Misfire no CEL

B

blindloser1080

New member
Hello, so recently my 2003 with 236k threw a P0303 code and replaced all 6 spark plugs. I replaced them with Denso iridium plugs. Drove fine for a few days.

Now I'm getting a misfire that I've been able to recreate every time going 55mph with about 1800k rpm. It's not throwing any codes either. I've ran a code scanner on it, plus I have tried running my BlueDriver on it also, with no luck.

Any input on what I should check out? I haven't replaced any coils and have yet to do the O2 sensors.

Sadly funds are currently strapped as someone broke into my friends vehicle while we were in Vancouver stole my keys out of it, so had to fork out $350 for two new keys to get programmed.

Thank you in advance :)
 
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When you replaced the plugs did you inspect the coils, if not one or some of them could be cracked where they connect to the plug causing a short to ground and not letting the plug/s fire properly?
 
Sorry it took so long to reply. Finally got a chance today to pull off all the coils. None we're damaged, cracked, e.t.c.

I did notice on the driver's side that it has a sticker to replace with a 'long reach spark plug'. Any possibility that might be causing something?
 
blindloser1080 said:
Sorry it took so long to reply. Finally got a chance today to pull off all the coils. None we're damaged, cracked, e.t.c.

I did notice on the driver's side that it has a sticker to replace with a 'long reach spark plug'. Any possibility that might be causing something?
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Just curious, are they Denso 3421 spark plugs like these?

More Information for DENSO 3421

Also, have you noticed if your fuel economy has gone down either using the number on the dash or by calculating at fill-ups?
 
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not too long ago there was another member on the forum that had the same issue using the denso, he bought dealer plugs and the misfire went away
 
Yes, they were the Denso 3421. They were of course the only one o'Reilly's had 6 in stock of.

So I checked all the coils, removed the plugs and reinstalled them. Went for a drive and it's still happening. You're recommending I get the plugs from the dealership and give them a try? Sadly o'Reilly won't return these as I have no packaging.

I haven't really noticed gas milage going down. I drive 60 miles daily for work and have been getting about 300-320 miles to a tank for a while now. I have to fill up once a week.
 
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It almost sounds like something is either interrupting fuel flow or causing an innacurate fuel flow for the given speed and rpm. I second [MENTION=78511]earthrealm[/MENTION], have you checked your short/long term fuel trims? Could be an issue there, I'm leaning towards bad O2 sensors or air/fuel sensor. Don't think actual fuel delivery is bad as there would be a much more noticeable misfire and likely a light. But if either of the above mentioned sensors isn't performing the way it should, it would affect the flow of fuel at some point.
 
blindloser1080 said:
Yes, they were the Denso 3421. They were of course the only one o'Reilly's had 6 in stock of.

So I checked all the coils, removed the plugs and reinstalled them. Went for a drive and it's still happening. You're recommending I get the plugs from the dealership and give them a try? Sadly o'Reilly won't return these as I have no packaging.

I haven't really noticed gas milage going down. I drive 60 miles daily for work and have been getting about 300-320 miles to a tank for a while now. I have to fill up once a week.
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They should return them if you gave them your number at checkout. I do most of my returns that way because I never have packaging or a receipt. They just look me up by my number and I'm good to return whatever it is.
 
The misfire was much more noticeable this morning, especially when I was accelerating between 50-60. I'll give the dealership plugs a try and see if maybe that fixes the whole issue. If not then I'll start with the O2 sensors.
 
blindloser1080 said:
The misfire was much more noticeable this morning, especially when I was accelerating between 50-60. I'll give the dealership plugs a try and see if maybe that fixes the whole issue. If not then I'll start with the O2 sensors.
Click to expand...

I'd strongly recommend getting your hands on an OBD2 reader that can give you live data. Even if it's a little ELM327 module that you can pair with the torque app. Would be nice to see what it is actually going on rather than just blindly throwing parts at it.
 
81runner said:
I'd strongly recommend getting your hands on an OBD2 reader that can give you live data. Even if it's a little ELM327 module that you can pair with the torque app. Would be nice to see what it is actually going on rather than just blindly throwing parts at it.
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I was just recently given a BlueDriver a few weeks ago. Not really sure how to use it or what I should be looking at while using it. I did have it on while trying to get the vehicle to misfire so it would read/throw a code with no luck.
 
Never worked with bluedriver before. I bought a cheapy Chinese ELM327 OBD2 module off eBay, think I paid like 12 bucks for it. Paired with torque pro, it gives you the ability to view live data from your running engine. Not sure if bluedriver can do that as well, I would guess it can. You want to know what your long term fuel trims are (ltft1 ltft2), short term trims (stft1 stft2) and also your o2 sensor voltages. This will help narrow down the issue. I would think if the plugs were a problem, you would get a code all the time. With fuel trims, you can be out a little bit or a lot, but the obd won't throw a code unless any of them is +-30%. So you could have a ltft1 reading of +25%, ltft2 of +12%, be running like shite, and still not get a code. Sure, you could just throw parts at it, but if you're in the dark about what's going on, that could get expensive quick, fast, and in a hurry.
 
81runner said:
Never worked with bluedriver before. I bought a cheapy Chinese ELM327 OBD2 module off eBay, think I paid like 12 bucks for it. Paired with torque pro, it gives you the ability to view live data from your running engine. Not sure if bluedriver can do that as well, I would guess it can. You want to know what your long term fuel trims are (ltft1 ltft2), short term trims (stft1 stft2) and also your o2 sensor voltages. This will help narrow down the issue. I would think if the plugs were a problem, you would get a code all the time. With fuel trims, you can be out a little bit or a lot, but the obd won't throw a code unless any of them is +-30%. So you could have a ltft1 reading of +25%, ltft2 of +12%, be running like shite, and still not get a code. Sure, you could just throw parts at it, but if you're in the dark about what's going on, that could get expensive quick, fast, and in a hurry.
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Will do. I'll put it on there tonight and do some driving. See what I can find out.
 
Did some driving around the block for about 10 minutes, max speed 40mph (having hesitation and misfire when stopping at a light and going again). Here's some info I found out:

Long term fuel trim bank 1: 0-4.7%
Short term fuel trim bank 1: -15.6%-9.4
Long term fuel trim bank 2: 3.1-6.3%
Short term fuel trim bank 2: -19.5%-7.8%
 
Tested the o2 voltages and such. Same drives, 40mph max. Here's the info:

Wide range os2 bank 2(3) sensor 1(1): voltage 2.884-3.442 (stayed very steady through drive)

Wide range os2 bank 2(3) sensor 1(1) equivalence ratio: .942-1.039 (again steady)

Wide range os2: bank 1 sensor 1 voltage: 2.893-3.501v (again steady)

Wide range os2: bank 1 sensor 1 equivalence ratio: .937-1.44 (steady)

O2 bank 2 sensor 2 (bank 3 sensor 2) oxygen sensor voltage- .055-.780V (peaks and valleys)

O2 bank 1 sensor 2 oxygen sensor voltage- .075-.76V (peaks and valleys)
 
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