Strange idle, now vacuum line replacement questions (Page 1/1)
dayv27 MAY 08, 11:07 PM
'86 SE V6 has been good, but has been developing a strange inconsistent bog at idle. Car will sit at the stop light at a nice smooth 900 RPM, and then bog a bit, and then be good and then bog again and then back to normal. Some days are better than others, there's no consistency or rhyme or reason to the miss.

Poking around with a buddy who has a better clue than I do, and we're thinking there's a vacuum leak somewhere.

So instead of chasing it, going to replace all the vacuum lines with the RD kit. It can't hurt right? To have all new lines?

So, searching here and other threads, I haven't found a concise how-to thread.

Can anyone please point me in the direction of either a forum thread of a 2.8 V6 vacuum like replacement thread or youtube video?

Or offer any advice for a rookie attempting the change?

Thank you!
olejoedad MAY 08, 11:09 PM
A vacuum leak and would cause a high idle condition.
dayv27 MAY 08, 11:32 PM

quote
Originally posted by olejoedad:

A vacuum leak and would cause a high idle condition.



So if not a vacuum leak, suggestions for where I should start for solving the bog?

And then yay me I get new new vacuum lines!
Patrick MAY 09, 12:34 AM

quote
Originally posted by dayv27:

So if not a vacuum leak, suggestions for where I should start for solving the bog?



Fuel pressure for one. It would be good to know what the fuel pressure is normally, and what it might be during a "bog".

Or it could be inconsistent spark at one plug, possibly due to an intermittent short.

Or maybe due to a worn EGR valve getting stuck in an open position on occasion.

Or one injector intermittently not providing fuel.

Or...?

[This message has been edited by Patrick (edited 05-09-2022).]

olejoedad MAY 09, 06:46 AM
By chance, do you have the A/C on when this happens?
theogre MAY 09, 08:46 AM

quote
Originally posted by olejoedad:
By chance, do you have the A/C on when this happens?

2x because AC can cause this problem. More so if AC has problems like clutch or compressor itself is "bad."

ECM should try to bump idle any time the AC compressor is on but if you mess up setting ignition timing the ECM will have problems.

Also Check/clean grounds bolted/screwed to block etc. Coat then w/ brake or silicone grease.
Crap power or grounds could make more or fake whatever problems. Even cause "Hunting Idle" for this as ECM sees iffy volts.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

dayv27 MAY 09, 09:51 PM

quote
Originally posted by theogre:

[QUOTE]Originally posted by olejoedad:
By chance, do you have the A/C on when this happens?

2x because AC can cause this problem. More so if AC has problems like clutch or compressor itself is "bad."

ECM should try to bump idle any time the AC compressor is on but if you mess up setting ignition timing the ECM will have problems.

Also Check/clean grounds bolted/screwed to block etc. Coat then w/ brake or silicone grease.
Crap power or grounds could make more or fake whatever problems. Even cause "Hunting Idle" for this as ECM sees iffy volts.

[/QUOTE]

No A/C. Nothing other than the cassette player turned on when it does it.


Changed the water pump recently and un screwed the ground from battery, will un-do and clean that area for better contact and see if that helps anything.
I'm dreading doing the wires/plugs/cap, but think that may be next on the list if the ground cleaning doesn't help.
hunter29 MAY 09, 10:24 PM
When was the last time the plugs were pulled?
dayv27 MAY 09, 10:49 PM

quote
Originally posted by hunter29:

When was the last time the plugs were pulled?



Unknown. I bought the car last August. I haven't done it. Previous owners took really good care, but I don't have full maintenance records.
Another One MAY 15, 12:07 PM

quote
Originally posted by dayv27:

'86 SE V6 has been good, but has been developing a strange inconsistent bog at idle. Car will sit at the stop light at a nice smooth 900 RPM, and then bog a bit, and then be good and then bog again and then back to normal. Some days are better than others, there's no consistency or rhyme or reason to the miss.

Poking around with a buddy who has a better clue than I do, and we're thinking there's a vacuum leak somewhere.

So instead of chasing it, going to replace all the vacuum lines with the RD kit. It can't hurt right? To have all new lines?

So, searching here and other threads, I haven't found a concise how-to thread.

Can anyone please point me in the direction of either a forum thread of a 2.8 V6 vacuum like replacement thread or youtube video?

Or offer any advice for a rookie attempting the change?

Thank you!



Dayv, I couldn’t find any info other then what’s on Rodney Dickmans site. I put mine on yesterday and they came with a sheet that had a few tips. Plus, he has a couple of pictures on his site with them installed.

My recommendations (for what they are worth)
Buy the plenum gaskets and a new EGR tube. If you take the EGR tube off at the EGR then it will stay with the plenum cover. Considerably easier to replace when it’s on the bench and they are known to crack causing small leaks.

I left the throttle body attached to the plenum cover because I did not have a new gasket for it. Unfortunately, I damaged 1 of the throttle body rubber coolant hoses and now have a coolant leak. Easy enough fix but a pain in the @$$ in my opinion.

Pull your vacuum fittings from the plenum cover but leave them in place. Once the plenum cover is removed, take pictures of the lines. Wish I had done this part.

The Stainless-steel lines are not very forgiving compared to plastic. I must have taken the plenum cover off a dozen times to get the lines routed the correct way. This line over that line but under the other line.

There is a short rubber line from the plenum cover to the intake manifold that is a challenge to verify so I removed the distributor cap so I had a better view. This also made it easier to connect the PCV valve line to the underside of the plenum cover.

As others have said, I do not believe this will correct your current issue as a vacuum leak will typically cause the opposite of what you describe.

Check your grounds. All of them. See http://fierocave.shorturl.com/ecmwire.htm about 1/2 way down for all the ground locations.