3.0 runs terrible after tune up

[Mosinguy]

I posted in the 3.0 forum but I need this to work for school tomorrow and it's starting to snow here.
I used Autolight plugs and "Xact" plug wires and now my truck runs terrible. I gapped the plugs to about .042. I pulled one wire from the distributor at a time when I was replacing them. I'm at wits end. It ran relatively smooth before the tune up.

 

[twb4525]

I would recheck the spark plug wire routing. make sure they are not touching each other or grounding out on the engine block/manifold.

 

[FritzTKatt]

Check gap again. Go with whatever is printed on the radiator support. Use one of the gap tools that looks like a coin, not a wire type one. Those wire ones suck (but I still use one to do the bending). Double check the P/N for the correct heat range rating of the plug. Sometimes you do get bad/incorrect parts.

Check for proper torque on the plugs. If by chance they are loose, then there's a problem. They only need to be a bit past hand tight.

Do a continuity test on the wires individually. It's possible you had broken one or gotten one broken. You can also check/swap with the old wires and see if a difference is made.

 

[Mosinguy]

Make sure the actual wires aren't touching? But they're insulated I didn't think that would be an issue. The plugs are pretty tight but I didn't crank down on them or anything. I did gap them with a blade type feeler gauge.

I just wanted a vehicle with mileage better than about 10 mpg not a last minute project.

 

[RonD]

Yes, recheck firing order .....at both ends
Firing Order 1-4-2-5-3-6, distributor turns clockwise

drivers side front---->
6 5 4
3 2 1
passenger side

Pop off distributor cap and reinstall, pulling off old wires could have made it cockeyed.
Also check wires on side of distributor, you could have pulled in loose.
Also a vacuum line could have come loose while changing wires

Unhook battery while doing this, just negative cable is OK, if battery is unhooked for at least 5 minutes computer will reset and learn about the new plugs and wires

 

[Mosinguy]

Double checked everything a billion times except the plugs. Anyone know the correct gap and torque spec? Guess I'll try that tomorrow.

 

[bmerr98]

Spark plug gap should be listed on one of the stickers in the engine compartment near the front of the vehicle. Somewhere in the. .052 - .056 range IIRC. Correct gap can make a big difference. As mentioned check for vacuum lines that may have been disconnected inadvertently during the tune up.
Just about guarantee it's something simple. You'll get it.

 

[Mark_88]

I agree with plug firing order, but if it actually starts and runs then maybe gap or vacuum...

I recently worked on a 3.0 that someone else had tuned up...they somehow managed to get the wires completely screwed up and the truck wouldn't start at all...and it took me three tries to actually get it right (probably because I had someone looking over my should telling me wrong information...lol)...

Another thing is to check the pedal for play...probably not related but the reason the 3.0 was being "tuned" was lack of power...I found a 1/2" of play in the pedal that "restored" the power loss instantly.

Sometimes things happen at the same time and you don't realize that there is more than one thing that needs attention.

 

[gw33gp]

Make sure the spark plug wires are fully seated on the spark plugs and distributor. Also check to make sure the connectors in the spark plug wires are not recessed to the point they are not actually connecting, especially the distributor end.

 

[ab_slack]

Make sure the spark plug wires are fully seated on the spark plugs and distributor. Also check to make sure the connectors in the spark plug wires are not recessed to the point they are not actually connecting, especially the distributor end.

^^^ This one.

I recently went thru it and while I was sure I had them all fully plugged, I actually had one at distributor and one on a plug which weren't fully seated.

There should be a nice reassuring kind of click, more felt than audible when they snap in. I find the plug wires particularly challenging at times to get on because of how tight the boot fits on the plug.

 

[Mosinguy]

So I'm stupid. Luckily my dad supervised me today. We regapped most of the spark plugs except the hard to get ones on the pass. side. Still ran bad. I commented on a hissing sound. If I held the throttle it ran fine. Dad found a little cap fell off the manifold and it was sucking air through the little fitting. Threw the cap back on and we were good.

Moral of the story: a second pair of eyes is always helpful!


To be more clear, it was a cap for some sort of fitting right next to the distributor cap. The brake booster runs off that fitting as well.

 

[RonD]

Good work

Thanks for posting the fix

 

[bmerr98]

We knew you'd get it! Pretty sure most of us here have done exactly the same thing. I had that motor years ago and recall a similar episode. As an added bonus, you have learned that old Dad might be smarter than you thought!

 

[Mosinguy]

Luckily things worked out where I got to drive dad's Explorer today. I liked sitting up that high on the road. Can't wait to drive my Ranger to school for the first time. It'll be one of the few pickups in a school of 2,500 students. It's probably the cleanest one there. thanks guys for the help. That cap sure had me stumped.

 

[zekew64]

Incidentally, where the cap had fallen off is the intake manifold vacuum tree. This is where the engine takes manifold vacuum and uses it for different things, such as the EGR, the fuel pressure regulator, and your cruise control, if you have it. Just some info for you, for future reference; also, make sure you have all the openings that aren't used sealed with good caps--if you don't, you'll get a vacuum leak and won't have good driveability/performance.