The van has 420k kms on it. It started stumbling just a little and very random times. Pulling away from a stop is fine. Accelerating is fine. But when I get up to speed and the RPM's begin to drop it will stumble! And its getting worse. And as a side note. I killed the battery by leaving a dash cam on while it was parked for a few days. So that clears any codes. I drove the van for about 3 hours with it acting up like I have said. But it wasn't triggering a check engine light. It finally did about 2 1/2 hours in.
Last fall my mechanic cleared the check engine light. It was an O2 code. He said its probably intermittent due to cold damp weather in the morning and not immediate concern. Probably because he knew i was shopping around for a replacement vehicle. The check engine light does come on and clears itself after so many start and stops.
A friend of mine who is a retired mechanic told me to change the fuel filter first. I just went for a look and can't even find the filter! I'm thinking somebody pulled it off and screwed up the fittings and put a length of hose in it's place! While I was under there I looked at the muffler which is leaking. There's a significant leak along the seam. I'm wondering what effect that has if any on the O2 sensors and if it could have any bearing on what's going on?

Any help of ideas????
Thanks
Menessis

 

Next time it happens again, pop the hood and locate the MAF sensor, remove just its electrical connector then start it up and drive. When your ECU can't detect the present of your MAF the default air-fuel ratio will be kicked in. If you get a CEL and rough idling just ignore and drive, if you feel major improvement then your MAF can be at fault and it requires component testing, and cleaning on the wiring and connectors, but cleaning the component itself doesn't help, the MAF cleaners out there are for routine cleaning, not for rescuing a failing MAF. Plug the MAF back the CEL relevant to MAF will go away.

 

Update. Got my buddy to read the codes...misfire on #1. Ok So pull it apart change out the plug. Wasn't thinking about the coil. I would have got a coil while I was at it right! Fire it up. Starts fine runs smooth. Job done right....nope......A few minutes down the road the Check Engine light is back on and flashing away.
So I go back to buddies and we read the code. Missfire bla bla bla. So we clear it again. The van sits the idling without missing a beat. Jim says there is now way its miss firing sitting there.
So drive across town to get some injector cleaner (since there isn't a friggin fillter on the Van). Runs fine, no lights. 30 minute drive home, no lights but it did do a little shakin at one point.....but I couldn't tell if its the transmission trying to decide to change gears or what. But still no light!

I just don't get it at this point.

Menessis

 

See if your buddy's scan tool can produce "Freeze Frame" info. That would tell us the conditions.and parameters at the time of the misfire.

Just like a doctor can tell a lot about your general health from your blood work, a good tech can tell a lot from your vehicle's data stream and freeze frame info..

 

Well I hit up another buddy with a code reader. Miss fire on one and four! Changed out the plug and the coils. All Is well now. I don't know how the first code reader missed the second miss fire on 4 .

 

Thank you for the update.

 

I finally got around to replacing all the spark plugs. What a job! It's been a few weeks now.

So the fuel consumption is still very poor. And it has kicked on the 02 sensor code again. Is it safe to assume that I need to replace that sensor or is there something else I need to check first. Given that It's always the same sensor.

Thanks
Menessis

 

If you need to replace your o2 sensor, don't buy cheap brand, buy Motorcraft. If you have poor fuel consumption you might want to run a bottle of berryman 2611 and do a deep cleaning before switching out your o2 sensor. Check here and search for berryman only.