My wife's car just had the same thing happen. Although it is a ford, we had that same code "multiple misfires", it turned out to be a head gasket. Though in your case I would guess cam position sensor. But I would let this soak and I'm sure someone with a little better knowledge will be along soon. But to help us a little more, give some more info on the vehicle,engine,miles, etc.

 

You really need to get someone with a scan tool that can look at the signals to see if they are in spec. You also may have lost a ground so reference voltage is not getting read properly. Improperly metered air/fuel can cause random misfire codes. Dont assume it is one problem, you could have multiple issues.

 

had that happen to my 04 f150 was a huge vacuum leak

 

unfortunately the nearest scan tool i can find for this is 300 miles away and they won`t lend it out ! the chances of driving it that far and staying in one piece are fairly remote ! i have checked and cleaned up all the grounds i can find but to no avail also throttle body cleaned out and visually looks ok ! my scanner will get into oxygen sensors and burn seems to be in spec even as engine is just about to shut down

 

Then buy one. They sell pocket scan tools now for about $50. it's a good thing to have. It will cost you double that to drive 300mi and pick one up anyway. Especially in a hummer

 

would cost lots more ! cheapest scan tool i can find in england that will get into h2 electronics is closer to £500 dunno what that is in dollars but its lots more than in the states does anybody know of a good one that i can get over internet ?

 

update :-

did another compression test with coils disabled and found zero compression on cylinder 8 with 125 to 135 psi on others so ripped into engine the inlet push rod on cyl 8 is in two pieces and very prettily folded although everything else looks ok ! the valve seems to be fully seated and undamaged ! is this likely to be the cause of all my fault codes and failure to idle ? don`t quite see why this would cause random multi cylinder missfire

 

One way to find out! If the rest of the valvetrain is mechanically sound then I would get a new pushrod, put it back together and see what happens. Be sure there isn't any fuel pooled behind that valve before you finish assembly.

 

ordered full set of pushrods lifters etc just in case it failed from old age ! will see what happens got head off anyway so seems daft not to rip other head off and do all of them ! is there anything else i should look for whilst in there ?

 

Did the rocker arms look ok, especially the one with the failed rod? I know those things can and do happen, but I would be scrutinizing for some sort of mechanical interference. Also would be checking for any metal shavings or bits in the pan and valley, just to be on the safe side.

 

ordered full set of pushrods lifters etc just in case it failed from old age !

The lifters making noise? If not and if the rollers feels smooth when rolled across the palm of your hand, they don't need to be replaced. Won't hurt anything to replace them, as long as it's in your budget. Pushrods are fine to replace, too- but in most cases don't need to be unless damaged like the one you have that's bent.

And while in there, do the valve stem seals. They'll prolly be in the gasket set that you will get, but there might be a better seal available than what's supplied.

I might have missed something, why is the head(s) off?

 

the rockers all look and feel fine oil in pan feels smooth between the fingers and magnetic sump plug is clear ! took head off to retrieve lower inch of pushrod that was wedged below it magnet wouldn`t get it ! i`m just concerned that codes came up as random multi cylinder missfire rather than just one pot ! even more so now that found inlet valve locked shut had thought perhaps oxygen sensor was detecting unburnt fuel and leaning out all cyls to compensate causing the multi cyl missfire but guess not ! prob just paranoia but want to cover all bases while engine in bits just ordered crank and cam sensor too anything else i should be looking at ? really don`t want to rebuild and then have to pull it again as fault still there

 

prob just paranoia but want to cover all bases while engine in bits just ordered crank and cam sensor too anything else i should be looking at ? really don`t want to rebuild and then have to pull it again as fault still there

I can certainly understand your concern and your wanting to touch all the bases while it's all apart!

Darn, this is where a scanner would have been worth its weight in, well, not gold, but you got the idea.

Lacking that, about all I can think of is the seals mentioned earlier, and possibly checking the valve guides and the valve to seat seal, the studs and rocker arms for wear or damage- that sort of thing. If there's a lot of miles, this might be a good time to do a valve job.

Was this engine ever run really hard? I ask because trashing a push rod doesn't usually happen while just idling around...

In any event, I'm of the opinion that your codes are most likely sensor or ignition related, more than bad cylinder heads. Even bad plugs will set those codes, along w/a host of other things (scan tool again :mwink: ).

Hopefully, other more knowledgeable folks will chime in w/the exact cure.

Good luck!

 

engine fairly high miles about 100thou and most of them been motorway so 70mph if the authorities are reading or generally 90ish if not and well loaded up most of time so i guess thats a fairly abused engine ! will do valve seats when i do seals ! if anyone has good knowledge of a decent scan tool i would be very happy to buy one ! ( lots on ebay but are they any good ??? )

 

it lives

fired up first time and runs smoother than it ever has before ! dunno what did it but decided to bite the bullet and do as much as i could afford so head gaskets lifters pushrods cam sensor crank sensor coils plugs and leads

in trouble with the woman cos i`m told thats not how to spend the holidays but never mind

a very happy new year to you all and thanks