Went on a run this weekend so this is when everything is fully up to temperature.

Driving between stop signs, i heard the oil pressure needle flick down and back up again as i came to a stop.
I noticed this was because the revs die and then recover.

So usual deal, slowing down to a stop, clutch in, revs hanging around 1600 until nearly stopped, then they drop down to idle levels, except they're being allowed to drop too low, then recovering. For what it's worth, the tach is suggesting maybe 500, but it's not accurate enough for this


Any ideas?

 

Look for vacuum leaks that is a typical symptom

 

Yeah..... :( I hate looking for them.

I'm assuming i should be starting with the intake system for this? There is a heavily worn looking pipe in that system, it's a possible candidate.

 

Chances of this being IAC related?

 

Clean the IAC valve and check for vacuum leaks, there is one hose towards the back going to the PCV valve that is known to collapse and crack, Ford has a revised one that has been revised.

 

Hmm, probably should have come back and updated this :(

I did check the IAC and clean it, along with the MAF clean again, i'm not sure if it changed or not, i have also inadvertently disconnected the battery for a short while as i saw the clamps had both started to walk upwards.

I have barely driven it lately, but the last couple of times since then, it doesn't appear to have had the problem.

However, i have not been able to get the truck fully warmed up in order to test this as it didn't do it until it had truly warmed through.

The hose you're referring to, are you referring to the actual vacuum hose attached to the PCV valve itself?

 

Yes it's a hose with a 90 degree bend about the size of a heater hose but rather short.

 

Thanks, i'll check it out.

 

here is a shot of the one I have it's the ribbed one, my original hose in that location was very soft and had cracked and was causing a vacuum leak, check it out to make sure the one you have is in good shape just in case. Hope the photo helps!

 

Oh, yes, yes it does help a lot, and i see you have the same plastic intake runners.

What's the deal with the PCV valve on these? worth replacing?

Actually, i just found a pic of my engine bay, it appears i have a ribbed pipe there after all, i'm assuming they're not as prone to cracking/leaking?

 

Replace the PCV valve, it's inexpensive.
They get gummed up with engine blow-by and work intermittently.
If the various lines and connections are available, replace them too.

If the valve itself is failing to close due to it being dirty, it could cause a drop in idle until the valve recovers with engine vacuum pulling on it.

 

I'll have to pull it, mines heated so I need to see if the attachment is part of the valve or not.

 

Are we talking about the same things, I've never heard of a heated PCV valve before ?

2002 FORD RANGER 3.0L V6 PCV (Positive Crankcase Ventilation) Valve | RockAuto

 

Yup, T pieces from the heater hoses head off to wrap around it - some fords have a electronic heater there I've seen.
helps keep the oil in gas form before intake instead of forming a fluid again.

 

So it's not the valve itself that's heated ?

 

Well, kinda - that's what I have look at in more than a passing observation, from memory, it's looped right around the exit of the valve.