Lambda Sensor and rough idle

[arm1984]

I'd just like a sanity check on my conclusions if someone could help me out.

I've been having issues with rough idle, occasional stalling and the engine running a little rough when revs increased. I spent a day cleaning MAF, idle control valve, checked all connections sprayed carb cleaner around to check for vacumm leaks. Disconnected plugs, ran engine with MAF disconnected none of this seemed to make a difference.

I eventually borrowed a code reader today and there were no codes stored in the ECU and none generated while the engine was running. MAF seemed to give good signal and responded to throttle changes. Throttle possition read as 18% assume that is ok. The only thing I could pick up was one of the lambda sensors (Bank 1) dropped and flat lined (assume to 0V wasn't very clear on the read out) then back up again to complete the wave form. Bank 2 sensor also dropped flattened a little but always stayed above the bottom never reaching the assumed 0V.

So I from the above I believe my bank 1 lambda sensor is on its way out and needs to be replaced. Can someone confirm this is the most logical step to take or have missed something obvious? Where would I buy a suitable lambda sensor ebay? could someone give me a link.

Andy

 

[kevin p]

Hi Andy, try starting the engine, and then pull the vacuum pipe off the egr valve. If the engine smooths out, then the egr valve needs cleaning. If the engine speed dosn't alter, put a length of pipe on the egr valve and suck. If the engine tries to die, then the egr is ok.
Kev.

 

[arm1984]

Ok I will try this thanks.

 

[arm1984]

Pulled egr hose off the top. No change to engine still ran the same. Attached hose to egr gave it a suck engine died almost instantly.
Any other ideas?

 

[kevin p]

Start engine and pull connector off idle speed control valve. Revs should drop.
Have you done a fuel pressure check?
Remove pcv valve at back of engine. You should be able to hear it rattle if you shake it.
Is the throttle [butterfly] valve got crud around the edges?

 

[arm1984]

I'll try those things tomorrow pcv was on my list. Will try disconnecting idle control valve also.
I have removed throttle body and cleaned already.
Haven't done fuel pressure check, but assume all is ok as problem is the same whether it is running on petrol or LPG. My thinking was if it was a fuel pressure/injector issue then it would go away on the change over to LPG.

Thanks for your help I'll report back tomorrow with findings.

Andy

 

[janolsson]

How are the upper and lower manifold o rings as they can cause rough idle and strange o2 readings as they let in unmetered air when old and brittle

 

[arm1984]

Pulled idle control valve connector while running, revs dropped then engine died.
Started raining so haven't checked pcv valve. Do you need to take the intake off? I can only just get my fingers to it. I may be able to disconnect it but reconnecting to would be problematic. How would I re-attach the bottom hose or am I going about to the wrong way?
Leaking o rings are also part of my list.

 

[kevin p]

This is up to you to try or not.
When you unplug the idle speed valve the engine should idle at about 600rpm. This is the base idle.
Put a mark on the throttle stop screw so you can return it to the original position if you so decide.
Warm the engine to operating temperature. Then unplug the idle speed valve, whilst turning the screw to open the throttle plate to achieve about 600rpm.
Disconnect battery for 10 mins or so. Reconnect the idle valve and see if its any different.
I assumed your inlet manifold gaskets are ok. If they have never been replaced, I would say they need doing. Is it worse when the engine is cold?

 

[arm1984]

Any other tips to test for vacumm leaks. I'm still not convinced there isn't a leak somewhere. If I rev the engine I can hear a faint hiss but I've used carb cleaner and not picked anything up. So I'm unsure if it is just my imagination.
Anyone tried using a cigar to detect a leak and had success?

 

[arm1984]

I can only assume inlet gaskets are the originals. I'm waiting to find out how much they are for a set.

Do you mean disconnect the idle control valve before starting the engine to get it to rev at it's base line 600rpm?

 

[kevin p]

Start the engine and let it warm up. Unplug idle valve and gently keep the engine going with the throttle linkage with one hand while turning screw in with the other. Remember to mark the original position of the screw in case you want to return it to where it was.

 

[arm1984]

Ok. I'll see how I get on and might give that a try.
To answer your other question it is the same cold or hot but when warm the revs are lower so it sometimes drops low enough to stall.

Thank you again for you input.

 

[arm1984]

Just an update.
Inlet manifold gaskets changed. What a pain that was. Lost a socket in the engine bay 1 hr to find, lpg hose obsured lower manifold bolts so had undo some of lpg system, couldn't undo electrical connector which added to the hastle of getting to the rear lower manifold bolts. Got stuck in race day traffic everything seemed to be against me. On the plus side, seems to start a bit better but issue is still there.
Took off PCV valve off, rattles when shaken so assume ok.
I've ordered an aftermarket IAC valve as it's the next cheapest thing to try.

Oh and the leak on the front diff has got worse so that needs sorting sooner than planned.

Will it ever end?:frustrate

 

[kevin p]

Are you using LPG spark plugs?

 

[arm1984]

It is running much better after a couple of days driving. Idles at 1100 ish from cold start, nice and stable slowly drops to around 600 as the engine warms. It hasn't tried to stall once. Maybe it was just a bit grumpy I'd been messing about with it again. I'm going to stop fiddling with it for now and see how things go. Hopefully mpg will increase slightly now as well. Though I didn't think 17mpg was too bad on lpg.
Don't know what plugs are in it. They were recently changed by Jason at explorerparts when I had some other work done so I assume they are lpg plugs.