'86 3.2: Bouncing idle after pushing in clutch.

[PabloX]

I have an '86 3.2 with about 66,000 miles on it. Occasionally, if I press the clutch in to come to a stop, the idle starts bouncing between say 800rpm up to 1200rpm. The frequency of it is about once per second or maybe a bit less and goes away if I give it a bit of throttle. The car runs great otherwise with no issues.

It is due (well, past due) for new wires, cap and rotor but the plugs are new as of last November.

Any ideas?

[stlrj]

Originally Posted by PabloX

I have an '86 3.2 with about 66,000 miles on it. Occasionally, if I press the clutch in to come to a stop, the idle starts bouncing between say 800rpm up to 1200rpm. The frequency of it is about once per second or maybe a bit less. The car runs great otherwise with no issues.

It is due (well, past due) for new wires, cap and rotor but the plugs are new as of last November.

Any ideas?

As the most common problem affecting the 3.2 engine, the answer might be concealed inside the "Search this Forum" key.

[PabloX]

Originally Posted by stlrj

As the most common problem affecting the 3.2 engine, the answer might be concealed inside the "Search this Forum" key.

Yes, I did search first. Since posting this though, I've since tried other terms which didn't immediately occur to me (like "hunting idle"). However, the posts I've found don't describe the exact problem I'm having, though they give me something to try.

Since you seem to be the master of the search engine, I also have an occasional, random click from behind the gauges. It sounds like it's from a relay. What search terms would I use for that oh master?

[Tippy]

Originally Posted by stlrj

As the most common problem affecting the 3.2 engine, the answer might be concealed inside the "Search this Forum" key.

Rennlist has the "DAFS" emotocon. It means Do A F-ing Search.....

Yes, there's is lots of threads on this with lots of different solutions that hasn't been a one-size-fits-all.

[AVDCAV]

Give it a few hours and the motor heads will chime in "
Everyone is at work or prepping for Hershey...

[CCM911]

The problem with this problem is that nobody has ever come up with the end-all and be-all solution. A ton of us have had this issue, yet it will sometimes be fixed, only to rear its ugly head and come back. Start by unplugging your O2 sensor.

[kidrock]

common "hunting idle" issues: bad O2 sensor, dirty or bad Idle Control Valve, and/or improper air/fuel mixture. Start with the tune up issues, you need to replace that stuff anyways.

[PabloX]

Originally Posted by CCM911

The problem with this problem is that nobody has ever come up with the end-all and be-all solution. A ton of us have had this issue, yet it will sometimes be fixed, only to rear its ugly head and come back. Start by unplugging your O2 sensor.

Thanks, the idle control valve and O2 sensor were my first items to check.

I'm more used to modern cars. With this one, are there any downsides to not plugging the O2 sensor back in?

[rusnak]

Don't unplug the O2 sensor. Find the root cause, which could be low fuel pressure, but most likely you have a vacuum leak. You'd fix this by tightening the hose clamps, replace cracked hoses, and tighten or replace the intake manifold gaskets/ bolts.

[turn6]

Do U have the original single wire cht sensor? Asking because of the low mileage of your car. If its determined to be your problem I have a like new updated 2 wire sensor for $50.

[PabloX]

Originally Posted by rusnak

Don't unplug the O2 sensor. Find the root cause, which could be low fuel pressure, but most likely you have a vacuum leak. You'd fix this by tightening the hose clamps, replace cracked hoses, and tighten or replace the intake manifold gaskets/ bolts.

If it were a vacuum leak, would it settle down by giving it a bit of throttle and letting off gently?

Basically, I can induce the effect by quickly blipping the throttle. If I let off more gently, it's fine.

[PabloX]

Originally Posted by turn6

Do U have the original single wire cht sensor? Asking because of the low mileage of your car. If its determined to be your problem I have a like new updated 2 wire sensor for $50.

Good question, I'll check this weekend.

If I go to the two wire version, do I need to run a new cable to it?

[Tippy]

Nope, plug-and-play

[rusnak]

The O2 Sensor for your car is actually a 3-wire. 2 wires are for heat, and the third obviously the dme feedback wire.

Blipping the throttle does not work to correct vacuum leaks. The reason the idle is hunting is that the DME is trying to maintain lambda with false air data from the afm, which is impossible.

[PabloX]

Originally Posted by rusnak

The O2 Sensor for your car is actually a 3-wire. 2 wires are for heat, and the third obviously the dme feedback wire.

Blipping the throttle does not work to correct vacuum leaks. The reason the idle is hunting is that the DME is trying to maintain lambda with false air data from the afm, which is impossible.

So clean the air flow meter? Sounds like I should clean the idle control valve while I'm in there.

Thanks.

[rusnak]

No, find and eliminate vacuum leaks.

You may want to wipe the oil from inside the intake boot if you have the AFM out to test it. You can clean and check the operation of the ICV too.

[PabloX]

I forgot to report back on this thread. I replaced the O2 sensor a couple of months ago and so far, the problem hasn't come back.

[Tippy]

Thanks for giving your fix. Lots never report back.

Did you clean the idle valve too?

[Arne2]

My 3.2 does this, but only on cold start. Will settle to normal idle after 15-20 seconds. Never does it warm. PO replaced the O2 sensor a few months (read as a couple hundred miles) before I bought the car. Since it never does it warm, I'm assuming that it's not a vacuum leak. I suppose the new O2 sensor (correct Bosch) could be bad, maybe contaminated during install. Haven't dug into it in depth yet.

[PabloX]

Originally Posted by Tippy

Thanks for giving your fix. Lots never report back.

Did you clean the idle valve too?

No problem. Hopefully this builds the body of knowledge.

I did inspect the idle valve and it didn't look too bad, so I didn't clean it. Also, I didn't want to do both at the same time so I could deduce what the correct fix was. However, I do plan on cleaning it anyway as the idle can be a bit rough when cold.