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Old 07-11-2002, 09:22 PM   #1
DJIMPREZA
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Member#: 1199
Join Date: Apr 2000
Location: Caracas, Venezuela
Vehicle:
1994 Supra+1K, 22b
alike, 07STI

Default canīt pass over 4500 rpms

Hi guys!!

First stage of the project is completed, right now I got the cobb engine with the big vishnu turbo kit in the car, I have being breaking it for more than 800km without any kind of boost, I think is a good time to boost it a little bit, but right now, using my stockj 2.0 ecu (as I have done before without this kind of trouble) and better fuel pump, higher pressure and piggy back system with wrx 440 cc as primaries, well the thing is that I canīt pass over 4500 rpms even at very very litle throttle, I was thinking on coils, spark plugs wires or any other kind of ignition system, simply it feels like a fuel cut at 4500 rpms, the a/F gauge shows a stoich condition, but the egt gauge goes down to 400c inmediatly, so what I was thinking is that just were the egt probe is (in cyl 3) the spark is not firing, I have check spark plugs, wires and everytime I plugged them hard, the trouble goes away for some seconds, and then comes back, this are my suggestions, please let me know yours:

Replace spark plug wires
Replace coil
check spark plug gap
check engine grounding (I canīt believe this as I have 5 grounding wires and one extra coming direct from my battery in the trunk)
The piggy backs?
Replace cam pos sensor
Replace crank pos sensor


I have all this sensors in my hands (as I have some spare engines)

What else could it be? remember it just canīt go over 4500 rpms, terrible misfire? maybe to much fuel???, but this misfire is like a ignition cut? how to know if its a igntion cut or fuel cut? a/r ratio says lean, but egt says super cold, but A/F sensor is colecting all cyl. and egt is more accurate just one cyl!!

Ideas please!!
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Old 07-11-2002, 09:29 PM   #2
KillerTHC
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01 SRP 2.5 RS-T
Ludespeed Stage 3 Link'd

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i know the MAPed ej25's do this when the MAP goes over a certain voltage because of the positive manifold pressure. But i'm sure the ej20 you used to have was MAFed so this is most likely not the case. Can you make boost at all? does it always happen at 4500 or does it happen when you hit boost?
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Old 07-11-2002, 10:39 PM   #3
ColinL
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disraeli-- do you have a scan tool?

4500 cut sounds like a sensor failure. only certain ones will do it... what about the Vehicle Speed Sensor?
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Old 07-11-2002, 11:46 PM   #4
DJIMPREZA
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1994 Supra+1K, 22b
alike, 07STI

Default

Well some info, but no any good luck yet, no scan tool at my hands now, and no any check engine light at all, I changed the coil and three of the spark plug wires, starting from the one I tought was having the misfiring issue (the number 3) but same thing, but after removing the piggiback computer and leaving all the ecu stock, the innatural rev limiter has raised to 5500 rpms, for some reason (as any piggy back) was changing the signal, the cut out feeling is the same one as the deceleration, is like the ecu, when hitting 5500 rpms activates the deceleration mapping, very strange, isnīt it?, well the egt are keeping going down very very fast when that happends and the stoich mixture is being kept, there is no way I could pass 5500 without having the starnge backfiring, terrible hesitation etc, keep in mind that I am not boosting the engine yet, I mean this is happening from very very litle throttle, I check the tps voltage while close and it was .4 volts, I think its in range, but tomorrow I will make this trick in order to find if the tps is the culprit, I will disconect it first, so the ecu wonīt see any of my possible mistakes, next I will try to start the car, it should start.

About the speed sensor, it was bad!!, but I changed when IU replace the diffs, now is reading good, and yes the car has a map sensor, and I am sure is not seeing a higher voltage, as I am not even letting the engine to breath at 1 atmos.

Keep going guys, I need any kind of sugestion from silly to very smart.

In sumary is a cut out, like decel mappin mode, ocasionating the misfiring and not letting to rev up more then 5500 rpms from very light throttle!!!

Thanks

Disraeli
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Old 07-11-2002, 11:48 PM   #5
DJIMPREZA
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Location: Caracas, Venezuela
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1994 Supra+1K, 22b
alike, 07STI

Default

I will change as well, the cam and cranck pos sensor, I am not to sure those are in good condition, this engine, passed trough many hands and a very long trip!!!

I am not making any boost, it could happend even with 20 mmhg of vacumm or 3 psi! just when hitting 5500 rpms

Thanks !
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Old 07-12-2002, 02:22 AM   #6
Aphex
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hey DJ, sorry to hijack your thread, but I wasn't sure if you got my PM or not, I was wondering where you got the WRX radiator overflow tank, the one that goes into the fender.

I looked on graham goode and didn't find one, didn't know if there was a place that could order one.

Thanks
Eli
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Old 07-12-2002, 02:28 AM   #7
Aphex
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also, a suggestion, from reading your posts, it seems that it may be possible that the stock ECU just can't compensate for the larger injectors, cobb fully built motor. with turbo cams (I'm assuming), not to mention it's an extra .5l larger.

even with piggy backs, the stock ecu may just be getting so confused that it just decides to give up..... really have no clue at all, just throwing out my completely uneducated guess, take it as you will
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Old 07-12-2002, 08:25 AM   #8
DJIMPREZA
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1994 Supra+1K, 22b
alike, 07STI

Default

I got the Oveflow tank, fro GG in UK, is a oem part so you wonīt see that there, I emailed you a big email some time ago, check all your files dudde


Itīs not a trouble of ECU compensation, I have done this before on many other cars without this strange cut, there has to be a sensor failure somewhere, and is not that big that is not trigering the CEL..

Keep on going friends, I need all the suggestions I could get

DJ
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Old 07-12-2002, 10:36 AM   #9
8Complex

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The only time I've sen this happen is when a ProECM chip was installed on a car and didn't have a good enough ground... caused a 4200-4300RPM rev limiter. Sucked hardcore.
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Old 07-12-2002, 11:11 AM   #10
Aphex
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'05 Legacy GT
Silver

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hmmm, I never got anything in my PM box, I check it all the time, also nothing through email, if you happen to still have a copy of it you can PM it to me, or send to my email ebarthelman@cox.net

is the ecu OBDII standard? if so you should get a cable and a laptop, I have some software that will work, and I found a place online that is only about $100-$200 (can't remember exactly) for the cable + software, a very good price considering a lot of places will charge upwards of $500

so the 2.0L N/A motor was a MAP sensor factory?

it idles and runs fine in all other cases, it's just that it cuts off at 4500-5500 correct? hmmm

like 8 said, could be some grounds, electrical systems do strange stuff when not properly grounded. just like how many people got rid of their 3-4k hesitation after doing the single point grounding mod for the battery. who knows though. timing belt on correct? not too much I can suggest with my limited knowledge, sorry bout that.

hope you get this figured out soon.

Eli
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