A battle I just can't win

[Manarius]

So, I just can't seem to figure out this stumbling issue. If you look in my other thread here you'll see that I replaced my spark plugs and picked up a stumbling and idle hunting issue. I've followed all the suggestions in that thread and even done some of my own and nothing has fixed the problem.

The problem is this: The car stumbles fairly badly when cold. It also can't find idle and stumbles enough to shake the engine. It will also stumble randomly when warm. Seems strong if I am really hard on the gas.

Here's what's been done:
Tested to see if the stumble follows a coil - no response from the car
Replaced fuel filter
Replaced front knock sensor (ECU threw a code - sensor was broken)
Greased all coil boots with dielectric grease
Replaced MAF with known good MAF
Cleaned throttle body with TB cleaner
Cleaned IACV with TB cleaner (emptied about 1/4 of the can into the IACV, made lots of smoke)
Ran Seafoam through gas
Sealed minor exhaust leak

After all that, still no change. I want this stumbling and idle hunting gone. If anyone has anymore suggestions I am open to them. If they involve spending a lot of money, I will probably be a little more hesitant.

[SilverSpear]

IACV... I wonder if that can be cleaned like that and still work properly...

[redlightningsvx]

Did you check to see if you have a vacuum leak?

[michael]

I hate to tell you this but you should undo everything you have done prior to the stumbling. As you undo everything look for what could have gone wrong. If it were me I would start with the connections on the battery and all of the vacuum lines after the TB in addition the seal for the intake to the TB. Check for any cracks in the intake especially the plastic fittings where the vacuum lines connect. Then I would check out the condition of the coil wires and finally check the threading and gap of the plugs. Did you use the right plugs? Are they free of any defects?

[Manarius]

Originally Posted by redlightningsvx

Did you check to see if you have a vacuum leak?

No I did not. However, it doesn't appear that I have one. I can't hear a leak and it goes away slightly as the car gets warmer.

Originally Posted by michael

I hate to tell you this but you should undo everything you have done prior to the stumbling. As you undo everything look for what could have gone wrong. If it were me I would start with the connections on the battery and all of the vacuum lines after the TB in addition the seal for the intake to the TB. Check for any cracks in the intake especially the plastic fittings where the vacuum lines connect. Then I would check out the condition of the coil wires and finally check the threading and gap of the plugs. Did you use the right plugs? Are they free of any defects?

The only thing I did prior to the stumbling was change the plugs and the air filter. The plugs were the recommended NGK ones.

[SVXRide]

Have you tried disconnecting the injectors to see what happens? The seafoam via the gas tank doesn't stand as much a chance of cleaning the injectors as when you connect a line from the vacuum port on the intake directly to the can of seafoam.

can you explain what you mean by "stumble follows a coil"? If you mean you disconnected each coil (one at a time), then I'm confused that you said "no response from car" (i.e., you should hear/feel a drop off of the cylinder when you disconnect a coil). The fact that the car did not stumble before you changed the spark plugs would lead me to put my focus here first (then again, it could just be a coincidence) -- while the plugs may be right, you might find that you've got a cracked insulator on one or more plugs.

-Bill