idle issue

[nyernga]

Here's what has been done in the last 3 weeks.

Plugs
wires
coil
distributor cap

The car was still having a bit of a stalling issue after being run for a bit. It started fine, idled fine until the engine was shut off for a few minutes. It would start fine, idle fine for a little while and then at a traffic light would just hover around 300 to 400 rpms and die. Started right back up and be very intermittent aftwewards.
I've removed and cleaned the IAC motor and throttle body, reset the idle using the prescribed procedures and finally checked the voltage at the TPS which I set to .054v
The idle isn't as bad now but it's still prone to the occassional stalling out. I did notice yesterday that once in a while it feels like something is "stopping" the accellerator pedal when I first hit it. Kind of as if the linkage mechanism was sticking slightly.
Another issue, and it may or may not be related, is when I go WOT, the tach actually begins to drop. I kow I'm close to redline yet the tach reads much lower and only drops. It reads fine at idle and during regular driving however.

Any thoughts guys?

Len

 

[ecss]

For test purposes, disconnect the white connector on the side of the distributor cap. (Tach wire) See if that cures the stalling problem. If it does, the tach filter may be bad.

Also you said you set the TPS for .054? Should be .54 volts DC.

Disconnect the linkage at the throttle body and manual move the linkage and check for any binding. The throttle body shaft may be worn out. It can be repaired by having bearings installed for the throttle body shaft.

 

[Moonunit 451]

For test purposes, disconnect the white connector on the side of the distributor cap. (Tach wire) See if that cures the stalling problem. If it does, the tach filter may be bad.

Also you said you set the TPS for .054? Should be .54 volts DC.

Disconnect the linkage at the throttle body and manual move the linkage and check for any binding. The throttle body shaft may be worn out. It can be repaired by having bearings installed for the throttle body shaft.

I agree. Also check for vacuum leaks, you may have accidentally disconected or damaged a line. And, change the fuel filter. Then check your fuel pressure if you're still having troubles.

 

[nyernga]

Thanks guys. I'll try the tach wire nect time I take the car out. That sounds like it may be the culprit since that's the area I was working in. If memory serves me, the tach filter is behind the dash right?

The throttle body was changed out 3 years ago and since I pretty much use the car on weekends only, that'll be my second place to look.

Len

 

[rrubel]

On my 86, the tach filter is bolted to the block just to the passenger side of the distributor. Little brownish cylinder.
[RICHR]

 

[ecss]

Thanks guys. I'll try the tach wire nect time I take the car out. That sounds like it may be the culprit since that's the area I was working in. If memory serves me, the tach filter is behind the dash right?

Look at your distributor cap. On the driver side of the distributor cap you should see a bump out in the cap. There should be two push on connectors. One is Battery (I think the connector is Red) and the other one is Tach (I think the connector is White).

Just pull off the Tach connector. That will disable the Tach filter and the Tach display on the Digital dash will not function.

 

[nyernga]

disconnect the white connector on the side of the distributor cap. (Tach wire) See if that cures the stalling problem. If it does, the tach filter may be bad.

Also you said you set the TPS for .054? Should be .54 volts DC.

Disconnected the tach wire and the car refused to start. It cranked but no ignition. Re connected it and the car started.

As to the .054? it's amazing what bad vision will do to you. I'll adjust that little error post haste.

Len

 

[ecss]

You must of disconnected the Battery terminal instead of the Tach terminal. Isn't there two sperate push on connectors?

Did you have your reading glasses on?

I believe the word Tach and Battery are etched on the Distributor cap.

 

[Moonunit 451]

Did you have your reading glasses on?

Ain't that the truth, I still can't get used to it, and it's been almost 10 yrs
I agree with the other stuff you stated in this post too.

 

[nyernga]

I believe the word Tach and Battery are etched on the Distributor cap.

Unless it's in braille I didn't notice but I'll double check. This weekend, I'll try an idle reset this weekend.

 

[Larry's Yellow Rdstr]

I have a seeing eye dog available if that will help!!

 

[nyernga]

I have a seeing eye dog available if that will help!!

only if he's housebroken.....

ps: It WAS the battery wire I removed. :nono I'm not sure what, if anything a bad tach filter would have to do with the idle though.


Len

 

[ecss]

The Tach Filter, filters a signal which is tapped off of the ignition control module and the primary of the ignition coil. The signal is used to drive the Tach. in the Digital Dash.

If the Tach Filter is failing/defective it will cause all kinds of weird problems. Since you said your Tach display is not working properly, the tach filter may be bad.

A new one goes for $50.00.

That's why I suggested you unplug the tach filter and see if the stalling problem goes away. If it doesn't cure the stalling problem, a new Tach Filter should cure your Tach problem.

 

[tigmaned]

so did you set the TPS at .054 volts or did you just hit the wrong key on the key board? if you set it at the .054 volt like you wrote i would change that first. your idle in drive should be a little higher then 300 -400 rpms. at a light mine is right around 600-700 rpms in drive. .054 and .54 volts is a big diff. and discount the IAC and set the idle at 400rpm.

 

[nyernga]

so did you set the TPS at .054 volts or did you just hit the wrong key on the key board? if you set it at the .054 volt like you wrote i would change that first. your idle in drive should be a little higher then 300 -400 rpms. at a light mine is right around 600-700 rpms in drive. .054 and .54 volts is a big diff. and discount the IAC and set the idle at 400rpm.

It was a typo. The TPS is set to .54v. I'm heading out in a while to see if disconnecting the tach filter makes any difference.

 

[nyernga]

disconnecting the tach wire made no improvement in the idle issue. Looke like it'll be a new in line fuel filter and total idle reset this weekend. If that fails then I may try a new IAC. Running out of ideas at this point.

Len

 

[ecss]

When you disconnect the IAC (closed position) to adjust idle speed, it's a mechanical adjustment using the screw on the driverside of the throttle body. It opens or closes the throttle body blades. So the idle really should never drop below that rpm.

Did you disconnect the linkage and check for any binding of the throttle body blades or worn throttle body shaft?

The IAC should maintain the proper rpm when the load on the engine changes.

When you turn the AC on, does the rpm increase? That would be an indication the IAC is working.

The IAC allows air to bypass the throttle body blades.

Did you clean the carbon that builds up on the bottom of the throttle body? That's the path for the air to enter the plenum when the IAC opens.

You won't see the idle passages unless you remove the gasket that goes from the throttle body to the plenum.

Also since you said the Tach is not working properly, what are you going to do about it?

If you do replace the IAC, make sure the shape of the Pintel is the same shape as your original one. There are three different shapes.

 

[nyernga]

When you disconnect the IAC (closed position) to adjust idle speed, it's a mechanical adjustment using the screw on the driverside of the throttle body. It opens or closes the throttle body blades. So the idle really should never drop below that rpm.

Did you disconnect the linkage and check for any binding of the throttle body blades or worn throttle body shaft?

The IAC should maintain the proper rpm when the load on the engine changes.

When you turn the AC on, does the rpm increase? That would be an indication the IAC is working.

The IAC allows air to bypass the throttle body blades.

Did you clean the carbon that builds up on the bottom of the throttle body? That's the path for the air to enter the plenum when the IAC opens.

You won't see the idle passages unless you remove the gasket that goes from the throttle body to the plenum.

Also since you said the Tach is not working properly, what are you going to do about it?

If you do replace the IAC, make sure the shape of the Pintel is the same shape as your original one. There are three different shapes.

Thanks for the solid advice ecss,
I did the idle reset tonight. I was able to maintain 400 - 450 rpms with the IAC disconnected using the set screw. I then reconnected the IAC and set the tps to .54v. Took it for a test run and it was idling just fine. So far, and this is after turning the car off and restarting, the reset seems to have done the trick.
What I found was that the set screw, was "stuck" and wasn't even hitting the linkage correctly. Once I turned it a little harder, it freed up and made contact thereby allowing the 400 rpms. My only concern is the pathetic mileage right now. 12.6 mpg but I believe after a long enough drive, the ECM will recalculate both that and the miles to empty.

You guys have been a tremendous help. Exactly what one comes to expect from the CAC.

Len

 

[nyernga]

spoke too soon

You guessed it......the gremlin is back and I'm not talking AMC. Ran fine this am taking my son to work. I pulled in to a convienence store and as I was waiting for him to come out......the idle "searched" and then died. Dropped him off, got home and it idled fine in the garage at 750-800.
Time to get out the floorjack and replace the inline filter. At least I know the idle adjustments are correct so the problem must lie elswhere. I hope


Len

 

[nyernga]

May have found the gremlin

I need input here guys. I went to summit racing online looking for tach filters. I found alot of info about tach adapters used when you upgrade to an MSD coil. Well that's exactly what I did. I replaced the stock coil with an MSD. The info states that some factory ECU's have trouble reading off the msd and will not have the correct output to the injectors causing among other things a no start condition. I think I'm going to reinstall the original coil (if I still have it) and see what happens. Thinking back, the stalling issue happened AFTER the tuneup.

make sense to anybody?

Len