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Discussion Starter · #1 · (Edited)
I have done a search through the forums but I'm not finding anything that covers my issue. I picked up an '02 GT MT recently for a good deal and have been fixing it up (My son picked up a '99 AT recently, 300k miles and he loves it!)

From the moment I picked up the '02, it has had some hesitation. I will get random P017X P030X codes but the cylinder is not consistent. I also get P0420 codes sometimes. If I drive gently, it runs just fine. I have done all of the following:
1. Replaced plugs with new NGK Iridium
2. Tried 5 different OEM MAF sensors (cleaning each one before trying)
3. Installed new air filter
4. Checked for loose intake plumbing (have not done smoke test yet)
5. Removed cat and soaked in detergent, cleaned O2 sensors with Elec Contact cleaner.
6. Picked up 6 additional used coils and tried moving them around but code doesn't follow.
7. Run seafoam through engine oil and fuel.
8. Fuel Injectors have been cleaned and tested and all their seals replaced.

I'm kind of lost at this point, anybody have any more ideas ?

update 4/25/2022
In addition to the items above, I have now done the following:
9. Run engine flush, replaced oil with fresh oil, run 2nd flush and replaced oil and filter.
10. Replaced front O2 sensor with new denso unit.
11. Cleaned up back O2 sensor.
Car does not appear to be throwing CEL but still has slight hesitation

Wheel Tire Car Vehicle Automotive tire
 

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Electromagnetic Wave :-h
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Look for a leaky intake manifold gasket (common issue on early GT) or other vacuum leak. You were on the right track with the MAF. Most hesitation as described is MAF reading related. Any unmetered airflow will cause issues.
 

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Discussion Starter · #5 ·
Look for a leaky intake manifold gasket (common issue on early GT) or other vacuum leak. You were on the right track with the MAF. Most hesitation as described is MAF reading related. Any unmetered airflow will cause issues.
sigh I suppose I'll try and get a smoke test. thanks for the suggestion.
 

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Electromagnetic Wave :-h
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Depending on the actual DOM, you've likely got an oil burner. P0420 is a common issue w/them fouling the cat. P0171 is a common CEL for MAF/vacuum issues (unmetered air entering). P03XX would misfires (which can be the result of P0171).

While it won't actually solve the cat problem, you can mask it by adding a spark plug defouler to the post-cat sensor.
 

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I'd imagine since you have done spark plugs & multiple coil packs that you would have noticed/already removed oil in your spark plug tubes when swapping them. My '02 GT-S had some hesitation when I purchased it, I started with cleaning the MAF, but it didn't help. When I went to change the plugs, I found over an inch of oil in a couple tubes. Put in new tube seals/vc gasket and plugs and cleaned the coil packs up a bit and the hesitation seems to be remedied.

Even though it won't help you, I'm posting for anyone in the future with hesitation problems.
 

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Discussion Starter · #11 ·
Noting to do with your issue..

But the rims..

All the 86’s I thought had 5x114 pcd where celica are 5x100

don’t doubt you though. Just odd
The guy I got them from assured me that they were 2017/18 Toyota 86 wheels. The back of the Toyota center caps actually say Subaru (because of course the BRZ is the sister car)
 

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Yeah that made sense my wrx rims fit the celica but the offset needs spacers. Well doesn’t NEED them but def should.

all the 86 rims I see here are 114 pcd.
Thanks,
 

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That's odd - I had JDM 16" Toyota 86 wheels when I had my FR-S. They were definitely 5x100, because I thought about keeping them for my '00 Celica when I was selling the FR-S. The bolt pattern fit fine, the offset is the issue and I didn't have spacers. Incidentally my '02 Celica had spacers when I bought it 10mm F and 25mm R I believe. I gave/sold the wheels to my brother, but if he lived close by I'd probably stick them on just to see how they look/fit.

 

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Discussion Starter · #14 ·
That's odd - I had JDM 16" Toyota 86 wheels when I had my FR-S. They were definitely 5x100, because I thought about keeping them for my '00 Celica when I was selling the FR-S. The bolt pattern fit fine, the offset is the issue and I didn't have spacers. Incidentally my '02 Celica had spacers when I bought it 10mm F and 25mm R I believe. I gave/sold the wheels to my brother, but if he lived close by I'd probably stick them on just to see how they look/fit.

I did need to use 8mm spacers on the wheels because they hit the front calipers otherwise. I also removed the little inserts that came in the wheels out so that I could use regular round end lug nuts. The bore is 1mm larger on the 86 wheels. I may put a spacer in there sometime. I have a tacoma that's had wheels with 6mm too large bore for years now with no issues so not too worried.
 

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Discussion Starter · #15 ·
Depending on the actual DOM, you've likely got an oil burner. P0420 is a common issue w/them fouling the cat. P0171 is a common CEL for MAF/vacuum issues (unmetered air entering). P03XX would misfires (which can be the result of P0171).

While it won't actually solve the cat problem, you can mask it by adding a spark plug defouler to the post-cat sensor.
Thanks for making me re-read my original post, I'm getting random P030X codes (cylinder misfire), not P017X codes.
Going to try the brake cleaner suggestion mxaustin suggested this morning.
 

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I did need to use 8mm spacers on the wheels because they hit the front calipers otherwise. I also removed the little inserts that came in the wheels out so that I could use regular round end lug nuts. The bore is 1mm larger on the 86 wheels. I may put a spacer in there sometime. I have a tacoma that's had wheels with 6mm too large bore for years now with no issues so not too worried.
Oh yeah, I forgot about the lug nuts. I think the FR-S had a different thread/pitch than the Celica if I remember right, so I would've needed to buy new lug nuts as well. I did buy hub/bore spacers for the tiny difference, even though it wouldn't really matter once all the lug nuts are torqued properly. I do remember the hub popping out the center caps because of the offset when I did a test fit with no spacers.

Sorry for the off-topic discussion!
 

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Discussion Starter · #17 ·
Oh yeah, I forgot about the lug nuts. I think the FR-S had a different thread/pitch than the Celica if I remember right, so I would've needed to buy new lug nuts as well. I did buy hub/bore spacers for the tiny difference, even though it wouldn't really matter once all the lug nuts are torqued properly. I do remember the hub popping out the center caps because of the offset when I did a test fit with no spacers.

Sorry for the off-topic discussion!
Initially I just used the lug nuts that came on the Celica but I have a whole garage full of crap from my countless car projects so I found some acorn nuts that had the correct thread pitch and worked well.
 

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Electromagnetic Wave :-h
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Can you look at your fuel trims or the freeze frame data from the P03XX cels?

This could be a cam or crank sensor issue or ignition related.
 

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Hesitation and random misfring at high speed are more likely caused by ignition.

Like someone posted, check the plug wells and clean out oil and contaminations. Oil will cause ground faults with the plugs therefore misfiring.

NGK plugs may not be compatible like DENSO plugs. Check gaps to make sure. Clean out contacts.

Check and test ignition cables for potential shorting to ground.

Off brand and counterfeit ignition coils will misfire intermittently.
 

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Discussion Starter · #20 ·
Hesitation and random misfring at high speed are more likely caused by ignition.

Like someone posted, check the plug wells and clean out oil and contaminations. Oil will cause ground faults with the plugs therefore misfiring.

NGK plugs may not be compatible like DENSO plugs. Check gaps to make sure. Clean out contacts.

Check and test ignition cables for potential shorting to ground.

Off brand and counterfeit ignition coils will misfire intermittently.
The car runs smoothly at WOT, and at lor RPM, just not in the middle.
There is no oil pooling in the plug wells.
 
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