Misfire

[97ranger4x4]

So I know there are dozens of posts on misfires, but I have an unusual case I think.

So I drove my truck down to the Bay Area and back this weekend. Which was a little over 300 miles freeway. Basically one full tank, exactly. I put some fuel injector cleaner in before I fueled up on the way down. Everything ran great down on Friday and back on Sunday. This morning I hop in my truck to go to school and I have a pretty bad misfire. No CEL so I do not know what cylinder. I drive it to the gas station. Fuel up with premium however, I always run Chevron 87. Keep on driving to school. Still misfires, but seems to go away at freeway speeds. Hop in my truck tonight to go home, over 12 hours later and its still misfireing like shit. After a couple of miles on the freeway it seems like it is running smoother. Pull off at the next exit and it is running like normal. I took it out of Overdrive on the freeway to get the RPMS around 3k to try and maybe burn off whatever was causing this issue. Once I got off the freeway I took side streets home for the remaining 5 miles and drove it pretty hard with no signs of misfire.

Any thoughts on what could have caused this? I will post again when I get to work in the morning to see how it drives tomorrow.

 

[97ranger4x4]

So I started it up this morning and all was well, but after work (8 hours later) it started running down again. But after it warmed up the misfire went away.

I am so lost. Any ideas.

 

[Big Jim M]

Check the spark plugs to see if any are discolored from the others or if they all have the proper gap.
Big Jim

 

[dogboy]

I am having a somewhat similar issue lately. It has stumbled when you let off the throttle, it's always done that, but the last two days, it has been doing axactly what you describe.

Sometimes runs good, then all the sudden it mises/ stumbles, then, with what seems like the flip of a switch, it runs better.
I am not getting a check engine light either.. well, kinda it has always set a code for engine bank 1 running lean, but the light only comes on maybe once a week if that, and it is that code everytime (code 176 I believe).

I replaced my fuel filter today, since with 155,000, I am not sure it has ever been changed, so it was good maintence anyways.
That did not solve it though.

I put a can of SeaFoam in the tank when I filled it up today, we'll see if that does anything. Sounds like you already did that to yours though..

My fuel milage also went through the floor in the last month or so. It has gone from 15-17mpg, down to 11mpg. granted the last week and a half have been after the manual swap, but it was just as low before the swap.

Hopefully we figure out the problems!

 

[97ranger4x4]

Yeh thats what weird me out about the whole thing. According to my records I last did plugs 10k miles ago w/ motorcraft. I have also changed my fuel filter in the last 15-20k miles as well.

I am just getting ready to leave to go to school right now. So we will see what it does. Ill report back later.

 

[97ranger4x4]

Alright good and bad news. Bad news is the problem is defenatly back. Good news is I have a Cyl 1 misfire CEL code that just popped up on the way home. So I will pull Plug 1 and go from there.

 

[dogboy]

At least you narrowed it to Cyl #1!!

I checked my plugs today and for being 10K miles old (last March) they are horrible! The ones on the passengers side actually have a groove in the electrode.. Drivers sides don't. I also checked my plug wires, and they are all under the 7,000 ohms resistance per foot cut off. (All of them are right around 5,500 per foot, accept for one wire which is 3,400 ohms per foot...)

I'm waiting for a CEL light on mien too, but no luck

 

[97ranger4x4]

Yeh I was pretty relieved to see my CEL as bad as that sounds. So tomorrow morning I will pull plug #1 before I go to the doctors and see how bad it looks. I may toss in a spare and see how that helps. I cant imagine a plug with 10k miles fouling after being driven for 150mi. but who knows.

 

[dogboy]

Are you sure it isn't that the plug wire simply rattled/ fell loose? Or, maybe it is partially connected, which would explain why it only sometimes misses, soemtimes it makes contact, and sometimes it doesn't.

 

[97ranger4x4]

I will check the connection at the plug in the morning. I checked the connection at the coil pack yesterday and everything was nice and tight. I figured the chance that it got loose was pretty uncommon but then again, this whole thing seems uncommon.

 

[97ranger4x4]

I had the P0301 CEL come on yesterday. That is a misfire in Cyl 1. I pulled the plug on 1 and it looked clean and fine. Definatly not my problem. I put it back in and drove it around the block. Still misfireing like crazy.

So now that I know its not a spark issue, I think it is fuel delivery. I ran some Fuel injector cleaner in my tank right before this happened. I am afraid something clogged up fuel injector #1. Unfortunatly I really have no time to play around with this for the next week and a half. I will proably throw on a new fuel filter, but I doubt that is going to do anything because then it would be all cyl running rough just not the 1st.

What are your thoughts. Ohh BTW, how can I test my fuel injector without pulling it? Cause that is a pain in the ass pulling the upper intake plenum off.

 

[AngryLepercon]

I would change plugs, wires, and the fuel filter. Just to be safe all the way around. I had the same problems with my 99. Only I was missing cylinder 4! The plugs, wires, and fuel filter fixed it all up for me.

 

[97ranger4x4]

yeh I have had misfires before, and i have changed plugs/wires, but my plugs are motorcrafts with like 10k miles and my wires are a little older. Its been a while since I did a fuel filter so ill do that.

I think my #1 injector might have got something clogging it because this happened immediadly after running a bottle of fuel injector cleaner through my last tank of gas. could a deposit that was broken loose really have caused this?

 

[dogboy]

I would think that if something broke loose and clogged the injector, that as more injector cleaner ran past it, it would slowly break down the clod that is plugging it.


I am starting to think my problem is related mroe toward the O2 sensor/s. It doesn't miss at highway speeds now, but it runs very poorly while around town. I have to keep the rpms up, otherwise it misses so bad, it seems like the motor wants to shut off. (I have only killed it once in the 2 weeks I have had the manual, today I killed it 3 times...) It just hates having any load (accelerating) under 2500-3000 rpm

Now that I think my problem is way different than yours, I quit making updates to mine, haha.

 

[97ranger4x4]

I would think that if something broke loose and clogged the injector, that as more injector cleaner ran past it, it would slowly break down the clod that is plugging it.


I am starting to think my problem is related mroe toward the O2 sensor/s. It doesn't miss at highway speeds now, but it runs very poorly while around town. I have to keep the rpms up, otherwise it misses so bad, it seems like the motor wants to shut off. (I have only killed it once in the 2 weeks I have had the manual, today I killed it 3 times...) It just hates having any load (accelerating) under 2500-3000 rpm

Now that I think my problem is way different than yours, I quit making updates to mine, haha.

Thats interesting. I changed the fuel filter last night and put in another bottle of fuel injector cleaner with under a half tank. I figured running a stronger mix of the cleaner will maybe help break down what ever is clogging this mess. I did notice that this morning the misfire seemed to go away quicker than it has the last few days. It is still there upon startup but it was not nearly as bad at 6.30 this morning than it was the last 3 days. I think running a more concentrated fuel/cleaner ratio will help. I am trying to drive on the freeway with OD off so I run around 3k rpms. I am hopeing that by running it higher it will help clear the injectors out faster than putting around at 2k rpms

Do you have a CEL on your truck?