Severe run issues- 1990 740T

a helpful menu for troubleshooting...

Sounds exactly like a bad AMM, could also be a large air leak, such as a hose has come off between the turbo and throttle body. If the check engine light came on, there should be a stored fault code.

Good day,

Car was outside and I needed to get it inside.

Had trouble getting it up the drive.

Disconnected AMM to see if that helped and it didn't.

I assume I introduced an error code by this action.

I have never read error codes before, only seen it done. I am not sure how to do it.

Took a very brief look on Brickboard, but haven't found anything as of yet as to the process and readings.

Only have a crappy manual.

Did notice oil around where the hose to the turbo attaches to the intercooler.

Will open up air cleaner box today hopefully.

TIA

jimB

I've got a hunch.

Loosen and disconnect the thick hose from the front of the turbo and put your finger in there to make certain that the turbine spins freely on the shaft.

If it is frozen: your turbo is toast.

Turbine spins thank goodness.

jimB

Check and see if the fuel pump is running, it's surprising how long an engine will idle on residual pressure in the line.

Well, I drove (in a fashion) about 3 miles plus and moved it around the door yard a bit the day after.

The surging under load must be the key.

I need to figure out how to fetch the error codes.

jimB

Have you checked carefully for air leaks? I've seen the rubber boot pop off the throttle body before, as well as oil collect and soften it, causing a section to blow out the bottom. Coolant temp sensor for the ECU fails from time to time as well.

Thanks Mr. V

now we'll see

jimB

Finally got to dump the OBD codes.

For the Fuel Injection (in order):

232 Fuel trim (lambda control) too lean or too rich at idle 223 Signal missing to/from idle air control valve 121 Faulty signal to/from Air Mass Meter

The third (and maybe all) I would imagine that I induced by disconnecting the AMM in order to "limp home"

Cleared the codes & started the car...

Check Engine light went out on it's own, car still runs crappy, light did not come on, no new codes.

For the ignition (in order):

234 Throttle Position Switch (TPS) idle signal faulty 214 RPM sensor signal absent intermittently

I have not cleared these as of yet to see if they come back.

I am in very unfamiliar territory here. Last car I really worked on had a carburetor and breaker points.

TIA

A bad RPM signal could certainly explain poor running. That could be the crank angle sensor, IIRC this is mounted to the back of the engine block pointing down in the top of the bellhousing on a '90. TPS switch is easy enough to check, it may just be out of adjustment.

121 and 232 could certainly be caused by unplugging the AMM. Not sure about 223.

That was Diagnostic Test 1

Will do the component tests (2 & 3) In a bit

TIA

-------------------------------------------- JimB

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Did test 2...

TPS and Crank Sensor test OK

TIA

jimB

-------------------------------------------- JimB

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