poor acceleration after manual trans swap in 325e/m20b27

[Leftlane]

Hello, all. I'm starting to run out of ideas to fix what is a poor acceleration issue which started immediately after I performed a manual transmission swap in a totally stock 1985 325e m20b27. I'm pinning my hopes on r3vlimited after "shopping" forum sites and deciding make my post here. Seems like this is the E30 place to be.

Background
Car ran fine in November '14 when I became its owner. It's been in my family since 1990 and I've got records going back to new. It's got 69k miles, has a full service history, and is very clean. I always liked the car, but never appreciated the fact that it was an auto. Once mine, I drove it for a few weeks to see if I could force myself to enjoy the car even though it was an auto. I couldn't.

It took me a _long_ time to perform the swap to a Getrag 260. My goal was to make the car appear as though it came from the factory with the manual. No intention of heavy modification or the like (at least not at this point in my ownership). Working a few hours on weekends I finally finished the swap with the odd help from friends and family along the way and put the car back on the ground in April of '15. I work slow but try to be methodical.

Problem Description
Starts fine warm or cold. Idles fine. If there's a miss, I can't tell. This is what the Bentley manual would call a "Normal Warm Running/Poor Acceleration" problem.

In neutral (whether in via the shift, the clutch, or both) while depressing the accelerator, the car is slow to climb the tach. Often it stops around 3200 rpms. Often it "flat spots" on its way up to ~4k rpm.

Underway it's much worse. It's as though the car has 10hp. It will eventually make it to 45mph if I have a landing strip's worth of straight in front of me. Intersection stop lights turn back to red before I can make it through the intersection. That kind of slow (yeah, I know it's an eta so slow is the norm <insert slow joke here>).

There is no blow-by at the exhaust or anything to indicate weak compression when looking at tailpipe emission. I will be performing a compression check when I change out the spark plugs.

What's Been Done
- new crank reference sensor and speed sensors (and they spec at ~1080 ohms (so did old ones, though))
- checked the Air Flow Meter for smooth actuation and ohm reading during actuation
- checked fuel delivery per Bentley manaul (30 secs of fuel pump running does indeed produce 30oz of fuel at the regulator)
- replaced distributor cap, rotor, and ignition coil
- dropped the catalytic converter downpipe and ran motor to ensure that it wasn't clogged
- switched out DME (motronic v1.0) unit with another
- replaced oxygen sensor
- intake boot replaced after crack discovered (was hoping this was it, but no)
- checked throttle position sensor per Bentley manual
- checked coolant sensor (the one of four i see on the coolant outlet) seemed okay but might be some jitter here based on ohm readings coming and going (or coulda been operator error)

My Thoughts on Upcoming Checks
- check for frayed/split/nicked wires under-dash where I shoved in the manual pedal box
- pinout motronic wires at the DME to see what's doing there
- pinout idle speed sensor unit (it's separate from the DME in this car)
- look for the magnetic pickup on the single-mass flywheel which should be the "early motronic single mass flywheel". Unfortunately, I only came to be aware that I needed this after installation, but the BMW salvage that put together everything I needed seems to have gotten it correct. I see the pickup in photos I took of the flywheel.
- throw on a new coolant temp sensor just to be safe
- adjust valves
- new plugs and wires (they're on the way). Current plugs are fouled, but I think it's a symptom and not the problem.
- bad gas? It did take 5 months to do the swap. Tank was 1/4 full at time. Put 3/4 of good gas in April.
- fuel injector clean (total shot in dark) and o-ring refresh

Where You Come In
That big brain of yours. I need it. I have simple fists of bacon. Suggest away. I haven't come across a manual swap that created such a condition by virtue of simply changing from auto to manual. I will say, however, that the wiring diagram has some interesting things going on with an automatic car vs a manual. Specifically, it's splitting off a wire from the Park/Neutral shifter (on the auto) to the starter solenoid (an obvious one) and also onto both the idle speed sendor AND the DME. Interesting. One wonders why the DME needs to know if we're in park/neutral for an automatic when neutral safety is being handled by the starter solenoid.

And now, pics :)

[enigmaticdream]

Is the throttle opening all the way? Easy way to check is take the rubber boots off into the throttle and have someone press the pedal down. It should open all the way. Maybe something got messed up during the pedal swap?

[LateFan]

^^^Right… cable length? Pedal mounting? Fittings slipped? Throttle arm or TPS got knocked? AFM is ok you said?

[TobyB]

Boy, if it was a more modern car, I'd say that it thinks it's in neutral, and is mapping the ECU accordingly- but E30 don't do dat shit...

Thoughts-
Mechanically check ignition timing, like with a light?
If it was timing you to TDC, you'd run like this.

Check running fuel pressure?

Release parking brake?

t

[Leftlane]

Is the throttle opening all the way? Easy way to check is take the rubber boots off into the throttle and have someone press the pedal down. It should open all the way. Maybe something got messed up during the pedal swap?

Thanks for the suggestion. I did have the wifey press down on the accelerator while I watched the connecting mechanisms, but I didn't pull the intake boot. Seemed to go all the way to full open. I did have to take off the automatic trans kickdown cable which connected right to this area, which is why I keep thinking about it.

I'll pull the boot and do again just to make sure the butterfly door is fully opening. The throttle switch seemed to spec out okay too.

[Leftlane]

^^^Right… cable length? Pedal mounting? Fittings slipped? Throttle arm or TPS got knocked? AFM is ok you said?

Thanks. For the record, I did not change out the accelerator pedal or cable. However, as noted above, I did remove the auto trans kickdown cable.

I _think_ the AFM is okay based on the fact I saw the ohms dial up as I slowly moved the door by actuating it as much as I could with my finger.

Since then I've seen various videos, like this one and this one that make me think I didn't test the AFM unit as thoroughly as I should have. :/

[Leftlane]

Boy, if it was a more modern car, I'd say that it thinks it's in neutral, and is mapping the ECU accordingly- but E30 don't do dat shit...

Thoughts-
Mechanically check ignition timing, like with a light?
If it was timing you to TDC, you'd run like this.

Check running fuel pressure?

Release parking brake?

t

Appreciate the suggestions. A local reputable independent german auto shop checked the timing as they thought the belt might have busted a single tooth. Told me it was fine. I need to do it myself just to double check as I'm retracing all steps not performed by me.

I sort of left that part of the story out. Local shop had the car 5-6 weeks and couldn't find the problem. They make their money on more recent German hardware these days, not the old E30's, so they were working on it as they could rotate it into the shop between real paying jobs and - much appreciated by me - not gouging me on hourly rates.

They did find a cracked intake boot and replaced it, but sadly that didn't prove to be the problem. Ultimately, they tried as many of the "easy things" as they could think of with this cheaper pricing model before wanting to tear into the trans (bad/wrong flywheel?) or other spendy operations.

So now it's home and up to me to figure it out.

Regarding fuel pressure, I've check the fuel _volume_ but not the fuel pressure. The Bentley manual has you disconnect just after the fuel pressure regulator and run the fuel pump for 30 seconds. It states you should fill 30oz of fuel in a container in those 30 seconds. I filled exactly 30oz of fuel for exactly 30secods of running the pump. That was impressive, actually. So I did not move on to checking pressure, but I suppose I should?

I wish it would be the parking brake, but it behaves this way in neutral (clutch in or gear in neutral position) too. Can't be the parking brake.


I've got a couple days off work coming up and I plan to do these:
- new plugs (got 'em waiting in a box)
- new plug wires
- compression/leak-down cylinder tests
- valve lash adjustment
- while #1 on TDC, pull the bellhousing reference sensor and make sure I can see the magnetic pickup on the flywheel (assuming this is where it would be when #1 is at TDC - feel free to chime in on this)
- more AFM futzery?


Again, thanks for all input. I'll keep this thread updated. Nothing worse than a thread that goes into detail for days/weeks/months and then leaves you hanging at the end.

If all else fails, I'm planning on taking it to a BMW dealer for a thorough cleaning out of my bank account. I really want this car to run properly. I called them and they said they've still got the equipment to work on these cars. My local independent guy did not. He'd "gotten rid of" all his E30 stuff long ago. My sense was that amounted to a spare Motronic computer they had lying about for diagnostic R&R purposes.

[vicecaptainred]

I had the same symptoms (starts but runs poor with no acceleration tops at 45mph) in my '84 (5-speed) after a motor swap from an '86(auto) for the life of me couldnt figure it out. Turned out when i put my single mass flywheel on the '86 auto, the dowel sleeve would only let it go on one way but the reference pin on the outside of the flywheel was 90 degrees behind when the motor was at TDC so i repulled the motor an trans, took out the dowel sleeve, reclocked the flywheel(pin should be in the second CPS hole when at TDC

[Leftlane]

I had the same symptoms (starts but runs poor with no acceleration tops at 45mph) in my '84 (5-speed) after a motor swap from an '86(auto) for the life of me couldnt figure it out. Turned out when i put my single mass flywheel on the '86 auto, the dowel sleeve would only let it go on one way but the reference pin on the outside of the flywheel was 90 degrees behind when the motor was at TDC so i repulled the motor an trans, took out the dowel sleeve, reclocked the flywheel(pin should be in the second CPS hole when at TDC

Thanks and oh dear gawd! This is my worst nightmare and up until I read your reply was only theory because I hadn't read about this even being possible.

Okay, vicecaptainred, bare with me. I've got questions.

Is it true that I should be able to see the sensor/reference pin (a rectangular chunk of metal on the outer flywheel if I understand correctly) when I pull the crank position sensor at #1 TDC and thereby diagnose a good or not-good flywheel setup without pulling the trans first?

Just so it permeates my thick skull: On your second attempt, you setup the engine at #1 TDC and pulled the crank sleeve (on the crank itself) which aligns the flywheel in only one mounting position, repositioned (pounding into place?) it into a new hole on the crank output end which would allow the reference pin to point at the CPS (or where it would be when the bellhousing is in place), and bolted everything back together?

Lastly, you did nothing to alter your "early motronic single mass" flywheel as part of your fix? Just the flywheel-locating sleeve on the crank getting put into the proper position?


I never knew that sleeve could be pulled out but it makes sense that it could. Of course it was in the correct hole for the automatic trans flexplate. I just assumed that would be the same spot for manual trans flywheel, but it seems not. None of the auto to manual trans swaps I've read so far have mentioned this little nuance - but then they'd have to have been performed against an early motronic (v1.0) car to run into this.

[vicecaptainred]

Yes pulling the sensor, if you look thru the hole on the bell housing you should see the pin in the hole with the engine lined up at TDC. if you only have yourself, slide a screwdriver in the sensor hole an slowly rotate the crank(22mm i believe) until you feel it hit the pin. Check location now vs tdc positioning. I did not put a new dowel sleeve back in as it wasnt really needed. Yeah i know, literally no one mentions this but i guess looking back it now....its one of those things you just end up like 'ohhhhhhhhh now i understand' was for me anyways. Pull that sensor and check that pin!

[Leftlane]

TDC and other news

Before I tell you what I found, allow me a few words on finding TDC. So it seems TDC is something of a challenge on these cars... compared to my 350cid Chevy-powered CJ5, anyway. Being an army of one, I found it impossible to turn the motor and hold my finger over the spark plug hole to see if I was on the compression stroke.

I read that you can pull the valve cover and ensure that both rockers on cyl #1 were not being actuated while having the piston at its highest travel. I found this to be easier said than done. I also used the straw trick whereby you use a long straw down the #1 cylinder to determine the piston depth. Various turns of the crank while marking the straw depth against a known point yielded a rough high water mark.

I found in the Bentley manual that there's a TDC locator sensor on the front crank pulley, too. It's not used by the DME. It's used by a special BMW Service-test unit. I don't have one of those, but I do have a silver Sharpie. There's a single hole in the perimeter circumference of the lower pulley where this sensor is mounted up against. I felt like this had to be the trigger for the sensor, so I marked it with a line.

Sure enough, when I used the calibrated eyeball on the rockers and the calibrated straw on the piston depth to get TDC on #1 compression stroke, I looked down at the pulley and saw this:


Woo hoo... theory proved by reality. What could be better?

Now it was time to check the location of the flywheel CPS trigger, if I even had one (i.e., if I had the correct flywheel which I wasn't 100% sure of).

It's funny. The Bentley manual doesn't exact say which of the two sensors mounted near each other is the reference sensor. There's a couple diagrams without a legend telling which end is up (or front, or anywhere). Witness:


With the #1 at TDC I took a shot in the dark and pulled the upper of the two sensors and saw this:

Hmmnnn... flywheel teeth. Must be the engine speed sensor. That's when it clicked that the lower one is actually set back further towards the rear of the car. These two sensors should be referred to as the front and rear sensors because it's this distinction that dictates what they're actually measuring. When the flywheel is mounted to the engine, the magnetic pickup for the CPS is actually more rearward than the teeth of the flywheel. So I pulled the lower...er... rear sensor and saw this:

Hmmnn... hard to see what's going on, but feeling around with a screwdriver didn't reveal any bumps of any kind. So I used vicecaptainred's suggestion and balanced the screwdriver in the port while slowly manually rotating the engine by the front pulley (yes, it's a 22mm nut).

Sure enough while turning the crank something bumped the screwdriver and it fell out of the hole. It took some back and forth with the pulley and the newly created site-hole (it was just me doing the work), but eventually I was able to find this:

That is indeed the rectangular reference pin. Well, at least I've got the correct flywheel for an early motronic. That's the good news.

Here's the bad news. The crank was now in this position:

That's about 180° from where it needs to be.

So thanks to all and especially vicecaptainred for their input. I now know what I need to do. I'm going to go into radio silence for a bit while I slowly pull the trans out and figure out a way to reclock the flywheel so that the pickup is in the proper spot. I'm thinking I'll mark the engine block with the location of the CPS sensor so I'll have something to reference once the bellhousing is out and the crank dowel sleeve is pulled. Since there are 8 bolts, each bolt represents 45° of rotation, so hopefully this method will be exact enough. Is that how you did it, vicecaptainred?

[LateFan]

Very thorough. Good sleuthing.

How did it even run?

[Andy.B]

Boy, if it was a more modern car, I'd say that it thinks it's in neutral, and is mapping the ECU accordingly- but E30 don't do dat shit...

IIRC, e30's DO do that. There is a wire connected to the shift selector that informs the DME when it is in neutral/park vs D/R. It was a while ago that I did a manual swap, but I should have some info here somewhere...

Edit: It looks like OP found their issue anyway. That's what I get for not reading to the bottom of a thread first.

[enigmaticdream]

Nice working figuring out what was going on.

[Leftlane]

IIRC, e30's DO do that. There is a wire connected to the shift selector that informs the DME when it is in neutral/park vs D/R. It was a while ago that I did a manual swap, but I should have some info here somewhere...

Edit: It looks like OP found their issue anyway. That's what I get for not reading to the bottom of a thread first.

I only think I've found the problem. I won't know for sure until I pull the trans, reclock, and all that jazz. I'd be very interested in your experiences with your manual swap as it relates to the DME and Idle Control Unit (for a motronic v1.0 car, naturally).

I am bugged by the fact that maybe the DME but certainly the Idle Speed Control unit (which is separate in a motronic 1.0 unit such as this) needs to know when we're in park or neutral in an automatic application.

Check out these wiring schematics...
Automatic:


Same but for manual (notice how it sends nothing to the ICU regarding neutral):


...page 122, the idle speed control unit showing either autos or manuals:


So it seems to me that the ICU gets a hot/not-hot signal from an automatic equipped car when the key is in run/start depending on if we're in park and neutral or not. It further seems to me that a manual trans equipped car gets an always-hot signal as long as the key position is in run or start on this same ICU pin (pin 7 just south of C131). This suggests a push by the engineers for manual cars that says "meh, we don't really care if a manual is in gear or not, just give this line some juice because the ____________ function isn't important for manuals." Now fill in the blank :)

Can someone with a factory manual transmission E30/325e from 1984 or 1985 tell me if they've got a neutral safety function? I cannot find that such a thing existed in these earlier cars. The pedal box I got did not have a provision for a switch on the clutch pedal, only the switch for the brake pedal for the brake lights. My car starts in gear the way I wired it and I'm starting to believe the factory manual cars did too (which seems weird, but the mid-80s were a different era, I suppose).

Meanwhile, I'm currently corralling my friends for assistance with the upcoming trans pull.