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Discussion Starter · #1 ·
Hey guys I need some diagnosing help on my 94 325IS. Ok first let me tell you the problem. The acceleration is to the point a geo might be able to keep up with me. Its really terrible. 0-60 is probably like 10 seconds now. Once I get up to 50-55mph it feels like it has a noticeable more amount of power, but nothing like it should be. On the highway if I'm in 5th and down shift to 4th, theres no acceleration at all really..and it really doesnt want to go past 4000 RPM, but it does and its really loud like the engine is being strained. The check engine light wasnt on, but I decided to see if there were any hard faults stored with my peake scan tool and there was code 45 - KNOCK SENSOR for cylinders 4,5,6. I'd been running 93 octane before the gas prices went up but then switched to 89 so I was thinking maybe I accidently grabbed the 87 handle??or got a bad batch of gas. But I ran all that gas through, put in some Lucas Octane booster and still no improvement. It sounds to me like it could very well be the Knock Sensor. I know if the Knock Sensor detects a sprak knock, the ECM retards the ignition timing to prevent major engine damage. So if the sensor isnt working..then i guess the ECM would keep the timing retarded as a safety feature to prevent engine damage??I'm almost embarassed to drive it right now because its soo slow. Please HELP!!!! Also..if it is the knock sensor..is there any way to replace it with the intake on?? That just seems like way too much work to remove.
 

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Hey buddy

Although it could be the knock sensor, i would actually put my money on the O2 sensor myself

Do you have any starting issues as this could be a crankshaft position sensor problem.

Have you cleared the Knock Sensr issue and taken the car for a run and seen if it comes back?
 

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Discussion Starter · #3 ·
No I havent fixed the knock sensor. I'm a little strapped for cash right now, but when I do have money to fix it I'm replacing both of them and any vaccum hoses/etc. I do know that the O2 Sensor needs to be replaced, but I dont think It would be giving me the problem I have now. Could be wrong..plus after I replaced the head gasket in '05 I use to get a Lambda code for the O2 sensor, but not recently. The only code I had was for the Knock Sensor. I'm betting that its cracked like alot of the ones I've read about. But before I do anything else, I'm about to go take a look at my spark plugs and go from there.
 

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O2 sensor on the blink will cause the mixture to be rich or lean and the car simply cant accelerate.

Clear the knock sensor code and re-start the car. See if it comes back mate.
 

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Discussion Starter · #5 ·
yeah I cleared the code. It hasnt come back yet. Maybe the lower octane gas might have set that code off. I'll check the plugs and go from there.
 

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Discussion Starter · #7 · (Edited)
Well I checked all the plugs. They all look good. I did however swap out #4,5,6 plugs to see if that would help, but it didnt. I took it out on a few test runs, but its still very very slow. The knock sensor code hasnt come back yet. I've noticed a noise I cant remember hearing before this..its not a ticking/clicking kinda noise either. Its more like a deep "whoommpf" when I accelerate. Almost sounds like the exhaust is coming from under the hood.Thats the best i can describe it really.It also does sound like a vaccum leak. I figured if there was a vaccum leak It'd run really crappy(barely idle) or keep cutting off. The car idles perfect..My car is just hesitating ALOT..and its just not wanting to go past 4k most the time!!!LoL .I have been looking for any loose wires,vaccum leaks, but its really hard to see much under the intake manifold. I'm really stumped right now. No Check engine light on- No codes. Oil/fluids look good. Spark plugs look good. WTF!!
 

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The sound is the engine being choked i recon

O2 and camshaft sensor mate. Not a massive cost so dont worry
 

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Discussion Starter · #9 ·
Now I'm wondering If it could just be the fuel filter? 134k Miles and i know it hasnt been replaced since I've had it and no records of it being done. I have from time to time and more recently been putting fuel additives in. Usually Lucas "tune up in a bottle" or redline fuel system cleaner, so maybe the filter is clogged? THat wouldnt set of the check engine light. The o2 sensor and camshaft sensor should/would trigger the check engine light. I think I may try the fuel filter. Its only $15 and a small P.I.T.A but its worth a shot.
 

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Discussion Starter · #10 ·
I'm now thinking that it might be a clogged Catalytic Converter. Now that I think about it, I'd been hearing a rattling noise usually after letting of the accelerator pedal after accelerating. And Also I had smelled the "rotten egg" sulfer smell a few times before. I put a rag in the left exhaust tip and reved to 2-3k and the rag flew out. I put it in the right side and the rag didnt move even all the way up to 4k..where the car seems to redline now.
Here are the symptoms:

-The acceleration is very dead all the way through
-The Car slows down up hills even with the pedal to the metal (i.e I will have the cruise control set to 70 and when I go up a hill it might drop down to 55 even if i floor it. Downshifting doesnt do anything but make more noise.

Someone please help!! I really need to fix this but I dont know where to begin. I dont want to just start throwing expensive sensors and parts at it. Any help at all would be greatly appreciated!!
-
 

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Discussion Starter · #11 ·
Its really sounding more like a clogging catalytic converter now, but I bought a fuel filter I plan on replacing tommorow at work. If that doesnt do the trick, I'm gonna take out the cat and see if that fixes it, if it does then I'll be gutting that bitch out. No way am I gonna pay $5-700 for a new one. If any one has ever had problems with their cat clogging up please let me know what your symptoms were. Today I noticed a whistling noise with the accelerator that wasnt there before which is another sign of a bad cat..so I really think thats the issue here. I'll keep you guys posted.
 

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Discussion Starter · #13 ·
I know gutting the cat may reduce back pressure and make the car slightly louder, but I'm wondering if it would give me any more mid-top end power?
 

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I would bet you money if you don't find a plugged cat (I forget what mileage you have) that you have the classic bad coil. You can not diagnosis this problem. The tests on Bentley are for only the primary coil and only replacing the coil will test the secondary coil.
If the cat is ok then I would put money on one coil being bad. You car is notorious for an occassional bad coil.
You can buy a good used one that is known to be ok and then start with 6 and work back swapping them in and out until the hesitation goes away. I trusted Bentley, they were wrong and Mike Miller on the Roundel tech talk posted that there is no way to test a bad coil right after I bought two and replaced 6 and 5, no hesistation car runs like a bat outta hell again.
Good luck...
 

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ummm, to be honest it sounds like transmission to me... do you have a stick or automatic? an automatic, your transmission could be failing-- it's not being able to shift into second fast enough, but then again, my car moves up 0-60 pretty darn fast
 

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I'm now thinking that it might be a clogged Catalytic Converter. Now that I think about it, I'd been hearing a rattling noise usually after letting of the accelerator pedal after accelerating. And Also I had smelled the "rotten egg" sulfer smell a few times before. I put a rag in the left exhaust tip and reved to 2-3k and the rag flew out. I put it in the right side and the rag didnt move even all the way up to 4k..where the car seems to redline now.
Here are the symptoms:

-The acceleration is very dead all the way through
-The Car slows down up hills even with the pedal to the metal (i.e I will have the cruise control set to 70 and when I go up a hill it might drop down to 55 even if i floor it. Downshifting doesnt do anything but make more noise.

Someone please help!! I really need to fix this but I dont know where to begin. I dont want to just start throwing expensive sensors and parts at it. Any help at all would be greatly appreciated!!
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As a side note for the exhaust deal, if you have stock exhaust, as I understand there is a baffle in the right exhaust pipe that only opens above 2500 RPM, so that wouldn't necessarily mean the right cat is bad if that's the problem, although it could be.

What about your fuel pump? Perhaps it is beginning to fail. Of course, a fuel filter on 134k could be clogging up too, but I doubt that would give you that many problems. Then again, I don't think the fuel pump would give that many symptoms either.

Still no codes?

ummm, to be honest it sounds like transmission to me... do you have a stick or automatic? an automatic, your transmission could be failing-- it's not being able to shift into second fast enough, but then again, my car moves up 0-60 pretty darn fast
It's not the tranny ;)
 

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Discussion Starter · #20 · (Edited)
So I replaced the fuel filter yesterday at work. The old filter was a BMW one that had a July 2000 date stamped on it. It was definately clogged up, but my problem didnt seem to go away at all. On the lift yesterday I found that my front struts are busted and leaking like crazy so thats a good $150-200 a piece right there. If I need a cat as well I might end up selling it. I understand that a bad coil would cause some hesitation, but unless I have 2-3 bad coils, I dont see how one bad coil would cause the problems I'm having. The problem seemed to be worse yesterday. About the fastest I could go on the highway was 55! And also I noticed that the MPG gas guage fluctuates and the cars feels like its surging back and forth. Upon talking to several other mechanics, most of which are ASE certified, the seem to think if it was the cat going bad that the check engine light would come on by the O2 sensor. I did have the code 'Od' from my peake scan tool for the o2 sensor about a year ago, but i never replaced it. I cleared the code and it hasnt come back up since. If the cat was clogging up the o2 sensor should be going haywire and the check engine light and code should come back on. Im pretty sure its gotta either be a clogged/clogging cat, fuel pressure reg/vaccum lines,fuel pump going bad ,bad coil(s) or a sensor or two not working right. But again..no check engine light and no Codes still. Wouldnt a bad coil usually illuminate the check engine light as well? I'm not really in a position to be throwing parts at it right now, but I'm still thinking the cats are bad anyways with 134k..but then again thats alot of money ($400-700)to guess the fix.
 
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