Rough Idle On 3.3 Petrol Auto

[TinTent]

Hi,

I am having trouble identifying a problem with my 2003 Grand Voyager 3.3 Petrol Auto (EGA engine). Ever since an overheated engine caused a head gasket to blow 2 years ago - (Heads removed, skimmed and replaced). The symptoms I have are an occasional rough idle when stationary. It is just slightly annoying and tends to happen when you stop in traffic with the transmission in Drive.It used to be that it happened about 30% of the time when stopped, but now it is nearly 90% of the time. Turning off the A/C and shifting to Neutral alleviates the slight body shake caused by the rough idle. Once the vehicle is moving though everything is fine, good acceleration, smooth, normal fuel consumption etc. I get no OBD error codes. When idling and hot, with a hand over the exhast, you can feel the occasional miss from the rough idle. When engine is cold, idle is OK

 

I have taken most of the steps that I would consider normal to fix a rough idle which would focus on things that cause a bad burn at idle.

So, I have replaced (with new) Spark Plugs, HT Leads, Coil Pack, IAT Sensor, MAP Sensor, CMP Sensor, PCV Valve, Upstream and Downstream O2 Sensors. I have also replaced the upper intake manifold, resealed lower intake manifold, changed throttle body with Idle Air control valve and throttle position sensor with second user replacement parts. I have also tried gas testing the air intake areas with no change in engine idle.

I have clamped/isolated the EVAP cannister and Crankcase vent hoses etc and checked their continuity. I have checked all cylinder compressions and although they vary they are within the manuals range of upper and lower. Nothing changes the idle symptoms.

 

I have a Launch CR123, to analyse the PCM. I can see the switching of the Upstream Sensor, Downstream seems to stay in the middle. The O2 test which is an option on the analyser does not work on the vehicle. There is an option with the scanner to check live data streams. These all check out OK ie pass, except $17 live data stream which registers a fail. I cannot find anything that tells me what this is.

 

I would be grateful if anyone has any info on the $17 data stream or anything else that could be suggested to help me stop this rough idle.

 

My next steps are to replace the lower intake manifold, change the o2 sensors again, replace the cat. I have assumed that all the new parts I have are OK but am thinking they may not be. I am beginning to run out of ideas and would welcome some thoughtful assistance.

 

Many Thanks...

[TinTent]

Oh,

Forgot to add that I have replaced the injectors and rail with second user parts and fitted new o-ring seals.!!

[bignev]

Hello there!

Well you've done them - but I was going to suggest the injectors, but it is much rarer in petrols for them to cock up, I would guess because of the lower levels of soot in the combustion chambers.

 

You've obviously done all the usual ignition parts I would have gone for myself. Getting worse when hot used to be a plug fault symptom.

Missing under load was too, and for the HT leads, but they're all new.

 

So I'm stumped, but will continue to mull it over and see if I can think of anything obscure!

[macuniyanukukuk]

Hi

Wow there you certainly have done a lot of work on your GV. I have a 2007 3.3 petrol, I have a very similar problem to yours. I don't have rough idle but do have body shake when in drive. I seem to think mine may be related to the engine mounts. I think maybe you should be looking at the same because rubber tends to be more softer when hot. Maybe something to try.

Let us know how you get on.

[TinTent]

Thanks for you comments guys.

The sparkplug issue got me thinking.This was the first thing I changed over a year ago when the problem first started.

So 6 new NGK iridium plugs have been fitted. I also fitted a second user temperature sender unit as well.

The idle has improved and while the body doesn't shake any more, there is still the odd miss that you can feel with your hand at the exhaust.

So not totally fixed, but a little better.

 

I am still keen to understand the $17 fail on the Launch Scanner Live Data feed. I seem to recall seeing something about the downstream sensor on a town and country forum related to this. I also recall that unlike some other manufacturers, Chrysler uses both o2 sensors to control the fuel injection, rather than the upstream one. So contemplating checking that I have the correct O2 Sensors etc and perhaps getting a downstream sensor.

 

Also, to my knowledge the catalytic converter has never been changed in its 15 year, 100k life. So may look into this, although the cost might be prohibitive, unless someone has noticed any change in the running of an engine after one has been changed.

 

Cheers...

[AustinM64]

Hi,

I am having trouble identifying a problem with my 2003 Grand Voyager 3.3 Petrol Auto (EGA engine). Ever since an overheated engine caused a head gasket to blow 2 years ago - (Heads removed, skimmed and replaced). 

 Hi There,

 

I have to replace my Head Gaskets and wondered if you have to buy replacement Head Bolts? You look like you have done this before so thought I'd ask.

 

Cheers

 

Austin