Misfire at speed, under load, runs smooth at idle, smell coolant when missing

[wagonteeth]

In the past week I've developed a misfire while driving. It's intermittent, usually starting after driving for 20+ minutes. The misfiring seems to clear up if I gas it, but running at cruising speed/rpms (45mph/2100rpm) it's pretty constant. Oddly, when I'm in a right hand turn it seems worse.

A few weeks ago I sprayed my engine down at the car wash to get a lot of dust off of it. I got the typical miss from getting the distributor wet, so I loosened the cap and tilted it for any water to drip out and retightened it and all was well for a couple weeks.

So this time it felt just the same, so I pulled the cap off and found that oil was leaking into the inside of the distributor. I replaced the distributor, plugs and wires, set the timing with a timing light to 8 degrees and the miss is still there. It actually sounds more constant than before.

While driving, when it's missing, I smell coolant, so I'm thinking head gasket, but there is absolutely o sign of oil in the radiator, and no milkshake on the dip stick or oil cap.

Next step is a leak down test to see if I have a HG leak. I was debating on the chemical test or a compression gauge.

Anyone have any tips on diagnosing? I don't want to assume that just because I smell coolant, that it's the HG if there is some electrical thing going on. I smell no coolant at all when it's at idle or at 2000 rpm in the driveway, just while under load of driving.

 

[Dave 2000]

Don't rely on oil in rad and vice verse, does not always happen. Is the engine running any hotter? Is the coolant level falling? Pale smoke at the exhaust, with the AF smell?

Is it possible you have a pin hole in a hose/rad or wherever spraying water onto electrics? All I can think of at the moment.

regards

Dave

 

[wagonteeth]

It's losing a bit of coolant, but over a long period of time. There is sign of coolant leak at a heater hose right behind the #6 spark plug going through the firewall. Even after driving it for 30 minutes and pulling over and checking, I can't find any wet spots or steam.

The greenish tint on the hard line at the heater hose is the only sign of a leak, and I'm wondering if it's spitting coolant when the misses happen due to a line pressure spike? and that perhaps that's why I'm smelling it only at that time. The harness that runs by the EGR tube has melted the protective shield, but I don't see any bare wires at all.

I also don't get any codes.

On start up it runs great, and even after skipping, when I stop and pop the hood, it's idle is consistent.

Temperature has not moved at all, and it hasn't overheated.

 

[Dave 2000]

Wedge a piece of card between the head and firewall, drive around and see what side is getting wet, that should help with diagnosis.

regards

Dave

 

[ajax1]

Possible when rev the engine it is rotating and your harness is rubbed through causing it to tweak and ground out wire in harness?

 

[Tedward]

Had a slow coolant loss myself and found a loose hose clamp on the hard pipe above the exhaust manifold. I could occasionally smell coolant. Was allways dry as it was burning off right away.
I spray wash the engine regularly and show no mercy. I don't get the expected miss afterwards. Probably due to the newer disrubutor cap gasket.
My distributor leaks a small amount of oil past the inner non serviceable o-ring. Then it seeps out through the small hole in the bottom of the cap with no ill effect (affect?).
As tools suggested look at your wire harness where it passes close to the egr tube and check your air intake tube.
Good luck chuck!

 

[LINUS]

If you search the headgasket failing threads, see if any other symptoms others have described line up with your running conditions.

You don't mention if the HG has been done previously - I'd hate to steer you down a path & get you worked up over it if the HG been done.

Did you have the issues prior to the powerwashing?

I'd also take a little sandpaper to your rotor & scrape cap contacts too - if you haven't already.

Maybe do the spraybottle / spray water while running in the dark to see if you're arcing anywhere.

Also, before we sell your HG down the river, any chance you possibly have a heater core issue, or cooling hoses in general?