P0306 Misfire & Rough Idle - 96 Eddie 4.0l 160k

[pclarke1]

Hi all, first time caller, long time listener!

Been having an intermitant CEL issue for a while now. It seems to only come on when the engine is hot. It runs, but idles rough. 90% of the time it is a P0306, occasionally it has thrown a P0300 (not very often, but it has happened). I had a less severe version of the problem last summer, but this seems to dissappear over winter (I live in Fargo ND). Which is why I suspect something to do with resistance.

My first step was to replace plugs and wires, then I replaced the coil pack. I am now in the process of replacing the number #6 injector. I checked the resistance on all injectors and they were between 0.16 and 0.17. So where I am right now is that I have the fuel rail apart and the injectors are out at the cleaners. They are all being cleaned and tested even the one I suspect is bad. I have also taken the opportunity to change the fuel filer, clean the throttle body, MAF and IAC, as well as get new leads (because I did not route the new set properly and found some burn marks on the outside). I am reassembling with new gaskets and injector seals.

Ok, so a long way to getting to my questions.

1/. Apart from a bad cylinder (I have not been game to check compression), have I covered all of the bases?

2/. What type of reassembly lubricant (apart from getting myself a beer) should I use on the gaskets and injector seals.

3/. Anything else you thing I should do while I have it apart?

4/. Are the top and bottom injector O rings the same?

 

[manaen]

1) that is everything that I would have checked did you test the leads going to the coil pack you may have a corrosion problem in one of the wires. I assume you checked the gap on all the plugs? Checked for vacum leaks?

2) dielectric grease works very well on the o-rings when assembling them.

3) sounds like you got it covered, the new gaskets may fix your problem, could be a vacum leak

4) depends on the injectors you have, my '01 that has the higher pressure closed loop system is totally different on the bottom, it has these huge hats that sit in a 3/4" to 1" diameter hole in the intake. However I believe that the return loop (lower pressure) system has the same on top and bottom.

 

[pclarke1]

Vacum Leaks

I had not tested for vacuum leaks. I guess I cant really do that now until I get it all back together. However I did not think vacum leak because the error code was specific to one cylinder P0306. If the error is not resolved by whay I am doing I will delve further into the vacum system. Also I changed the plugs and wires to no avail, then changed the coil to no avail, so in my mind eliminated (short of the ECM) all ignition type issues. I will take a look at the wires going in just to be sure (will be very annoyed if it was something simple like that).

The rail and manifold holes look the same size, I guess I should not be quite so lazy and pull out my caliper and measure them.

Thanks for your advice I will let you know what happens when I get the injectors back from the cleaners and get this puppy put back together.

 

[pclarke1]

All Back Together

Got the injectors back today, they all tested out good after cleaning and replacing the basket filters. Total cost $113, including new o-rings. Put everything back together and so far (10 mile run) everying is running like a champ. The proof will be if in a week or so the CEL does not come back on and the idle stays nice.

Thanks for your help.

 

[manaen]

Sounds like you got it nailed down. Glad to hear your injectors check out, that can be a pricey ordeal if they start going south. Believe me I know, I am still trying to recover financially from my little expirience.

Anyway, glad it all worked out

 

[pclarke1]

Actually No

Actually the miss came back after about 20 miles. Had it tested I have low compression in #6 @ 90psi. Trying an additive (Restore) not very hopeful, but I can live with the miss for a while it is not too bad.

 

[pclarke1]

Restore

Can't speak for those who have had good experience from Restore, but so far (200 miles in) it has not done anything. Idle same, CEL same. Not that I seriously thought it would.

 

[manaen]

yeah, don't expect miracles from additives. have you tried some type of cleaner for the upper end? could be as simple as carbon on the valves. You may want to try seafoam, or a fuel additive like marvel mystery oil, something that will help remove the carbon. A good long highway trip sometimes will help, get that thing opened up a little. I always notice a performance difference after a long highway trip, after a long period (few weeks) of short hops around town things can get gunked up. Ford even recommends that the 4.0 be rev'd above 3grand at least once each time it is driven to clean out carbon. Just don't push it too hard you could also have your cylinder scoped to see if there are any ring/piston problems. When you had the intake off what did it look like inside there? were there a lot of deposits and oil etc... ?

 

[pclarke1]

Additives

Well 1000 miles into using Restore, I can confirm, that at least in my experience that it did not do anything. On the plus side, it does not seem like it has done any damage.

I am doubtfull that a carbon build up is my issue. I drove 350 miles at 80 MPH on Thursday and will do it again today. It drives ok at high speed, fuel economy is not good at best 15MPG, there is no miss in evidence. I will try Seafoam but at this stage I am not thinking it will help.

When I pulled the manifold, I saw no difference between cylinder 6 and any other, nor was there any difference on the plugs. No oil was evident on any plug, they had around 20K on them, and they all what I would consider to be normal sooting. In fact I pulled the plug on 6 and 5 last weekend. They had about 3K on them, each were covered in a very light ash coating. Which is what I would have expected, but there was no real difference between the plugs.

I am thinking that there is a new engine in my future. Ryan Engine Exchange in Minneapolis quoted me about $1900 installed for a reconditioned engine.

 

[manaen]

That's actually not a bad price for the engine. Is it a full rebuilt engine? if so, the rebuild kit alone for the SOHC is in the range of 1500, with all seals timing chains etc etc..


If you've driven the highway miles that would rule out the sooting problem. So the plugs look good? I guess that rules out the rings. I would think you would see some oil fouling if that were the case. which kinda leads me back to a sticky/bent valve or head gasket problem.

 

[pclarke1]

Engine Quote Details

I would have thought thatif it is the heat gasket then I would see some overheating or chocolate milk in the coolant, so far I have seen neither, nor is any loss of power particularly evident (it always was a slug with bad economy). It sounds like then I should do a wet test for compression to check out the valves.

Here is the quote from Ryan Engine Exchange in MN. Maybe they are not including installation (I am checking with them)

*****************************

REMANUFACTURED ENGINES are built from the block up. Each casting is cleaned, magnetic particle inspected and machined to exacting standards. All moving components are inspected and replaced as needed to insure the engine performs to original specifications. All engines include new pistons and rings, new bearings throughout, refurbished valves and valve seats. Camshafts and the crankshaft are returned to OEM specifications and gaskets and seals are all replaced to insure trouble free operation.

Remember each install includes the following:

New Oil Filter New Air Filter
New PCV Valve New Thermostat
New Spark Plugs All Fluids

We tow the first 20 miles for FREE!


Vehicle: 1996 Ford Explorer
Engine: 4.0L

Estimate: $3,275 (Plus Tax) Engine Only: $1,895 (Plus Tax)
Warranty: 3yr/100,000 miles
(Worn or damaged parts may be extra)
All estimates are good for 60 days

 

[toypaseo]

Did you change the DPFE?

That helped out my rough idle alot on my 96. The hoses that went to it were shot also.

 

[pclarke1]

A New Wrinkle

Started the car at lunchtime and it did not want to run. Would kick, run rough then die. After a few trys it started no problem, then I drove back to the office and then up to the gas station to head home. Fueled up and no start. Had it towed to a local mechanic, he has tested the fuel pressure and tells me I have only 5 PSI when I should have 40, so my pump is bad.

Maybe that was my problem all along?

The good news here is that right now I am in Bismarck ND and I was just getting on to the interstate before I decided to fuel up. I live in Fargo ND (180 miles of scenic prairie away). Had this decided to take a dump 45 minutes later, I would have literally been in the middle of nowhere.



To be continued......

 

[manaen]

AT 5 PSI I cant beleive the truck even would let you pull out. Well hopefully that will get you back up and running.

Oh and depending how the head gasket is leaking you may not get a mix of oil into water or visversa. It may just be a pressure leak.

But anyway, lets see what happens after the fuel pump.

 

[pclarke1]

It Didn't

You are right at 5 PSI the truck would not pull out and in fact it did not. It had to be towed and they put in a new fuel pump. However 90 minutes and $425 later I was back on the road. Car ran well over the 190 miles home, and seemed to use less fuel. Thought the idle was a little rough when I pulled back into town, but that could have just been some panting. The run for Bismarck to Fargo is a straight shot and I was not going to hazzard a pit stop, so the car did not drop below 70 miles for the entire run and cruised mostly at 80, with occasional acceleration to 90.

Proof that it is actually fixed would be if the CEL does not re-appear in a day or so.

 

[pclarke1]

CEL P0306 Persists

While truck is up and running again, and it does feel better. THE CEL came back on this morning and is still giving me a P0306. Did not see it on the drive back from Bismarck 190 miles on highway just around town this morning.

The hunt continues...

Next step will be a new round of compression (wet and dry).

 

[manaen]

It is strange that it is calling out cylinder 6, I would be suspect of a bad plug or wire, but since you already changed them out along with the coil pack I am at a loss here. Did you check the resistance on your plug and wire on cylinder 6 ? just to make sure everything is good, maybe even try swapping them for another cylinder to see if the problem follows the plug and/or wire. It would not be the first time I've seen a new wire go bad, in fact I just had one 2 months ago. These new wires seem to be assembled with butter, as soon as you try to remove them once they pull apart. Oh and I've also seen the conductor fall out of a new plug leaving nothing which is kinda scary. I guess it exited the scene through the exhaust.

actually come to think of it, that was on my cylinder 6 as well (just a coincidence?) Since it is one of the easy cylinders to get to it wouldn't hurt just to check them again.

 

[pclarke1]

I have replaced the coil, and 2 sets of leads. I pulled the 5 & 6 plugs 2 weeks ago and checked and regapped the #6. I have another set of plugs I will replace the lot on the weekend, when I run a new set of compression tests. I am currently running NGK V groves, I had NGK Truck plugs before that. I am going to try Autolite. I will try swapping one of the wires too see what happes. However the problem has persisted through these changes.

I bought a new ECU on Ebay I might change this out and see what happens.

 

[manaen]

I've tried many types of plugs and IMHO you are wasting money on anything but the stock autolite's. In fact I had a set of "V" type plugs that ran like crap until I replaceds them with the stockers.