check engine light just came on and had the codes pulled and it showed PO302,PO307, PO316. misfires in number 2 and 7 clinders. also crank shaft sensor. question is it has a rough idle but not at highway speeds. were do i begin to starts fixing this problem. ive checked all the ignition coils and they are tight but how do you test if they are working? would the crank shaft sensor cause a rough idle? any input would be apreciated thanks.

 

can see where the Crankshaft Position sensor could maybe do this..is the code P0316 or P0315?? 316 is just upon start up...1st 1000 rev

to test the COP... I'd Ohm them against a good one...if they would be iffy, then they'd probably show up as greater resistance compared to the known good one. or call around to your local parts stores, see if they can test them? IDK

you could also take 1 of the suspect COP's and place it on another cylinder...see if this misfire follows to that cylinder also note weather the Crankshaft Position sensor code still continues...if not maybe the misfires are generating the Crankshaft Position sensor code

the idle could also be a sticky IAC

 

yes exactly PO316-1st 1000 rev

should i buy a new crank sensor and swap the coils around to see if that helps? i really hate to have to buy new coils being 50 bucks a peice but if i have to i will. guess it will just be trial and error till i narrow it down.

 

First thing is what year and motor do you have?
It makes a difference as to what coils it uses.
The 316 code will clear when you get the missfireing cylinders cleared.
Measuring the coil resistance usually dosn't result in picking out a bad coil.
What happened to suddenly cause 2 cylinders to missfire? Was there a rain condition or some other event? The 2 cylinders are on oppisite banks!
Remove the coils/wires (?) for those two cylinders to see what the condition of the boots are and if there is water in the plug well..
Don't keep on running the truck with cylinders out.
Raw gas is pumped through and may over heat the cats then your in for a huge expense if they melt down.
Good luck.

 

multiple missfire and "failure at startup", would normally make one think of the crank sensor or other "common" problem.... I assume your radiator tank level is o.k., no antifreeze usage (internal). ?

 

yea im driving my wifes chevy but it hasent rained here in my part of texas since january. the truck is 2002 with 4.6. i dont know what happened just the other morning on my way to work it started loosing power and check engine light started blinkin. it cleared up so i just thought is was a fluke but when i left work it was idleling bad and thats when i had the codes ran. good radiator fluid just had it flushed 3500 miles ago.

 

Ok, you have coils over plugs (cop).
Strange you get two at the same time but stranger things have happened.
Pull coils and plugs and inspect them. Might as well plan on putting new plugs in those hole while you have then out for the minor cost.
Inspect the boots for being hard, cracked or have pin holes.
Then if the issues are not corrected, plan on putting new coils in those holes.
The blinking CEL light was telling you raw gas was being passed to the cats on both sides. This causes their temperature to rise beyond normal and is detected by the OX sensors.
Good luck.

 

ive always wondered what people were talking about COP. duh! this weekend i guess i will plan on new plugs and 2 new coils. had a similer problem couple a years ago and replaced all of them. thanks for the help.

 

Don't throw parts at it, diagnose it by swapping things around. Go plugs first, cheap. Only thing, make sure it is completely cool before you do it, not to keep from burning yourself, so you don't strip the heads..
The misfire/rough idle sounds more like injectors are dirty to me. Don't waste your time and money on the cleaners at Wal Mart. They will not clean up a dirty injector. If it is dirty to that point, replacement is the only way to clean it out. Some will yank your chain about that crap, but they are tiny ports and once they are stopped up chemicals will not clean them up. That may or may not be your problem, but a whole set of injectors off ebay are less than 100 bucks usually, and I have put them in 5.4s and 4.6s. I think the seller I used was "fuelinjectionconnection".

 

i have never had an injector problem. Drove my 1989 F250 250k miles, 2001 F150 215k miles, 2002 Exp 140k miles.... WE have ethanol in the gas in Illinois, that problem helps. Dont know what all other states have... MY first guess would not be two injectors failing at the same time.

 

well yesterday i changed all the plugs, one from #2 cylinder was toast. the insulator was melted?! also replaced crank case and camshaft sensor cause those were bad i guess. swapped the cops's around to different cylinders but still getting same missfires in #2 and #7. put a can of sea foam to see if it would clean the injectors but still no luck. anything else? or is it time to go to the mechanic?

 

also did a compression check on all cylinders and they all have good compression.

 

Barring faulty coils for those cylinders, plugs and harness, the PCM could have bad coil switches for those two cylinders.
Check for a signal ground from the PCM while the motor is at idle, for each cylinder.
The coils all have 12 volts from the same source waiting for the ground from the PCM in the fire order sequence.
Good luck.

 

talked to a shop the other day and they said sounds like injector problem and to replace them. how hard is that and what are some good injectors to buy?

 

Well I don't know about you but I like to prove a fault before spending money like that and time trying to get lucky.
For an injector to cause a miss it either has to be plugged, open circuited or stuck open.
Checks for this are easy by looking at the plug for the cylinder and testing for injector operation.
If stuck open the plug/cylinder gets flooded and get a code for that cylinder.
Plugged or open circuited, the plug is dry and you would see a code P030x for that cylinder as well.
If you still want to change them, they are held in by fuel rails and 'O' ring seals.
Unbolt the rails and pull them out of the rails and heads.
Good luck.