88Rx-7turboII

iTrader: (2)

Ok so i still havent gotten any solid answer yet.. anyway my car is an s4 t2 with a 3" turbo back and other than that its pretty much stock..it ran perfect until recently started sputtering upon start-up and calmed down after about 30s-1 minute and also sputtered when maintaining speed. now it wont come out of the sputtering when idling and it runs very rough and doesnt sound very healthy... I've been told it could be bad grounds, but its doesnt at all feel like that, it feels like its choking.. I am yet to change the fuel filter and iv got an fd pump to throw in but i would like to know what could be possibly wrong with it.. any help is greatly appreciated!

freemanrx7

Is your wastegate ported? You say the exhaust is the only mod you have! If you haven't ported your wastegate then you may have overboosted which means bye bye engine.

If you ported the wastegate I would look for vac leaks.

cheddarrr

iTrader: (2)

sounds like a vac leak to me too.

pnthr879

maybe check your tps too?

88Rx-7turboII

iTrader: (2)

the wastegate is not ported but i ran it on the dyno to make sure im within safe limits and i am before 5k rpm at wot whcih i havent revved past. i dont think it is a vac leak because it doesnt even fire properly, i know how it runs with a vac leak and right now its running like an out of time piston motor. the fuel filter doesnt appear to have been changed in a really long time but could that be causing it run so rough?

freemanrx7

Stock TII + 3" exhaust = BOOM! If you don't have an aftermarket guage your clueless of what boost really is. The factory is giving a false reading. Also you say you had it on a dyno(indoors). Well let's say you drive your car on cold morning the air/oxygen is diffrent . I say BOOM but I hope not.


Check fuel filter, TPS, and compression just for fun

88Rx-7turboII

iTrader: (2)

The dyno run was indoors at night time. we did 4 pulls and I'm boosting 9.75 psi. we cut the run short at 5k because it was leaning out so we left it as is while i stock up on parts over the winter. It hasnt been pushed past 5k wot since the install and it only just started running like this. it began running like this at idle for maybe a minute then it smoothed out and ran like a charm but now it won't smooth out. I dont wanna run it again because it doesnt sound healthy at all but there was no smoke or anything coming out of the exhaust...If it were blown then how could it have been smoothing out after idling?

totpkg

I am by no means an expert, but my N/A was running similar when running on one rotor. With mine, I had let the engine sit for a month and when I went back to start it, one of the seals were stuck, causing it to run on one rotor. I fixed by: identifying which rotor, then I saturated rotor with Marval Mistry Oil and let sit for a couple of days, before start-up I spun it w/o plugs then started. Initally it was running one one rotor ... then I reved the **** outa it 6K - 7K and seals came back to life ... I was lucky.
Yours sounds similar ... go back to square one ... make sure you have fuel (fuel filter change - cheap fix, also these cars have history of fuel pump wiring/grounding issues); make sure you have spark ... then go from there ... hopefully its just a fuel problem, not a stuck seal.
my 2 cents ... good luck

88Rx-7turboII

iTrader: (2)

It may be a fuel/spark issue but i dont think it would be a stuck rotor because it has been by dd since the snow melted so it hasnt sat for more than a day or two without being driven within the last 4 months. It does feel like it is running on one rotor though..

freemanrx7

Port the wastegate asap once you figure out your problem. Have you done a compression check?

88Rx-7turboII

iTrader: (2)

Not since it started running like this. I don't want to drive it the way it is and i don't have one at hand. I may be able to get a hold of a piston compression gauge if i can get that to gimme some kinda reading.

88Rx-7turboII

iTrader: (2)

And i should have a newly rebuilt turbo w/ ported wastegate in the mail about now.

freemanrx7

A piston guage will work. There should be 3 even bounces on the guage.

dot_txt

iTrader: (1)

From aaroncake.net:
A simple tester can be made by using a standard automotive compression gauge. Remove the one way check valve, and install the tester into the leading (lower) spark plug hole in the front rotor. Make sure your battery is fully charged, remove the EGI fuse, then floor the pedal and crank the engine while an observer looks at the gauge. You are not looking for excellent numbers, just three even bounces above 70 PSI. If the rotor has lost one apex seal, you will get one strong bounce followed by two very low bounces. If all seals are damaged, then you will get three bounces that barely register on the gauge. Repeat for the other rotor.

If the compression comes back good then you are either looking at a air / fuel issue or an electrical issue. I would check the TPS ans AFM immediately after seeing as how those could both cause the issues you are having. If those test out fine, move on to the ignition and fuel system.

Good luck.

nopistons87124

iTrader: (2)

my car also did that sputterin on start up for the first 30 sec to min then i pulled the plugs and did compression test found that rear housing had no compression

88Rx-7turboII

iTrader: (2)

i had it compression tested at mazda this time last year and it came up all good, but of course that was last year.. I don't see how my exhaust upgrade to hurt it if i've been keepin it in the safe afr range..

freemanrx7

It's common TII knowledge. Your story has been told before. The stock injectors/computer were not designed to handle 9lbs of boost. That is why there is a fuel cut at 8lbs. Sure it will work for awhile but will eventually BLOW.

What is causing the boost to go to 9lbs?

88Rx-7turboII

iTrader: (2)

3" turbo back

freemanrx7

I was being sarcastic!

I run a stock setup with the smaller 2 1/2 inch RB exhaust. I upgraded to a S5 ported turbo. I stay at 5.5lbs in all gears. IF you have to rebuild this would be the way to go until you learn more about turbo rotaries.

88Rx-7turboII

iTrader: (2)

it been a few months now, and after replacing the fuel filter i decided to give it a crank to see how it will run. it was rough to start but it was cold out and it has been sitting for a few months now. so once it started it was rough like before but would smooth for split second so i let it warm up. after warming up it ran fine. took it for a drive and runs good, at first there was no sputtering on cruising but after about 5 mins of driving it began to jump a little when maintaining a constant speed. I've only replaced the fuel filter so far and judging by the way it ran last night it doesn't feel as if anything is wrong internally.

88Rx-7turboII

iTrader: (2)

Again today upon start-up it sputtered and was rough but smoothed out after a few minutes, but was rougher at cruising speed. I'm thinking its a vac leak but i'd like it confirmed.. any info would be appreciated. Also, if its smoothing out after running and runs perfect when i give it some throttle would that cancel out the possibility of a blown rotor? or do they like to intermittently cut out?

88Rx-7turboII

iTrader: (2)

sparkplugs maybe?..bump

gear_grinder

iTrader: (4)

did you comp check yet??

if you think its running on one rotor, take the fan and shroud off and do a *pop/chug* compretion test to asure that one rotor is not totaly gone. should be a total of 6 pops/chugs, one every 180degree rotation.

have you even checked the plugs yet? my motor is getting tired so it fouls at least one rotor out about once a year (and i dont have MSD 6A yet ether). pull the pump relay, pull the primary (lower) plug and hold it against the block or a/c compressor or somthing grounded, then have someone role the engine over and do a visual inspection for spark.

freemanrx7

My 7 does this also. It kinda jumps while at an even cruising speed. I put in new plugs and it seemed OK for a day or 2 but went right back to jumping. I'm thinking it might be because it's running pig rich. Could to much fuel cause it to do this at cruising speeds?

Could it also be some kind of leak after the turbo?

88Rx-7turboII

iTrader: (2)

I am yet to chug test or pull the plugs because its pretty cold out right now. i was just curious as to what could cause it to jump at cruising. I'm assuming its the plugs but you know what assuming does...