Topic: leaking injector(s)?

[21Rouge]

I did an oil analysis on my 2000 Montana minivan (109,000 km). The lab red flagged this report as there was huge fuel dilution in this sample ie approx 6%!

Some background on this vehicle:  Oil Change Interval: 4 months (September to January) and 1200 miles. (This car's weekday routine is generally 2 trips per day, 3 miles each way. Additional trips are short...almost no hwy miles)


But I am a bit confused....

first, the previous oil change was analyzed and there was no evidence of fuel dilution.

secondly I had the following service done last April at the Pontiac dealer; less than 8000 km ago (prompted by a CEL):

replaced EGR valve and gasket
replaced fuel filter
injector service
replaced fuel filter
replaced spark plugs and spark plug wires
replaced ignition coil
clean throttle body

again ALL this was done less 9 months ago and less than 8000 km has elapsed.

And so far there has been no CEL.

What do you think?

[articsteve]

What do you think?

Stop doing oil analysis on this vehicle.   

It will be very costly to get to the bottom of this fuel dilution given that the vehicle is driven under very severe conditions.

What I would do is, when the temps are above 0C, use SAE30.  GM insisted on SAE30 for their older diesels above 0C because that oil is good at fighting fuel and moisture dilution and the 6.2 and 6.5 GM Diesel had that in spades.

[yugrus]

I'm not sure how any oil would fight fuel dilution of this magnitude... Fight with what?

[barrie1]

As I suspect this is a Gas Engine and dosen't go for at all on many Daily trips then you are not driving it enough to Heat it up to proper temps. 1200 miles in so many months is not a lot of milage at all. 3 miles will not fully warm up this engine and only load up the oil with Fuel. It needs to be driven more longer trips to get up to full operating temperatures.  If you were to take it out on a highway for a run for an hour ot 2 you will find a difference on your oil specs. I am sure the whole performance would increase from just blowing the carbon out of it as well. Oil testing is great but drive the vehicle properly and save a few bucks and have less worry. 

[smainville]

Was there a time in this period where the engine would not start and was flooded?

[21Rouge]

Was there a time in this period where the engine would not start and was flooded?

Never.

[21Rouge]

It will be very costly to get to the bottom of this fuel dilution given that the vehicle is driven under very severe conditions.

If one checks the plugs and all looks fine then......all is fine? Checking the plugs for fouling would be a first, relatively simple test?

GM insisted on SAE30 for their older diesels above 0C because that oil is good at fighting fuel and moisture dilution and the 6.2 and 6.5 GM Diesel had that in spades.

Funny you mention that: although the Montana is a gas engine I did replace the tested oil with the dual rated (gas/diesel) Esso XD 0W-30.

[21Rouge]

As I suspect this is a Gas Engine and dosen't go for at all on many Daily trips then you are not driving it enough to Heat it up to proper temps. 1200 miles in so many months is not a lot of milage at all. 3 miles will not fully warm up this engine and only load up the oil with Fuel.

I agree that low mileage and short trips  do contribute to fuel dilution but 6% is huge. Wouldnt a leaking injector be a definite possibility?...worth checking the plugs?

[articsteve]

I agree that low mileage and short trips  do contribute to fuel dilution but 6% is huge. Wouldnt a leaking injector be a definite possibility?...worth checking the plugs?

You can always do that.  However, since you mentioned that you replaced the coil (this is a single coil motor, yes) I would suspect that instead of a leaking injector you have an under performing plug or juice to that plug.

So, yes, I would look at the plugs.

[21Rouge]

I agree that low mileage and short trips  do contribute to fuel dilution but 6% is huge. Wouldnt a leaking injector be a definite possibility?...worth checking the plugs?

You can always do that.  However, since you mentioned that you replaced the coil (this is a single coil motor, yes) I would suspect that instead of a leaking injector you have an under performing plug or juice to that plug.

Artic, if it was a plug problem as you are describing wouldnt likely a CEL be generated?

[articsteve]

Artic, if it was a plug problem as you are describing wouldnt likely a CEL be generated?

Firstly, I don't think you have a mechanical problem worth looking into.

Secondly, when I say an under preforming plug I'm not meaning that it is not firing.  You can look at each plug and see if there is a difference between them, but that could be a result of a under performing cylinder (which you'd rather not find out about) .  I don't think an under preforming plug will set off a code in a 2000 Montana.  How would it know which cylinder it was?

If you find one plug different then you could have a new o -ring fitted on that injector I suppose. When it comes to used vehicles like yours my personal opinion is not to go looking for troubles that aren't effecting the daily operation of the unit.  Not to offend, but that 3.4 is a turkey and if it runs smoothly then quite frankly it's not worth fretting over because it will run and the something else on the van will die and not be worth repairing and that will be it.

If it were mine I would not waste the syn oil on it year round.  I'd get a case of Esso SAE30. that they use in diesels and just change the oil every 4 months and use SAE30 for 8 of those months because that van is operated under severe usage.  So from December 1 to April 1 I would use the Esso 3D.

[barrie1]

You should be able to almost feel which cylinder is underworking if that is the case just by having your hand close to each wire. The one with the least amount of heat coming from it will be the suspect wire or plug. As it would not be working correctly it will not generate as much heat as the others. One of the new Heat temp tools which you aim and point will also tell you the same thing but more accurate. Warm the engine up to full operating temp before you do this test. 

[yugrus]

I'd suggest going with the cheapest SL dino oil you can get, take the car on the highway for one hour weekly. Change  the oil at 2000km or less and do UOA. See how it looks like then.

[tpl]

I agree.  Italian tuneup of at least 100 km. and pick a longer route for those two trips a day.   regular  dino oil

I suspect that you might find the oil level will drop a lot after the 'tune-up" as all the dilutants ( fuel and maybe even water from condensation) in the oil will disappear.

[21Rouge]

Firstly, I don't think you have a mechanical problem worth looking into.

You really think such shorts trips could produce such a large fule dilution?

Maybe as a precaution I will have the plugs looked at. If no evidence here I will do my best to get her some hwy miles.

[barrie1]

There's only one real way to find out and that is to drive this vehicle further almost everyday as the fuel dilution will be a lot less. It can add up very quickly if its never gets up to temperature correctly.  It really dosen't take all that long at all for this to occur. 

[21Rouge]

It can add up very quickly if its never gets up to temperature correctly.  It really dosen't take all that long at all for this to occur. 

That is a good point. I dont like taking it 'cause the tranny is wonky  http://www.cartalkcanada.com/forum/index.php/topic,31907.0.html AND this car doesnt have the satellite antenna like the other. (Off topic but sat. radio is the best money I have spent on 'stuff' in a very long time).

But one son has a hockey game tonight in Orillia tonight...1.5 hour drive. Will give it a run.

[barrie1]

Have you had this tranny serviced yet as a new filter and oil change just might do some good as well. They can inspect the bands when they are in there and adjust things as necessary as well. The Change out should cost around $75. to $100. on average. 

[21Rouge]

So, yes, I would look at the plugs.

Okay so I went to a mechanic I have used before. He had only enough time to check the front three plugs. I did not tell him when I had them last changed as he removed them. All three looked equally very worn. They were to be gapped at .06 he observed from the info on the bottom side of the hood but these three were much closer to .08. He said they looked about 5 years old. It was than I told him they were replaced April 2005, 5k miles ago. He couldnt believe this was so. I then showed him the dealer invoice/receipt. Any suggestions as a next step? 

[barrie1]

Who ever did the last tuneup may not have checked the gap correctly. A lot of Mechanics take for granted that they are Factory preset for the car or vehicle. Yes they are but the same plug also fits different models and may have different specs for each on gapping. Either that or they did not do the work you paid for. They should not be that worn yet or dirty looking either.  Those actually seem like very unusal gap figures for this vehicle as normaly most GM's have a plug gap of around .045 on the electronic ignitions. Some of the early ones went to .060 but that was the extreme at that time.  Which grade of plugs and brand was installed the last time?