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3-Series (E36) Chat relating to the BMW 3-Series from 1992-1999. Autodoodad Specific models include: BMW 316i, BMW 318i, BMW 318iS/ti, BMW 320, BMW 323, BMW 320, BMW 324, BMW 325, BMW 328.

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Old 08-27-2008, 06:08 AM   #1 (permalink)
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RPM very low, performance is low too!! help

Since I bought my 325i 1993 I note that the RPM is too low itís around 600 some time after driving raised to 700 with AC ON will be 750-800, Actually that wasnít too low in my last 320i 1992 it was exactly in the middle between 500 &1000. also the exhaust was to loud and noisy specially in low RPM with AC On. + The emissions which is coming from the exhaust is too weak ( Iím not sure if that normal )
In addition to this low RPM there is leak in power. I have already tuned it up by changing ( sparks plug, Oils, air and fuel filters)

I have made a full check for my car in BMW maintenance; the engineer made a test drive for my car and he direct felt the low power of my car. After full check, he told me: you have to change your exhaust. I asked the engineer about any failed sensors, he said no problem about sensors.

Now I changed the exhaust sys, itís nice, low deep sound with some better performance but not much. I was thinking that this low RPM and performance will be better after changing the exhaust sys. But it still as it is.


Is that low RPM is normal, what is your 325i RPM?
Could you help me to get the real performance of my 325i.

Here is a shut of my car RPM.
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Old 08-27-2008, 09:29 AM   #2 (permalink)
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idle seems normal to me
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Old 08-27-2008, 12:04 PM   #3 (permalink)
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i agree 6-7 hundred is a fine idle. also saves on gas (incase your worried about that). as for the exhaust. Exhaust systems really dont give much power to the car. the will put a bit more performance on the top end but the sacrafice is a loss in power on the bottom end. the reason behind this is when you make the exhaust flow better you loose backpressure which helps create and build power down low but helps flow better on the top end to create more power, in my opinion you should really only be buying exhaust systems if you have more bolt ons and if your interested in the better sound it produces.
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Old 08-28-2008, 05:34 AM   #4 (permalink)
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i agree 6-7 hundred is a fine idle. also saves on gas (incase your worried about that). as for the exhaust. Exhaust systems really dont give much power to the car. the will put a bit more performance on the top end but the sacrafice is a loss in power on the bottom end. the reason behind this is when you make the exhaust flow better you loose backpressure which helps create and build power down low but helps flow better on the top end to create more power, in my opinion you should really only be buying exhaust systems if you have more bolt ons and if your interested in the better sound it produces.
there is no loose in backpressure, They assum this point whin thy made me the exhaust.

But Why the exhaust emissions push is very weak. I mean very little air coming out the exhaust. seems like it's plugged. even after changing the exhaust.

Last edited by MAXI; 08-28-2008 at 05:36 AM.
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Old 08-28-2008, 09:23 AM   #5 (permalink)
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if you are doing the work yourself... take a compression check on all cylinders.

I think you are focused on the wrong things... Backpressure in 4stroke engines don't exactly mean too much; unlike in 2 stroke engines where backpressure accounts for maybe 30% of power.

Q: what spark plugs did you use?
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Old 08-31-2008, 03:20 AM   #6 (permalink)
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I'm using NGK spark plugs.
How to do compression check for the cylinders, is there DIY for that, is it need special tools?
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Old 08-31-2008, 03:21 AM   #7 (permalink)
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One more symptom, sometimes it takes a while of time to start, It cranks but it taks time to start. after strating get some vibration, then it goes while warming up, with some misfire smill.
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Old 08-31-2008, 10:22 AM   #8 (permalink)
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Did you use the +2 NGK plugs? We've found that the BEST for all the BMW's are the various copper +2 models. The +4 models offer more spark than the cars are designed for and actually according to some affect performance negatively.

Is your idle steady even after the hard starts?
Do you ever get a check engine light?
Does your transmission slip at all?
At what rpm do you feel the power "come on"?

Yes you do need some tools to do the compression test. It may be a good thing to have done. You are looking for numbers that are near the same on all cylinders. They should give you a print out with the numbers as well.
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Old 09-01-2008, 03:55 AM   #9 (permalink)
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  • Is your idle steady even after the hard starts?
    Yes.
  • Do you ever get a check engine light?
    No
  • Does your transmission slip at all?
    Yes, somtimes it slip, I thought that because of leak in transmission and shortag in fluid, but after reparing it, and increasing the fluid, the transmission is still sliping sometimes. but most of the time is smoth shefting.
  • At what rpm do you feel the power "come on"?
    the power come after 3000 or 3500

Thanks for your concerne, Hope these answers help you to find the power leak source.

Last edited by MAXI; 09-01-2008 at 03:59 AM.
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Old 09-02-2008, 04:15 AM   #10 (permalink)
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Some told me to make a compression test. ( that's good idea )
Some told me may be your TPS?


!!????

Yesterday was trying accelerating from 0 to 100k, it take 11.2-11.6Sec. the is so slow for 2.5L -24valve vanos. Suppose to be better than that. I cleand the air filter which was much dusty. but no thing changed.

let me explain again what happining with me. Read carefully and tell me what do you think the problem.
When I push the pedal to accelerate from 0 the RPM going slow until 3800-4000 then open.
Sometims have vibration while warming up, but it vibrates for a while then gone.
Sometime the trnsmission slip.
Exhaust prussure is very low and has a bad smill like misfire. you feel there is a very very lettle exhaust air comming out when you put your hand infront the tips ( exhaust not clogged ). This let me scratch my head. Where is the emessins of 2.5L engine.Isnt burning any thing.

I have this problem since I bought this car before 10 monthes.
the car got checked ( diagnosed )at bmw maintenace, with no sensors faults!!?
I did tune up and change every thing ( sprk plugs, filters, oils) = nothing changed.got exhaust changed too.

In general, the car Idling steady,No engine check light. these days the RPM rised up to 700, specially after changing the exhaust I note that. but performance is still not good.

I did take a look in engine to see if there is any thing wrong but cant find.

So if the RPM is normal, and diagnostic says no faults, why my car is leaking power?!!

Last edited by MAXI; 09-02-2008 at 04:34 AM.
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Old 09-02-2008, 12:37 PM   #11 (permalink)
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The power range sounds correct. Since the idle is steady I doubt it is a common fault like the maf, o2 sensor, or something simliar. Did you replace the plugs yourself? Did you use the copper +2's? Did you or the mechanic see any oil or gunk in the plugs? Did you/them happen to look at the coils or anything else during the process?
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Old 09-02-2008, 08:14 PM   #12 (permalink)
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Ok... when you say you replaced the exhaust... what part of the exhaust? The muffler? Did you replace the Catalytic converter? It sounds dead ringer for a broken or plugged cat. Get under the car with it cooled off and bang on the Catalytic converter (muffler lookin thingy in the middle of the car in the exhaust). If it rattles, it's bad. If you can't tell that way, take out an oxygen sensor and see if it runs better... if it does, you need a cat.
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Old 09-03-2008, 05:10 AM   #13 (permalink)
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Ok... when you say you replaced the exhaust... what part of the exhaust? The muffler? Did you replace the Catalytic converter? It sounds dead ringer for a broken or plugged cat. Get under the car with it cooled off and bang on the Catalytic converter (muffler lookin thingy in the middle of the car in the exhaust). If it rattles, it's bad. If you can't tell that way, take out an oxygen sensor and see if it runs better... if it does, you need a cat.
I have this problem before changing the exhaust. Replacing the exhaust was one of the solutions which I start with. I have replaced the cat and the rare muffler.
The old stock exhaust sys was bad. That's why I start with it.
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Old 09-03-2008, 05:13 AM   #14 (permalink)
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Do recommande cleaning the MAF.
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Old 09-05-2008, 04:07 AM   #15 (permalink)
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Seems that I discovered somthing.
Yesterday I tryed to take a look and recheck engine hoses again, and I saw that the one hose which is coming from underneath the manifold and stick on the big hose of throattle bore was cracked.
I just tryed to open that big hose of the throattle bore and pul it out, then the 2 hoses disconnected them selve, which means they werent sticking will into their holes, because the two holes which is in the throttle hose was cracked too:.
url=http://up.x333x.com][/url]



I have seen so many carbon mixed with oil became like black silicon inside the throttle bore. I tryed to clean the throattle bore by tissue. but it seems there is more inside the manifold. where is that carb comming from?(is that normal?)




What came in my minde.. if the manifold is dirty like that, how about the ICV and the TPS?

I'm gonna fix new hoses and clean the ICV, but Should I clean the manifold first? Or no need.
What about the TPS, Can be cleand or do somthing for it?
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