Good evening,

I have been wrenching on my girl friends 2007 on and off for the last few nights and unable to make any progress.

Here is a little backstory:
2007 with 170K and manual tranny.

For the last 1K or so miles the car has felt like it has had a misfire and down one cylinder when under more than say 50% load. No check engine light so I could not really dig into it. I checked the pugs and coils and they looked good. For the last 50 or so miles the car is having multiple misfire codes for all cylinders and check engine flashes under more than 50% load. The car is also very down on power and feels as if its running on only 2 cylinders power wise. The car is pretty much undriveable and we are not driving it.

When at idle or not till 50% load the car runs fine and does not even throw a check engine light. As soon as its under load the CEL flashes and ca has no power. Every time i read the codes they are all the same and its multiple misfires on every cylinder.

What i have done:

1. Removed both o2 sensors and drive the car to check for a melted catalytic converter. Having the upstream o2 out did not change the power of the car one bit.
2. Coils and plugs look good, they are OEM NGK and gapped to about .050". One coil pack is a Denso, others are factory Hitachi.
3. Fuel seems good, but how do i check this? I can't seem to find the fuel pressure test port.
4. Car has 170K and I am unsure if the valves have ever been checked. Due to the fact the misfire is on all cylinders and went from minor to extreme i am guessing its not the valves.
5. I was going to change the fuel filter but from what i have read it a lifetime part and located in the tank.

Any ideas on what else to check?
fuel pressure regulator or fuel pump?

Any input would be great.

Thanks--Stephan

 

I am guessing the coils (common problem)

 

Any idea how many miles are on the plugs? If those bad boys are originals, they're way past due for a swap. Even if they're the second set of plugs, depending on when they were swapped out, they may be due for a change.

If the plugs aren't too old, then I'd change out at least the three original coilpacks (if it were my rig, I'd change out all four, but then I'm kind of anal like that). Not all that expensive online.

 

Birdman, first make sure you have the correct plugs. The wrong heat range can cause similar symptoms.
If you do have the correct plugs, try closing the gaps down to 0.032” and see if that helps. I had the same problem, misfire under load, and this fixed the problem.
When I got my second set of plugs, I installed Denso IK22 plugs and set them with a 0.032” gap . IIRC, I started doing this back in ‘08 after reading about Oscar Jackson finding positive results from a Dyno experiment he did back then. The IK22s are one step colder in heat range. These colder plugs help deter pre-ignition.
I recently installed an HKS Turbo system and have found that it prefers spark plugs that are 2 steps lower in heat range, and requires a 0.018” spark plug gap before it will stop misfiring.
If you are NA, I think a 0.032” gap should do the trick. BTW, in regards to coilpacks, I have over 330,000 miles, and still have 3 original OEM coils that are still functioning. My theory is that the tighter gap puts less strain on my coils, therefore resulting in longer life.
Also, in regards to the IK22s, I was able to go at least 75,000 miles before replacing them with a new set.

 

Just to summarize past threads:

1. Adjust valve clearances
2. replace ALL coils with Hitachi # ending in 053
3. Replace spark plugs with OEM Denso

If the exhaust valves were really tight, then you are well-advised to do a compression test after adjustment.

You cannot visually look at the coils and pronounce them 'good'. They often produce a weak spark as they get old. Tighter plug gap is a work-around.

 

If an electronic circuit inside of the coil has a problem (typically coils with 3 or 4 wires) troubleshooting an intermittent miss is a challenge.
However if coil is old enough (say 15 years old on older) the boot will deteriorate causing spark to jump around the plug leaving distinct marks on the boot section of the coil:
this problem is characterized by a constant dead miss on idle

 

Thanks for all the input guys. I have the coils, plugs, and gaskets for the valve adjustment.

Yesterday I gaped the plugs from the 0.050 that they were down to around 0.32 and there was a noticeable improvement. Only getting (3) codes, cylinder 1 misfire, cylinder 4 misfire, and multiple misfire. Before i was getting individual misfire codes for all cylinders. This has be a sign of weak coils right?

I will update everyone in a few days once the parts come in.

cheers

 

Just an FYI...no gaskets are required. Just a small dab of import gray RTV for the valve cover.

Remove the entire air box, throttle body, upper intake assembly as one piece so you don't break any seals.

Make sure to use Denso or Hitachi coils and OEM type iridium plugs and all will be good.

 

If you are troubleshooting the ignition coils, you don't have to buy the expensive $50/ea Hitachi coils, the cheapie ebay $25 for a set of 4 shipped ones work just as well. Though another member questioned their longevity. But for me, I just needed immediate confirmation for a fix, and at $25 for 4 ignition coils shipped to me brand new, that makes it a no brainer for troubleshooting. Also I suspect its not the coils that are going bad, but rather the ignition boot contact springs getting oxidation and build up that is causing issues.