It started a few weeks ago. Mid-day, in the heat. It would stutter, bog down and then die. Let it rest for an hour or so and it would start back up and run fine. At first I thought it was a fuel issue but I ran the codes, pulled PO171 and PO174. So a vacuum leak, right? I put a long hose to the metal pipe that connects the manifold to the brake booster and blew smoke into the engine. The only place I found smoke coming out was at the very beginning of the air intake. Before the air gets to the filter. So I just started replacing vacuum lines. And everything from the pcv and grommet to the IAC valve. The problem keeps getting worse. Now it'll run for an hour in the morning and won't start again till late at night, last night it didn't start until 10pm. A few days ago,

I took it to a mechanic, I paid him $150 to diagnose it. He said it needed a new head gasket. I got it home and decided to look at it from that angle. I did a block test and the fluid stayed blue so no combustion fumes in the coolant. Checked the oil, not milky at all. Decided to check the plugs, if coolant or oil was getting into a chamber, I would see it on one of the plugs, right? Well, all the plugs looked the same. Like they were lean and overheated. Very white, with some darker (dalmatian like) spots. I'll try to post a picture below. But that makes since because I've gotten a knock in the last week as well.

I still think the problem is vacuum related but the new Idle air control valve has a vent on top so when I blow smoke into it now, I just get a bunch of smoke coming out of it.

Anywhere I should check for a vacuum leak? I remember one my 66 f100, I found a vacuum leak on the back side of the transmission. Any sneaky places I should look on a 98 F150 4.6l?

Thanks

 

 

 

I realized I haven't been able to get it to turn over since I replaced IAC valve and some of the rubber. I mean, like it doesn't even sound like it wants to start. Just the sound of the starter. I put the key into the on position, and I hear the relay "click" but I don't hear the fuel pump.

Change of plans for tomorrow. Looks like I'll be checking and chasing fuel issue.

I'll let you guys know how that goes.