Got towed home by a Ford

[EricG]

Had a bad loss of power tonight on the way home from work. Kicked it on N Powers to get around a truck on a hill, and lost all power. Engine seems to run fine, revs fine, no stumble or such. Starts fine, no smoking or obvious leaks. No CEL, gauges look normal.

I limped it toward home at about 40 until I got about 2 miles from home on Black Forest road, then couldn't maintain even 10 mph, so pulled over before the steeper hill before the trees.

Got a ride home and had a quick dinner with the thought that I wanted to let it cool down a bit to look at the coolant. Went back after about 45 minutes. IR thermometer showed about 155-160 F on the block & water pump. Coolant is full and not obviously corrupted, oil fill cap is clean.

Got in and drove, hit top speed of 25 mph for another 1/4 mile, then lost even that and pulled over again. My wife pulled me home with our old beater truck

Checked with the IR thermometer again at home (kept the truck running while we towed). Temps still around 160.

Two more things - at one point looking under the hood I saw a small whiff of smoke or steam back in the vicinity of the EGR valve. I have wrapped and tied back the problematic writing harness there. Also, there is a sound coming from back in that area - it sounds like a massive vacuum leak.

So that sounds like the place to start looking in daylight with a cool engine. Any suggestions?

 

[CO_Hunter]

Bummer. I would start with a compression check. Your last part about the white puff and noise makes me think head gasket but the temps and other things are okay, so that is odd. Any vacuum lines on the tranny?

 

[EricG]

Bummer. I would start with a compression check. Your last part about the white puff and noise makes me think head gasket but the temps and other things are okay, so that is odd. Any vacuum lines on the tranny?

I don't think there are any vacuum hoses to the tranny, but there are to the EGR valve stuff. I've never had one of those apart, but it looks like there might be some sort of diaphragm in their - if that ruptured it would be a vacuum leak, but the small lines to it don't seem capable of the level of noise I'm hearing.

I've never heard of a head gasket sounding like that, but I guess it could if it failed to the outside. rom what I've read, the HG failures on these trucks are almost always at the fire ring on the #5 or #6 cylinder and leak coolant into the cylinder, so wouldn't present as an external leak that could give a wisp of steam in the engine bay.

 

[black95]

Idle air controller stuck wide open?

 

[EricG]

Idle air controller stuck wide open?

I'll take a look... as soon as I figure out what it is and how to check it

 

[EricG]

Ok Hardy boys, here's another clue. This is the bottom of the EGR vacuum modulator and the sound I heard was exhaust (or something) blowing out of it. Off to get a replacement, but don't want to install it until I understand what's going on

 

[EricG]

Those things are unobtainium in town. But I don't think it's the root cause. The rubber hose/tube thing that connects to the bottom port goes to the bottom of the EGR valve, and it's spewing hot exhaust. That can't be right.

Off to read up on EGR systems...

 

[EricG]

Another bit of info - when I first checked the vacuum modulator, the lower hose was off.

I found this thread that sounds very similar: near RTH: Vacuum Modulator Meltdown

The conclusion there was that excess back pressure from a clogged catalytic converter blew the hose off the bottom nipple, and exhaust gas from that hose then melted a hole in the modulator. Sounds reasonable I guess. My EGR valve has apparently been working correctly since it's not throwing codes.

Thing is, I replaced the catalytic converter a few years ago. Seems odd that it would be tanked already. Any suggestions on how to check it short of cutting it out?

 

[EricG]

So final resolution on this was a clogged catalytic converter. Excess exhaust back pressure blew the hose off the EGR vacuum modulator and melted it. New cat & vacuum modulator, and everything is running well again. Little disapointed that the previous one only lasted about 7 years. Also surprised at how quickly this happened - I would've expected a clogged cat being kind of a gradual thing,

 

[SAS]

"gradually, then suddenly." --Hemingway, The Sun Also Rises

 

[EricG]

"gradually, then suddenly." --Hemingway, The Sun Also Rises

Well, hopefully this thing doesn't bankrupt me

 

[CO_Hunter]

Glad you got it figured out.