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Old 11-20-2021, 12:30 AM   #1
Lethidox
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Can catalytic converter cause misfire?

been driving my car for a while now it's a 1998 ford windstar 3.0L trying to learn how to fix things on it since it's a hand me down and yea it needs a lot of work. took it to a shop recently maybe a month ago because it wasn't accelerating properly. Was some sensor in the transmission. after i got it back maybe a 1-2 days later Service engine light comes on. was driving fine then now it's just getting worse.

ran my scanner already assuming it was bad catalytic converter due to the sound and just how it feels to drive. ran the car for a good month like this waiting on my scanner so i didn't know prior. runs a p0420 code. think it is clogged but i just bought a new catalytic online so waiting on that to come in to replace. might take a while though couldn't find much options for where i live that will ship to me without costing so much.

Anyways today coming home from work Service engine light starts to blink assuming it's very bad and car felt different. shaking/rough idle, started to feel slow acceleration as well. went up a steep hill on the free way to get home. couldn't even push past 30mph. got home safely, ran my scanner again and read p0301 ( cylinder 1 misfire ).

so my question is could the bad catalytic converter cause the cylinder misfire?

What i've replaced so far

1. Water pump - failed recently causing coolant leak everyday.
2. All 6 spark plugs- tried my best to gap them properly
3. OEM spark plug wires all 6 of um
4. Master Cylinder pump - had failing brake ( pedal went to floor ) and pump was leaking after my dad got into a hit and run accident.
5. Brake Booster pump
6. Alternator
7. Starter - this went bad
8. lower water pump hose - thought it was leaking from here but was the water pump
9. transmission speed sensor ( done by shop )

I was wondering if it could just be the catalytic converter causing the misfire or what others think? i mean it just recently started doing this but i've been driving with the bad catalytic for a little over a month now. I am not sure if Ignition coil needs to be replaced as well or not. i replaced the spark plugs and wires maybe 2 weeks ago.
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Old 11-20-2021, 09:54 AM   #2
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Re: Can catalytic converter cause misfire?

It's less likely for a catalytic converter to cause a misfire than it is for a misfire to cause a catalytic converter efficiency code, and possibly even damage to the converter if ignored for too long. I'd be more inclined that the cylinder misfire was what was causing the catalyst code, and eventually the misfire got bad enough to send the van to limp home mode and trigger the P0301.

Are you certain that the spark plug wires are good and securely connected to the cylinder #1 spark plug? If you pull the #1 spark plug now, does the color suggest it's burning rich, lean, or maybe some contaminant? Do you have access to a cylinder leak down tester? I think the 1998 3.0L has coil packs an not a distributor, correct? Could you swap coil packs around to see if the misfire changes cylinders?

-Rod
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Old 11-20-2021, 10:57 AM   #3
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Re: Can catalytic converter cause misfire?

the weird part about it was i scanned it maybe 2-3 weeks ago when i got my scanner didn't even show a p0301 code at all give or take when im accelerating it did have small bursts of knock back but i guess to me this was always normal with this car because since i got it this has always happened especially at higher speeds.

it has a distributerless coil pack i believe. looks like a block with all 6 coils in 1. i ended up buying an OEM one from motorcraft last night after doing some research and having a hunch that maybe this is what is the issue. won't be here until tuesday/wednesday though.

when i changed out my spark plug wires i used brand new ones from motorcraft. laid it all out by length ( don't think it was marked by cylinder like some seem to be on the wires ). and when changing out spark plugs i just pulled each one out 1 by 1 NOT all at once.

this car is kinda idk "old" i guess. grandpa let it sit in the sun/rain for years on end didn't drive it often maybe once a week at most, barely did any maintenance on it.

the catalytic converter though it's louder then usual and have a weird smell. doesn't smell like sulphor to me but smells like it's running more on the rich side maybe. it does run a p0420 code though talking about something Bank 1 and Bank 2. i assume this is before it hits the catalytic converter assuming it is blocked causing less flow/heat up issues.
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Old 11-21-2021, 11:54 AM   #4
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Re: Can catalytic converter cause misfire?

If the engine is running rich, which an ignition misfire will do, it will cause the exhaust to smell rich. It will also cause the catalytic converter to get really hot as it tries to convert the unburned fuel into water, but at a much higher rate than it's designed to do. That rich exhaust can also cause the up and downstream oxygen sensors to register that the catalytic converter is not working efficiently, which it's not. Also, you can have a misfire that might trigger a pending code, but not all scan tools are able to access pending codes.

I'd still recommend you pull the spark plug from cylinder #1 and see if it appears to be wet with fuel. Also, understand that if you keep driving your vehicle with a misfire that is causing a rich condition, it will continue to do damage to the catalytic converter. If the converter is not already damaged, continuing to drive it may end up getting really expensive.

-Rod
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Old 11-21-2021, 06:47 PM   #5
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Re: Can catalytic converter cause misfire?

I will check my plug on #1. Right now I'm not driving it. Doesn't feel safe especially stop and go traffic. Would replacing the coil pack fix this issue if not wet?

I got my catalytic coming In maybe 2 weeks at earliest.
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Old 11-21-2021, 10:00 PM   #6
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Re: Can catalytic converter cause misfire?

A plugged cat can cause a misfire.
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Old 11-21-2021, 11:13 PM   #7
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Re: Can catalytic converter cause misfire?

Yea that is what i was assuming maybe it broke down over time and got plugged up and idk guessing it has little to no where to exhaust out of due to clogged catalytic so maybe it causing misfiring that way. won't be getting the catalytic for a while doesn't ship out until the 29th :/
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Old 11-22-2021, 07:43 AM   #8
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Re: Can catalytic converter cause misfire?

You could try removing the oxygen sensor before the bank 1 catalytic converter and see if that helps it idle better. If it's a plugged converter, pulling the front HO2S and giving the exhaust a place to vent should make a noticeable difference. However, if the converter is plugged and you're getting a code for a misfire, just replacing the converter will most likely not fix the issue and will lead to a premature failure of the new converter.

-Rod
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Old 11-22-2021, 11:32 PM   #9
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Re: Can catalytic converter cause misfire?

I am planning to change out the coil pack + check on the spark plug in cyclinder 1 as you suggested first, hopefully that fixes it if not then probably change out the catalytic after. i am planning to change out the 02 sensors as well though but give or take how long the damn catalytic takes to get to me so far it says shipping on the 29th so i likely won't even get it until early december :/ so probably will change out the o2 sensors before then.

Bank 1 and Bank 2 are the front sensors correct? i only have 2 catalytic converters and i believe 4 o2 sensors unless i am mistaken. getting to one of them might be hell it looks like it's in a tight area but i've read i can actually reach in from the top and get to it given i don't have to remove anything like the 2 cowls
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Old 11-25-2021, 02:30 PM   #10
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Re: Can catalytic converter cause misfire?

put in the new coil pack seems no different.

car is reading overheating coils bank 1 and 2 i believe only but no p0420 code anymore. still reading misfire cylinder 1 though. drove it on the freeway since i quick cleared the codes but service engine light came back on.

it feels better then before though when stopped at a light or in traffic it's not shaking dramatically when accelerating from a complete stop though it shakes until i hit about 10-15mph then it stops. so it's slightly an improvement from before.

letting the engine cool down so i can take a look at the spark plug/wires but looking at the coil pack and if i am not mistaken it looks like originally the plugs were put in wrong.

coil pack goes 521 right side and left side it goes 463 according to the manufacturing label on the coil ( motorcraft ) same exact part originally installed i believe nothing different. when removing anything plugs/spark plugs i did it 1 by 1 as to not mix them up. remove 1 plug at a time, find that matching length plug and removed the spark plug installed new spark plug and put in new plug and attached it to coil.

issue now is idk if i have to check the original cylinder 1 or if it's actually scanning the cylinder 1 correlating to cylinder 1 spot on the coil pack. this gonna make it a lot harder thats why if going by coil pack that means the cylinder 1 is gonna be a PITA just to get to. if by motor i believe it is easy. checked the front 3 plugs they were on good. back 3 plugs might be the issue since it's hard to reach spot and can't even see. will probably check both though but letting engine cool down for now.
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Old 11-25-2021, 06:43 PM   #11
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Re: Can catalytic converter cause misfire?

checked spark plug on cylinder 1 didn't look wet but had some sort of small amount of grease looking thing on it. it didn't look like it was wet though. it did look like it wasn't firing properly seen some burnt part under the tip on the white part. wasn't cracked. ended up getting 6 new spark plugs. replaced them all. all other 5 spark plugs looked good though compared to cylinder 1.

i didn't gap the plugs this time. guy at the shop said it was pre gapped. the other set i had in i gapped. ran it around the block twice see if the light would come on again. so far it didn't but on my way home on the 2nd lap i felt and heard 2 weird burps. could feel it on the pedal not entirely sure what it was. will test it again tonight when roads die down a bit on the freeway. feels a lot better now though acceleration wise.

my dad said it doesn't sound loud either but idk in idle it seems okay but when slowly accelerating it feels weird and sounds loud. it does push past 30mph easily now though compared to prior.
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Old 11-26-2021, 10:06 AM   #12
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Re: Can catalytic converter cause misfire?

Quote:
Originally Posted by Lethidox View Post
coil pack goes 521 right side and left side it goes 463 according to the manufacturing label on the coil ( motorcraft ) same exact part originally installed i believe nothing different. when removing anything plugs/spark plugs i did it 1 by 1 as to not mix them up. remove 1 plug at a time, find that matching length plug and removed the spark plug installed new spark plug and put in new plug and attached it to coil.

issue now is idk if i have to check the original cylinder 1 or if it's actually scanning the cylinder 1 correlating to cylinder 1 spot on the coil pack. this gonna make it a lot harder thats why if going by coil pack that means the cylinder 1 is gonna be a PITA just to get to. if by motor i believe it is easy. checked the front 3 plugs they were on good. back 3 plugs might be the issue since it's hard to reach spot and can't even see. will probably check both though but letting engine cool down for now.
I'm confused by what you mean here. The P0301 code should be relative to the cylinder number which should be the same on the engine and on the coil pack. Cylinder 1 of the coil pack should go to cylinder 1 of the engine block, which should be the left-most cylinder near the firewall on your car (Bank 1) if you are standing in front of the car looking at the engine. Those cylinders against the firewall (bank 1) should be 1, 2, and 3, with cylinder 1 closest to the serpentine belt. Bank 2, closest to the front of the car, should be cylinders 4, 5, and 6. According to the factory service manual, the coil pack for the 3L is laid out this way as well.

There will be one oxygen sensor before each catalytic converter, probably mounted in each exhaust manifold. These upstream sensors will be the Bank 1 Sensor 1 (B1S1) and Bank 2 Sensor 1 (B2S1). If you have 4 total oxygen sensors, then there will also be 1 sensor after each catalytic converter corresponding to the cylinder bank. For the Bank 1 cylinder bank converter, this downstream sensor will be B1S2 and for Bank 2 after the converter the sensor will be B2S2.

You mention what appears to be a grease blob on the spark plug you removed. That might be unburned fuel.

-Rod
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Old 11-26-2021, 11:45 AM   #13
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Re: Can catalytic converter cause misfire?

I ended up reading the cylinders wrong but yea it was correct way. Put in the new coil pack still misfire. I ended up replacing all the spark plugs and seemed to work now.

Drove to work today which is about 11 miles no light came on. So yea you were right the misfire seemed to cause the 420 code. Drives 60 uphill too.

They turned it 1 time clock wise the engine that is so I read it wrong. So my cylinder 1 is in the back left corner near my compressor I believe. Cylinder 6 is next to the serpentine belt in the front of the car. I was reading it backwards though so I thought 6 was 1.

I think it has 4 sensors but I got to check so far I only found 2. 1 by my header in the front and 1 right before the catalytic. Planning to replace them with the catalytic next week.

Thanks for the help likely wouldn't have figure wtf is wrong without you guys. I added some additive to clean out my injectors if that doesn't work I'll probably replace that after.

Didn't hear a burp sound like yesterday so hopefully that is good but I think it could of been the water pump because I didn't burp my radiator good when I flushed it after replacing the pump. Runs colder but still fluctuates at least once when warming up
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Old 11-27-2021, 01:42 AM   #14
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Re: Can catalytic converter cause misfire?

Service engine light came on again only after i drove home :/ was kind of expecting it though tbh. rescanned the car when i got home same issues it seems.

p0420 popped right back up

p0301 ( cylinder 1 misfire; AFTER i changed all spark plugs a second time; i think it's only been 1 month or less since i changed them the first time )

p0156 ( i believe this is bank 2 o2 sensor says malfunction )
p0161 ( again i believe this is o2 sensor bank 2? )


ended up going to the shop buying 2 o2 sensors changed the driver side downstream one which i think is bank 2? tried to change the passenger side downstream one but man that one giving me hell just to take off.
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Old 11-27-2021, 07:49 AM   #15
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Re: Can catalytic converter cause misfire?

Both the P0156 and P0161 diagnostic codes are related to the Bank 2 Sensor 2 oxygen sensor readings/current draw. The Bank 2 catalytic converter is the converter that is connected to the exhaust manifold for the cylinder bank closest to the front of your Windstar. Sensor 2 will be the sensor that is after the converter, closer to the back of the vehicle.

I agree with you on the location of cylinder 1, but cylinder 6 should be the cylinder on the far right of the front engine bank as you stand, looking at the engine from in front of your vehicle. It will be on the end of the engine furthest from the serpentine belt.

[Firewall]
1 2 3
4 5 6
[front of vehicle]

You can use penetrating oil, but if the hex of the sensor is already rounded, you'll probably need a locking pliers with sharp jaws and some means of providing extra leverage to break the sensor free. Let the penetrating oil soak for a few hours, then apply more and let it soak. I've had good luck with SeaFoam Deep Creep and Rust Eater penetrating oils.

-Rod
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