Hi - my '91 vert (m20b25) has just begun stumbling a bit. It's barely noticeable at idle, but more pronounced under rev's above 3k. It had fresh plugs at the t/belt-change last year, and had run fine since, over the last several thousand miles.
No apparent vacuum issues - per spray tests - and/but it just doesn't "feel" that way; more like a misfire or injector. I did run some upper-end cleaner through it, with no improvement. The sense of it (from back-in-the-day) is spark... I'll check for arcing, and maybe toss in new wires and plugs for fun, but assuming that doesn't do it:
Since it doesn't have coil-packs, does the main-coil/dizzy typically begin to fail like this? How about a cam sensor? I have the Bentley's but that (nor web-crawling) has not yielded much guidance for a analytical process-of-deduction!
Thanks in advance for strategy and guidance, amigos!
Hesitation/Misfire - logical troubleshooting strategy...?
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paultv
- E30 Zone Squatter
- Posts: 1541
- Joined: Mon Apr 21, 2014 11:00 pm
- Location: Auf dem Schnee: Germany
Cleaning the rotor and points inside the distributor has significant effect on smooth running, even after a few thousand miles - make sure all is clean and shiny - also the carbon brush - springy and clean?
Obviously plugs may be an issue, but I'd check the leads carefully - measure resistance if you have a meter - to confirm the cables are good - ( they have an internal resistor before the plug socket so you should get about 6k ohms IIRC but check they are all the same ( except the coil to dizzy which should be 2K ohms ) - bend the cables looking for cracks and search for arching -
If you get new cables, buy an oem set - they'll last for years.
Poke around the coil for anything loose ( engine off cos it really hurts if you get a belt ! )
Have you cleaned the injector socket under the inlet manifold - common problem with water and oil corrodes the connections.
As a check up - measure resistance hot and cold of the Blue temp sensor at the ECU for clearest results.
Paul
Obviously plugs may be an issue, but I'd check the leads carefully - measure resistance if you have a meter - to confirm the cables are good - ( they have an internal resistor before the plug socket so you should get about 6k ohms IIRC but check they are all the same ( except the coil to dizzy which should be 2K ohms ) - bend the cables looking for cracks and search for arching -
If you get new cables, buy an oem set - they'll last for years.
Poke around the coil for anything loose ( engine off cos it really hurts if you get a belt ! )
Have you cleaned the injector socket under the inlet manifold - common problem with water and oil corrodes the connections.
As a check up - measure resistance hot and cold of the Blue temp sensor at the ECU for clearest results.
Paul
4th May 1990 325i Convertible.
BMW E30 Cabriolet Best Mod Ever:
https://bmwe30cabriolet-wdm.blogspot.com/
BMW E30 Cabriolet Best Mod Ever:
https://bmwe30cabriolet-wdm.blogspot.com/
Hi paultv,I've got the same sort of problem ie at around 1500-2000 rpm or rolling off the throttle mine misfires and kangaroos,I've tried countless things.you mentioned cleaning the injector socket which I have heard of before, but how do you clean it. The bottom part of the socket which is in the bracket doesn't seen to separate from it.Going back to cleaning am I cleaning the connectors? or the soldered joints? Many thanks.
Born on the 23 April 1990 320i Alpinweiss ll kabriolett! (SOLD BUT NOT FORGOTTEN !)
The Bentley does have some good troubleshooting guides in the 'Driveability' section iirc.
After that I would be just going through Fuel, Air, Spark; as you have been.
Since it's more noticeable above 3k, I'd probably be starting with fuel, by checking pressure at the rail and maybe changing the filter(s).
Then air flow,
Is the AFM flap opening freely?
Is your air filter fresh?
Multimeter can check alot of things quickly - resistance on coil, injectors.... etc. (though resistance doesnt always tell the whole story)
After all that there's the AFM track, TPS and some other common things to check.
Foe electrical stuff, use this;
http://www.armchair.mb.ca/~dave/BMW/e30/
So, maybe not a perfectly systematic approach but better than throwing money at the problem.
After that I would be just going through Fuel, Air, Spark; as you have been.
Since it's more noticeable above 3k, I'd probably be starting with fuel, by checking pressure at the rail and maybe changing the filter(s).
Then air flow,
Is the AFM flap opening freely?
Is your air filter fresh?
Multimeter can check alot of things quickly - resistance on coil, injectors.... etc. (though resistance doesnt always tell the whole story)
After all that there's the AFM track, TPS and some other common things to check.
Foe electrical stuff, use this;
http://www.armchair.mb.ca/~dave/BMW/e30/
So, maybe not a perfectly systematic approach but better than throwing money at the problem.
-
paultv
- E30 Zone Squatter
- Posts: 1541
- Joined: Mon Apr 21, 2014 11:00 pm
- Location: Auf dem Schnee: Germany
The bottom half should pull down from the bracket, once the top half is unscrewed - maybe its seized up.
Once separated, inspect the pins and sockets, clean with electrical cleaner aerosol switch cleaner if you have it - also brake disc cleaner will wash away grease and goo very efficiently, if the pins and sockets are corroded, clean with a finely rolled up piece of 2000/3000 grit wet and dry - making an inside grit roll for the pins and an outside grit for the sockets - use with switch cleaner as a lubricant and do this sparingly - you don't want to remove all the flashing on the pins.
Check the solder joints - if its all rotten you can hard wire the cables and remove the socket all together - it's still possible to buy the pins/sockets - as it is for the door pillar connectors - and you need a tool to get the pins out - re solder and so on - best to remove the injector rail to go this root.
Once separated, inspect the pins and sockets, clean with electrical cleaner aerosol switch cleaner if you have it - also brake disc cleaner will wash away grease and goo very efficiently, if the pins and sockets are corroded, clean with a finely rolled up piece of 2000/3000 grit wet and dry - making an inside grit roll for the pins and an outside grit for the sockets - use with switch cleaner as a lubricant and do this sparingly - you don't want to remove all the flashing on the pins.
Check the solder joints - if its all rotten you can hard wire the cables and remove the socket all together - it's still possible to buy the pins/sockets - as it is for the door pillar connectors - and you need a tool to get the pins out - re solder and so on - best to remove the injector rail to go this root.
4th May 1990 325i Convertible.
BMW E30 Cabriolet Best Mod Ever:
https://bmwe30cabriolet-wdm.blogspot.com/
BMW E30 Cabriolet Best Mod Ever:
https://bmwe30cabriolet-wdm.blogspot.com/
Since it doesn't have coil-packs, does the main-coil/dizzy typically begin to fail like this? How about a cam sensor? I have the Bentley's but that (nor web-crawling) has not yielded much guidance for a analytical process-of-deduction!
our cars don,t have a cam sensor. as a modern vehicle would.
they have the cid lead from the last cylinder 4 / 6 plug lead depending on engine 4 or 6 pots.
a lot of after market h/t leads have this missing. which tell ecu which piston is at tdc , more info on here wiki cid
our cars don,t have a cam sensor. as a modern vehicle would.
they have the cid lead from the last cylinder 4 / 6 plug lead depending on engine 4 or 6 pots.
a lot of after market h/t leads have this missing. which tell ecu which piston is at tdc , more info on here wiki cid