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Discussion Starter · #1 ·
Hey guys this is my first post here. I searched the forum but I couldn't find anything that quite fit my problem.

2000 Trooper ~92K on it. 3.5L well maintained.

Recently in the colder winter weather the CEL has been blinking until the motor is warmed up. Once it's warmed up it remains on, but doesn't blink. I also experience a sluggish acceleration when the vehicle is cold. If I'm driving more often during the day and I start the car warm, it won't blink and sometimes the CEL even turns off entirely! I have experienced a shuddering idle/ engine stall once or twice in the past month accompanying the blinking light. I believe the CEL code is for random engine misfire but I will confirm this on my way home.

I have had a tuneup within the past 10k (new sparks and wires) but I don't know if the shop used Denso plugs or not? I have gotten rid of a blinking CEL in the past with a good EGR clean and PCV change but it wasn't for the same "misfire code."

My questions:
1. Where should I start?
2. Could it be bad gas?
3. Could the wrong plugs cause this? (I know these troops are sensitive to the wrong plugs)
4. I recently seafoamed the car. Could this be the culprit?
5. Will driving it with the blinking CEL hurt the car? (other than the cat converter?)
6. How long until I do damage to the cat converter?
 

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The first thing to do is remove one of the spark plugs and see what brand and part number it is, the wrong plugs will cause misfires. The cats are about 500 bucks each, so you need to sort out the problem before you destroy them.
 

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Is it when it is cold or when it is damp/wet? If it is when it is damp/wet I would pull each coil (only takes a few moments with an 8mm or 5/32" socket) and look at the boots from the coil to the plug. I had one which was torn and when it was humid outside would exhibit the symptoms you describe. Also make sure the one different boot is on the drivers side rear plug (the one that is tough to get to because of the brake booster).
 

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Discussion Starter · #4 ·
OK so the code is indeed P0300- random engine misfire. I reset the codes and drove it all day yesterday without the CEL coming on. Then, after a cold night below freezing, I started it up and sure enough the CEL started blinking the whole way to work (~5 miles) until about .5 miles away when it mysteriously stopped blinking and did not stay on! I'm so confused.

vanduker said:
Is it when it is cold or when it is damp/wet? If it is when it is damp/wet I would pull each coil (only takes a few moments with an 8mm or 5/32" socket) and look at the boots from the coil to the plug. I had one which was torn and when it was humid outside would exhibit the symptoms you describe. Also make sure the one different boot is on the drivers side rear plug (the one that is tough to get to because of the brake booster).
It's not dampness/ wetness. Its pretty much only when the engine is cold and it started when the weather started to get cold. After it is warmed up I can turn the car off, wait a few minutes, and drive away with no CEL.

What do you mean "different boot"?
 

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On the coil packs normally there are five that are the same but the one in the drivers side rear plug is slightly different/shorter as Isuzu tried to make it easier to clear the brake booster when you install or remove it. You can use the longer boots on that plug with no issue but if you use a short boot on the other cylinders folks have claimed issues. Since you say it is just when cold and is random misfire I'd wonder about intake manifold gaskets. Maybe cracked and when the metal is cold and shrinks a bit they leak but then when the aluminum expands it is enough to seal up?
 

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Does your car consume much oil, like more than a quart per 1000 milesl? If it does, this can foul the plugs within less than 10000 miles. I has the same symptoms and replace my plugs as soon as I get a blinking CEL.
 

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Discussion Starter · #7 ·
Uhralt said:
Does your car consume much oil, like more than a quart per 1000 milesl? If it does, this can foul the plugs within less than 10000 miles. I has the same symptoms and replace my plugs as soon as I get a blinking CEL.
Like a quart every 500 miles? Yea, sure does. Its been about 10000 miles since my last tuneup so I will check those when I look at the boots today.
 

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Discussion Starter · #8 ·
Ok so I pulled the plugs- 4/6 were fouled and they were all some cheap ****ty brand plug. I replaced them with Densos and no light since. I also did not notice a different sized boot and i pulled all of them. Is it possible I have all the same sized boots?
 

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With the oil you are burning, have you cleaned the PCV and EGR valves recently? Also in another post with blinking CEL, the poster said that seafoam in the tank cleared his problem. Wonder if you may have varnish buildup in the injector system or perhaps some water? If so the seafoam may help. My '99 burns about the same amount of oil, but I'm trying the Rotella Synthetic 5W-40 to see if it makes any difference, just put it in this morning so don't expect any results for a few months...

Any other codes being thrown or just the misfire?

Good Luck! Bill
 

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Discussion Starter · #12 ·
Bill62 said:
With the oil you are burning, have you cleaned the PCV and EGR valves recently? Also in another post with blinking CEL, the poster said that seafoam in the tank cleared his problem. Wonder if you may have varnish buildup in the injector system or perhaps some water? If so the seafoam may help. My '99 burns about the same amount of oil, but I'm trying the Rotella Synthetic 5W-40 to see if it makes any difference, just put it in this morning so don't expect any results for a few months...

Any other codes being thrown or just the misfire?

Good Luck! Bill
I recently ran a can of seafoam with a tank of gas. No results. I have also recently cleaned PCV/EGR valve and tubes. The EGR was really bad and I wasn't able to get it completely clean. The pintle was sticking when pushed open all the way.
 
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