M20 running strange

[6670charger]

Hi. I have an 88 325ic with the M20. Been having a problem the past few weeks with an intermittent idle issue is the best way I can describe it. The car starts and runs fine. I recently put a new IACV, air intake boot and plugs into the car. The problem I'm having is that at various times the engine will seemingly cut out for a fraction of a second. This happens usually when I'm on the highway and start to accelerate a little, but also happens at idle. It's like the engine has a hiccup. Usually when this happens, the check engine light with flash on for an instant and then back off again. It doesn't seem to effect drivability or power. It has to be something in the engine management somewhere. It seems like an idle issue. I haven't yet swapped out the new IACV for the old one to see if that's the issue or not.

Any other suggestions?

Thanks.

[squidmaster]

could be fuel pump. This happened on one of my e30s and it turned out to be a broken grounding bracket on the pump.... I'm just happy it never sparked and ignited my tank!

[101]

subscribed. My IX is doing the same thing. The check engine light is more active when the engine is cold.

I've installed a completely new fuel system with new pump, tank, lines, etc., new intake gaskets and associated seals (bitch tube, intake boot), new vacuum lines, new throttle position sensor and a new coolant temperature sensor. Stomp test gives a "1223" code for the coolant temperature sensor even after the new one was installed and the battery disconnected to reset the DME. ICV and the air flow meter are clean.

[squidmaster]

check conductivity and grounds for your sensor. test conductivity from ecu-side to sensor-side.

[101]

6670charger:

Everything I'm reading about this particular issue on the R3v and E30Tech boards is pointing me in the direction of the C191 connector under the manifold.

I'm going to start with squidmaster's suggestion and recheck all the wiring from the DME connector out to all of the sensors and grounds. I did that a few weeks ago and everything checked out OK at that time - but that was BEFORE I pulled the C191 apart and replaced the intake manifold gaskets and the TPS. My econometer in the cluster is also acting possessed (it only ever reads "0" or "40" and swings rather violently between them at wide open throttle) - which is also a new development since the intake gaskets were replaced.

I'll report back once I get a chance to muck around with it.

If there are any other ideas - lets hear 'em.

[6670charger]

That could be it. My econometer also swings wild when this blip occurs. Seems to operate normally otherwise.

I have an oil leak that I need to sort out at some point, but that's just gaskets and seals. This momentary cut-out thing is really annoying, and something I'd like to figure out sooner than later.

[squidmaster]

oop sounds like wiring/c191 something similar. fuel pump shorts might cause the econometer to act strangely, but I haven't experienced that issue.

[101]

UPDATE

TL/DR:
I cleaned and checked all the wiring and connectors on the injector harness. Potential causes found - loose DME mounting, poor connection in C191 connector.

FULL STORY:
Pulled the injector harness off the car and cleaned all the pins and connectors. Checked the resistance between the injector / sensor connectors and found everything OK. Checked the new coolant temperature sensor and it was within spec. Reinstalled the injector harness and reattached it to the engine harness, making sure to "work" the connector in and out a few times before screwing it together.

I also cleaned the connectors and pins of the ICV and the AFM.

Then I went inside the car and took the connector off the DME. Did the full suite of Bentley checks at the connector and everything passed and was within spec. I DID find the three bolts holding the DME to the dash frame loose and tightened those. Put everything back together, started the car and it seemed to idle somewhat better and the check engine light did not come on nor did the car try to stall.

I turned the car off and did a stomp test ... code "1444" this time. That's good! The code for the coolant temperature sensor is gone.

I installed my fuel pressure gauge and checked my fuel pressure - I have about 40psi at idle. I'll leave the gauge installed for a few days - in the event it starts misbehaving again I can at least see what's going on with the fuel pressure and if that is causing the issue.

I'll drive her tomorrow see if she still has a death wish for me.

I'm thinking the econometer issue is just my SI board telling me its time to do something with it. Cluster rebuild time me thinks.

[101]

update:

After 50 miles of mixed city and highway driving my old friend the "Check Engine" light was no where to be seen. The car idles much better and the surging / stalling issues are gone. Stomp test is still clear of problem codes.

I'm not sure exactly which thing(s) I did corrected the problem, but complete engine wiring harness checks, cleaning of all connectors and grounds and liberal application of dielectric grease will be part of my standard operating procedure going forward.

[stikrz]

Sounds like the AFM connector was loose or needed a cleaning. My 86 528e had the same problem and I made it a point to clean all connectors with CRC when I buy another vintage BMW.