I have an 04 cavalier ecotec l61. I did a p&p job on it for a comp at wyotec did the valve angle job on the head and the valves put new valve springs in 78lb supertech dual springs. got all new timing components including tensioners.
My problem: started and runs but at half throttle (3000 rpm) it misfires cylinders 1 and 4 once or twice in a lets say 10 sec. interval. when i take it out of the shop with the scan tool hooked up and put it 100% load 1st gear and 2gear it cuts out cylinder 3 138 times in a given 6-8 sec interval. that starts to happen at the 5500 rpm and deteriotates all the way to rev limiter. we checked plugs and swapped them around and plug boots.
There brand new ac delco plugs btw. not ruling out a bad ground but i put all the grounds back to where they go except for the valve to cyl head grd strap it snapped and had to relocate the bolt hole to the transmission side of the head.
Timing has been checked twice and redone by me and an instructor (owner of tpg tuning). were all scratching our heads and cant figure it out
Please help if you can any insight will help.
Maybe it's running out of fuel. Eco injectors are not known for low duty cycles. PJ or one of the other eco people could tell you more but it looks like a fuel issue.what do the spark plugs say? Could be a bad coil pack or injector just have to test.
Pull the plugs see if their runnin hot lean or rich? if you suspect an injector switch the injectors around and see if it switches cylinders. Coil pack barrow a known good one.
Also remeber you P&P adds air to the mix if some one has HP tunners and a Wideband let them take a look. Might have to have the fuel curve adjjusted.
You didn't do too much polishing on the intake side to where the fuel isn't atomizing and mixing with the air properly did you? I don't know if this wohld cause your issued but I know the intake ports can't be too smooth. Just an idea.
First it needs to be tuned, doing such a big step in work requires bigger injectors and a good tune at least. Are you sure all the valve jobs were done right? Head reassembled right? I'd do a compression check and go from there
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i would check for spark. aren't the eco's waste spark? so one and four are together? thats what i would do...kinda the only thing linking those two cylinders and only those two...
good point dave, did you try a new IDI/ICM coilpack?
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ive had this issue with a bad intake gasket before.
sounds like you need a tune. And if he polished too much he'd have more fuel puddling issues down low than up high.
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Leafy wrote:sounds like you need a tune. And if he polished too much he'd have more fuel puddling issues down low than up high.
Meh idk know about that, I know the eco ecu is a lil different, but on my LD9 I went from stock to PnP 086 head with nothing more than timing mods. It ran like a champ!
every cars different, hell with the eco literally every car is different, way different in what the @!#$ it decides it wants for a tune.
1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
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update we swapped plugs around again did dyno pull checked compression its all within 160-155 psi which is good and we did a leak down test which was good. swapped injectors and its still doing it. got a wideband on the dyno at school and it said it was lean for the first couple runs and then it said it was fine and ive lost power from 136 to 98 hp wth?
160 is very low imo for a 10:1 motor.
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I suggest swapping coil packs, triple checking the timing, and check fuel pressure
Currently #4 in Ecotec Forced Induction horsepower ratings. 505.8 WHP 414WTQ!!!
Currently 3rd quickest Ecotec on the .org - 10.949 @ 131.50 MPH!!!
I checked, compression is way low, should be 190+
what other mods do you have? Miles on the motor? more info if possible
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comp may be low, but it is enough for it to run properly by far. i still say its ignition related
all data said minimum 100psi. for compression but if stock spec is 190 then i guess it is a little low. Theres 131XXX on it. bottom end is untouched. bought it at 12X,XXX.
you didn't reuse the headstuds did you?
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id guess more air flow like he has could be resulting in lower numbers, id go with ignition too.
how aggressive were you on the port?
what size injectors are you running?
what is your AFR?
what is the duty cycle on the inejctors?
changing airflow on an alpha-n fuel injection system leads to all kinds of problems because alpha-n doesn't reference actual airflow when it calculates fuel... it just uses pre-programmed tables.
only other possibility i can think of is you hit a water jacket and the head is pissing coolant into the chamber (if you went too aggressive on the port)
no i have arp head bolts in it now and i didnt go to aggressive just cleaned them up a good bit didnt make the ports too much bigger than stock just a little bit.
I pretty much just smoothed everything up. and i did use a new head gasket felpro. i didnt hit a water jacket im pretty sure of that.
Stock injectors no tune just the P&P and k&n short ram. stock int mani. stock valves 78lb valve springs.
you need hp tuners bad, it needs to be tuned, guranteed that clears up the problems then.
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DaFlyinSkwirl (Pj) v2.0 wrote:how aggressive were you on the port?
what size injectors are you running?
what is your AFR?
what is the duty cycle on the inejctors?
changing airflow on an alpha-n fuel injection system leads to all kinds of problems because alpha-n doesn't reference actual airflow when it calculates fuel... it just uses pre-programmed tables.
only other possibility i can think of is you hit a water jacket and the head is pissing coolant into the chamber (if you went too aggressive on the port)
just to make sure of what eco god here said(if he talks about an eco, pretty much, just listen...he knows more about em than most), i would check out those old plug you took out. if they are tinted like your coolant, you have coolant in your cylinder. the way this makes you show low compression numbers is it doesn't allow the rings to seal to the wall correctly. they need oil on the wall of the cylinder to make a good sealing surface. coolant in the cylinder washes everything away. it makes the cyinder look super clean, and doesn't allow for proper sealing, and then excessive blow by follows, giving low compression numbers.
but i'm still feeling like this is an ignition thing
