daily doubler build

[wahlstrom1]

How about the typical 4.0L plug wire screw-up, easy enough to do with a project this big.

 

[NMB2]

you need to get a fuel pressure gauge and find out what the fuel pressure is while driving.

 

[kroussinoffroad]

just my .02 cent's but you would think if your dropping spark on a cylinder because of a faulty part (plug's or wire's) it would throw a code for miss on cylinder #__. sound's kinda like the computer is trying to compensate for something and droping spark in turn.

Hard to tell what is going on over the computer. why dont you just put the computer infront of the truck and let us talk to it.

 

[Kyle M.]

My thoughts, before you start tossing money at it, compression check, vacuum check, and fuel pressure check. It could be a number of things but lets start with the basics. You running new gas? And I have had it happen where I gapped my plugs too big and had a stumble under load....
Just my thoughts

 

[RangerSVT]

Bray, I believe the 3.0L coil pack will work on the 4.0L, a quick search on autozone.com will verify. Try using that, if you still have your 3.0L coil pack it won't cost you anything to use it...
SVT

 

[Bray D]

SVT - I did just that. Swapped coils. Ran the same.

New fuel filter and air filter just for good measure. Ran the same. Checked the fuel pressure at the rail. It was just under 30, call it 29psi, at idle, and it would jump up to 36-38 under hard throttle. This was all in neutral, free running the engine.

Pulled the plugs, they are indeed Motorcraft Platinums. Here's what they looked like.

Yes, my cell takes super shitty pics. haha. You can see the color anyways. It was a redish brown.

Checked the gap, all of them were .010" under spec. I must've gapped them all to .045" instead of .054". My bad.

Gapped them all to .054" and reinstalled. Ran the same.

The tank was full when the 3.0 died. 13 gallon tank. I've put ~180 miles on it so far. The last time I filled up was this morning, and I was getting 19.6 mpg. That's 2 mpg better than my 3.0 got when it was running good. At 20 mpg, I've burned up 9 of the 13 gallons of bad gas. Runs the same with the full fresh tank.

When I gave it gas while I was checking the fuel pressure, I could hear it sucking air. I couldn't tell if it was just the air passing through the butterfly valve or not. Sounded like it was coming from the intake on the engine. I felt around, and didn't feel any huge "suck zones" haha.

So, judging by the plugs, hows it running? Rich?

edit: checking the tech library, the fuel pressure is dead on. Hmmm

 

[NMB2]

not running rich at all. Plugs would be black.

 

[Bray D]

I checked a few "spark plug inspection diagrams" and it looks to be more like "normal" than anything else.

Would an intake leak cause it to stumble like it is? It seems first and second gear it doesn't do it as much. 3rd and 4th is gets worst. Most likely due to the higher load on the engine. Cruising at a constant speed its pretty good, just an occasional blip.

 

[Kyle M.]

do you have cruise? Is the sensor at the tranny hooked up?

A gasket leak would do this, cause it to run lean. Spray some carb cleaner around on the engine while it is running, if there is a large vacuum leak it should suck in some of the cab cleaner and idle up.

 

[Bray D]

I have cruise. It works. I'll have to wait till tonight to try the carb cleaner trick.

 

[Bray D]

Went to the autoparts store and picked up a vacuum tester. Read a steady 20 in Hg at idle. Same at higher RPM. If I punched it off of idle, it dropped past 0. If I held it at higher RPM and let off, the vacuum would jump up a couple inches and settle back at 20 once the engine settled back at idle.

I sprayed around halfass with carb cleaner. Couldn't find anything. It def. sounds like its sucking air at the back of the intake. Like I said, couldn't find it though.

Compression test in the morning hopefully.

 

[Bray D]

Is the sensor at the tranny hooked up?

What sensor? With my manual trans, the only plugs that are on the trans harness are the reverse lights, speedo sensor, and the driver's side upstream o2 sensor. All are hooked up.

 

[Kyle M.]

What sensor? With my manual trans, the only plugs that are on the trans harness are the reverse lights, speedo sensor, and the driver's side upstream o2 sensor. All are hooked up.

I meant the speedo sensor, that is for your cruise to work and your engine uses that to know how fast you are going to control idle. If that isn't working or unpluged it will idle low and hesitate, sometimes even stall while slowing. If your cruise works you should be fine.

 

[Kyle M.]

ANy you know, I don't know for sure how much vacuum you should be pulling, but at WOT there will be none so you are alright there.

I might have to find a gauge and hook up one of my 4.0's and compair for you. To me this has got to be something simple.

 

[Bray D]

I checked the tech library, and it says 17-21 inches is normal. Doesn't say what engine that's for though. It also says it should drop to like 2 at WOT. If it drops to 0 there's issues. idk.

http://www.therangerstation.com/Magazine/Summer2003/VacuumLeaks.htm