hesitation with WOT after plugs

I have 2010 with 74k on it. It was stage 1 93 now back to stock.

 

I just replaced my plugs with stock NGK and everything went as planned. Started it up with a misfire and found a cracked insulator. This threw a misfire code and I replaced the plug.

 

 

 

Everything is in working order now with no codes. It drives noticeably better than before the plugs except for wide open throttle. It has a hesitation in 2nd gear and higher on/off from 4k to redline. I had stage 1 on it and the hesitation was much more severe. It is still present at stock but less severe.

 

 

This was not present before replacing the plugs. I don't see evidence of misfires on the datalog and no further codes. I have only noticed it at WOT. Thank you for any help.

datalog2.csv

there have been a lot of issues with counterfeit NGK plugs (mostly on Amazon and eBay) - any chance there's an issue with the plugs? if you put the old ones back in, does the hesitation go away?

on partial throttle it's ok? If so it could be as easy as a boost leak. I do see it touching 14psi at WOT, but otherwise it has to be down to the plugs, coils or wiring to them. Were all of your coil plug clips intact or did you have to do the zip tie trick to hold them on?

I-wire sells replacement plugs if so.

Would boost error provide insight on a boost leak? The coils looked fine and the clips engaged fine.

 

The plugs came from Rockauto and looked identical to the ones that came out. Unfortunately... I think all but one original plugs are gone. Tossed them when it initially seemed fine with the new plugs.

 

I’ll look for boost leaks and maybe get anther log with boost error and fewer parameters?

I agree with a boost leak.

 

Check the coupler pipe between the intercooler and intake. The coupler has two rubber covers, one on each end that many of us have found cracked/compromised and leaking under load.

There are other places to look, but I would start there. Unfortunately a boost leak most likely won't be visible to your eye...

Yeah I got this leak tester and hook it up to my turbo inlet

https://www.amazon.com/gp/product/B0825WNGP3/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

Found out that the charge pipe connection to the intercooler was leaking like crazy even if I tightened it a lot. I had to line the intercooler flange with electrical tape to get it to seal okay. But I did not have any hesitation like you. Either way, this may be the only other plausible explanation other than the spark system.

 

TD Boost error may help, but my tuner did say that it wasn't completely abnormal for it to go +/- 1.5 depending on atmospheric conditions

Edited November 24, 2020 by Aphex28

I have 2010 with 74k on it. It was stage 1 93 now back to stock.

 

I just replaced my plugs with stock NGK and everything went as planned. Started it up with a misfire and found a cracked insulator. This threw a misfire code and I replaced the plug.

 

 

 

Everything is in working order now with no codes. It drives noticeably better than before the plugs except for wide open throttle. It has a hesitation in 2nd gear and higher on/off from 4k to redline. I had stage 1 on it and the hesitation was much more severe. It is still present at stock but less severe.

 

 

This was not present before replacing the plugs. I don't see evidence of misfires on the datalog and no further codes. I have only noticed it at WOT. Thank you for any help.

Did you check the gap?

I have a car with a 2.0 turbo and I run hks plugs. I have to check the spark plug gap every six months due to I'm running 20psi on a aftermarket larger turbo. I also check the spark plug gap when I buy new plugs. If the gap is too wide you will get hesitation. Just my 2 cents.

 

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Did you happen to notice if the coil heat sinks were at all corroded or swelled?

 

When I did my clutch I had pulled the motor to do it. Did some maintenance items on the motor while it was out. Plugs being one of them.

 

I started getting a misfire, eventually bad enough to set a CEL in #3 on WOT not long after putting the car back together.

 

It was a failing coil. Disturbing it must have sent it over the edge. The heat sinks were swelling from corrosion. Looking at them I would have never thought that would do it.

 

I got replacement NGK coils (#49122) from Rockauto for like $65 each

 

No more misfire

Did you happen to notice if the coil heat sinks were at all corroded or swelled?

 

It's not a heatsink; it's the laminate core of the coil. I've had mutiple coils on my H6 Outback fail from the laminates "rust jacking".

I have not taken the plugs or coils out again but double checked my connections and everything seems seated correctly. I was concerned that the connection at the air box wasn't tight or flush but no change.

 

 

Seems weird that a boost leak would develop after plug replacement but I did unbolt the motor mounts and lift ~1" for clearance. Am I right in assuming that I would probably get a miss fire code at times other than WOT if it was a coil or plug problem? Aren't the coils firing at the same rate at 5k regardless if the throttle is depressed?

 

 

 

I did check the gaps and the coils looked fine. No noticeable difference other than some mild white corrosion on the bolt threads only.

 

 

I have added another data log with boost, target boost, and boost error. This is with the Stage 1 again so boost targets are higher. The stock tune was realtime and it defaulted to this after an ecu reset. I am not hitting boost targets in the 4K+ and I notice the hesitation most in the mid rpm range. I don't know how to tell from a data log if the ECU is pulling boost for safety or if I am leaking as you all stated. My wastegate duty cycle decreases slightly at 4406 RPM which leads me to believe that it is trying to build more boost but can't? The wastegate duty cycle increase with RPM is consistent with the programmed boost taper?

 

If the next step is to test for boost leaks, where do you recommend placing the tester? Do I have to start at the turbo inlet or can I place it at the airbox coupling?

 

If I give up and take it to the mechanic, do you recommend a "specialist" or to take it to my regular mechanic? I assume that most mechanics can handle a turbo in this day and age? I'd rather not take it to the dealer will if I have to. Thanks again for the advice.

datalog2.csv

When you say you replaced the plugs with stock NGK, did you gap them at all or just check them? What type of gauge did you use (feeler or round ramp style)? Sounds like the spark might be blowing out.

 

The stock gap spec is 0.028-0.031" and I can tell you from experience that NGK plugs out of the box tend to have a bigger gap than specified. Even then they show that their gap for this application is 0.032, which is over the max OEM spec. Personally I would re-gap the plugs to 0.028 using quality feeler gauges.

be careful when gapping Ir plugs - the center electrode is easy to damage. For bringing it in, I would strongly recommend having the tech handling the vehicle ride with you in the car so you can show them exactly what you want looked into - if this is a subtle thing, some folks might not notice it.

be careful when gapping Ir plugs - the center electrode is easy to damage.

 

If you're doing it correctly, you never even come close to touching the center electrode. Carefully press on the back of the ground strap to close the gap, and use a pry bar style gapping tool to open it up.

I am guessing most folks that manage to damage the center electrode (snapping off the Ir tip) do so when measuring the gap, rather than adjusting it... when measuring the gap, you definitely come close to/touch the center electrode.

I run hks racing ir plugs in my Hyundai. I constantly pull them and check the gaps. I use feeler blades. I run somewhat high boost so I make it a rule just to check them every 6 months. I also change the gap whenever I replace them . If the gap is too wide all you have to do is tap them on a hard surface to close it. I use a gap tool to adjust by pulling if needed. I've been doing it for so long its really not a big deal. If you

Are only buying spark plugs and installing them without checking to make sure they are gapped properly then you are missing a step in your troubleshooting steps. It will hesitate when you get to WOT by blowing out the spark completely due to the gap being too wide.

 

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I checked with a ramp gauge and believe they were .03 dead. They are the NGK SILFR6B8. I also have a feeler gauge but don’t know how quality it is. It’s older than i am at 40. I’ll pull them out to check again and maybe tighten up to .028

I checked with a ramp gauge and believe they were .03 dead. They are the NGK SILFR6B8. I also have a feeler gauge but don’t know how quality it is. It’s older than i am at 40. I’ll pull them out to check again and maybe tighten up to .028

 

On a bone stock, engine 0.030 is going to be fine. I don't think spark plugs is you issue unless one one of plugs's ceramics is damaged. My car is basically stock with a 18.5 psi tune. My stock plugs have 0.031 gaps.

I did a boost leak test today and you all were right on the intercooler to throttle body coupling. I started at the intake and couldn't hold pressure for any amount of time. Hopefully this will fix the problem with hesitation. I ordered the Cobb part. Edited December 2, 2020 by msmy300z

I did a boost leak test today and you all were right on the intercooler to throttle body coupling. I started at the intake and couldn't hold pressure for any amount of time. Hopefully this will fix the problem with hesitation. Any recommendations on best place to find a replacement?

 

Just pull the rubber ends off of each side of the coupler and then just reuse the coupler. Should work great if the coupler isn't ripped. The useless rubber end pieces are your issue, so get rid of em.

So I fixed the boost leak at the coupler and the issue was still there. I had hesitation and misfire P0304 with a PFFFF code.

 

 

I have removed the plugs and checked the gaps (~0.029). I also swapped the coils between 2 and 4. Still the same problem and misfire P0304, PFFFF, and PFFFE.

 

 

I assume that swapping the coil ruled out the pack. The issue is still only present with WOT. So finally, should I swap the plugs and see if it follows or do I have a bigger problem? I did not specifically inspect the #4 plug but did not see any damage to it when I went through all of them yesterday.

Try swapping the plugs and see if the misfire follows the plug - if it doesn't, take a look at the injectors (measure the resistance of the injector for cylinder 4, also verify the wiring is in good shape and the connectors are all mated soundly.

 

 

So did the misfire just come back, or did it never go away?

No, it never went away. I haven’t been able to resolve it since I decided to change the plugs. It wasn’t throwing a code until I fixed the boost leak. I assume the leak was a coincidental finding that I found trying to fix the original problem.

So I fixed the boost leak at the coupler and the issue was still there. I had hesitation and misfire P0304 with a PFFFF code.

 

 

I have removed the plugs and checked the gaps (~0.029). I also swapped the coils between 2 and 4. Still the same problem and misfire P0304, PFFFF, and PFFFE.

 

 

I assume that swapping the coil ruled out the pack. The issue is still only present with WOT. So finally, should I swap the plugs and see if it follows or do I have a bigger problem? I did not specifically inspect the #4 plug but did not see any damage to it when I went through all of them yesterday.

 

I just had the ," I had hesitation and misfire P0304 with a PFFFF code" and it was the coil pak, I just bought one and swapped in the new one. I didn't swap 2 and 4 since considering it a 10 year old car I assume that number 2 may not be in the best shape, that being said where I live they salt the road in the winter, just a thought