minimum 140

I suspect that you will find one of the cylinders in the 100 to 110 range
If you know what to look for the spark plug will tell you what is happening

 

[leez]

Not plugs

do a compression test whilst hot.
should read minimum 140

I suspect that you will find one of the cylinders in the 100 to 110 range
If you know what to look for the spark plug will tell you what is happening

do you no of a link that i can follow tp do a compression test?
i was thinking of doing it when cold then filling a cap full of oil in each cylinder and testing again. i will then get the car up to full operating temperature and test again

 

[Peter@AEW]

Not plugs

do a compression test whilst hot.
should read minimum 140

I suspect that you will find one of the cylinders in the 100 to 110 range
If you know what to look for the spark plug will tell you what is happening

do you no of a link that i can follow tp do a compression test?
i was thinking of doing it when cold then filling a cap full of oil in each cylinder and testing again. i will then get the car up to full operating temperature and test again

Not cold as it will tell you little.

Do a hot test by removing plugs disconnect fuel pump fuse press accelerator pedal flat and crank motor untill compression no longer increases +-5 cranks.

Once readings recorded place a very small amount of oil in cylinder and crank again whilst accelerator is flat if compression increases piston rings if it stays the same valve issue which could be guides or burned valves

If 2 cylinders record the same compression and are next to each other test the compression on both after having introduced oil in the 1 and record the variance

If both show an increase when only 1 has had oil introduced into it likelyhood of gasket issues with leaks.

As to a site I guess Google is your friend

 

[hoosain]

when you use the words incline and when cold fuel pressure decrease comes to mind as the car car needs more fuel on the start up map
did you prime the pump before you installed it?
could be a faulty fuel pump?
check pressure while driving under load

 

[leez]

when you use the words incline and when cold fuel pressure decrease comes to mind as the car car needs more fuel on the start up map
did you prime the pump before you installed it?
could be a faulty fuel pump?
check pressure while driving under load

no i did not prime the pump. i did test fuel pressure but not under load. how would i test under load?