Topic: Mercury Cougar Engine Problem

[Drup44]

Hello everyone!

I have a Mercury Cougar V6 2002, and its engine has been acting up lately.
Me and my brother have been trying to figure it out, but we're not quite sure what to think.

First of all, I thought my problem could be solved by changing the spark plugs, which I did. I found quite a lot of oil on some of them (not burnt residue, actual oil).
Because of that I thought that my problem could be coming from there; oil excess might have perturbed somehow the combustion. We think the problem is more electrical, I'd like to know what you guys think before we proceed to try and fix it.

The engine is running very irregularly, I have an intermittent problem. In idle, the engine sometimes stalls by itself. When it doesn't stall, I often get big RPM drops; most likely caused by missfires.
While driving, I often get missfires too. If I'm pressing on the gas when it happens, the engine starts right back up and the whole thing feels as if I tapped the brakes.
If I'm going downhill, not pressing the gas pedal, the engine doesn't start back up, but a little tap on the gas is enough to start it up again.

I don't have any coolant leak problem, the oil is of a normal color, although the engine does drink up oil.
We are not sure if the problem is in any way linked to that oil leak in the combustion chambers. I'm ok with an engine drinking up a bit of oil, I'm less OK with an engine stalling when it feels like it.
I do not own an OBD2 scanner, so I can't provide any diagnosis from that for now. I will manage to get one if necessary, but before that, I'd like to have you guys input.

Did any of you have/has heard of a similar situation?
Any of you have an idea what we should look into first?
I don't think it's linked to the fuel system. The pedal always answers perfectly.
Thanks in advance!

[Fobroader]

The 3.8 V6 always had head problems. Probably valve oil seals

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[Firm]

These had the 2.5L V6 (a Mazda unit?) not the 3.8L. However, from the sounds of it, I'd say that the oil is fouling up the plugs and causing your miss-fire. Why there's oil there, could be a number of reasons, none of them very good news. I'd do some research on google to see if there are any common failure points on that engine; heads, headgaskets, valve seals, etc. Hopefully that'll give you something to go on.

[Fobroader]

Oh .....that kind of Cougar, ha, yeah, never mind what I said.

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[Drup44]

Ok, thanks for the input!
I actually found a Cougar owners forum that I somehow managed to overlook before.
The general opinion seems to be head gasket blown up over there. Bad news is that the V6 is apparently twice as much work as the standard 4 cylinders. Yay for me!

Thanks for your help!

[EV-Light]

buy one of these: https://www.amazon.ca/gp/product/B00WPW6BAE/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

...worth checking for codes, what you are experiencing could be the result of failed senors, EGR, etc...

[Drup44]

Hello everyone!

So the problem on my car is now solved, and I just felt like giving you guys some input about it, so we can all learn. ;P
First of all, the whole thing ended up being much cheaper than expected.

I braught my car to a garage to have a final diagnosis before starting the dirty work.
When the garagist pluged in the OBD2, there were indeed error codes, but no miss fires.
There were 5 codes in total, only one regarding the engine: EGR sensor malfunction.
Now I have an exhaust leak on my car, it's been there for a while, but never really bothered me all that much.
He first didn't think that sensor could be a problem, so he ignored it. He poured water over the engine to ensure there weren't any leaks, he checked the mass airflow and cleaned it, the whole air intake seemed good.
The spark plugs were good, the wiring didn't seem faulty, although I think that was somewhere on his list of things to check.
In the end, that EGR sensor problem lead him to the real problem. The car was constantly rerouting exhaust gas in the intake. It is normal to a certain extent, that extent was being exceeded. That's why I would sometimes stall while in idle; not enough oxygen available in the combustion chambers so my engine couldn't keep up.
There was a constant vacuum in the EGR valve, always sending exhaust gas in the intake. He just unpluged the vacuum and stuck a screw in it to prevent dust from accumulating.

The oil on the spark plugs certainly isn't 100% healthy, but didn't cause anything else than a minor oil consumption and maybe a bit of carbon deposits there and there.

Just wanted to close the case, in case anyone encountered similar conditions.