My continuously problematic 525i

Hello everyone, I know I have posted about this issue before but that was long ago and I'm still having problems, so here I am. I'm really losing my sanity with this car, many times have I considered selling, only reason I didn't is because I would never get near what I put into it. I've had a love/hate relationship with my E34 since I bought it, lots of love, and lots of hate. Right now, it's hate.

So as some of you may know I had a misfire a while back, one which I thought was resolved, it wasn't. I'm going utilize some listing action to make this post as easy to understand as possible, here goes.

SYMPTOMS
-Difficulty starting when cold, long cranks but still starts, starts much quicker once hot
-Seemingly random "COOLANT LEVEL" notification when turning the car off
-Poor fuel economy, 15-16mpg, about equal highway and city driving
-Misfire when below 2000rpm, occasionally above but much less often, also seems to be correlated with medium to fast acceleration
-Idles fast at first, about 1100rpm, then usually settles to 700rpm after a few seconds, sometimes will continue to rise to 1500rpm
-Frequently hesitates when starting off, when letting off the clutch it jumps forward a bit then takes off like normal
-Closing the throttle when cruising will sometimes cause it to rock forward because it decelerates so fast
-Feels like there's a bit of power that's being held back, not too much though
-Occasional groaning inside the dash that varies with rpm, lasts only a few seconds

I'm fairly certain those are all the symptoms, I'll be sure to add more as they arise. Now, so no ones throwing out things I've already done here are two more lists to make life even easier!

IGNITION
-NEW coil
-NEW wires
-NEW plugs
-NEW distributor
-Crank sensor

FUEL
-NEW AFM
-NEW fuel pump
-Fuel pressure regulator (already ordered)
-Injectors
-Idle control valve
-Throttle position switch
-Engine coolant temperature sensor
-Oxygen sensor

I remember the misfire thread. I dont know if this was discussed or not but I am very perplexed by your situation and theres no harm in a suggestion...

Battery?

When was the last time it was changed? how old is it? Are we so close to the forest that we can't see the trees...

EDIT: I see you have Spark and Fuel lists but no Air. I know its not a major player in a misfire situation but it doesnt hurt to look at the quality of the air filter.

Originally Posted by Monsignor

I remember the misfire thread. I dont know if this was discussed or not but I am very perplexed by your situation and theres no harm in a suggestion...

Battery?

When was the last time it was changed? how old is it? Are we so close to the forest that we can't see the trees...

EDIT: I see you have Spark and Fuel lists but no Air. I know its not a major player in a misfire situation but it doesnt hurt to look at the quality of the air filter.

Battery and air filter were replaced no more than 2 months ago. At this point I'm beyond confused with this car I'm probably just gonna end up throwing parts at it until it's fixed...

By now I wouldn't even call that reckless considering there aren't many parts that I haven't replaced.

Well a miss is either fuel or spark and it looks like you covered everything. I would check the leads to the injectors see if there is any wear or cracks in the insulation on the wires also check the grounds. The way i check is disconnect while the engine is running if the miss gets worse then its working if it doesnt you know you have a problem do the same with the plug wires

How is the power on the car? Do you feel the engine is lacking power?
Do a compression test?

Originally Posted by cutter67

Well a miss is either fuel or spark and it looks like you covered everything. I would check the leads to the injectors see if there is any wear or cracks in the insulation on the wires also check the grounds. The way i check is disconnect while the engine is running if the miss gets worse then its working if it doesnt you know you have a problem do the same with the plug wires

On M20 engines you can't disconnect injectors individually, but I've done this test with my plug wires but each cylinder had the same effect.

Originally Posted by kelhasna

How is the power on the car? Do you feel the engine is lacking power?
Do a compression test?

I did a compression test and read about 175psi all around.

Since you guys brought it up I guess I will run both of these tests again, just to confirm

I have a jumper harness for the injectors sorry....is this just a high rpm miss or at low rpm's miss? Or is it constant i read where you said 2k or lower but sometimes higher. If it is a lower you should be able to find the the dead spot by pulling the sparkplug leads

Didn't you recently change your fuel injection system, and got yourself a new chip and a free flow maf to replace the stock afm ? Could there be something wrong with all that?

Okay so, I've decided that the "cold start" problem may actually be a result of not retaining fuel pressure, I recently noticed there was a small crack in the fuel line connecting to the rail. I'll fix that soon and see what effect it has. The misfire has miraculously gotten much better, but still exists, and my miles per gallon hasn't improved a bit. Given that Should I be looking for a faulty O2 sensor? There is no check engine light but I don't know when it was last changed so it could be clogged up.

O2 and check charging voltage.

Originally Posted by BMWFatherFigure

O2 and check charging voltage.

I apologize if this is a stupid question, but what would charging voltage have to do with it? The battery light isn't on and I've replaced the alternator brushes so it should be good, but I suppose it never hurts to check.

So my new fuel pressure regulator from Ireland Engineering came in the mail today I'll install it as soon as I can find a good place to mount it, hopefully tomorrow. Also I tested the output voltage of my alternator and got a little over 13.9V so that checks out. I did a power balance test as previously suggested and each cylinder had basically the same effect, number 3 MAY have caused a bit less of an RPM drop, but that's probably just my mind playing tricks on me. She drove quite a bit better today, at least that's how it seems, MPG is still way down. I ordered a new O2 sensor in hopes that's my problem, which I suspect it's at least part of it. Will check compression and vacuum tomorrow if I have time too.

Okay so my O2 sensor came in the mail today, I got it installed and it's made quite a big difference . My MPG has gone up from about 16.5 this morning to 23.0 tonight, and this misfire has gotten much better. The idle is now very consistent and the hesitation is almost completely gone. Still seems like there's more power to be had though. Still very long cranking to start, but I've decided that must be a loose connection on my new fuel pump, since the problem didn't exist before that.

It seems like now the misfire almost exclusively occurs with light throttle, particularly at low RPM as usual. I'm no expert on diagnosis solely based on sound but to me it sounds like it's too rich. I still plan to do another compression test soon, very hopeful that's all good. Also I want to bring her in for a valve adjustment and see whatever wisdom they can give me.

Here are the things I haven't replaced:
CPS - I have a new one, but mine tested okay so I left it.
ECT - Tested multiple times, seems good.
TPS - Tested, probably should adjust WOT setting.
ICV - Cleaned and tested, works fine.
Fuel pressure regulator - I also have a new one, just need to find a place to mount it since it doesn't sit on the rail like it should.

Agh, double posted