[dman4486]

Or Maybe just running rough....Started about 5 miles after an oil change....

- replaced spark plugs
- new pcv
- Fuel sys cleaner
- ran OBD II scan with 0 faults.

Will be pulling intake to check for leaks tomorrow when the new gaskets come in.

Anything else anyone can think of? Is an intake leak common on these motors?

 

[psguardian]

Mediamonkey11 gave me a trick to test for intake leaks...

Warm up the motor & Get a big can of o2 sensor safe carb cleaner, get it running around 1500rpms & spray anything intake/vacuum related, minus the shriek actual air inlet for your air box. If there is a leak it will suck in the non-combustible cleaner & the engine will stumble! (a rare few are combustible & will give an increase in rpms) If no change you know it's not an intake/vacuum leak, & can trouble shoot something else.

~psguardian

 

[vanduker]

Any of the plugs look different from the others? In the intake leak that would impact part throttle but little impact at WOT as little to no vacuum in the intake to cause it to leak.

 

[dman4486]

after replacing the plugs... i ran it again for another few miles and checked them again... They all looked about the same.

 

[vanduker]

Is coil on plug if i remember correctly. If so you should be able to pull the wire from one plug at a time and see if there is one where disconnecting it has less impact. If so that't the impacted cylinder. Then move that coil to another cylinder and see if the problem follows the coil pack.

 

[dman4486]

I would have expected a misfire code from the computer....

also, I tested EGT and found cyls 4 & 6 were 100 degrees F higher than the rest. (lean?)

 

[dman4486]

update... the intake gasket was intact. I checked the plugs again just before tearing into this and found one that looked overly wet and very clean like it had never fired. Think I am going to try replacing the coil after I get the head rebuild complete and everything back together.

 

[Mediamonkey11]

update... the intake gasket was intact. I checked the plugs again just before tearing into this and found one that looked overly wet and very clean like it had never fired. Think I am going to try replacing the coil after I get the head rebuild complete and everything back together.

Check for white spots along the boot of the coil, may have begun to ground out through the boot, if so, wrap it in electrical tape and see if that fixes it...

 

[dman4486]

update... the intake gasket was intact. I checked the plugs again just before tearing into this and found one that looked overly wet and very clean like it had never fired. Think I am going to try replacing the coil after I get the head rebuild complete and everything back together.

Check for white spots along the boot of the coil, may have begun to ground out through the boot, if so, wrap it in electrical tape and see if that fixes it...

No white... the boots look like brand new on all of them

 

[bradzuzu]

Does that one have the coil pack up front or th single coil per cyl. ? Did you move things around to see if probblem followed coils, plugs, or cylinders? hard to do compresion tests on those deep holed bad boys..Was it running like crap olla before you put on all the tune up stuff? Ive had spark plugs be bad out of the box its rare and it sucks but an easy fix

 

[dman4486]

Tore the motor apart to replace everything in the heads... when I put it all back together I replaced the one coil that did not look like the plug was firing and the truck runs great now!

Why would the Computer not tell me that I had a misfire or bad coil?

 

[basic]

Does that one have the coil pack up front or th single coil per cyl. ?

the 96 and 97 are the coil on plug style.

 

[bradzuzu]

I had a mis fire code on my 00 amigo. Still didn't tell me which cylinder.
I did the plugs anyway 40'000 sat 4 1/2 years wrecked. anyway they all looked good but no more code run's fine. I thought it was the used coil i bought off E bay. And suposedly # 6 coil is a different part number. I worried for well five minutes maybe.. lol I drive it every day

 

[bradzuzu]

I also blapped dielectric grease into the end of every boot...Easyer insertion lol... When i tryed to pull the coils out to r & r the busted valve covers and destroyed coil a couple boots where one with the plug.

 

[CatFuzz]

Why would the Computer not tell me that I had a misfire or bad coil?

The ECM can count the mis-fires of each cylinder. There is a threshold that must be surpassed before it throws a code. A certain number of misfires within a certain period of time. It was maybe just below the threshold.

 

[dman4486]

Thanks FUZZ

 

[Big Jay]

Why would the Computer not tell me that I had a misfire or bad coil?

The ECM can count the mis-fires of each cylinder. There is a threshold that must be surpassed before it throws a code. A certain number of misfires within a certain period of time. It was maybe just below the threshold.

That and...correct me if I'm wrong...if you don't use the OEM specified plugs they don't read misfires beyond a certain threshold. Actually learned that on here. Isuzu recommends a specific type of plug. Apparently, it enables the ignition/ECM to detect misfires at a lower threshold or something.

 

[bradzuzu]

Thats an interesting thought. So far My amigo is running fine and i havent gotton another missfire code. I did go for the platnum plugs more expensive but I don't want to change plugs every 10,000 miles or less

 

[Wickedclown]

Tore the motor apart to replace everything in the heads... when I put it all back together I replaced the one coil that did not look like the plug was firing and the truck runs great now!

Why would the Computer not tell me that I had a misfire or bad coil?

my coil was firing just enough not to get a code but not good enough to run like it should.
weak spark from coil.