really weird issue

[bmwman91]

Crazy. Try popping the cover off and getting a peek inside. You might be able to fix it by cleaning the track and adjusting the radial position of the wiper. If there's any definitive damage, I would be curious to see a pic of it.

[ThatOneEuroE30]

Crazy. Try popping the cover off and getting a peek inside. You might be able to fix it by cleaning the track and adjusting the radial position of the wiper. If there's any definitive damage, I would be curious to see a pic of it.

I had cleaned it once so inside is nice and clean. Are you talking about take the black cover off and messing with the dials to see if it comes back to life? My plan is to go get a buddies afm later today make sure its in working order and then put it on and see what happens. If it fixes it. Im going to buy a couple used ones to have around. Might try and pick a dme as well. I need to start stock piling m42 parts

[ThatOneEuroE30]

scratch that thought ifound the issue to be the afm it is not. I thought ohm meter had to be set to ohms not kilaohms. restested and its good. got engine code
1215 though

[ThatOneEuroE30]

Tested and cleaned the tps and icv still have issue. Idle got a little better and the engine light went away but still has no power when trying to drive it and headers get hot

[bmwman91]

Intake air temp sensor? You should see ~2.1kOhm at 25degC. Maybe it had an internal short, making the ECU think that it is super duper hot out, which would cause a greatly reduced quantity of fuel to be injected.

[ThatOneEuroE30]

Intake air temp sensor? You should see ~2.1kOhm at 25degC. Maybe it had an internal short, making the ECU think that it is super duper hot out, which would cause a greatly reduced quantity of fuel to be injected.

Where is that located. You sure thats on m1.7 cause I’m not seeing anything for it in the bentley manual

[ThatOneEuroE30]

I tested coolant temp sensor found out thats what you mean. It has .776 kilaohms with the engine semi warm not to omp temp though

[roguetoaster]

There is an air temp sensor as part of the AFM.

Bmwman could be on to something here.

Would think that a CTS only determines open or closed loop, or a range within on more advanced systems.

[ThatOneEuroE30]

There is an air temp sensor as part of the AFM.

Bmwman could be on to something here.

Would think that a CTS only determines open or closed loop, or a range within on more advanced systems.

i tried a second AFM that was tested and working and got the same result. I tested the coolant temp senor and got .771 k Ohms thats in spec correct? the engine was barely warm like just registering on the temp gauge


i pulled the trigger on an oscilloscope so i can see how every things is functioning not just test to see if its in spec

[bmwman91]

OK, so if the AFM swap did not help, then it can't be the IAT sensor.

So red hot headers should only be the result of one of two things:
1) Lean mixture
2) Exhaust blockage

It would seem that you have ruled-out #2. So if it is #1, then let's look at what can cause it. M1.7 uses a few things to determine the fuel injection quantity. Those are:
- RPM (via crank position/speed sensor)
- Air flow sensor
- IAT sensor
- CLT sensor
- O2 sensor
- Throttle position

RPM + crank angle is the biggest and most important factor of all, for every aspect of operation. This effectively ends up as a digital frequency signal in the ECU, and if the sensor or toothed wheel were going I think that you would find the car running very poorly or not at all. Now, if the toothed wheel somehow got damaged when you removed the lower timing cover to replace the gasket, this MIGHT be it. See this thread for the symptoms of a failing one:

https://www.r3vlimited.com/board/showthread.php?t=414344

It might be this, although I am not sure if the lean running can be due to this. If you are idling below 500RPM, then flashing dash lights make sense because the ECU is switching between Accessory-II and Run modes (the ECU suspects a stall, which again could be from a failing damper wheel causing tooth-sync losses). IMO this is the least desirable cause since the dampers are $$$$$, and a big pain in the ass to remove/reinstall!

You can check this with the little scope that you are buying (and it is always good to have one!). Little wires can carefully be shoved into the ECU connector housing so that you can scope the crank sensor signal. It may be noisy from ignition and stuff, but it should look like the stuff in here:

https://www.r3vlimited.com/board/showthread.php?t=374858

If it is super noisy, and you can export the scope captures to your PC (CSV/Excel/etc), I can help you to filter them if you need.

Air flow is the single largest determinant of the load variable, which is proportional to the injected fuel quantity. It would seem that the sensor itself is not the issue. That leaves a couple of possibilities: a MASSIVE vacuum leak which effectively circumvents the AFM, and damage somewhere in the wire harness coming from the AFM. Maybe try to check for continuity between the pins on the AFM plug and ECU plug ends (M42/M1.7 wiring diagrams here: http://www.armchair.mb.ca/~dave/BMW/e30/e30_92.zip).

Next would be the IAT sensor since this enables the ECU to convert volume air flow to mass air flow (since the quantity of fuel to inject is calculated as a mass). In this case, if the wire harness broke, the ECU would think that the air temp is very very cold, and lead to rich running. It wouldn't hurt to check continuity between plug ends anyway since it is part of the AFM.

The CLT sensor really only is used to tell the ECu if the engine is up to operating temp or not. Generally when these go bad you run rich.

The O2 sensor can have a big effect on fuel economy, but the ECU would (I think) toss an error code way before you ran so lean as to lose all power and get the headers red hot. IIRC, the limits on O2 feedback correction are plus/minus 25% of stoich, so if it was totally messed up you would get an O2 sensor CEL code. Since unplugging it made no difference, it is probably not this.

The TPS is mainly used to switch between maps in the EPROM, and while I suspect that it has some enrichment function on its own, it is not as critical to operation as other things. Or at least not enough to cause your problems.


Lastly, what condition where the 19# injectors in when you bought them? It is a huge long shot, but maybe one or two of them have clogged or sticking valves?

[ThatOneEuroE30]

OK, so if the AFM swap did not help, then it can't be the IAT sensor.

So red hot headers should only be the result of one of two things:
1) Lean mixture
2) Exhaust blockage

It would seem that you have ruled-out #2. So if it is #1, then let's look at what can cause it. M1.7 uses a few things to determine the fuel injection quantity. Those are:
- RPM (via crank position/speed sensor)
- Air flow sensor
- IAT sensor
- CLT sensor
- O2 sensor
- Throttle position

RPM + crank angle is the biggest and most important factor of all, for every aspect of operation. This effectively ends up as a digital frequency signal in the ECU, and if the sensor or toothed wheel were going I think that you would find the car running very poorly or not at all. Now, if the toothed wheel somehow got damaged when you removed the lower timing cover to replace the gasket, this MIGHT be it. See this thread for the symptoms of a failing one:

https://www.r3vlimited.com/board/showthread.php?t=414344

It might be this, although I am not sure if the lean running can be due to this. If you are idling below 500RPM, then flashing dash lights make sense because the ECU is switching between Accessory-II and Run modes (the ECU suspects a stall, which again could be from a failing damper wheel causing tooth-sync losses). IMO this is the least desirable cause since the dampers are $$$$$, and a big pain in the ass to remove/reinstall!

You can check this with the little scope that you are buying (and it is always good to have one!). Little wires can carefully be shoved into the ECU connector housing so that you can scope the crank sensor signal. It may be noisy from ignition and stuff, but it should look like the stuff in here:

https://www.r3vlimited.com/board/showthread.php?t=374858

If it is super noisy, and you can export the scope captures to your PC (CSV/Excel/etc), I can help you to filter them if you need.

Air flow is the single largest determinant of the load variable, which is proportional to the injected fuel quantity. It would seem that the sensor itself is not the issue. That leaves a couple of possibilities: a MASSIVE vacuum leak which effectively circumvents the AFM, and damage somewhere in the wire harness coming from the AFM. Maybe try to check for continuity between the pins on the AFM plug and ECU plug ends (M42/M1.7 wiring diagrams here: http://www.armchair.mb.ca/~dave/BMW/e30/e30_92.zip).

Next would be the IAT sensor since this enables the ECU to convert volume air flow to mass air flow (since the quantity of fuel to inject is calculated as a mass). In this case, if the wire harness broke, the ECU would think that the air temp is very very cold, and lead to rich running. It wouldn't hurt to check continuity between plug ends anyway since it is part of the AFM.

The CLT sensor really only is used to tell the ECu if the engine is up to operating temp or not. Generally when these go bad you run rich.

The O2 sensor can have a big effect on fuel economy, but the ECU would (I think) toss an error code way before you ran so lean as to lose all power and get the headers red hot. IIRC, the limits on O2 feedback correction are plus/minus 25% of stoich, so if it was totally messed up you would get an O2 sensor CEL code. Since unplugging it made no difference, it is probably not this.

The TPS is mainly used to switch between maps in the EPROM, and while I suspect that it has some enrichment function on its own, it is not as critical to operation as other things. Or at least not enough to cause your problems.


Lastly, what condition where the 19# injectors in when you bought them? It is a huge long shot, but maybe one or two of them have clogged or sticking valves?

Wow that was a mouth full LOL. from a visual inspection my toothed wheel seemed to e in good shape the rubber didn't appear to be cracked or splitting. I Plan to plug the scope into the CPS sensor and see whats going on once I get it. If you would like to PM me you phone number or Email to have that would be greatly appreciated. I tested for a vacuum leak and found nothing.

I doused the bay in some carb cleaner and the idle didn't change and nothing happened I can make a homemade smoke machine to confirm but not sure that is needed.

I will check for continuity from the ECU and the AFM. I am also going to do a voltage drop test from the ground pins on the ECU and the G103 ground in the battery tray. For the AFM wires i would think unplugging it would of had an effect on it if there was a short but after unplugging it the first time Monday night I have not been able to replicate the results and unplugged or plugged in my dash lights still come on. They don't flash they just stay on until the engine hits about 5-600 RPM and then they go off and stay off even after i let off the throttle.

My injector were Rebuilt injectors and were tested for quality assurance i can also hear all 4 of them firing with the engine running.

I am going to do another fuel pressure test. after taking with instructors it is possible it could be that because the pressure is only 36-38 psi at idle and once i rev it the pressure goes up to 42-44 and fluctuates this could be just cause it has a vacuum on it. So i am going to connect it and try and drive the car up my drive way and put and actual load on it and see what it sits at that way i know if its getting the correct volume and not just correct fuel pressure.

[ThatOneEuroE30]

Okay so i did a load fuel pressure test and it was good held steady at 44 psi.

Tested the grounds on the ECU its ground on pins 55, 34 and 6 voltage reading read 0 so no excessive voltage being left behind.

Check continuity on the ECU for the AFM and i got continuity on all wires pin 76 but from my diagram it says that pin 76 is wired in but on vehicles with a cat like mine. Pin 76 is cut and tied back in the harness. So not continuity on that one makes sense. The wire i was most worried about getting continuity was it IAT sensor and its getting its signal. At this point could it be that my ECU it self is bad so no matter what chip i put in its still going to have an issue?

Just got a shipping notice for the oscilloscope hopefully have it Friday or Saturday. I also talked with my instructors if i cant figured this out by the end of the month then they will let me trailer it in and all of us will try and fix it. Hopefully 60 some years of combined experience can nail this issue down if i cant.

[ThatOneEuroE30]

Just double checked timing i stuck my bore scope down cyl one spark plug hole with the engine at what it says was TDC it definitely is. Pistons was all the way to the top don’t get any higher then what it was

[TobyB]

1) Lean mixture
2) Exhaust blockage
3) Timing

way late will do that. The gas is still at maximum burn when the exhaust valve lets it out.

t

[ThatOneEuroE30]

way late will do that. The gas is still at maximum burn when the exhaust valve lets it out.

t

I really don’t think its timing. I double checked it with a bore scope and the pistons was at TDC with the wheel lined up with mark at oil filter stand. I unplugged the AFM and got the same result as monday. The lights went off and it idled fine its just it cut out once the it got above the max Idle rpm