Pinging under load 1986 325e 180,000

[kjard_us]

Quick question... I have already replaced the AFM and checked for air leaks in the system. Idle is fine acceleration in first is fantastic for a car with 180,000+. However if I open the throttle too much in higher gears I get the little old pitter patter of light pinging and god awful acceleration. If I gently open the throttle it accelerates smoothly without pings.

Currently using 87 octane gas.

Fuel pump is in unknown condition but makes bad sounds. I also believe there is a very small leak back there. So small it evaporates before I can find it.

O2 sensor seems to read OK from my simple testing. no idea how old it is.

Any ideas? I dont think it could be the o2 sensor since that shouldnt be affecting anything while under heavy acceleration....

Thanks!

[kjard_us]

After driving around a bit it really appears to me that the fuel smell is coming from the exhaust... I believe it is from braking using the engine before a stop. This is not normal right? Also brand new bosch platinum 2 spark plugs and the old spark plugs looked great. I will fill it with premium gas tomorrow.

[Jon_Bmw]

87 octane, jesus where are you dude?

I would think that 87 octane and the hot weather(possibly depends where you are) are not helping things

[kjard_us]

Ahhhh... Well I am in Washington DC and it is hot, humid, and in the nineties (32-35 C). Did I also mention there is corn in the gas here?

I am going to fill it up with 91 octane today and keep my fingers crossed.

I really didnt think octane could be responsible for such awful performance but I guess my only other 'real' car was a 72 opel gt.

Thanks...

[Jon_Bmw]

Ahhhh... Well I am in Washington DC and it is hot, humid, and in the nineties (32-35 C). Did I also mention there is corn in the gas here?

I am going to fill it up with 91 octane today and keep my fingers crossed.

I really didnt think octane could be responsible for such awful performance but I guess my only other 'real' car was a 72 opel gt.

Thanks...

Its probably not helping thats for sure, for £20 it would be worth trying anyway. You said it was a 325e, so that only revs to 4500rpm doesn't it? So where does it pink what rpm and what gears?

[buster]

sounds like the low octane fuel is causing this.
It should be fine on 91

[kjard_us]

Just put the 91 octane in and the car runs better all round but the ping is unchanged. It really almost feels like a bad accelerator pump (if it were a carb). And yes it is a stock 2.7 eta engine.

The pinging occurs only when in gears 2345 and happens around 2k - 3k. (edit: it will happen lower as well, it is not really rpm dependent, just throttle dependent)

If I rev up to 4k in first and shift into second any immediate jump on the gas will cause hesitation. If I gently give it gas in second it will accelerate nicely. Again if it were a carb I would say it is the accelerator pump. Is there some kind of equivalent on the motronic? I listened for the click on the TPS and it sounds good but I have not checked it with the ohm meter yet. Could that be it?

[buster]

maybe a blocked fuel filter.When was it last changed ?

[kjard_us]

Just ran all the diagnostics on the TPS and it is clean and working great. 5v going to it and the behavior of the switch is spot on with the specs. Also runs like crap when I leave it unplugged and operate the engine.

I will check that vacuum line.

I hope it is just the fuel pump. Still a pretty expensive bit of equipment. May have to drive like Grandma for a little while. No idea on the filters. I will go for that first I guess. Anybody know the secret to getting that POS out of the engine bay on an 86 325? Hire a garden gnome with skinny little hands?

[kjard_us]

Further news.... I checked the fuel pressure regulator vacum hose and it is good with strong vacum at the regulator. Regulator looks okay... but get this... When I unplug the vacum hose and plug it the engine runs just like it always does. According to the books my idle should be rough with low rpm issues while driving.

Now... this makes me believe that it is a fuel pressure issue.

Does this seem right to you guys?

I bought a new fuel filter and will install it tomorrow.

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http://141.161.196.100/cgi-bin/car.pl

[kjard_us]

Changed fuel filter. Idle is stronger (up to 750-800 now), cold start is better. Power is there when accelerating, but under heavy acceleration the little pitter patter is still there.

As time and money come in I will begin checking/replacing the fuel pumps.

[buster]

maybe the regulater itself ?

[kjard_us]

Is that common? I guess a failed spring in the regulator would divert the gas back to the tank. Do you think its safe to squeeze off the return line and try that?

I am going to recheck the new (reman) afm. I will kick myself if that is causing it.

[kjard_us]

Also took it for a long highway drive today and the top speed is like 110kph. No guts at all up there. Couldnt climb hills at speed. Nothin. Uggh.

[kjard_us]

I did some preliminary troubleshooting on the AFM and it seems to be working.

Does anyone know what the symptoms are of ....

a) A dead or dying fuel tank pump.

b) A dead or dying external fuel pump.

c) Injectors that should be taken out behind the barn and shot.

I have a 1 yr warranty on the AFM so I have some time to return it.
The external fuel pump looks original, and for that matter the fuel filter looked original.

Also, does anyone have any ideas on how to test the fuel pressure regulator?

To better define the symptoms..
No power at high speeds.
Usable power up til 40mph.
Very lite pitter patter pinging (not strong knocking or detonation) under heavy throttle.
Along with the pitter patter there is no power. To accelerate I have to let off the throttle till the pinging stops than slowly allow it to accelerate and give it ever increasing throttle. This stops working at highway speeds.

Thanks you guys are great.

[kjard_us]

Things do appear to be getting worse but some problems did go away with the new afm. I think I will return it later and pay the extra for a brand new one.

You make some very good points. The pressure 'seems' to be OK considering how much pressure was left in the lines even after running the engine to a stop (fuse 11) when replacing all the hoses. I could imagine a situation where the lift pump has failed and under high demand for fuel the external is no longer able to draw enough out.

Thats an expensive piece though....

I think I will pinch the regulator tomorrow. I noticed that it doesnt fly up to revs like it should when I just pull the throttle by hand while idling. I just get the deep and loud BWWWWAAAA sound from the intake and the engine revs up much slower than it should. Again exactly like a busted accelerator pump on a carb. This could be either but the regulator should have an instant effect when vacum drops that suddenly.

I would just bring it in to the bmw garage, but I have to drive to New York on thursday and there is no time for an appointment (300 miles). Thanks for the suggestions.

[kjard_us]

ugggh.

I replaced the pressure regulator. Little better.

I replaced the dead fuel tank pump. Just a very little better.

I will now drive the gutless wonder through the mountains of Pennsylvania and try to get the external fuel pump replaced in New York.

Not Happy.

It really feels like the engine wants to scream, it doesnt seem fundamentally trashed. Very smooth and strong through the upper rpms (under low throttle). No smoke whatsoever and very little noise from rocker arms or other scary engine sounds.

If I replace the external pump and the engine still performs like described above, what other options do I have? Could this be caused by the reman AFM?