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Old 03-09-2010, 07:38 PM   #1
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Default throttle cut issue?

okay, i know i only post on here when i need help, and as of now i'm kind of in need.

today i drove the miata to my dad's house (i don't drive it much) and on the way home i decided to get into it. well, at 5k in 1st gear, 4800 in 2nd, and 4500 in 3rd the car just stops pulling. it's not backfiring and it doesn't completely cut out, but it just stays at that rpm for no apparent reason. it still pulls hard up until then, so i'm clueless.

i called a buddy of mine and he said it could be a stretched throttle cable, i have yet had the time to check this because it's now dark. but it could also be a spark issue. i honestly have no clue. any input is appreciated.
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Old 03-09-2010, 07:50 PM   #2
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Needs more datalog. I had a similar issue recently while going WOT up a hill, In 3rd gear my car just stopped accelerating at 5000 rpm. It wasn't like a rev limiter, but more like it just ran out of power. I changed out my plugs and wires and haven't had a problem since.
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Old 03-09-2010, 07:51 PM   #3
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Originally Posted by Jeff_Ciesielski View Post
Needs more datalog. I had a similar issue recently while going WOT up a hill, In 3rd gear my car just stopped accelerating at 5000 rpm. It wasn't like a rev limiter, but more like it just ran out of power. I changed out my plugs and wires and haven't had a problem since.
hm, cool. maybe i'll try plugs+wires and dist. because i just changed the plugs and wires a few months ago with some ngk #6 plugs. and that's basically how mine's acting. i'm just hoping it's not a head gasket, but i have no smoke, and i don't see any coolant leaking.
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Old 03-09-2010, 07:54 PM   #4
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hm, cool. maybe i'll try plugs+wires and dist. because i just changed the plugs and wires a few months ago with some ngk #6 plugs. and that's basically how mine's acting. i'm just hoping it's not a head gasket, but i have no smoke, and i don't see any coolant leaking.
Dist?

Also, seriously try to datalog it.
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Old 03-09-2010, 08:00 PM   #5
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Dist?

Also, seriously try to datalog it.
distributor.

and for some reason i can't get megatune and my megasquirt to work well together. i didn't build the car as far as the ecu and all goes, i just put it all back together after i bought it. but i didn't touch anything as far as the wires go.
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Old 03-09-2010, 08:04 PM   #6
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distributor.

and for some reason i can't get megatune and my megasquirt to work well together. i didn't build the car as far as the ecu and all goes, i just put it all back together after i bought it. but i didn't touch anything as far as the wires go.

Good luck changing out the distributor, I hear its a real bitch on these cars.
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Old 03-11-2010, 06:54 PM   #7
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okay, today i changed the plugs and wires and i noticed that a vacuum line going from the turbo piping to the boost controller was cut, so i replaced it too. i drove the car a while. it felt fine during normal operation (always did) but once i got into it it proved that it wasn't fine.

at about 3500 rpm, it starts building boost, gets to 1-2psi and falls at around 4-4500 rpm, but it will keep revving, just VERY slowly. and i noticed slight smoke at idle, and a slight teapot-like whistle under the hood, i'm assuming coolant, but you can only notice this after driving it a while, stopping and revving slightly.

i'm guessing it's a blown head gasket, but i hate to order all the stuff, waste the time replacing it all only to find out it wasn't the problem at all.

any input?
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Old 03-11-2010, 07:21 PM   #8
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Did you try using a Dematta?
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Old 03-11-2010, 07:25 PM   #9
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Did you try using a Dematta?
call me stupid, but wut?
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Old 03-12-2010, 01:32 PM   #10
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No, you were supposed to say "What's a Dematta?"
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Old 03-12-2010, 01:53 PM   #11
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Boost leak somewhere that opens up once it gets a certain amount of air flowing through it?
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Old 03-12-2010, 04:57 PM   #12
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Boost leak somewhere that opens up once it gets a certain amount of air flowing through it?
that wouldn't cause the revs to slow down this dramatically, would it? i'd never owned a boosted car before this one. so i'm still kinda learning about all the problems that arise with it. especially when i didn't build it and the person that did half assed it.
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Old 03-12-2010, 05:00 PM   #13
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Get tunerstudio/megatune working and DATALOG THE PROBLEM. I can speculate all day as to why your car stops accelerating, but I could take one look at a datalog and tell you exactly why.
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Old 03-12-2010, 06:08 PM   #14
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A boost leak will probably not cause the car to totaly stop accelerating.
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Old 03-12-2010, 07:30 PM   #15
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Agreed, I misinterpreted the problem
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Old 03-12-2010, 10:23 PM   #16
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Originally Posted by Jeff_Ciesielski View Post
Get tunerstudio/megatune working and DATALOG THE PROBLEM. I can speculate all day as to why your car stops accelerating, but I could take one look at a datalog and tell you exactly why.
i'll give it a try. it sucks having no one around here able to help me get **** going.

i bought a compression tester today. but i pulled a muscle in my back this afternoon at work, so i'm on my butt for a while.
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Old 03-16-2010, 10:08 PM   #17
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i finally managed to datalog it today with tunerstudio. keep in mind, i had my uncle operating the laptop and i was driving. so it's hella long for no reason. it's to be viewed in megalogviewer.

i have no clue how to edit it or how to read it exactly. so i guess i just posted it for the guys that requested it. the first min or so is all that really matters, i guess the rest is basically me just driving around and him forgetting to cut it off.

as of now, it'll rev high, but slowly after 4k, and the boost cuts at 4k.
Attached Files
File Type: msl 2010-03-16_18.36.08.msl (433.5 KB, 61 views)
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Old 03-16-2010, 10:18 PM   #18
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According to that log, the most boost you made was 3psi which rapidly trailed off, most of the time it got BARELY over atmospheric even when you were at WOT. Also, you don't have a wideband, so its pretty impossible to comment on what your AFRs might be doing. Timing looks a bit retarded, but not terrible or anything. 1. Your wastegate is malfunctioning/completely disconnected, or 2.you have a massive boost leak somewhere. Also, get a wideband.
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Old 03-16-2010, 10:23 PM   #19
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Originally Posted by Jeff_Ciesielski View Post
According to that log, the most boost you made was 3psi which rapidly trailed off, most of the time it got BARELY over atmospheric even when you were at WOT. Also, you don't have a wideband, so its pretty impossible to comment on what your AFRs might be doing. Timing looks a bit retarded, but not terrible or anything. 1. Your wastegate is malfunctioning/completely disconnected, or 2.you have a massive boost leak somewhere. Also, get a wideband.
thanks. so basically it could be just the wastegate actuator since i'm using a piece of **** td04? if not that i'm basically going to have to replace the whole turbo?

as far as i can tell i don't have any boost leaks. i mean, i'm sure there's a small one somewhere but not one that would be doing THAT much damage.

and monies is tight right now so a wideband may be out of question for a while.
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Old 03-17-2010, 07:52 PM   #20
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replaced the actuator today, didn't do ****.

looked everywhere for a vacuum line leak, couldn't find any of those either.
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