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Troubleshooting M20 rough running


TurkisM2002

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3 hours ago, jimk said:

@6600 ft elev, the pressure correction from sea level is 0.79.  Note the correction is to Psia, not Psig.  Std atmosphere at 6600 ft is 11.6 psia

142 psig = 156.7 psia, so the corrected pressure is 156.7 x 0.79 = 122.6 psia,  Gauge pressure is 122.6 psia - 11.6 psia = 110.9 psig or 111 psig. and is why NA engines run glutless here.


thanks Jim. I got my correction numbers out from that Pelican book. Either way it’s significantly down. I moved here from DC and was amazed how lame my M3 became. 

 

Given the numbers and wet comp test, is it conclusive to think it’s the piston rings? 
 


 

 

 

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Certain parties believed more power can be obtained by more fuel by inserting a resistor in series with the wiring to the engine temperature sensor (to the Motronic) to try to make the system believe it is colder than it actually is.  (The sensor resistance increases with decreasing temperatures.)  End result is a very over rich condition.  The resistor would be hidden in the boot at the connector to the water temp sensor.  Take a look and remove the resistor if it is there.

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A radiator shop is a good place to take a leak.

 

I have no idea what I'm doing but I know I'm really good at it.

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No resistor. Ohm reading is to spec in the Bentley. Hmm. 
 

im sure I’m battling a couple different issues here between the idle and the low compression. When I ran the wet comp test there was milky oil in the compression tester hose.  

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When you rev the engine good, does it clear up a bit?  The first video sounded like it needed to be cleared out.  The low compression shouldn't keep it from running somewhat better than that shown.

Also, I don't think it is a cause of the major issue at present, but is it ok for the AFM to be mounted not plumb?  The flap door in it may be sensitive not being on the level.  

A radiator shop is a good place to take a leak.

 

I have no idea what I'm doing but I know I'm really good at it.

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Did it run any better with the standard spark plugs?

 

You replaced the distributor cap?  How about the rotor?

 

From what I see in the videos, I'm assuming you can't get it out on the road and blow it out (Italian Tuneup) ?

 

1 hour ago, jimk said:

but is it ok for the AFM to be mounted not plumb?  The flap door in it may be sensitive not being on the level.  

 

+1 with Jim here...

 

Great videos here to check and repair your AFM (also instructions on how to richen/lean the mixture near the end of the second video...perhaps your car would benefit from that, being at high elevation)

 

 

 

 

Edited by zinz

'69 Granada... long, long ago  

'71 Manila..such a great car

'67 Granada 2000CS...way cool

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I did replace the rotor, but I have not run the car with all the new stuff yet. The low comp #s and milky oil and white steam have me wondering how to move forward.  I have to ask if there is a point to addressing the rough idle issue given the other issues with comp and white smoke? Let me rephrase that and ask what the priority should be? 

 

No can't do an in-motion italian tune up. I've done one stationary in the garage a handful of times, which has me wondering if that's how the spark plugs got so black.   It sounds good when the throttle is open but the exhaust is fairly loud so hard to tell.  

 

Is there any harm in firing up the car with the new plugs and injectors at this point given all the other conditions? 

 

I don't know about the AFM being plumb. It's positioned that way since I don't have any clearance to get it plumb.  I swapped in an E12 or E28 (can't remember...) master cylinder with a top mount brake fluid reservoir so the AFM had to be cocked a little.   I can always go back to the remove reservoir. 

 

I'll have a look at those videos thanks for the links.  Not sure I have the proper tools to measure how well the car is running. 

 

 

Thanks

 

 

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12 minutes ago, TurkisM2002 said:

Is there any harm in firing up the car with the new plugs and injectors at this point given all the other conditions?

 

I don't see how you could hurt it.  I would certainly want to know if it ran better after installing all the new parts.  

 

If you think you may have a headgasket leak, check Ray's thread on the Bar's Leak stop.  It may be worth a shot?  :)

 

 

 

'69 Granada... long, long ago  

'71 Manila..such a great car

'67 Granada 2000CS...way cool

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I'm not paying close attention to this thread, but 2 things. Other than the Pt plugs:

 

Some motors have the AFMs mounted upside down like yours is. Mine on the M88 is right-side up ? so I don't think not plumb is an issue.

 

You've looked at the track on the AFM, right? also there's a great Motronics troubleshooting guide online.

 

That's Motronics 1.0 right?

 

If so there's a 6 position FQS (fuel quality switch) in the ECU, which can be used to futz with timing and richness. Tho I don't think that is your issue. You might trace the CTS lead from the sensor to the ECU.

 

I do think that you initially managed to gas foul those plugs and that has exacerbated your troubleshooting.

 

Could be wrong, tho :)

 

GL.

Edited by ray_

Ray

Stop reading this! Don't you have anything better to do?? :P
Two running things. Two broken things.

 

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46 minutes ago, ray_ said:

I do think that you initially managed to gas foul those plugs and that has exacerbated your troubleshooting.

Yeah, when cold starting it runs on an enrichment setting.  If it isn't fully warmed up so the O2 feedback loop operates, and run only short periods for a number of times, it will eventually load up and it needs to be heated up and revd to clear things out.

A radiator shop is a good place to take a leak.

 

I have no idea what I'm doing but I know I'm really good at it.

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13 minutes ago, flagoworld said:

Hold a piece of white paper over the exhaust for a minute and then post a pic of it and describe it as best you can.


I can. 

It certainly looks white to me. I had to top off the coolant since it was pretty low.

 

Coolant is definitely in the oil. 

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4 minutes ago, TurkisM2002 said:


I can. 

It certainly looks white to me. I had to top off the coolant since it was pretty low.

 

Coolant is definitely in the oil. 

Oh yikes.  

 

Try the Bar's Leaks or pull the motor.... I mean the head...

Edited by ray_

Ray

Stop reading this! Don't you have anything better to do?? :P
Two running things. Two broken things.

 

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