running lean and misfire

[Tader82]

About a month ago i changed my plugs and wires with motorcraft plugs and autolite wires. Seemed to fix my misfire at first, but its back. In the past few weeks I have had times where it starts running like crap and the cel flashes, but not as often as before I changed the plugs. Just got back from advance auto to pull the codes. It came up with P0302- cylinder 2 misfire and P0171- lean bank 1.

Any ideas where to start are appreciated. I think I need to check for vacuum leaks and check the fuel system, but Im not sure about how to go about doing this.

The guy at the store suggested running some injector cleaner with a tank of 93 octane, said it would burn anything out of there but im skeptical.

I should also mention that I averaged 11.5 mpg on my last tank, which I just filled up yesterday. Any help greatly appreciated!

as he said he is getting a LEAN on bank 1 i have had it pop on a cam shaft poison sensor tons of time (i have put 5 cam poisoning senors in my truck i finally fixed it with a hole new synchro.) and he said that he has replaced ALL but the coil. and I'm not saying to buy the pricey stuff thats y i say to use the accel coils 80 bucks not 180 something. so i short i was not Throwing parts at it remember we r not there we can only make judgments on what he said he has checked. the Alone thing else i can think of is bad injectors

 

[Ranger44]

Bad injectors? Properly maintained injectors will out last the engine. And will go well above 400K miles.

This is what listening to them and the resistance checks are for. Checking the resistance of the injectors will show if the solenoid is indeed "bad" or not.

I do agree that it's hard to diagnose a problem over the internet, but a decent knowledge of engines and fuel injection systems can allow somebody to make a few educated suggestions.

 

[Tader82]

i agree, about if the injector is plugged up in ether input or output areas a resistance test is no good it only tells u that the unit is opening up not plugged up lol, one time i had to have help with a truck. had to use a coolant catch pan and take the injectors and rail off in one peace and turn the key to see witch one was not firing because the rail was plugged up on the injector port lol was a mess but we got it fixed lol

 

[snomaker321]

Some diagnosis and testing needs to be done in order to fix this truck.

Thinking about it, a lean code would mean an air intake leak or lack of fuel, maybe a misreading HO2S.

A misfire would mean an inappropriate amount of fuel or ignition fault.

What thing do the 2 have in common? Fuel.

Some suggestions though......

1). Do try and run a fuel system cleaner through. Fuel systems do get dirty.

2). Check pressure at the rail. Maybe even check volume. A pump can deliver correct fuel pressure but not enough volume under load.

3). Just do a general, yet thorough, visual inspection of the fuel system. Have a stethoscope? Listen to each injector with the engine running. Do they sound about the same? There should be a nice even click click, and have about the same tone. You can measure the resistance of each injector. They should all be within .04 ohms of each other. Look at the connectors, wiring.

4). As I mentioned above. The CAM PS times the injectors. These are prone to wearing teeth and failing. Have you been hearing is squeal? Chirp? How many miles do you have on the truck?

1)I have a bottle of techron im going to put in, probably tomorrow.

2)Pressure I know I need to check once I get my hands on a pressure gauge. how do you check volume?

3)I do not have a stethoscope, but i might be able to get my hands on one. Can't you also listen to them with a screwdriver? Where do i check the resistance?

4)No squeal or chirp. Just turned 128,000 miles.

I dont know if this would make a difference or not, but I have an exhaust leak. Its been there since a bought it and isnt that bad. We've tried sealing it with some exhaust joint and crack sealer but with no luck. It is at the joint right after the cat. I've passed inspection with this leak twice.

Thanks for all the help

 

[snomaker321]

have run about 60 miles on a tank with techron added. if anything its been running worse

 

[triumphrider-1]

Have you checked the pressure yet?

As far as the exhuast leak mentioned in the previous post. It will sound bad and maybe hurt the fuel economy; but it shouldn't affect the stoich for the engine or it firing.

 

[snomaker321]

Have you checked the pressure yet?

As far as the exhuast leak mentioned in the previous post. It will sound bad and maybe hurt the fuel economy; but it shouldn't affect the stoich for the engine or it firing.

not yet. i dont have a gauge and dont want to spend like $40 on something ill only use once but ill probably have to. and i havent had all that much free time.

what about compression? do you think a valve issue or something could cause this? thanks

 

[triumphrider-1]

Drop by Autozone and see if they have a gauge you can get one from their loan-a-tool (or whatever its called) program.

Hmm, not sure about the valves. They may make it run rougher, feel like less power but not positive. Compression I don't think would cause the syptoms, but may want to see what others have to say.

 

[Runnin'OnEmpty]

Since it's running lean and misfiring, I'd suspect the upper
plenum O-rings are leaking vacuum. This is very common
on the 4.0s, and the 3.0 has a similiar plenum design.

These O-rings harden and shrink over time, causing the
lean misfire problem....

 

[snomaker321]

sorry for the delayed response but i just got back from florida.

are the upper plenum o rings the same as the upper plenum gasket? What does replacing it entail?

i feel like autozone wouldnt really have one to rent since theyre not all that expensive, im just cheap, but ill take a look.

Anyone else have any input on the compression? I thought low compression would cause it to misfire.

thanks for all the help guys. hopefully i can get this fixed soon since its already like 20deg out

 

[skinner]

You have to look at both problems together. One tells you too much air on one side, and the other tells you the middle chamber on that side isn't firing right. While this could be two separate problems, it's unlikely, so you'd want to assume something is happening at or near that particular cylinder. My best guesses are vacuum leak at the plenum or intake, clogged injector, or dead injector. I'd be hesitant to blame the FPR or filter, as they would affect both banks, and would cause random misfires. I'd take it apart, swap the middle injector out with an end one, and put it back together with new plenum gaskets and injector o-rings. If the problem goes away, it was the plenum gasket. If the cylinder misfire changes, it's the injector. And if the same 2 problems still exist, well,could be a few things, but sounds like the lower intake is leaking.

 

[snomaker321]

You have to look at both problems together. One tells you too much air on one side, and the other tells you the middle chamber on that side isn't firing right. While this could be two separate problems, it's unlikely, so you'd want to assume something is happening at or near that particular cylinder. My best guesses are vacuum leak at the plenum or intake, clogged injector, or dead injector. I'd be hesitant to blame the FPR or filter, as they would affect both banks, and would cause random misfires. I'd take it apart, swap the middle injector out with an end one, and put it back together with new plenum gaskets and injector o-rings. If the problem goes away, it was the plenum gasket. If the cylinder misfire changes, it's the injector. And if the same 2 problems still exist, well,could be a few things, but sounds like the lower intake is leaking.

hey, changing around the injectors sounds like a good idea. thanks!
in that last part, are you saying you think its the lower intake? or is that your guess if its not the above?

this is my first car so im not too familiar with all the parts but is this gasket accessible to say spray around with carb cleaner and check for a leak? my guess is not but it would be a heck of a lot easier.

How labor intensive/complicated is it to take it apart and switch injectors? Are there any write ups around that tell you how to do it do i dont screw up? thanks for the help!

 

[skinner]

Newer engines have 2 "intakes", one called an upper, the other a lower(sometimes abbreviated ui and li). The upper intake is the large plastic(not always plastic, i suppose) piece on top of the engine that hooks to your air hose/air filter. Below that, you have the lower intake, and it's the lower intake that the injectors are pushed into. To get to the injectors, you only need to remove the upper intake. There's nothing hard about it, just different things that need to be removed...you'll see them as you go. Once you get that off, you'll see the fuel rails. The rails are usually bolted on, but the injectors just push in. Assuming you have all the tools, and the upper intake gasket and fuel injector orings, you can have all this done and back together in a few hours, but seeing as this is your first time, give yourself a day or a weekend. You may need to remove the lower intake too, but that gets a bit more involved as you'll have lifters and pushrods to worry about...so i'd probably just stick to the injector/upper intake for now if you aren't familiar enough with engines.

 

[Gillbilly]

I just had a very similar thing happen on my 96 3.0. I replaced plugs wires and such .... seemed to get better then worse.
I eventually had catastrophic failure of 2 plugs while driving long distance.
I soon come to find out that once the ignition coil fails you will see 2 plugs begin to give you problems. The reason for the level of failure on mine was that I had to keep driving (pushing high rpms to keep moving).
If you plugs are fairly new you may want to pull them and take a look. If 2 of them seem in bad shape you could be certain that it is you I.C.
Once I replaced mine ( $70.00) it was all fixed.... though I did follow up by cleaning out the combustion chambers that the failures occured in.

Good Luck Man

 

[snomaker321]

I just had a very similar thing happen on my 96 3.0. I replaced plugs wires and such .... seemed to get better then worse.
I eventually had catastrophic failure of 2 plugs while driving long distance.
I soon come to find out that once the ignition coil fails you will see 2 plugs begin to give you problems. The reason for the level of failure on mine was that I had to keep driving (pushing high rpms to keep moving).
If you plugs are fairly new you may want to pull them and take a look. If 2 of them seem in bad shape you could be certain that it is you I.C.
Once I replaced mine ( $70.00) it was all fixed.... though I did follow up by cleaning out the combustion chambers that the failures occured in.

Good Luck Man

but it only misfires on 1 cylinder and it has off and on since i got the truck about 1.5 years ago. only recently(within the past few months) did it get really bad. I believe now believe its either the injector or that gasket which i'll be trying once we get all the snowmobiles out of our garage so i have an above freezing place to work.

Also a pulled my #2 plug, which is the misfiring cylinder, about a month or so after installing them and it looked fine but its been running worse lately. On my last tank I only got about 8mpg. I have a tank of 93 octane now just to see what happens. Im not expecting it to do anything but I figured for like $5 what the heck.