Thread: V8 4.4 hunting idle under strange conditions

Do a search. Someone recently went through this exact issue only a few months back.

Had the same with a 4l d2 and it was a vac leak from a split hose.

Def do the MAF tho.

As I was reading your post, my immediate thought was vac leak! And then you came up with that yourself. Remember that vac leaks aren't necessarily there or not there. A split can open and close up under various conditions, pressures, temperatures etc. I have no experience at all with your motor, but I'd start by physically tracing by hand (with the motor off) all accessible vacuum hoses looking and feeling for wear and splits and anything that doesn't seem quite right. I'd also inspect any plastic bits. If nothing pops up I'd do it again with the motor running taking safety into consideration. With luck the idle will change when you touch the naughty bit.
If that fails, I'd probably try a smoke test. If that fails I'd find someone who knows what they're talking about!

Originally Posted by DieselLSE

As I was reading your post, my immediate thought was vac leak! And then you came up with that yourself. Remember that vac leaks aren't necessarily there or not there. A split can open and close up under various conditions, pressures, temperatures etc. I have no experience at all with your motor, but I'd start by physically tracing by hand (with the motor off) all accessible vacuum hoses looking and feeling for wear and splits and anything that doesn't seem quite right. I'd also inspect any plastic bits. If nothing pops up I'd do it again with the motor running taking safety into consideration. With luck the idle will change when you touch the naughty bit.
If that fails, I'd probably try a smoke test. If that fails I'd find someone who knows what they're talking about!

Hahahah this cracked me up !

I will check all vac lines tomorrow.
Just did the maf clean - no change;

I would not recommend this but my son found our vac leak by spraying WD 40 around the lines. Engine note changed where the split was.

Or was it Start You B?

Hope not😞

Originally Posted by INter674

I would not recommend this but my son found our vac leak by spraying WD 40 around the lines. Engine note changed where the split was.

Or was it Start You B?

Hope not😞

Yes, i've seen this done with propane - with one of those little blue portable burners, obviously with no flame.
I dont love this method as you need to havesome sort of idea where the leak could be, rather than flush it out.

I willprobably do a smoke test first with a DIY smoke machine.

I just wanted to give an update.

So I cleaned the MAF with maf cleaner, and I got no results.
Today I had an action plan, to first check out the throttle body, and then do a vac leak test with a smoke machine that I was gonna build off a youtube video that I found the other day.

So - this is what I found when I opened up the throttle body.
WhatsApp Image 2020-02-17 at 19.26.51.jpgWhatsApp Image 2020-02-17 at 19.26.51 (1).jpg



So i took it off - but left it on the car as I didn't want to disconnect the coolant pipe. Call me lazy but I couldn't be bothered re bleeding the system.
There is quite a bit of room there so its fine. I just covered it all in my shop rags and it was fine.

I sprayed carb cleaner, but that wasn't really getting the grime off. I considered taking it off and putting it in the parts cleaner, but refer to previous point re:lazy.
I just started using petrol and some thinners with scouring pad (not very abrasive) and i scrubbed and scrubbed and scrubbed. It was very very stubborn.
Once i was done I gave it all a quick polish with some brasso, just to stop grime from sticking again so easily.

I also noticed when looking down the manifold, that the EGR port (sorry didn't take pics) had a huge build up of ash/charcoal that was building up.

I stuffed the mainfold inlet with rags and scrubbed it all off, vacuumed it up, then cleaned it with degreaser and repeat until there were no more chunks left.

This was the result. Not perfect but about x10000 better.

WhatsApp Image 2020-02-17 at 19.26.51 (2).jpgWhatsApp Image 2020-02-17 at 19.26.51 (3).jpg

Result - dead steady idle. No more hunting. Car is behaving and its so good!

Cheers to everyone that helped.

Good result