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02-14-2008, 07:11 AM #1
Wierd stutter problem on colder days
Over the summer my 96 trans got flooded out, but there was no engine damage. The opti, cables, plugs and fluids where all changed (along with the brakes), the top end was a total rebuild with le2 heads cam etc etc etc. There was no problem when i first got the car back, but as it got colder out every once in awhile the car would stutter. No other way to describe it... id be cruisin along at 70mph then all of the sudden for a half second the rpm needle would "drop and pop" very quickly down then up say about 1-1.5krpm like it was going to stall, then resume like nothing happened. It would feel like i smacked into a pothole or like when traction control comes on but much more fiercely. It might do this once in a hour drive, or for a period of a few minutes ever few seconds then go away. Now that its cold all the time, every morning for less then a 100 yards distance the car stutters like mad then it goes away like nothing happened... and resumes its once out of the blue occurance, maybe 1ce a week... it kinda happens most at steady low rpm but sometimes it will still occur if im flooring it but it seems to have enough umph to get through it sorta speak. back to the morning... when i first start it up, you can hear the car sounds choppy toned, louder, deaper and almsot poppy but no backfire or anything... but def not the normal tone. driving off down the road it feels like only every other cyclinder fires (i dont know if its true just what it feels like is happening) like theres rapidly changing amounts of available power like driving over railroad tracks. then before you know it its gone by the time i get aroudn the block. the colder out it is, the worse the symtoms in severity. on warm days i can barely feel it but its still there to some degree. theres almost a tapping noise from the engine bay (from where i can tell while sitting in the drivers seat) if you apply alot of throttle as the engine speeds up, but doesnt sound like pinging or knocking, almost like metal tapping at 3x per second roughly.
any ideas? i recorded it in obd2 software but i dont always know what im looking at. theres no knock retard or misfire recorded over all, and the live data sensors dont show anything, but then again it happens so quick it might not even be refreshing fast enough to record the right sensor when its happening. i can post it if anyone wants to take a look... i get no trouble codes, past or present or engine light.
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02-14-2008, 10:43 PM #2
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I had the same problem in the summer time and I'm still trying to figure it out. Only mine seems to do it more when its hot. I could be cruising at 40 mph and the rpm would drop rapidly and come back up as if I had taken my foot off the accelerator and then applied pressure again.
Have you tried letting the car get up to operating temp?
Does the noise sound like its coming from the top or the bottom end?
After the flood did you check the bottom end to be sure there wasn't any damage?
If the knock sensor is picking up that tapping sound it would retard the spark causing that hesitation. However, you said the program didn't record any knock retard.
It seems like more of a mechanical problem. Do you have anyone around that you could swap the computer out with?
Jay
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02-14-2008, 10:51 PM #3
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- WI
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09 EclipseGT 75 Chevy 4x4- 2001 Trans-Am 13 F-XT
My 95 T/A did something similar then the fuel pump went out.
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02-16-2008, 09:03 AM #4
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- Feb 2008
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- Cedar Falls, Iowa
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Arctic White- 2001 Firebird Formula
my 93 formula does the same thing...its not as bad now that i put so much work into it. it drove me nuts...id be cruising at around 50-60 and want to go a little faster so i press the pedal a little bit to go only 5mph faster and it would do that studder, dam near violently shake. i couldnt tell if it was from the engine or in the driveline. i had the fuel pump replaced, the air pump, the computer module replaced too. then i noticed the water pump was leaking really bad so i had that replaced along with the distributor cap/rotor cuz it was fried lol. the hesitation became minimal but still occurs. the car actually has stalled a few times as well and has a hard time starting sometimes.
i new there was something that the engine wasnt getting enough of...i thought fuel at first, then air and spark. once it gets warm again im going to take it back to the shop and have it looked at.
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02-21-2008, 08:59 PM #5
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- Sep 2006
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I get the same thing too when I'm cruising the rpm's jump around some times and sometimes when I'm hammering down on it they jump and as soon the car hits 4th gear if I try to accelerate at all it accelerates really slow acting like it wants to dies and damn near shakes the car apart.
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02-21-2008, 09:57 PM #6
mine never gets to that point, liek it lasts for such a short period of time when it happens, seems the more gas i give it the less the problem is, but i could be runnin for an hour at redline and it feels strong as ever.
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02-22-2008, 04:13 AM #7
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Oh, it happens to me right in the morning or if I'm driving it a little hard it starts doing and 9 times out of 10 it always shakes violently in 4th, yours could like an injector going bad or plug wires maybe, you don't use e85 gas do you?
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02-22-2008, 09:07 AM #8
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- Feb 2008
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Arctic White- 2001 Firebird Formula
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02-22-2008, 10:24 AM #9
no ive only ever put 94 octane in it, about a year or so ago i had to switch to 93 cause they stopped selling it in NJ except at tracks. compressions almost 11.2:1 so i never wanted to risk going lower.
I have 37# delphi injectors but they went in last summer, but i only have the le1 cam in it right now because i was afraid of emissions, i was going to wait until this summer to but in the beefier le2 cam (i have le2 heads in now) so i didnt think id be anywhere near fuel cutoff... which i dont think i am cause it worked fine for the first few months, and still does now really except when its cold.
i did notice the other day though, when it happens when its warmed up, its when im cruisin around 2.2-2.5k rpm... and i noticed that if im really fuckin with the car say on the highway or at lights, when i stop, a few minutes later it will happen for a few seconds then go away... but not nearly as severe as when the cars first on.
i relized i have a freakin video camera on my cellphone thats pretty good quality, ill try catchin it next time i start up and drive down the road... only problem is now, i'm snowed in i aint goin no where, my policy is snow on the ground, i call out sick
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02-22-2008, 04:50 PM #10
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The only reason I asked about the e85 is because a guy I know with a 2000 Z/28 started running it because it was cheap and it messed his car up bad, he said it took like 3000k mi. to purge the car of it
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02-23-2008, 09:49 AM #11
holy hell... does "bad gas" exist? ive always heard of people bitchin that they got a tank of bad gas but i have no idea what that means, that a legit thing, and does that sound like somethin that i might have? maybe i should let it run empty till it stalls and throw in some fuel booster injector cleaner shit they sell?
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02-23-2008, 10:34 AM #12
this seems to be the same problem im faced with. everyones symptoms seems to match my own. its getting worse and worse for me though. still comes and goes but the low rpm acceleration makes the car seem likes its missing badly but ive replaced everything . i dont know what to do. i hate to put so much money into it. has anyone had this problem and fixed it?
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02-23-2008, 10:46 PM #13
I have experienced a miss right after filling my car up on two occasions. I have since written it off as bad gas and avoid those gas stations.
Oh and dont run your car out of gas, many a people have ruined a fuel pump doin that. Just not a good idea.
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02-24-2008, 12:28 AM #14
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white- 94 camaro z28
well i ran ethanol in my car and it ran like shit for a few weeks. i ran gas from florida ( has a fairly high amount of ethanol in all of their gas) and it ran like shit
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02-24-2008, 06:48 AM #15
thats not true. just for the record when trying to help a problem dont post ignorant statements.
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02-24-2008, 09:41 AM #16
Do you still have the stock fuel pump?
It is well documented that a stroker will burn out the stock fuel pump within the first year of use.
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02-24-2008, 06:58 PM #17
yea i have stock pump but its still stock bottom end, just heads mild cam and boltons...
i did notice though while lookin under the hood that im leakin oil, cant tell from where but its above the opti/pump... have to look closer when its daylight.
also noticed that when they put the strut tower brace in they bent 4 fuel lines to fit around it... atleast it looks like they were bent, anyone have a pick of what they look like stock? i cant recall.
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02-28-2008, 03:08 PM #18
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02-28-2008, 08:56 PM #19
isnt e85 like 105 octane? you need diff injectors and tune anyway, no? think that shit eats plastic or aluminum forget which so enw lines are in order or maybe even heads!
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03-01-2008, 02:30 PM #20
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