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idle miss..have I done everything to try to fix the problem


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86 loyale/ 2wdr./ turbo/ auto /205,000 mi/..the MISS is only felt when the car is in gear and has been like this since I bought the car 2yrs ago, but now I would like to deal with the problem and discover or learn from this one...other then that, all seems to be very good if not excellent... pulls hard when wanted and still passes the Emissions test with no problem and also the compression is still within near new specs...I have changed out the ECU/idle control valve ( the part on top of the thermostate) /O2 sensor/spark plugs/ plug wires/new distributor with new vac pot/dist. cap/ rotor/checked timing/fuel pump is OK/new fuel fiter/changed out the timing belts/ cleaned out the MAF and throttle body inside and out with electronic cleaner/ I have gone over the vacuum lines on 3 different occasions with WD40/propane/starter fluid and resulted in NOT a waver to the RPM gauge..I also took the idle adjusting screw out to clean it, which only resulted in setting the idle a little easier/checked with digital muti-meter for proper grounding and could not find any real difference between the various testing points when comparing the 2 battery posts...one thing that this car does differently, is when checking the spark plugs...they only burn WHITE, not even a hint of tan color which is unlike the other sub's I have....

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This should be a 3AT with vacuum modulator; parts stores call it something else, but I can't remember what. (It is used to let the tranny know when you have the throttle fairly wide open, so that it can "kick-down" into a lower gear.)

 

The modulator is a can, approx 1.5" in diameter and perhaps 2" long on the right- (US passenger-) side of the tranny just above the fluid pan joint and is just forward of a similar (but knurled exterior) can with wires going to it. The modulator has a rubber vacuum hose running to it, and if you pull it off and the hose is wet or drips ATF then the diaphram on the modulator has ruptured.

 

Another thought, since you mentioned your spark plugs are white: How is your EGO (Oxygen) sensor? My plugs tend to be fairly clean/white, and theat seems pretty normal. Is yours ashen white?

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I forgot to mention at the beginning that the O2 sensor was also changed and yes, the modular has some tranny oil leaking from it unto the driveway...the plugs are also ashen white as you described and it has been raining for 2 days so I will have to wait till it dries up...

This should be a 3AT with vacuum modulator; parts stores call it something else, but I can't remember what. (It is used to let the tranny know when you have the throttle fairly wide open, so that it can "kick-down" into a lower gear.)

 

The modulator is a can, approx 1.5" in diameter and perhaps 2" long on the right- (US passenger-) side of the tranny just above the fluid pan joint and is just forward of a similar (but knurled exterior) can with wires going to it. The modulator has a rubber vacuum hose running to it, and if you pull it off and the hose is wet or drips ATF then the diaphram on the modulator has ruptured.

 

Another thought, since you mentioned your spark plugs are white: How is your EGO (Oxygen) sensor? My plugs tend to be fairly clean/white, and theat seems pretty normal. Is yours ashen white?

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The 3AT is all hydro-mechanical. The 4EAT is electrically controlled.

 

Replace the vacuum modulator. It is only a $15-30 part. NAPA shows 2 different sizes (diameter), don't know what the diff is though. This may or may not help your idle, but it will keep you from draining your ATF and causing grief with your tranny.

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there is no tranny fluid being sucked up into the plenam..I disconnected the rubber hose there and it was clean...I think the ashen white color of the plugs is from the additives in the gas....

If tranny fluid is leaking into the intake that may what is causing the plugs to look like that.
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one thing for sure is to replace the modular(s)... would you know the purpose of the other small canister...one can has the vac hose and the other can has 2 wires coming out of it....

The 3AT is all hydro-mechanical. The 4EAT is electrically controlled.

 

Replace the vacuum modulator. It is only a $15-30 part. NAPA shows 2 different sizes (diameter), don't know what the diff is though. This may or may not help your idle, but it will keep you from draining your ATF and causing grief with your tranny.

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I just finished up disconnecting the hose from the tranny and plugging it up...There was no change to the idle..it still shakes like before (just a little)

The 3AT is all hydro-mechanical. The 4EAT is electrically controlled.

 

Replace the vacuum modulator. It is only a $15-30 part. NAPA shows 2 different sizes (diameter), don't know what the diff is though. This may or may not help your idle, but it will keep you from draining your ATF and causing grief with your tranny.

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The other device is the Neutral switch, IIRC.

 

OK, some basics. What do you consider "misfire"? You mention it shakes a little. It is a 4-cylinder, so it will have some shake, and since it is a boxer some of that shake will be as if an axle was stuck from the ground to the sky and the engine pivots around it. The engine mounts are pretty simple and not designed to dampen/isolate the shake much. All of mine shake. A misfire should show up as a definite bump, and usually accompanied by a change in engine sound. (Sorry if you already know this, just trying to "get on the same page".)

 

Also, is your idle at spec, both for in Neutral and in Drive?

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No problem, I don't feel insulted..how do I define "shake"?...well, my 86 loyale(200,000mi) with an old carb runs smoother and my SPFI with one very low cyl.compression is also smoother....I just finished up useing a half can of seafoam thru one of the vacuum hoses into the plenim and I will say there is a small improvement...it's almost there ...maybe there is something developeing internally (valve?)...I also checked and cleaned the injector and Maf electrical connections( but they did not need it) ...the car idles at 750-800rpm in gear and 1050-1100rpm in neutral...another characteristic I forgot to mention is that the rough idle will completely disappear and then re-appear a few minutes later when sitting at the street corner....

The other device is the Neutral switch, IIRC.

 

OK, some basics. What do you consider "misfire"? You mention it shakes a little. It is a 4-cylinder, so it will have some shake, and since it is a boxer some of that shake will be as if an axle was stuck from the ground to the sky and the engine pivots around it. The engine mounts are pretty simple and not designed to dampen/isolate the shake much. All of mine shake. A misfire should show up as a definite bump, and usually accompanied by a change in engine sound. (Sorry if you already know this, just trying to "get on the same page".)

 

Also, is your idle at spec, both for in Neutral and in Drive?

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Thanks for your understanding. Having 2 better-running examples certainly gives good context.

 

I re-read the thread, and did not see mention of the Coolant Temperature Sensor (CTS) being checked. The connection and connector wiring on this item seems to corrode easily and often. If you haven't already done so, it would be good to check. It is hard to get at, behind the intake manifold and kind of underneath the EGR solenoid (easy to break!!!). They don't seem to fail so much as just develop corrosion.

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I did not mention the coolant sensor because I put one in last year...but I will check for the corrosion...

Thanks for your understanding. Having 2 better-running examples certainly gives good context.

 

I re-read the thread, and did not see mention of the Coolant Temperature Sensor (CTS) being checked. The connection and connector wiring on this item seems to corrode easily and often. If you haven't already done so, it would be good to check. It is hard to get at, behind the intake manifold and kind of underneath the EGR solenoid (easy to break!!!). They don't seem to fail so much as just develop corrosion.

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The CTS corrosion is such a problem that some of us have taken to soldering wires directly to the CTS and bringing the connection out a foot or so further. One Member has posted that he started doing this after finding not only the connector corroded but also the first 4-5 inches of the connector wiring, which was in an almost inflexible state.

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I know what you mean about corrsion with that particular part because yesterday I was taking apart pieces from another MPFI plenim and noticed how extremely corroded that wireing etc was...I will look with even greater care in my situation..thanks...

The CTS corrosion is such a problem that some of us have taken to soldering wires directly to the CTS and bringing the connection out a foot or so further. One Member has posted that he started doing this after finding not only the connector corroded but also the first 4-5 inches of the connector wiring, which was in an almost inflexible state.
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I think I now found the general area of why the car has a slightly rough idle ..on the back and sitting on the throttle body is a long looking like nut with a wire going to it and snaps on from the top...I took the part off and cleaned out the "gunk" on the end of the small rod and blew some cleaner down into the plenim...the car idles nearly like new(close enough for now) and also apon starting when cold, it no longer revs up to 1600rpm before warming up to the normal idle...concerning the switch, is this some sort of shut-off or anti - dieseling switch?

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