Author Topic: (OPEN STILL) My BMW keeps back firing, at low idle speeds, i wanna punch it  (Read 9371 times)

tjts1

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My BMW keeps back firing, at low idle speeds, i wanna punch it
« Reply #15 on: December 19, 2009, 09:55:38 PM »
The black gunk on the tops of the pistons is normal. All of our engines have it. Don't worry about it. Its not the cause of this problem. it built up over many thousands of miles. You can clean the inside of the combustion chamber with something like seafoam through a very thin vacuum hose to the manifold or even water in very small amounts.
Sold but not forgotten

This is whats wrong with your car.
http://www.m42club.com/forums/showthread.php?t=2742
[/thread]

92BMW318is

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My BMW keeps back firing, at low idle speeds, i wanna punch it
« Reply #16 on: December 19, 2009, 10:03:37 PM »
Quote from: tjts1;83279
I LOLed!

Ok this is just a guess. Your engine is running but its making crazy popping noises so at least 1 or 2 and probably 3 of the cylinders are firing as they should. There is a chance you could have damaged one of the spark plug wires in the process of changing the plugs. If the plug wire is damaged the unburned air fuel mixture from one of the cyls is igniting in the exhaust, hence the crazy noises. I don't know how to test the plug wires. Seeing how expensive the 4 foot+ long wires are, I'm betting they're pretty old (mine still had the cosmoline coating from the factory). Take a close look inside the connector at each plug wire. If you want to cheap alternative to M42 plug wires...
http://m42club.com/forums/showthread.php?t=5309
Again, this is just a guess.

good luck
Justin


sorry i forgot to tell you that my car isnt running anymore now its just starting and then stalling and or starting then misfiring and backfiring then stalling, the car wont run for more then a second or 2 if that, before it stalls out or back fires.

but if this doesnt change anything in your first reply then thanks for your help

ak96ss

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My BMW keeps back firing, at low idle speeds, i wanna punch it
« Reply #17 on: December 19, 2009, 10:11:31 PM »
Quote from: 92BMW318is;83271
i hooked up the plugs in the correct order and still, the engine back fires,
from what i can see when i took the other new spark plugs out and replaced them with newly newer pre gaped plugs, i shined a light down the spark plug shaft to see black carbon tar in the cylinder, now this is what i think is stalling out and making my car backfire but, the damn car wont start so i cant perform a "blow out",(rev engine high burn up excess carbon tarr).

so i think im left with one option. is to take apart the cylinder head cover,
oooo mannn is that going to suck.

if you guys have any other ways to do this besides taking off the header let me know,

ALSO, i know there are some gaskets im going to have to replace,
if you know what those gaskets are please include in your reply to this post,

ALSO #2,  is the cylinder head cover the only thing im going to have to take off to get to the cylinders to clean them out, whats the best way to clean them?



is removing cylinder head cover really nessicary, thats the only option i can see that would be plausable right now

#3. any special tools required?

 thanks again,


No special tools are required, but what do you hope to accomplish by removing the cover?

The first thing I would try is testing each of the wires. Easiest way is probably to just get an old spark plug, break the electrode off, and put it in the spark plug boot. Then, using pliers, hold it near the engine block while someone else cranks the engine over. You should see a good spark. Check all four wires and make sure you are getting spark from all of them.

Double-check your wiring and make sure you have the right coil going to the right plug. Anyone know if these use wasted spark?
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John in MD
uh, it's a '91 318is, like everyone else...

ak96ss

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My BMW keeps back firing, at low idle speeds, i wanna punch it
« Reply #18 on: December 19, 2009, 10:13:48 PM »
Just for my own edification, has it run since you redid all the main wiring harness stuff?
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John in MD
uh, it's a '91 318is, like everyone else...

92BMW318is

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My BMW keeps back firing, at low idle speeds, i wanna punch it
« Reply #19 on: December 19, 2009, 10:21:54 PM »
Quote from: ak96ss;83285
Just for my own edification, has it run since you redid all the main wiring harness stuff?


it ran for like 10- 15 mins while i was trying to find what was doing, or making the noise,( while it was running it was poping and backfiring, sounded like gun shot and small firecrackers like every 2-3 seconds it would do eather one) i figured it was the spark plugs so i bought new pregaped spark plugs took the other new ones i bought out and replaced them with the pregaped ones, but since then i try to turn over the car it revs then dies i do it agian it revs then dies do it agian it revs then back fires then dies, some times the rpm gauge wont move at all tho it only moves when its about to backfire, it gets up to about 1-1.5 before it backfires or misfires, some times only .5 rpms,

i was thinking if the engine was warmer maybe this would help the starting process? is it?

92BMW318is

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My BMW keeps back firing, at low idle speeds, i wanna punch it
« Reply #20 on: December 19, 2009, 10:23:31 PM »
Quote from: ak96ss;83284
No special tools are required, but what do you hope to accomplish by removing the cover?

The first thing I would try is testing each of the wires. Easiest way is probably to just get an old spark plug, break the electrode off, and put it in the spark plug boot. Then, using pliers, hold it near the engine block while someone else cranks the engine over. You should see a good spark. Check all four wires and make sure you are getting spark from all of them.

Double-check your wiring and make sure you have the right coil going to the right plug. Anyone know if these use wasted spark?



i was hoping to clean out the cylinders and the tops of the pistons, but i dont or didnt know if that was causing it so i thought i would ask someone first,

im sure the head gasket needs replaced anyways

ak96ss

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My BMW keeps back firing, at low idle speeds, i wanna punch it
« Reply #21 on: December 19, 2009, 10:32:59 PM »
I just want to make sure you have some sort of plan before you just start pulling pieces off the car. Honestly, I would get it running right first...  you don't need to add anything to the equation.

Backing up a bit here, why did you need to redo main engine harness?

I am starting to think there are larger issues here - in particular, I would recommend that you confirm that all connectors have been routed to the right spot.

Backfire/popping sounds like a timing issue - was the timing chain off at any point while you had the main harness disconnected?
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We're here to preserve democracy, not practice it.
[INDENT]- Captain Frank Ramsey, Crimson Tide[/INDENT]
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John in MD
uh, it's a '91 318is, like everyone else...

92BMW318is

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My BMW keeps back firing, at low idle speeds, i wanna punch it
« Reply #22 on: December 19, 2009, 10:49:14 PM »
Quote from: ak96ss;83290
I just want to make sure you have some sort of plan before you just start pulling pieces off the car. Honestly, I would get it running right first...  you don't need to add anything to the equation.

Backing up a bit here, why did you need to redo main engine harness?

I am starting to think there are larger issues here - in particular, I would recommend that you confirm that all connectors have been routed to the right spot.

Backfire/popping sounds like a timing issue - was the timing chain off at any point while you had the main harness disconnected?


okay the only thing i have done to the car so far was replace the spark plugs and the starter, i also replace the gaskets for the lower and upper manifold, ran a straight wire form the starter to the alternator the same gauge that was on it originally, and i replace alot of old bolts, but i never took off the clinder head cover or anything inside there or the timing chain never messesd with any of that,

what do you mean by redo the main engine harness?
i didnt think i said i was going to



in order of what i did,

1/2. took off air intake
1. took off upper manifold
2. took off fuel injection
3. unplugged feeds to sensors and regulator like idle air control valve, knock sensor
4. moved octopus of wires
5. took off lower intake manifold
6. took off starter replaced it with new one,
7. ran new wire from alt to the starter,
8. replace gaskets on lower manifold
9. reinstalled #5-1 in reverse order
10. put a new gasket on upper intake.
11. changed spark plugs


note that i never took the throttle body off, left it attached to the uper manifold i fliped it upside down and moved it out of the way, also i check all connections and vac lines
« Last Edit: December 19, 2009, 11:28:18 PM by 92BMW318is »

nickmpower

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My BMW keeps back firing, at low idle speeds, i wanna punch it
« Reply #23 on: December 19, 2009, 11:23:38 PM »
the spark plug wires should be numbered. And the coil pack cover should be numbered too. I think. look closely at the wires and make sure they are in the right place

92BMW318is

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My BMW keeps back firing, at low idle speeds, i wanna punch it
« Reply #24 on: December 19, 2009, 11:25:58 PM »
Quote from: nickmpower;83295
the spark plug wires should be numbered. And the coil pack cover should be numbered too. I think. look closely at the wires and make sure they are in the right place

there arent numbers on the coil packs or on the spark plug connectors ive look like 3 times all over the wire and tube and the coil packs



this is the diagram some one gave me to the best of my knowledge this is correct

92BMW318is

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My BMW keeps back firing, at low idle speeds, i wanna punch it
« Reply #25 on: December 19, 2009, 11:37:06 PM »
i will take pictures after i get off here and post them try to get every one a better understanding on what is going on, but feel free to keep posting ideas

just double checking is this diagram right?