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Skuyler
 
e30 Creates its own rev limiter

1990 325i, roughly 180k. i bought an e36 a few months ago, had this one primarily parked, and drive it about once a week. i've finally gotten off my ass and put forth the effort to get it sold.

the car was my daily driver so i always tried to keep it in optimum condition. well, of course, with a new car in the driveway and trying to sell this one, it decided to make my life hard.

the car has been chipped, which raises the redline to 6900, uses 91 octane, etc. this was never a problem at all, and was actually a great improvement. test driving the car this week, while going towards redline, the car decided to hit a "rev limiter" at about 6500. A few minutes later, getting warmer, it redlined at 5500. Now, I had just seafoamed the car and changed the oil and some seafoam could have still been in the tank. the fuel filter is about 5k old, so it shouldn't be that either.

I highly doubt it is the chip because i switched to an entirely stock ECU and it consistently redlined at 6000 (stock is 6500).

i'm stumped. i pulled the plugs and they look like this. Online picture "reading spark plug" guides compare to being normal and the deposits may be related to the fuel additive that was just in there. i on'y did the first three and then got lazy. I'm going to change them soon anyway

hep. also, please don't yell at me for "gross negligence." i've always tried really hard to make sure the car's in good shape.
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Old 04-05-2008, 10:11 PM Skuyler is offline  
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ZeroCool
 
What's it doing when you say its red lining at these different rpms? Is it just running out of power and not really revving anymore, or is it like hitting a hard cutoff like the fuel cut or whatever it used to do at 6900?

edit: definitely change those plugs
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Old 04-05-2008, 10:25 PM ZeroCool is offline  
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ILuvPussy
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your engine only has 3 spark plugs?
Old 04-05-2008, 10:26 PM ILuvPussy is offline  
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Skuyler
 
lol, only three yeap. maybe that's my problem

no, it acts like it actually has a rev limiter. it will "bounce" off there. i thought it was a fuel issue, yet to diagnose that. it'll hold RPMs at 4-5k consistently without cutting out. i just want to be able to get this car running smoothly and sold!

oh yeah, and right towards the end of the rev range (5k), the power will come in surges. not an even powerband, but surges and flatspots. also, in general, i'm pretty sure its lost power. i could be used to my 328, but this seems slow now
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Old 04-05-2008, 10:30 PM Skuyler is offline  
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That's really weird. Only thing I can think of is a minor crack in the engine
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Old 04-05-2008, 10:58 PM tegandje is offline  
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Lantec
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Quote:
Originally Posted by Skuyler View Post
lol, only three yeap. maybe that's my problem

no, it acts like it actually has a rev limiter. it will "bounce" off there. i thought it was a fuel issue, yet to diagnose that. it'll hold RPMs at 4-5k consistently without cutting out. i just want to be able to get this car running smoothly and sold!

oh yeah, and right towards the end of the rev range (5k), the power will come in surges. not an even powerband, but surges and flatspots. also, in general, i'm pretty sure its lost power. i could be used to my 328, but this seems slow now

uhh..maybe?

If your car has 4 cylinders and only 3 firing may cause a problem?
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Old 04-05-2008, 11:16 PM Lantec is offline  
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Skuyler
 
okay, the car has 6 cylinders and 6 spark plugs. i only pulled three because, well, i got bored of pulling spark plugs. that's an example. look at them all twice if you want
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Old 04-05-2008, 11:34 PM Skuyler is offline  
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looks kinda like burned coolant to me... either that or VERY lean
Old 04-05-2008, 11:44 PM Junkie Mod is offline  
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James Crivellone
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check the following

Fuel Pressure/Flow
Air Flow Meter (AFM)
Speed Reference Sensor (located on the front of the motor, passenger side)

The ECU will ONLY cut fuel (which is done by firing only one set of injectors *1,2,3 and 4,5,6 are fired separately) if the speed reference sensor is indicating 6550 rpm (stock) or ~6900 chipped.
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Old 04-06-2008, 12:02 AM James Crivellone is offline  
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Skuyler
 
speed reference sensor the same as the crankshaft position sensor? because i changed that out (after failure) about 6 months ago. luckily i got a spare AFM just in case and don't know how to check fuel pressure/flow.
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Old 04-06-2008, 01:47 AM Skuyler is offline  
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AFM

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Old 04-06-2008, 03:01 AM chuckybob is offline  
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yoda634
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Are they Bosch Supers - W8LCR?

If not, I know the E30s can be finicky with different plugs. Weird that it would start after all this time with them in there, but it's just something else to think about -- I know my car did all kinds of weird shit when I used platinums for about a week -- rough idle, cut out at high rpms, etc. -- never got the "rev limiter" though.

My first guess would have been ECU, but since you've troubleshooted that possibility, I'm not sure what it would be. Probably hard to tell, but is it maybe just an issue with the tach (i.e., car actually revs to 6900/6500 even though the tach says lower?). I'd kinda guess no because of the fact that it changes as the engine warms up, but that could be another possibility.

I'd ask over at r3vlimited.
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Old 04-06-2008, 04:05 AM yoda634 is offline  
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mctwin2kman
 
Check Cat! Seems like what happens when it clogs.
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Old 04-06-2008, 11:45 AM mctwin2kman is offline  
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I'd be checking r3vlimited or e30tech bro

ran the heck out of my e30 eta today, pulled the plugs because i just chipped her and i gotta say, heck of a motor.
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Last edited by testshootcom; 04-06-2008 at 01:58 PM..
Old 04-06-2008, 01:42 PM testshootcom is offline  
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Quote:
Originally Posted by yoda634 View Post
I'd ask over at r3vlimited.
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Old 04-06-2008, 01:52 PM Neo-Tokyo is offline  
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