missfire!!!!
08-01-2011, 11:38 AM
#1
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missfire!!!! im trying to figure out my 5000rpm and higher missfire. pulled the plugs and it looks alittle lean not crazy but its lean, number 7 plug looks very lean. thought it might be injectors so i put a set of injectors in and nothing changed. the car was not missing before it came apart for a headgasket fix. i put new opti, coil, icm, crank sensor, wires and plugs, fuel pump and regulator and injectors in the car with no change. compression reads:
#1 195
#2 165
#3 165
#4 195
#5 190
#6 190
#7 190
#8 190
im out of ideas plz help
#1 195
#2 165
#3 165
#4 195
#5 190
#6 190
#7 190
#8 190
im out of ideas plz help
08-01-2011, 12:08 PM
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You need to test fuel pressure to eliminate it being fuel related. Sounds more like ignition. So you replaced all the ignition parts because of this problem, or you did all that at the same time as the head gasket replacement?
Is it stock? or what are your mods? Might as well make a signature and tell us a little bit about the car.
Welcome to the site...
Is it stock? or what are your mods? Might as well make a signature and tell us a little bit about the car.
Welcome to the site...
08-01-2011, 03:11 PM
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i just made a sig. so it should come up, i replaced the opti and fuel pump when i bought the car about a year ago. acdelco of course. it never did it before the headgasket. then when i put it back together i had the miss. i replaced the opti again thinking maybe i bumped it around while it sat in the shop for afew months,at the same time i did plugs and wires. didnt fix it. so i tryed the icm, nope. coil, same as before. thanks for your fast replies 
08-01-2011, 04:05 PM
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No power steering? That's no fun.
Don't really know what to tell you on the misfire problem. Kind of hard to diagnose over the internet. Maybe a better explanation will get you some more replies. Is it subtle or real noticable? does it buck or stutter? or is like hitting a rev limiter? or does it feel like you lose one cylinder?
And you're saying no problems exist under 5000 rpm, correct?
How are your plug wires ran? Anywhere near the headers? And you triple checked the wires are in the right order on the opti...
Don't really know what to tell you on the misfire problem. Kind of hard to diagnose over the internet. Maybe a better explanation will get you some more replies. Is it subtle or real noticable? does it buck or stutter? or is like hitting a rev limiter? or does it feel like you lose one cylinder?
And you're saying no problems exist under 5000 rpm, correct?
How are your plug wires ran? Anywhere near the headers? And you triple checked the wires are in the right order on the opti...
08-01-2011, 04:18 PM
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its not too bad i dont get the car out unless its perfect outside so its not like im drivin it everyday lol. yea it is very noticable. no it doesnt feel like the rev limiter bc it just drops off power. it feels like im losing a cylinder. under 5000ish it runs just fine pulls hard and everything. wires are in stock location but have heat socks on them. 100 percent sure the wires are in the right place. its very easy to check since all i have is an alt down there 
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08-01-2011, 10:26 PM
#8
First things first. You have a 15% difference between two cylinders! The numbers aren't horrible, but it was enough to catch my attention.....
Does it do it when it's cold too or only after it is hot?
Fuel pressure is......
I don't think it is (but it is possible) but you could probably look up stall wall and see if that pertains to you or not.
Does it do it when it's cold too or only after it is hot?
Fuel pressure is......
I don't think it is (but it is possible) but you could probably look up stall wall and see if that pertains to you or not.
08-02-2011, 08:53 AM
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it does it alll the time hot cold it doesnt matter. i know im kind of confused about y those 2 are so low. could weak valvesprings cause this?
i will be checking the fuel pressure tonight.
what is a stall wall i have never heard of that
the most confusing thing is that it did not do this before it came apart for head gasket...
i will be checking the fuel pressure tonight.
what is a stall wall i have never heard of that
the most confusing thing is that it did not do this before it came apart for head gasket...
08-02-2011, 11:51 AM
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i sure hope my fuel pump isnt going bad. i just put it in not 3000 miles ago.
1997 trans am- 2800 stall with built trans,cam and bigger stall waiting for install, headers, cold air, alt relocation, no heat, no ac, no powersteering, gutted! TTm wheels
theres my sig bud. if that helps
1997 trans am- 2800 stall with built trans,cam and bigger stall waiting for install, headers, cold air, alt relocation, no heat, no ac, no powersteering, gutted! TTm wheels
theres my sig bud. if that helps
08-02-2011, 12:07 PM
#12
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i researched "stall wall" and i dont think that is my problem
most people said stalls above 3000 rpm, and obd2 cars will not have stall wall issues. but it did the same thing when i had my 4000 fuddle stall in there.
most people said stalls above 3000 rpm, and obd2 cars will not have stall wall issues. but it did the same thing when i had my 4000 fuddle stall in there.
08-02-2011, 01:54 PM
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anytime it gets to 5000ish rpm. no matter what throttle. but its not as bad at part to 3/4 thottle, it just kinda "hiccups" then shifts. its very violant at full.
08-02-2011, 02:41 PM
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I had the exact same symptoms when my rotor screws backed out inside my MSD opti. Me and a buddy took it apart, put some slightly longer screws in with loctite and it has never run better.
08-02-2011, 07:07 PM
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fuel pressure as follows:
idle/start: 36psi
normal driving/ 1750rpm: 38psi
wot/ all the way to 5500rpm threw missfire: 42 to 44psi
throttle bump/ throttle tap from 1000 to 1500 rpm jump: 42 to 44 psi
not sure if thats good or not but thats was it is from the port on the fuel rail
idle/start: 36psi
normal driving/ 1750rpm: 38psi
wot/ all the way to 5500rpm threw missfire: 42 to 44psi
throttle bump/ throttle tap from 1000 to 1500 rpm jump: 42 to 44 psi
not sure if thats good or not but thats was it is from the port on the fuel rail
08-03-2011, 11:36 AM
#20
Well that is a little low for fuel pressure. Again its not horrible but it may be just enough.
I kinda like the comment about the rotor screws backing out, but it would be anytime the rotor gets under high rpm not just post 5k.
Have you made sure all your grounds are good under the coil mounting bracket?
BTW your fuel pressure should be 43 at idle with line off regulator. Also check the regulator vac line.If it has gas in it, then it is bad.
I kinda like the comment about the rotor screws backing out, but it would be anytime the rotor gets under high rpm not just post 5k.
Have you made sure all your grounds are good under the coil mounting bracket?
BTW your fuel pressure should be 43 at idle with line off regulator. Also check the regulator vac line.If it has gas in it, then it is bad.