Random Misfire, Flashing CEL, P0301

[Browning]

This will be long and probably ramble on but it's driving me nuts.

2005 Pontiac Vibe base model. 180, XXX miles. This has all been happening since Saturday.

We've been getting a really rough idle at stop lights which drops the RPM's really low but never stalls. Putting it in neutral cleared it up we could take off and go with no check engine light. Now, it has progressed to happening randomly throughout the day sometimes it clears up sometimes it continues as we take off and clear around 3,000 RPM but is accompanied by a flashing CEL for cylinder 1 misfire P0301. At one point it also threw a bank 1 lean P0171 but only once and hasn't come back. The P0301 is occurring quite a bit but it is random.

For instance, sometimes I can drive it into town without any missing or codes, other times it acts up for a bit then clears up and then another time it misses like crazy and throws the flashing CEL for the P0301.

Things I have done already:

1. Chevron in the tank
2. Changed plugs (Autolite iridium)
3. New coil (also swapped around and the code did not follow)
4. New Air filter
5. Cleaned and then replaced MAF sensor
6. Checked for vacuum leaks but I couldn't find any

Went for a ride today after changing the MAf and it ran good for 15 minutes then started acting up. Got home, restarted it still rough. Rinse and repeat and it cleared up on like the 3rd restart but if you gas it fast there's a quick hesitation before it revs.

From all of the reading I've done the last couple of days from mostly here other things it could be are:

A. Intake Manifold Gasket (wouldn't this be more consistent and heat dependant?)
B. Fuel Injector (My gut is now saying this)
C. IAC (didn't clean this because I cannot get the gasket and o-ring locally and it scares me to reuse the rubber gasket because the coolant lines)
D. Fuel Pump
E. O2 sensor. I've read this is very unlikely

Any thoughts? I'm ready to toss in the towel.+

[andrewclaus]

I'd focus on that one cylinder, rather than general tune-up items. Get new wires. Change fuel injector with another cylinder, see if the code "moves." Do a compression test to rule out an internal mechanical problem.

[Browning]

Since I can't get a fuel injector at my local autoparts stores nor the good intake gasket I decided to check the pcv. It was stuck open and gunked up and while I doubt that is the cause I sprayed it down and soaked it in tb cleaner. It now rattles way better and you can't blow through it.

[Browning]

Ok got the now cleaned up pcv back on. Just took two trips with me pulling over at random spots shutting it down, waiting a couple minutes firing it up and taking off. I drove like a grandma some of the time, other time I got on it a bit. Then I drove in between which is my normal driving. One tiny stumble taking off from a stop sign but no missing, no code or of the recent norm. Coincidence? Maybe but this pcv is definitely getting replaced as I think the spring is a little weak.

I'll be taking it for another drive a little later after I get done smoking some steaks lol

[Browning]

Spoke too soon. It seemed to be running really great. Got 2 miles from home on the last trip and it started again flashing CEL, missing like crazy until we got up to around 30mph. get home, check the light P0301

[jolt]

Check compression on all cylinders. Swap injectors to see if problem moves. Intake gasket?

[Browning]

Check compression on all cylinders. Swap injectors to see if problem moves. Intake gasket?

I don't have access to a compression tester at the moment but today I am going to go ahead and change the intake manifold gasket with the orange one as well as the valve cover gasket. Haven't decided if I just want to knock those out and see what happens or do those and swap in a remanufactured injector at the same time.

I keep trying to find out if when the intake manifold gasket messes up if it's constant or randomly like what I am experiencing. When it isn't doing the missing it runs strong

[jolt]

And also OEM or Denso coils. Other brands can give problems and shorter live then the Denso coils. andrewclaus already touched on some of these in his post. Guessing what is the problem can get expensive and new parts can be defective also, so testing to eliminate what is good and finding what is bad is the way to go. Some parts stores have loaner tools, like a compression gauge, that you can rent. Test all the mechanical things first to eliminate them as the problem and then go after the electrical/ECM items (codes).

[Browning]

intake manifold gasket and valve cover gasket replaced(both leaked.) TB gasket too. The problem came back 15 minutes after firing it up. 3 restarts later and it was gone. Drove a few miles and it didn't occur again.

Used a screwdriver to listen to the injectors and 2, 3, and 4 sounds the same. #1 injector is toned different and sounds real clunky. Getting a remanufactured injector tomorrow and if that doesn't cure it, I am just going to suggest to the wife we trade her in. I need a truck anyways lol

[Browning]

Also, while it was missing I went up and was sort of twisting the injector back and forth, lightly tapped on the fuel rail over the #1 injector and unplugged/replugged it and it was the restart after that when it got smooth. However, on that start, I got some white smoke from the exhaust which cleared up on that test drive.

[zbyers]

P0171 = intake manifold gasket, as a general rule of a thumb on theses cars. This is unlikely to cause your misfire.

As others mentioned, Denso ignition coils are usually the go-to. These cars are quite picky.

I'm not sure how difficult the injectors are to remove as I haven't messed with them, but try swapping it to a different cylinder and see if the misfire follows.

[Browning]

after putting a reman. injector in there's been no problem. Today is the 3rd day of no issue and hopefully, that fixed it. Had to reuse the old oring as the one that came on the injector was too big and got sliced.

[Bookworm]

after putting a reman. injector in there's been no problem. Today is the 3rd day of no issue and hopefully, that fixed it. Had to reuse the old oring as the one that came on the injector was too big and got sliced.

At least you can order those separately, and you had a functional one to use for now.

[Browning]

Definitely. Car is still running great no missing nor codes. Next to get these motor mount replaced to get rid of that awful idle vibration.

[Browning]

new issue but I can't help but feel it is connected.

P0420 - Catalyst system efficiency below threhold bank 1

Everything I have read points to one of the o2 sensors and/or the cat itself.

Car still runs good, we're getting better fuel mileage than we were before but still seems the idle could be a tad smoother. The light comes on and stays on for a couple days before it goes away and comes back a few days later. rinse and repeat.

What would you do?

[zbyers]

P0420 indicates the o2 sensors are working properly as it's detecting the cat is below efficiency thresholds, so that would not be the o2 sensors.

Nearly 100% of the time it means the converter is on it's way out. Depending on your location, you could add a defouler to the downstream o2 and call it a day. otherwise the solution is to replace the cat.

Magnaflow 99205HM is a great fit. $100 part, $50 weld job at a local exhaust shop.

[Bookworm]

P0420 indicates the o2 sensors are working properly as it's detecting the cat is below efficiency thresholds, so that would not be the o2 sensors.

Nearly 100% of the time it means the converter is on it's way out. Depending on your location, you could add a defouler to the downstream o2 and call it a day. otherwise the solution is to replace the cat.

Magnaflow 99205HM is a great fit. $100 part, $50 weld job at a local exhaust shop.

Always wondered about that replacement - we do have _two_ cats on the OEM.

[zbyers]

P0420 indicates the o2 sensors are working properly as it's detecting the cat is below efficiency thresholds, so that would not be the o2 sensors.

Nearly 100% of the time it means the converter is on it's way out. Depending on your location, you could add a defouler to the downstream o2 and call it a day. otherwise the solution is to replace the cat.

Magnaflow 99205HM is a great fit. $100 part, $50 weld job at a local exhaust shop.

Always wondered about that replacement - we do have _two_ cats on the OEM.

Yeah, I've been curious too.. The shop that did mine did the downstream one, and I never had another issue. But afterwards, I questioned if it should have been the upstream cat, since the lower one isn't even monitored by the o2 sensors. Logic says it should be the upstream cat that needs replaced.

[Bookworm]

P0420 indicates the o2 sensors are working properly as it's detecting the cat is below efficiency thresholds, so that would not be the o2 sensors.

Nearly 100% of the time it means the converter is on it's way out. Depending on your location, you could add a defouler to the downstream o2 and call it a day. otherwise the solution is to replace the cat.

Magnaflow 99205HM is a great fit. $100 part, $50 weld job at a local exhaust shop.

Always wondered about that replacement - we do have _two_ cats on the OEM.

Yeah, I've been curious too.. The shop that did mine did the downstream one, and I never had another issue. But afterwards, I questioned if it should have been the upstream cat, since the lower one isn't even monitored by the o2 sensors. Logic says it should be the upstream cat that needs replaced.

When I replaced the cat on my '03, I just bought a direct replacement, with dual cats. Paid someone else $50 to put it in with the two replacement O2 sensors (they had a lift, I didn't). I'll probably do that with this car sometime in the next 20k miles. Yes, it cost a bit more than $100, but I knew everything would just _work_

[Browning]

Just got back from the dealer. Wanted to have them test everything over but I'm not actually sure what they did, if anything really. all the said was everything was in working order except the cat. Said they verified little flow from the exhaust but didn't elaborate and me being in a hurry to travel 30 miles back home in time to pick my son up didn't allow me much to ask. He did say it was flowing at only about 50%.

I think it's running too good to be that clogged. At 50% I would expect not much power at all, all the time, no?

Anyways, since ours has two cats and a resonator, what is my best option as far as repairing this thing? The one linked above is a single cat. The dealer quoted the OEM converter at $1400 lol. I wish we could just get a new vehicle but sadly it is not an option right now.

Looking around Advance, rockauto, Walker Part # 53717 looks like it might be the best overall choice to save some money? I called a local exhaust shop but they want to do a backpressure test $33 before even quoting me. However, this place does a monthly payment option and will put on parts you bring them, but they do charge a little more for that

[Browning]

this is the walker cat

https://www.amazon.com/Walker-53717-Cer ... 0049JD2JY/


and hell, I am tempted to just go with this. Reviews look good. amazon says it doesn't fit but the listing says it does. Being an amazon seller myself, I know this could easily be a measurements thing when listing

https://www.amazon.com/TED-Direct-Fit-C ... 06XZJ46RW/

[Bookworm]

This is what I used.

https://www.discountconverter.com/direc ... ctID=44103

It's just under $500, but a direct fit, and high quality. Their Houston office is just up the street from me.

[Browning]

This is what I used.

https://www.discountconverter.com/direc ... ctID=44103

It's just under $500, but a direct fit, and high quality. Their Houston office is just up the street from me.

interesting. so that's both pipes that takes it to where it goes over the rear crossmember?

[zbyers]

This is what I used.

https://www.discountconverter.com/direc ... ctID=44103

It's just under $500, but a direct fit, and high quality. Their Houston office is just up the street from me.

interesting. so that's both pipes that takes it to where it goes over the rear crossmember?

Yes, it's the exhaust all the way to the muffler flange.

[Bookworm]

This is what I used.

https://www.discountconverter.com/direc ... ctID=44103

It's just under $500, but a direct fit, and high quality. Their Houston office is just up the street from me.

interesting. so that's both pipes that takes it to where it goes over the rear crossmember?

Yes, it's the exhaust all the way to the muffler flange.

This.

That, two oxygen sensors, and $50 for labor, and I had a car that stopped throwing error codes at me

[Browning]

Thanks for the replies and sorry I am just now responding. I went ahead and ordered this one

https://www.carid.com/2005-pontiac-vibe ... 62880.html

Main reason I went this route is the ability to use affirm.

[Bookworm]

Thanks for the replies and sorry I am just now responding. I went ahead and ordered this one

https://www.carid.com/2005-pontiac-vibe ... 62880.html

Main reason I went this route is the ability to use affirm.

No idea what affirm might be, but go for it, as it's an exact replacement. Although since the OEM passes CARB, I don't know how they can call it an 'exact' replacement. The one I posted, I believe, does pass carb.

[Browning]

Thanks for the replies and sorry I am just now responding. I went ahead and ordered this one

https://www.carid.com/2005-pontiac-vibe ... 62880.html

Main reason I went this route is the ability to use affirm.

No idea what affirm might be, but go for it, as it's an exact replacement. Although since the OEM passes CARB, I don't know how they can call it an 'exact' replacement. The one I posted, I believe, does pass carb.

yea that was my mistake I didn't think I needed to order a CARB compliant system. I contacted them right after posting and they are in the process of switching it out with this one

https://www.carid.com/eastern-catalytic ... rl=5331631

Affirm is a monthly payment loan thing some sites are slowly adding.

I still need to order a bolt/spring kit, a rear exhaust gasket and the two sensors. Hopefully, this thing is in top shape after this lol

[Browning]

I remembered tonight that I have one of those temperature guns so I took it for a 6 miles or so cruise, running it fairly hard the last mile or two. Got home and while in park I hit it with the infrared temp gun:

Right after the exhaust manifold just below the flange=360 degrees

After the first cat=590 degrees

After the second=560 degrees

First time ever trying it this way. Does this still sound like a failing cat? After the videos I watched it leads me to believe the cat is working, however, none of them had a temp that high before the cat. so maybe it's just not too clogged yet but getting there?

[Bookworm]

It's safer to have CARB, because there's no telling if your state follows those standards. I try to err on the part of caution, because vehicle inspections in Texas are a PITA now. It's directly tied into your vehicle registration (AKA yearly taxes)

I really don't know how hot the flange and cats are supposed to be - I've never measured them, and I think my only measurement device peters out at 300 degrees.

[zbyers]

I really don't know how hot the flange and cats are supposed to be - I've never measured them, and I think my only measurement device peters out at 300 degrees.

I'm not sure how it they should measure either... My measurement device stops when my hand starts burning

[Browning]

apparently they didn't catch it in time and shipped the non-carb compliant out which will be here Monday. Now I'll have to wait while it's shipped back and they ship another out after they get it back