86' 3.2L starts fine then idle falls -

[fallingat120mph]

1986 3.2L

Last week/weekend: Cold start was fine and idled at 1000 then lowers to 800rpm and would drop but after warming up problem wasn't as bad.

As I have discovered the last few days if I let it sit at idle and warm up the engine (which I don't like doing for very long) drops from 800 to 500-650 and stays there. If I blip the throttle it climbs back to 800, stays there for a few minutes, and then out of nowhere drops again back to 500-650.


At a stop light the other day, car warmed, actually driven for an hour, stopped at the light, idle was fine and then dropped to 500ish. Blipped the gas pedal, jsut a bit, and idle went back to 800...

When the car idle drops it almost feels like an old under powered VW, Mazda, etc. when you would turn on the A/C. It feels like a pump kicks on and pulls from the engine/idle.

This is new to me and never have had this issue.

-Fixed oil leak at triangle of death (Parts and seals) and checked vacuum lines, etc. all good.
-New plugs, distributor cap (kit)
-Cleaned and checked ICV
-New fuel filter
-New fuel pump
-Checked screen in fuel tank

Also:
-New alternator (13.8 to 14.2 depending on what's running)
-New battery
-Removed entire A/C system

Have set the base idle (per guidance, bridging test ports B/C) and that was fine.

Basically, did a minor tune up and everything has been great until a few weeks ago.

I am chasing a few oil leaks, but nothing significant.

Have been researching the forums for a few hours and finding a lot of surging issues or messing with the AFM, etc...kinda' frustrated so thought I would ask here.



The last couple days when cold it now takes two attemps to start - then idles briefly at 1000 then drops for a few minutes at 800. THEN...drops to 500-650 as it warms up.

Driving and warming the car up it does the same at stop lights, etc.


Any thoughts?

[fallingat120mph]

Alright after running two tanks (one non ethanol (91) and the other Chevron (93)) through it and giving it the ole' "Italian Tune-Up" it in the Hill Country have finally got the idle manageable BUT still have the issue of it 'falling' for no reason.

My video below with the car warmed (and level -if that matters) in the garage after driving for a few hours. The idle is fine (800rpm as this is an 86 coupe) but then drops for no reason to below 750 and will not come back to 800 on it's own. I can 'blip' the throttle and it will idle normal but a few minutes and it falls again to below 700rpm.


https://youtu.be/za5-DbQbBSY


Finding a lot of surging idle threads and discussions but not seeing much else similar to my issue...


Still in the novice mechanic category and thinking maybe it could be the air/fuel mixture?

Thanks,
Erik

[brianlay]

The Idle Control Valve could sticking. Remove it, clean and check for movement to both ends.
Also could be unmetered air leaking into the intake…also called vacuum leak.
Does the idle drop when you remove the oil cap?

[fallingat120mph]

Originally Posted by brianlay

The Idle Control Valve could sticking. Remove it, clean and check for movement to both ends.
Also could be unmetered air leaking into the intake…also called vacuum leak.
Does the idle drop when you remove the oil cap?

ICV was cleaned (and checked) -- also swapped with a good one just to verify.

Yes, idle drops when cap is removed.

Checked for vacuum leaks but maybe I missed something. All vacuum lines are in good shape to include attachment points...

Thanks for chiming in...

[mysocal911]

Originally Posted by fallingat120mph

1986 3.2L

Last week/weekend: Cold start was fine and idled at 1000 then lowers to 800rpm and would drop but after warming up problem wasn't as bad.

As I have discovered the last few days if I let it sit at idle and warm up the engine (which I don't like doing for very long) drops from 800 to 500-650 and stays there. If I blip the throttle it climbs back to 800, stays there for a few minutes, and then out of nowhere drops again back to 500-650.


At a stop light the other day, car warmed, actually driven for an hour, stopped at the light, idle was fine and then dropped to 500ish. Blipped the gas pedal, jsut a bit, and idle went back to 800...

When the car idle drops it almost feels like an old under powered VW, Mazda, etc. when you would turn on the A/C. It feels like a pump kicks on and pulls from the engine/idle.

This is new to me and never have had this issue.

-Fixed oil leak at triangle of death (Parts and seals) and checked vacuum lines, etc. all good.
-New plugs, distributor cap (kit)
-Cleaned and checked ICV
-New fuel filter
-New fuel pump
-Checked screen in fuel tank

Also:
-New alternator (13.8 to 14.2 depending on what's running)
-New battery
-Removed entire A/C system

Have set the base idle (per guidance, bridging test ports B/C) and that was fine.

Basically, did a minor tune up and everything has been great until a few weeks ago.

I am chasing a few oil leaks, but nothing significant.

Have been researching the forums for a few hours and finding a lot of surging issues or messing with the AFM, etc...kinda' frustrated so thought I would ask here.



The last couple days when cold it now takes two attemps to start - then idles briefly at 1000 then drops for a few minutes at 800. THEN...drops to 500-650 as it warms up.

Driving and warming the car up it does the same at stop lights, etc.


Any thoughts?

Could be "dropping" cylinders.

[brianlay]

It that were the case it’s not clear why blipping the throttle would restore the idle speed.
You could test for a dropped cylinder by pulling spark plug wires one by one while it’s in the low idle condition.
If a cylinder is not working the idle would not drop further

[fallingat120mph]

Originally Posted by brianlay

It that were the case it’s not clear why blipping the throttle would restore the idle speed.
You could test for a dropped cylinder by pulling spark plug wires one by one while it’s in the low idle condition.
If a cylinder is not working the idle would not drop further

Just bookmarked a thread (from here) about this. I will try this, and a few more things but feel the engine is tired and needs to finally be dropped.



Runs like a champ just won't hold idle.



Thanks-
Erik

[fallingat120mph]

Forgot to mention...after going through everything this morning with closer inspection it appears the AFM has been tapped and possibly "adjusted" by the previous owner or his mechanic.

[mysocal911]

Originally Posted by brianlay

It that were the case it’s not clear why blipping the throttle would restore the idle speed.
You could test for a dropped cylinder by pulling spark plug wires one by one while it’s in the low idle condition.
If a cylinder is not working the idle would not drop further

How about a weak injector not fully opening with the narrow pulse width (PW) at a continuous idle, verses a much wider PW while revving which results in a good idle for awhile.?
Time for an injector cleaner solution?

[fallingat120mph]

Last video, just curious if others have had this issue.

This morning, cold start, turned over but struggled to steady idle initially. Temp in the garage is 70/75F...

Not sure what the 'ticking/"clanking" is right before finally finding an idle. Never have heard the stutter, then clicking, then finally idle.


https://youtu.be/mcME87uIx5I?si=OqTRsZ-MGqWMDIUz

Just want to figure this out (on my own) before I drop the engine and/or take it to the local shop.

Cold starts in the mornings are sporadic the last few weeks.


Could a bad valve adjustment cause this? I did one this past summer, actually twice to check and double check. Other than that, everything is fresh from this year (plugs, distributor, o2, etc...)

As always, thanks for any insight.
Erik

[fallingat120mph]

Still getting odd start ups but got the idle issue somewhat figured out.



Looks like it was this:


I thought I checked last year (triangle of death repairs) but it's been (to my surprise) almost two years of physically feeling/checking the lines. It was extremely soft, almost sponge like at the ends. Terrible connection...looked good but felt terrible.

I just wanted to say thanks to those that hit me up here and in my PM's.

Not sure about the starting (video) but the idle is holding at stops and in the garage.

Again, thanks to those that chimed in.

Oh, and physically feel your lines and connectors...mine all "looked" fine.

Lesson learned.


Erik

[Nick Triesch]

Please check the intake runner bolts!! I have had problems with them over the years. Tighten them to 18 foot pounds. If loose, injection does note work right and air can get in. Vacuum leak.

[fallingat120mph]

Originally Posted by Nick Triesch

Please check the intake runner bolts!! I have had problems with them over the years. Tighten them to 18 foot pounds. If loose, injection does note work right and air can get in. Vacuum leak.

Good call. Found a few threads this past week on exactly that issue. Did check a few I was able to get to and they were well below the 18 ft-lb. Taking things apart to gain access this weekend.

Years and years of driving and once again learning/finding something new...

Again, thanks!