I just installed the Goodyear Gatorback belt and was taking it out for a spin and all the sudden i noticed the check engine light blinking on and off which i knew was a misfire so I went easy on the way back got out the code scanner and found this, I got a pending code for 300 - Random Multiple Cylinder Misfire Detected. I know misfires are not good this is the first one I've ever had, I want to know what causes them and how I fix the problem
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
i had the same problem when i became boosted. the problem was my plugs. they were either gapped to small or were the wrong size plug. i just ended up changing them all out and the code never came back on
well stock specs according to owners manual are .040 should I be going with something different
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
I found some items in the GM tech manual with misfires without internal engine noise
I do have 73k on the car and most parts have not been replaced as I have had no problems
Serpentine Belt - Mine does need replacing
Faulty Map Sensor - Still running the original
Improper Sealing between TB and intake manifold - Possible but unlikely
Faulty cylinder head gaskets and/or cracking or other damage to the cylinder heads and engine block cooling system passages - I sure as hell hope not
ICM - I did swap out to a another one I had when the charger went on
Coils and plug boots - same as above
Plugs- Running stock OEM AC Delco plugs just replaced 2000 miles ago
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
Rodimus Prime wrote:I found some items in the GM tech manual with misfires without internal engine noise
I do have 73k on the car and most parts have not been replaced as I have had no problems
Serpentine Belt - Mine does need replacing
Faulty Map Sensor - Still running the original
Improper Sealing between TB and intake manifold - Possible but unlikely
Faulty cylinder head gaskets and/or cracking or other damage to the cylinder heads and engine block cooling system passages - I sure as hell hope not
ICM - I did swap out to a another one I had when the charger went on
Coils and plug boots - same as above
Plugs- Running stock OEM AC Delco plugs just replaced 2000 miles ago
Get rid of the stock plugs. They are platinum tipped (I think) and you shouldn't be using them with boost. You should look for as plug that is one or two heat ranges cooler and not platinum. You may also need to decrease the gap as the boost could be "blowing out" your spark (unlikely).
Mark P.
im running autolite 103's on my eco. Ive heard all on this board about gapping plugs around .030-.035 ish, but befor i could tell my bro (when he installed them) he gapped them the same as the factory ones that came out...and they were at .060. I was kinda worried about that..but its been about 1500 miles and not one misfire ..so far so good.
the autolites are too short a plug but I am wondering what gap should I be running
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
Rodimus Prime wrote:I just installed the Goodyear Gatorback belt and was taking it out for a spin and all the sudden i noticed the check engine light blinking on and off which i knew was a misfire so I went easy on the way back got out the code scanner and found this, I got a pending code for 300 - Random Multiple Cylinder Misfire Detected. I know misfires are not good this is the first one I've ever had, I want to know what causes them and how I fix the problem
also when it blinks, that means the misfires can do damage to the cat and or engine.
gotta love proper plugs
Heheh I look forward to his next post where his engine is blown.. Misfires under boost.. Detonation? You have the wrong plugs in. You've been told that by several people already, but are too stuborn to change them or too lazy.. Whatever.. Have fun buying a new engine soon..
Dark blue 2002 Z24, 2.4 Ltr.
i know that the plugs i have are not ideal putting in a shorter hotter plug isnt the answer either
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
I'f your plugs are in good condition regap them down to .030-.032. Worked for me and I'm still on OEM plugs.
yep, reduce your gap....... thats fixed every missfire problem under boost I have come across yet....... (that or put in fresh plugs, regapped to .030-.035)
Good luck.
SPD RCR Z -
'02 Z24 420whp
SLO GOAT -
'04 GTO 305whp
W41 BOI -
'78 Buick Opel Isuzu W41 Swap
I believe they are gapped to .040 right now I'll have to pull them out and inspect this weekend
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
regapped down to .034 still got a misfire last night even worse than before
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
k dude the stock plugs are not going to work so if they are still in, take them out, the platnium is going to melt off sooner or later and either the spark plugs will foul or the engine will detonate its not a matter of if its a matter of when
Well I guess im going to have to try to use the shorter plug even though id rather not but appears there is no other option, i cant keep on having this happening
What will work better the
NGK - I forget the part number but which one is the coldest one that works with an eco
Denso - 5338s
Autolite 103s
Or is there some other plug that users of boosted ecos are using? I am also going to have an msd hooked up down the road after I fix this problem
Gap - .030 will that work ok with the above listed plugs or will .035 be a little more suitable
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
atolite 103's but my plugs are gapped to .030" and was getting a blinking cel last night a lot as well, more so then I have EVER seen... so idk man, its york air LOL
LE61T PTE6262 Powered 
hehe yea i guess so
ever get cels any other times?
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
DENSO IRIDIUM 5339 1stage colder that stock. DO NOT GAP. took care of the misfire.
Check if the plug wires are in the right order. If there right than check the end ot the boots of the wires. maybe can even be your ignition module.
Colin Gee wrote:Check if the plug wires are in the right order. If there right than check the end ot the boots of the wires. maybe can even be your ignition module.
ecotecs dont have plug wires....
direct boot to sparkplug ignition, like the 2.4;s
only the ohvs 2.2 came with sparkplug wires.
if you upgrade ignition you can use em.. but the dohc engines usually dont have em
it def seems plug related because last night it went right to the misfire code not pending this time and I just regapped last night
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
Dam-it Muffins (Event) wrote:Colin Gee wrote:Check if the plug wires are in the right order. If there right than check the end ot the boots of the wires. maybe can even be your ignition module.
ecotecs dont have plug wires....
direct boot to sparkplug ignition, like the 2.4;s
only the ohvs 2.2 came with sparkplug wires.
if you upgrade ignition you can use em.. but the dohc engines usually dont have em
I realized what motor he had after I hit the post button. My mistake. I couldn't edit it after that.
what plug's does RSM suggest?
