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3-Series (E21, E30) Chat relating to the BMW 3-Series from 1975-1983 and 1984-1991 line. Specific models: BMW 315, BMW 316, BMW 318, BMW 318i, BMW 320/4, BMW 320i, BMW 320/6, BMW 323i, BMW 320i. E30 Family models include: BMW 325e, BMW 325i, BMW 325is, BMW 325ix.

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Old 06-13-2005, 10:15 AM   #1 (permalink)
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BMW '89 with M40 Engine having 100000 miles on it. Recently (last 3-4 months) I noticed a problem regarding engine idle.

1. Engine would not idle properly, even if cold/hot/ winter/summer & the revs would go from ~650 to ~950 up and down. This happens randomly though and I couldn't figure a pattern for it.
Also when the engine is left idle and you opened the hood, you could hear & see the engine running smoothly but for a split fraction of a second it would stop working thus shaking the engine a bit and droping the revs below 650.

My mechanic checked the car for vaccum problems but did not find any. The oil & fuel filter were changed with OEMs, and for intake I placed a K&N air filter. I also replaced the idle valve with a brand new one but still no fix. Afterwards, my mechanic also changed a relay that was not in the fuse box but near the engine compartment (don't know where exactly cause I wasn't there) and he said that that relay is used somehow in managing the engine idle revolutions. Oh and in adition, all the fuel hoses were replaced because I had a fuel leak a while ago. Still no fix!!!

The only visible problem that i *think* it may promote an idle problem, is the oil re-circulation hose, which is used to take evaporated oil and send it back to the engine. There seems to be oil around that hose which leads to an oil leak from the hose but I haven't changed that. Could that create idle problem?

Any other suggestions? What other problems are related with bad idling and are common for this engine?

2. When the engine is cold, and i press the gas petal, a cracking sound can be heard from the engine at exactly 1500 revs. Like the valves are hitting somewhere or something similar. This goes away as soon as engine reaches it's operating temperature. Any ideas?

I don't know if this plays a role in everything but the car was powered with LEADED fuel 98 octane from 1989-2004 and then I migraded to UNLeaded 98 octane fuel due to the fact that regular fuel production stopped in my home country. I also tried 95 Octane Unleaded fuel bad I had same problems as well as 100 Octane.

Engine is being serviced at regular intervals, never taken out of it's limits, opened,abused etc. I use 98 Octane Unleaded fuel. Even clutch is the same from 1989

Thank you for your time
Paris
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Old 06-14-2005, 01:03 AM   #2 (permalink)
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The car should be able to run on unleaded gas. I can't see how that should be your problem. Maybe it just needs the valves adjusted with regards to the valvetrain noise?

Now, as to the idle, I have two ideas, though I'm not sure they apply to the M40 engine. On my '85 325e I have a very similar erratic idle problem, and I've traced it to one of two things, both of which will be replaced when I get the money. Does you engine have an idle control valve? If it does, get it cleaned, or if i hasn't been done before, replaced. That might help. What I've also been told is that the MAF sensor (mass air flow) can cause this. When you hooked up your K&N, you left in the air flow sensor assembly and added the K&N intake to the end of that, right? If not, that could be your problem.

Those are my two shots at it. Hope they help.
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Old 06-14-2005, 02:20 AM   #3 (permalink)
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Originally posted by offabroadway@Jun 14 2005, 12:03 AM
The car should be able to run on unleaded gas. I can't see how that should be your problem. Maybe it just needs the valves adjusted with regards to the valvetrain noise?

Now, as to the idle, I have two ideas, though I'm not sure they apply to the M40 engine. On my '85 325e I have a very similar erratic idle problem, and I've traced it to one of two things, both of which will be replaced when I get the money. Does you engine have an idle control valve? If it does, get it cleaned, or if i hasn't been done before, replaced. That might help. What I've also been told is that the MAF sensor (mass air flow) can cause this. When you hooked up your K&N, you left in the air flow sensor assembly and added the K&N intake to the end of that, right? If not, that could be your problem.

Those are my two shots at it. Hope they help.
[snapback]353415[/snapback]
I have replaced the idle valve with a brand new one but still no fix. The K&N filter is not an intake Kit but just a better airflow filter. It fitted in the same airbox. I haven't messed the MAF sensor in any way
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Old 06-14-2005, 12:33 PM   #4 (permalink)
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if you were running leaded, if you are running a catalytic converter, its probably slag by now.

if you have a clogged cat, your car is going to run like shit.

just something to check.
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Old 06-14-2005, 03:44 PM   #5 (permalink)
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Originally posted by nukeduster@Jun 14 2005, 11:33 AM
if you were running leaded, if you are running a catalytic converter, its probably slag by now.

if you have a clogged cat, your car is going to run like shit.

just something to check.
[snapback]353509[/snapback]
Car doesn't have a catalytic converter
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Old 06-15-2005, 10:31 AM   #6 (permalink)
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If the car was designed and sold for use in a country with leaded gas, it won't have one, unless it was an Unleaded Fuel Only machine. You'd have to check the owner's manual.

As to the idle, now I'm really stumped. When was the last time the plugs, caps, wires, etc were done on the ignition? This would help. Also, you know anyone who could plug the car in to a BMW Diag computer for you? You might get something out of that.
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Old 06-15-2005, 11:16 AM   #7 (permalink)
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Originally posted by offabroadway@Jun 15 2005, 09:31 AM
If the car was designed and sold for use in a country with leaded gas, it won't have one, unless it was an Unleaded Fuel Only machine. You'd have to check the owner's manual.

As to the idle, now I'm really stumped. When was the last time the plugs, caps, wires, etc were done on the ignition? This would help. Also, you know anyone who could plug the car in to a BMW Diag computer for you? You might get something out of that.
[snapback]353699[/snapback]
The car doesn't have a cat.converter because in my country we had to use unleaded gas the last year (EU regulations) but the car was bought 16 years ago so it came without the cat...

Sparks have been replaced 500km ago. Caps, wires, etc, are still the same, untoutched from 1989
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Old 06-15-2005, 08:34 PM   #8 (permalink)
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Well, that might help you out a bit there, dude. All those ignition components (minus the coil of course) are supposed to go every 5 years or thereabouts, or 100,000kms. Just keeps the car's electrics in good shape. You should try it.

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Old 06-16-2005, 05:29 AM   #9 (permalink)
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Originally posted by offabroadway@Jun 15 2005, 07:34 PM
Well, that might help you out a bit there, dude. All those ignition components (minus the coil of course) are supposed to go every 5 years or thereabouts, or 100,000kms. Just keeps the car's electrics in good shape. You should try it.


[snapback]353878[/snapback]
Yep that's the next thing I'm gonna do. Any other places/parts to look at?
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Old 06-16-2005, 09:16 PM   #10 (permalink)
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Quote:
Originally posted by Paraklas@Jun 13 2005, 08:15 AM
BMW '89 with M40 Engine having 100000 miles on it. Recently (last 3-4 months) I noticed a problem regarding engine idle.

1. Engine would not idle properly, even if cold/hot/ winter/summer & the revs would go from ~650 to ~950 up and down. This happens randomly though and I couldn't figure a pattern for it.
Also when the engine is left idle and you opened the hood, you could hear & see the engine running smoothly but for a split fraction of a second it would stop working thus shaking the engine a bit and droping the revs below 650.

My mechanic checked the car for vaccum problems but did not find any. The oil & fuel filter were changed with OEMs, and for intake I placed a K&N air filter. I also replaced the idle valve with a brand new one but still no fix. Afterwards, my mechanic also changed a relay that was not in the fuse box but near the engine compartment (don't know where exactly cause I wasn't there) and he said that that relay is used somehow in managing the engine idle revolutions. Oh and in adition, all the fuel hoses were replaced because I had a fuel leak a while ago. Still no fix!!!

The only visible problem that i *think* it may promote an idle problem, is the oil re-circulation hose, which is used to take evaporated oil and send it back to the engine. There seems to be oil around that hose which leads to an oil leak from the hose but I haven't changed that. Could that create idle problem?

Any other suggestions? What other problems are related with bad idling and are common for this engine?

2. When the engine is cold, and i press the gas petal, a cracking sound can be heard from the engine at exactly 1500 revs. Like the valves are hitting somewhere or something similar. This goes away as soon as engine reaches it's operating temperature. Any ideas?

I don't know if this plays a role in everything but the car was powered with LEADED fuel 98 octane from 1989-2004 and then I migraded to UNLeaded 98 octane fuel due to the fact that regular fuel production stopped in my home country. I also tried 95 Octane Unleaded fuel bad I had same problems as well as 100 Octane.

Engine is being serviced at regular intervals, never taken out of it's limits, opened,abused etc. I use 98 Octane Unleaded fuel. Even clutch is the same from 1989

Thank you for your time
Paris
[snapback]353146[/snapback]
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Old 06-16-2005, 09:25 PM   #11 (permalink)
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Quote:
Originally posted by Paraklas@Jun 13 2005, 08:15 AM
BMW '89 with M40 Engine having 100000 miles on it. Recently (last 3-4 months) I noticed a problem regarding engine idle.

1. Engine would not idle properly, even if cold/hot/ winter/summer & the revs would go from ~650 to ~950 up and down. This happens randomly though and I couldn't figure a pattern for it.
Also when the engine is left idle and you opened the hood, you could hear & see the engine running smoothly but for a split fraction of a second it would stop working thus shaking the engine a bit and droping the revs below 650.

My mechanic checked the car for vaccum problems but did not find any. The oil & fuel filter were changed with OEMs, and for intake I placed a K&N air filter. I also replaced the idle valve with a brand new one but still no fix. Afterwards, my mechanic also changed a relay that was not in the fuse box but near the engine compartment (don't know where exactly cause I wasn't there) and he said that that relay is used somehow in managing the engine idle revolutions. Oh and in adition, all the fuel hoses were replaced because I had a fuel leak a while ago. Still no fix!!!

The only visible problem that i *think* it may promote an idle problem, is the oil re-circulation hose, which is used to take evaporated oil and send it back to the engine. There seems to be oil around that hose which leads to an oil leak from the hose but I haven't changed that. Could that create idle problem?

Any other suggestions? What other problems are related with bad idling and are common for this engine?

2. When the engine is cold, and i press the gas petal, a cracking sound can be heard from the engine at exactly 1500 revs. Like the valves are hitting somewhere or something similar. This goes away as soon as engine reaches it's operating temperature. Any ideas?

I don't know if this plays a role in everything but the car was powered with LEADED fuel 98 octane from 1989-2004 and then I migraded to UNLeaded 98 octane fuel due to the fact that regular fuel production stopped in my home country. I also tried 95 Octane Unleaded fuel bad I had same problems as well as 100 Octane.

Engine is being serviced at regular intervals, never taken out of it's limits, opened,abused etc. I use 98 Octane Unleaded fuel. Even clutch is the same from 1989

Thank you for your time
Paris
[snapback]353146[/snapback]
I hope this helps you out. I have an '85 318i that has the same problem, so I called my friend that has a euro service center and he told me that this is a common problem... and the source is from the idle control unit, I'm having mine replaced this weekend. here is a link to where i found the part http://shop.bmw-engine-parts.com/318-fuel_...0_30340pro.html, also there is another part you may want to check and that is the idle control valve, which I think you can just have cleaned, befor replacing... good luck!
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