Truck check engine light came on....

**jmw_man** · 04-25-09, 10:20 AM

I would like to get people's opinions and experiences of a situation I have or had with my truck.

My girl and I were driving slowly down the road in a traffic jam. My truck studders a little bit and it goes away. I think, "that's weird." It did it some more here and there while we were moving at about 5 mpg. Then one of the times it did it continuously until the check engine light came on then it finally went away when I got to higher RPM's. It was fine for the rest of the day as I spent them mostly at high RPM's but even when I was at low RPM's it didn't studder like before.

Anyhow, I got home and got the code reader out and it read P0303 and P0171. I looked them up and found the first to be related to cylinder 3 misfire detected. The second was system too lean which most likely is a result of the first.

Well, I look EVERYwhere to see if other people have had this problem with their vehicles and had found the one guy with the same year, make, and model of my truck (2001 Ford F150 XL) who had the 2 identical codes. I read through his entire thread and in the end he said the problem was a cracked ignition coil.

I did some research online and found a list of things that would cause this problem. Bad spark plug at the number 3 cylinder I presume, bad spark plug wires, bad ignition coil, and bad compression.

spark plug wires - $35
ignition coil - $75
spark plugs - had these replaced a while back so I just disregarded this as the problem.
Bad compression - probably associated to bad o-rings, worried that this might have caused the problem.

Anyhow, I don't want to spend a whole lot of money, I only want to spend it on the problem. I looked under the hood, the ignition coil looks fine, the wires look fine. I went ahead and bought the wires since they are the cheapest thing.

Here's the problem, my truck hasn't studdered all week long. I did pull the number 3 spark plug wire out of the coil and plug it back in so maybe it had bad contact...not sure. Though, it hasn't studdered ALL WEEK LONG and I haven't replaced a thing.

Should I just wait for the problem to start up again and return the plugs I already bought from Autozone oooorrrrrr should I go ahead and just replace my wires hoping they will solve the problem that could potentially come back and maybe even improve things in my performance anyhow.

My deal is, if the problem were something else then why spend the extra dough....

Here's my other question, the plugs I bought are Duralast, will they improve anything performance wise over the ones that came with the truck stock?

**deathgodusmc** · 04-25-09, 11:21 AM

jmw i have 2 f150's one is a 99 the other an 07. The 99 did the same thing and still does once is a great while. It's not a problem worth spending money on. Now if it continues then you need to start looking. Pay attention when it going on. Look at your od light on the shifter i know it sounds stupid but there is a reason for it.

If it starts blinking then the shutter is not from the engine but the transmission is the problem which will also pop those codes. I have torn my truck apart and have replaced some sensors on it doing just what you are talking about avoiding.

Then i stepped back and used my 25 years of mechanics exsperience to trouble shoot the problem instead of replacing everything that could cause the issue. It can down to the bulk head harness got dirty and was lossing connection every once in a while.

Don't waste your money trying to solve it. Wait and see if it really is a problem first. If you need help try to figure it out by all means pm me i will help you. Oh yeah if you want to see if your coil is cracked just start the truck when it's dark you'll know if it cracked.

**Big_Boze** · 04-28-09, 04:11 PM

Well, I had the same problem with a misfire on my wifes car a while back. (01' 3.8 v6 mustang)

I checked the resistance on the coil, which actually checked out fine on each pair. but the #2 hole was dead. The way I found out was I started the car, and pulled one wire at a time off of the coil and checked if it was sparking. If it was good, you could tell 2 ways.... One was, that shit will spark like crazy. Two, your car will deffinetly run worse when you take one off that is good.

SO, I would try that. Your could doesn't neccesarily have to be cracked, but could just have a dead hole like mine did.

And be careful when you do this, cause you don't want to get a jolt... Pretty powerfull spark

**Sleepybean2** · 04-28-09, 04:29 PM

Originally Posted by Big_Boze

Well, I had the same problem with a misfire on my wifes car a while back. (01' 3.8 v6 mustang)

I checked the resistance on the coil, which actually checked out fine on each pair. but the #2 hole was dead. The way I found out was I started the car, and pulled one wire at a time off of the coil and checked if it was sparking. If it was good, you could tell 2 ways.... One was, that shit will spark like crazy. Two, your car will deffinetly run worse when you take one off that is good.

SO, I would try that. Your could doesn't neccesarily have to be cracked, but could just have a dead hole like mine did.

And be careful when you do this, cause you don't want to get a jolt... Pretty powerfull spark

hehe especially when .5 amps is enough to stop the heart from beating... (What do alternators put out? 60amps, 14v?)

**Big_Boze** · 04-28-09, 04:34 PM

Originally Posted by Sleepybean2

Originally Posted by Big_Boze

Well, I had the same problem with a misfire on my wifes car a while back. (01' 3.8 v6 mustang)

I checked the resistance on the coil, which actually checked out fine on each pair. but the #2 hole was dead. The way I found out was I started the car, and pulled one wire at a time off of the coil and checked if it was sparking. If it was good, you could tell 2 ways.... One was, that shit will spark like crazy. Two, your car will deffinetly run worse when you take one off that is good.

SO, I would try that. Your could doesn't neccesarily have to be cracked, but could just have a dead hole like mine did.

And be careful when you do this, cause you don't want to get a jolt... Pretty powerfull spark

hehe especially when .5 amps is enough to stop the heart from beating... (What do alternators put out? 60amps, 14v?)

Somewhere inbetween 60-80 is normal. H.O.'s are 105 and 130, even higher.

Should be 12v though, if I remember correctly.

**SAMBO** · 04-28-09, 04:53 PM

I'd pull all the spark plugs out and check them for symptoms of running lean. Start from there since it's the cheapest thing to do. High glaze wear will look burnt black, running lean will look white brown.

**dex71** · 04-28-09, 06:10 PM

No doubt in my mind it is one of your coils. Just went thru the same crap with my truck (2001 Expedition). Had the same symptoms...it only got worse. Figure out which coil it is and replace it. Might not be a bad idea to replace the plugs too...I'm guessing you are in the hood of 100,000...
I ended up replacing two of my coils....fingers are crossed...so far,so good.

**teXasStorm** · 04-29-09, 01:04 PM

Your stock motorcraft spark plugs are of a lot more quality than the duralast. I worked at autozone for a year and most things that were duralast were crap except some of the brake pads we carried. I'd stick with the motorcraft for a ford. But i can tell you that those trouble codes are wacky, Ive read codes dealing with one bank running lean and it end up being a cracked intake plenum.