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Old 01-16-2013, 12:55 PM   #1
Stealth Bomber
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Angry Engine cuts out above 5000 RPMs

I have an issue that I have not been able to remedy since I purchased the car. It is a 2002 WRX wagon with 163k on the body. Previous owner did a lot of work to the car, mostly good parts, not so good work. It has a STi ej20k v3 swap and a lower mileage WRX 5spd transmission. The car will not rev past 5500 RPMs, sometimes won't get over 5000. It happens in all gears and in neutral, under boost and not. Car jerks as the revs bounce and won't continue past. No CEL.
Mods-
FMIC
850cc injectors
walbro 255
vf28 turbo
SR intake
turbo back exhaust, no cats
clutch upgrade
amongst others...
Since I purchased I have-
Swapped fuel pump, fpr, fuel filter, spark plugs, coil packs, MAF, Turbo, down-pipe, injectors.
I cleaned the IACV and replaced gasket, compression test was all good, boost leak test was good, tried several tunes with a reputable tuner, had a subaru guy look at it and do/help with some of the swapping of parts.
The car seems to hold boost well, AFR looks good, idles well, starts well... It just won't rev! Previous owner is not very helpful, makes suggestions like "ecu?" or "Maybe the timing belt is on wrong?" I was told the car was detuned and the rev limiter was set low. I know, I'm stupid. Don't trust anyone, even if they have a speech impediment and seem like a real nice guy.
I have searched on the site and online, I have worked with one of the most well known Subaru tuners in the state, I have had someone that regularly swaps subaru motors, I took it to a local shop... Next option seems to be a leak down test to check the condition of the heads? I just need some more suggestions, before I pull out this motor. Let me know if I can answer any specifics, thanks.
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Old 01-16-2013, 12:58 PM   #2
WRXChops
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Hook it up to a Subaru scan tool and check the readings.(fuel,maf) did you tune it after you added those mods?
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Old 01-16-2013, 12:59 PM   #3
the suicidal eggroll
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I doubt a leakdown will tell you anything. Compression problems won't cause a fuel cut at a certain RPM, only the ECU or fueling/ignition problems will. Have you checked the various position sensors (crank position, cam position)? A bad position sensor or a bad reading from a position sensor can cause issues like this.
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Old 01-16-2013, 01:01 PM   #4
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You've worked with one of the most well known subaru tuners in the state... at diagnosing this issue?
You've had someone that regularly swaps subaru motors... I'm assuming look at it.
You took it to a local shop.

What was the outcome of each of these? Obviously they didn't fix it, or you wouldn't be posting.
Do you know what tune has been done to it? If you were told it was detuned and the rev limiter set low, isn't that your issue right there? Sounds like it's a crap tune.
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Old 01-16-2013, 01:22 PM   #5
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The car came tuned with a Cobb AP. Was previously done at P n L in Chicago, even had Jorge's name on the map, and I called to confirm that they had a record of my car. The car was tuned by NF performance when I was first trying some things out, and he tried again after the parts swap. Tried the map that was in there and created a new one, no improvements. I don't think the guy that tuned one of the fastest STis in the state does crap tunes? He saw no issues that he could remedy with tuning, said it must be mechanical.
How do I acquire a Subaru scan tool, from the dealer?
I remember them saying they changed out either the cam or crank sensor at PnL back in 2010. But ill look into those. Thanks.
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Old 01-16-2013, 11:49 PM   #6
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Called PnL back and now they do not have a record of changing one of those sensors? I am fairly positive they said that before, I don't know where else i go that idea. They had done a timing belt service, injector change and plugs. Also did a dyne tune, 264hp. The car was able to rev back in 2010 at least. I am going to change those out anyway. Any other ideas?
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Old 01-16-2013, 11:58 PM   #7
punchjamesarnol
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It sounds like fuel cut to me. I had that problem a while back when I was road tuning my car. Try Phatbotti Tuning let them know the problem and see if they can help.
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Old 01-17-2013, 12:31 PM   #8
Stealth Bomber
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I know the afr gauge is not exactley precise but isn't it close? The fuel looks good whether im under boost or not. Is it possible that it is that dramatic of a change to go from a low 11mileage to lean?
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Old 01-17-2013, 12:49 PM   #9
wgr73
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Double check launch control if you have it setup in the tune, if so turn it off. Check crank/cam sensors and gap as mentioned above, and check grounding on the car. Finally if you have to, get a leakdown done because I'm pretty sure that can tell you if you have a bent valve (no?) which can cause this as well. Valve float can be the cause too.

There are a few threads around here about this. It can be a pain to track down if it's not something easy. Could very well be a mechanical issue
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Old 01-17-2013, 03:13 PM   #10
Stealth Bomber
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Ok, thanks. My tuner suggested the leak down test. Ill ask him about the launch control. Gonna check the sensors thus weekend. Ive checked the grounds, when you said gap are you referring to spark plugs? Those were changed and gapped proper.
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Old 01-17-2013, 03:39 PM   #11
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Why would launch control even be related to this? It should only activate when the clutch is pressed.
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Old 01-17-2013, 04:03 PM   #12
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Check your speedo sensor on the tranny cause that can also cause it to do that. I had a rock fly up and hit that sensor and my speedo worked but I couldn't rev above 5000 rpms. Most of the time with subarus its dumb little stuff like that
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Old 01-17-2013, 04:08 PM   #13
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But my car was doing the same thing and I spent alot of Money tryin to figure it out untill I replaced that speedo sensor. It's around 80 bucks I would check that out
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Old 01-17-2013, 04:08 PM   #14
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Quote:
Originally Posted by Mr Wrex View Post
Why would launch control even be related to this? It should only activate when the clutch is pressed.
If everything was working the way it should be, he wouldn't have an issue. Since ~5000 is around where the launch control cut out is at, it may play a roll if the tune is off.
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Old 01-17-2013, 04:33 PM   #15
Mr Wrex
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Quote:
Originally Posted by Loyale93 View Post
If everything was working the way it should be, he wouldn't have an issue. Since ~5000 is around where the launch control cut out is at, it may play a roll if the tune is off.
You can set the LC at whatever value you want. No wrx comes with an LC from the factory (see http://forums.nasioc.com/forums/show...0&postcount=14). If OP has LC set on his car, then the only relevant reason I can think of is that the ECU thinks the clutch is always pushed in, even while driving.

OP, you mentioned the previous owner lowered the rev limiter. Are you talking about the engine redline set by the ECU? Also, you said the original owner detuned it. Are you even properly tuned for your current mods?

Last edited by Mr Wrex; 01-17-2013 at 04:50 PM. Reason: added link
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Old 01-17-2013, 05:13 PM   #16
Stealth Bomber
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I started looking for that speed sensor but got side tracked, ill take another look at it. Would it matter though if i cant rev no matter if the car is moving or not, under boost or not, in gear or not? Or is that sensor based on a calculation that pressumes the speed of the car?
Its hard to trust anything the past owner said, as far as saying the revs were limited. I think i may be assuming that he was saying the ecus rev limiter was lowered.
The car had been tuned prior to me getting it. I tried a few minor things to fix it, then took it to get tuned, he got the car to run much bette, mostly by rescaling the injectors to a smaller size than was told were in there, but not able to fix the rev issue. I changed the plugs, did the boost leak test and attempted to tune again. That did not work so i changed the fpr and coil packs, still not fixed. So i located some injectors and a smaller turbo( was a 18g), and athe maf,and tried another tune. Its been tuned to hell, multiple runs, does well all the way up to that 5-5500 point.
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Old 01-17-2013, 05:30 PM   #17
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Yea you should defiantly check that before spending alot more money cause I went though the same thing with my car I spent over 1g trying to figure out what it was and it was that sensor and my car wouldn't rev above 5 at all untill that sensor was replaced
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Old 01-17-2013, 05:48 PM   #18
Loyale93
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Quote:
Originally Posted by Mr Wrex View Post
You can set the LC at whatever value you want. No wrx comes with an LC from the factory (see http://forums.nasioc.com/forums/show...0&postcount=14). If OP has LC set on his car, then the only relevant reason I can think of is that the ECU thinks the clutch is always pushed in, even while driving.
Well aware of that. My '04 STI actually got a beta of the Cobb LC and Flat Foot Shifting back in '06 (I think it was '06).

The OP has had the car tuned. Do you know his car doesn't have LC on it? Because I didn't see him say that. Nor anything about him changing the set point for the LC. So it's entirely possible that it could be causing a problem.

Criminy. I was just trying to explain to Boosted92 why the LC could be causing an issue. Could be the tune is not properly registering the clutch being depressed. Who knows. Worth taking a look though.
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Old 01-17-2013, 06:43 PM   #19
wgr73
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Quote:
Originally Posted by Stealth Bomber View Post
Ok,rq thanks. My tuner suggested the leak down test. Ill ask him about the launch control. Gonna check the sensors thus weekend. Ive checked the grounds, when you said gap are you referring to spark plugs? Those were changed and gapped proper.
Crank sensor.
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Old 01-17-2013, 07:17 PM   #20
Stealth Bomber
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boosted92, did your speedometer still work with the bad sensor?
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Old 01-17-2013, 07:47 PM   #21
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Most of the time it did but sometimes it wouldn't work and the way I tested it was I unhooked the positive terminal on the battery and then hooked it back up and start the car and if its your speed sensor then you should be able to fully rev to tack point and after about 1-2 minutes it will go back to only being able to rev to 5000 rpms again. And my car did that so I changed it and like I said before it fixed my car but I have no idea if that's what's wrong with yours just sayin it might be something to look into cause that sensor is cheap compared to a shops labor rates
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Old 01-17-2013, 09:24 PM   #22
flores412
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Just like loyal93 said rev limiter I set way low. Have it tuned I bet that's what it is.
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Old 01-17-2013, 09:58 PM   #23
Stealth Bomber
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I looked into the VSS, another $85 guess... This is a tough one. Ill check the start up and rev attempt
If it was actually the rev limiter would it not be limited to a specific RPM? Sometimes it will got to 5500 other times its at like 5100. I would think it would always limit at an exact?
I tuned it before I really made any changes. I tuned it after I made some more changes, not fixed, so I took the advice of my tuner and what to try next. Then I returned to see if those changes helped and had him tune again. Its been tuned with the AP that came with it, and its been unmarried and tuned. I don't know how much more tuned I could get?!
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Old 01-17-2013, 10:00 PM   #24
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No because mine is set to 6200 to 6500 until I get bigger injectors, tuners or I know my tuner set the rev limiter there so I don't lean my motor out and blow it. But no it won't be set at a specific rpm it will move a little.
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Old 01-17-2013, 10:01 PM   #25
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Open source. Have him hook It up and see what he may have set it at or the ap has it set at.
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