Miss under load

So the 96 3.4 I bought a week ago started to miss on my way home last night.

I only live about 4 miles away from work currently, I made a quick stop just up the street and on my way up the hill the truck has a miss, once I got to the top where it leveled out the truck idles smooth, under slow acceleration runs smooth, and cruising runs smooth.

I ordered plugs, wires, air filter and fuel filter, because they are all things I want to do, but was going to do them next weekend because I'm moving this week.

My question is other then a coil, are there any other parts that may fail causing the truck to miss under a load? I think it's only 1 cylinder, because the sound changes and you can tell the power drops off, but it doesn't run as rough as a 4 cylinder with 1 missing.

Any info would be really appreciated

 

No MIL on?

 

Not sure what the MIL is...

I went to change all this this afternoon, only to realize I didn't have an extension in my embarrassingly cheap tool set..

That being said I cleaned the maf, replaced the air filter, and pulled the boots on each sparkplug to see if I could see anything obvious and in the spark plug hole in the front on the passenger side under the coil there was what I believe was oil in the bottom of the spark plug tube, also the coil boot was misshapen.

I wiped out what I could and dried the boot off, and reinstalled it because I didn't have a replacement. On my drive afterword the miss was better, but not completely gone.

 

This just stands for Maintenance Illumination Light, or check engine light. and FYI had a bad miss for a while and it never threw a MIL or a code.

I recommend you get a a compression gauge and do a compression check when you replace the spark plugs, especially since its a new to you truck. It's a generally cheap and useful tool to have and the process is is simple. This way you can make sure the miss isn't caused by anything internal to the head or block before you start replacing everything else.

And when you replace the spark plugs make sure you get the correct kind, and the are gapped correctly or else you might do more harm than good.

 

You haven't installed those items yet? It's spark plugs like 95% guaranteed. Save yourself some money and install those first, install the rest if you still want to.

 

Malfunction Indicator Lamp. What Toyota calls the check engine light. So if no MIL on, than as suggested before, the plugs are good place to start.

 

So,

I drove to work this morning, everything was as it was last night, right before my lunch, I drove about half a mile, in which the miss never went away, it wouldn't even idle smoothly.

On my way back to the building the check engine light came on, which I felt good and bad about.

On my lunch I replaced all 6 spark plugs, and the 3 wires and here is what I found. Now in the picture these plugs are placed just like your looking at the motor. The dark one in the front left, didn't break loose when I went to b unscrew it. Once it came out and I saw the color, I realized what was causing the coil boot to swell was fuel in the spark plug tube. The rest of them unscrewed like they were almost tight enough.

So I figured I had found my issue, the plug was finally completely fouled because it was running incorrect fuel ratio!

I put the truck back together with the new plugs, installed the wires and fired it up to drive to grab some food. And about 1 minute into my drive the miss came back. I ran to the nearest napa and borrowed there code scanner where I got a p0301, so I decided to replace the coil, which came with a new boot. Got back to work and swapped it out real fast, and now it's smooth as glass

 

If the boot is oil soaked you have a bad valve cover gasket.

 

So the culprit was a coil pack? Did you have an MIL before? Or check engine light? Looks like that coil and/or plug hasn't fired correctly in a while. Glad it's taken care of.
Had you reported before that you had an MIL for incorrect firing on cylinder 1, we would've told you to try swapping that coil pack with another one on your engine and to see if the MIL follows that cylinder you swapped the 'bad' coil pack with. This would be so you don't buy unnecessary parts. But spark plugs aren't too big a deal. Prolly needed changing anyways.

 

I did get an mil before I changed the plugs, but didn't have much time due to the fact I only had a lunch I wanted to do the parts swap on.

 

Or the bolts could just be loose. I had a leak start and checked the bolts and they were extremely loose. Tightened them and the leak stopped

 

Had the same issue. Coil pack went bad. Only have 1 stock one left. Ha OEM is best but I'm having good luck with that Napa one. Was about $86 I believe.

 

Amazon has the OEM Denso coil pack for under 60 bucks.

Denso 673-1201 Ignition Coil

$61 Denso- 6731201 DIRECT IGNITION COIL

https://www.amazon.com/dp/B002Y39NFY/ref=cm_sw_r_cp_apa_OoEUybREC9GYR

 

Well my fuel mileage says the truck hasn't been running right also,

Just before I changed the coil I had filled the truck up and got 14.1 mpg on that tank.

Since replacing the coil, and spark plugs, my mileage went up to 16.5 mpg