4.0L missfire problem

[Little Egypt]

Hello all! I've been lurking about trying to find an answer to my problem for a while, but to no avail. I apologize for the long post, but I'm at my wit's end.

Anyway, here's the deal: I have a 2000 4.0L 4WD Ranger. For the past couple of years, about every 6 months I would start to get a misfire. I would change the plugs and the problem disappeared. The strange thing is that the driver's side plugs (cyl 4, 5, & 6) would be fouled far worse than the rest of the plugs. Cyl 5 would just have carbon and a little oil on the outside, but cyl 4 and cyl 6 would have oil and carbon and oil on the outside. Cyl 3 would have some oil on the outside and would occasionally be fouled by some oil/carbon. Cyl 1 and 2 would be clean as a whistle.

I had read about the MAF and intake manifold bolts here on the site, but never got around to dealing with them. Finally, about a month ago, the MAF starts sending codes to the computer. I tried cleaning, but that didn't work, so I got a new one (rebuild from Advance), replaced it Monday, and I thought the problem was solved.

Within 20 miles after replacing the MAF, I start getting the misfire again (it's been a little while since my last plug replacement), so I pulled over and replaced the plugs. I continued on my trip (~750 miles round trip) and I'm getting terrible gas mileage the whole time. At first I thought it was just the strong wind, but when I started getting less than 10-11mpg, I started to get irritated. I made it back home, but the misfires started up again Friday. So, it's been only about 800 miles since the change.

For the record, I seem to get the best mileage and durability with the NGK iridium plugs, but I decided to try Motorcraft this time. I got the firewire platinum plugs for this change.

I had kept the old plugs (they weren't that old and didn't look that bad), so I cleaned them with carb cleaner and reinstalled them. The truck runs smooth now, but I haven't driven it down the road yet.

So, here are my questions: 1/ Does it sound like I need to torque down the lower intake manifold bolts to solve my problem? 2/ Is the rebuilt MAF sensor I got from Advance crap and I should have got a "new" one instead? 3/ Is it something completely different?

Thanks for any help you can give me!!

Cheers,
Aaron

 

[almostclueless]

I would definitely check the manifold bolts if my truck acted like that.


The only plugs I'll use in these rangers are autolite DUAL PLATINUM plugs. It matters IMO.

 

[mhughes165]

newer vehicles REQUIRE platinum tipped plugs, thats why u seem to get the better responce with the NGK, they have a hotter spark and the ECM is tuned accordingly from the factory.

that being said, check ur intake bolts, it definatly sounds like u have a ongoing problem...

also are u losing any liquids, oil coolant etc.

 

[almostclueless]

newer vehicles REQUIRE platinum tipped plugs, thats why u seem to get the better responce with the NGK, they have a hotter spark and the ECM is tuned accordingly from the factory.

Newer vehicles with "wasted spark" systems essentially require dual plats otherwise the side electrodes that arent platinum tipped will get eroded away very quickly.

 

[Little Egypt]

also are u losing any liquids, oil coolant etc.

Now that I think about it, I think I have lost some coolant. Do you think it's leaking into the cyl through the loose gasket?

So the dual platinums are better than the iridiums?

Any other possibilities/things to check?

Cheers,
Aaron

 

[rangerbert]

I read somewhere that someone whent to replace the plugs they were given plugs for a ohv instead of for sohc. Double check the part numbers to make sure you got the right ones. Change your wires, if you have make sure they are tight.

 

[Little Egypt]

Ok, so I checked the part #s on the plugs and they're the same as the previous set of NGKs and I have been having the same problems with all brands of plugs from different stores. However, partsamerica.com lists this plug for both the OHV and the SOHC.

The wires are only about 1 year old and they're all on the plugs nice and snug.

I checked the coolant level, and I was ~3/4 of a gal low. In fact, just today it started getting a little hot before I topped up the coolant level. Now, the temp is fine.

I tried to get to the lower intake manifold bolts, but I couldn't see them all. I don't want to torque the bolts incorrectly, so I decided not to mess with it.

I purchased a gasket set today, and tomorrow I will replace the lower intake manifold gasket as well as the upper intake and valve cover gaskets (they have to come off to replace the lower gasket).

The truck still misfires like crazy and it's driving me nuts. Hopefully changing the gasket will solve the problem.

Cheers,
Aaron

 

[Little Egypt]

Ok, Tuesday I changed the lower intake manifold gasket, the fuel rail gasket, the plenum gaskets, valve cover gaskets, and torqued all the bolts according to specs. Everything was cool for the first 50 miles or so and then I thought I noticed a misfire again. Today I felt several misfires and the check engine light came on. I haven't pulled the code yet (I will tomorrow), but I'm willing to bet it's just going to tell me it detected a misfire or lean fuel mix. What now????

Cheers,
Aaron

edit: I almost forgot to mention that I changed the plugs while I was at it. I used the motorcraft finewire.

 

[rangerbert]

check for vaccum leaks.

 

[KELLY88]

Could be dirty injectors or clogged fuel filter.

 

[mhughes165]

if you are still losing coolant, check the condition of all the plugs, it sounds as if you have a headgasket leak allowing coolant to enter the combustion chamber, which in turn will cause a misfire, this is also most likely the reason for losing coolant

 

[rangerbert]

If your losing coolant ypu may have some bad freeze plugs. If you have had this problem for awhile (losing coolant) is it leaking into the engine oil. Just wondering

 

[Little Egypt]

Ok, I pulled the code and it said lean fuel mix. I haven't checked all the vaccum lines yet, but the large rubber line from the bottom of the throttle body to something on the drivers side fender well (looked like something to do with the brakes) was in pretty bad shape, so I replaced it.

It was kind of a strange vaccum line in that it had a hard plastic elbow in the middle of the line. Anyway, no problems so far, but I've only driven about 3 miles since then. I have to drive 10-15 miles home, so we'll see then.

I changed the fuel filter not that long ago, so I don't think it's clogged yet. However, I've certainly been wrong before and I'm not ruling anything out!

I don't think I've lost any coolant since I changed the lower intake manifold gasket. Although the coolant I was loosing before wasn't exactly disappearing overnight. It was quite a while before I noticed it. I haven't seen any water in the oil, but I'll change it soon and check again. I don't see any smoke in the exhaust. Is there any other way to diagnose a head gasket leak?

I use fuel injector cleaner fairly regularly (about every 10K) and the last time was about 2 weeks ago. I used Lucas injector cleaner. Does anyone have a picture of what a dirty injector looks like? I pulled them when I changed the gaskets.

Cheers,
Aaron

 

[Little Egypt]

Well the check engine light came on yesterday on my way home and there were a couple of misfires. This morning the misfired most of the way to work and started as soon as I started the this evening on my way home. It was as bad (or worse) as it was before I changed the manifold gaskets. It was barely drivable on the way home.

While the manifold bolts WERE loose, apparently they weren't the primary cause of the misfire. I'm beginning to doubt if a vacuum leak is even causing the problem. Could injectors be causing this?? I'm desperate for any help!

Cheers,
Aaron

 

[Royawest]

How about the coilpak.It could cause a missfire or two. As Far as lost coolant I would run a compression check.