Sr breaking up...I need help.

[DrtyRat]

I have an s14sr and I'm having a prob. w/it lately. First of it's difficult to start in the morning(I have to give it gas and crank it a few times) and when I hit 3500-4000 rpm @ WOT it starts to break up. I can rev past that point w/no prob as long as I do it w/partial throttle. I boost up to 9lbs and it holds steady as long as I don't floor it, but when I floor it it starts to break up.
The following is a list of things that I've done to try and fix it:
1. Change the spark plugs and gapped them to 30
2. Checked all of the coils to make sure they were getting spark
3. Changed the MAF and cone filter
4. Changed the fuel filter
5. Had it checked for boost/vacuum leaks
6. Checked fuel pump (pump is from a supra tt and was purchased brand new) and the grounds for it
I'm stumped as to what it could be, and I know its one of the common, vague problems, but I'm all out of ideas.
Mods are as follows:
MBC
fmic
blitz nur spec exhaust
test pipe
I doubt the mods are causing the prob. but I figured I'd include it.

[ladiesman8527]

check for codes. could be a bad coolant temp sensor.

[Z U L8R]

a friend of mine ran into a problem like this, he did everything u did plus a coolant temp sensor. turned out to be one of his o2 sensor wires was burned up and grounding out causing the same symptom. take a look at that on your car.

if you're running more boost than stock ( i saw mbc listed as a mod ) then you should gap your plugs to .028 , and i'd recommend ngk bcpr7es #3330.

[s14unimog]

I'm having the same EXACT problem.

mines pulling about 15Hg at idle too, same with you?

Also mine breaks up when its cold and eventually it seems it "warms up" and the idle will go to around 1050 and it will pull hard. Otherwise it idles at 650 or 700 and sounds really loppy.

Also as well as what you were saying it does the samething in the morning with not wanting to start and somehow pushing the gas pedal helps.

[DrtyRat]

Originally Posted by Z U L8R

if you're running more boost than stock ( i saw mbc listed as a mod ) then you should gap your plugs to .028 , and i'd recommend ngk bcpr7es #3330.

I had my prev. spark plugs gapped to 28 and that's when the prob. started. I'm not saying that it was the cause of it but that I was having the same prob. w/them gapped to 28, and I'm only running 9lbs w/the mbc.

[Z U L8R]

9lbs .030 is fine, #3330's come at .030 drop right in ^_^ but you're correct that's not your problem. i guess check - or change if you're really frustrated - your o2 sensor but i'd start by checking those wires and replacing the coolant temp sensor for the ecu (not the sending unit for the guage they're two different things, right next to each other, and the parts guy's at the parts stores are fucking retarded) because it's cheaper ooOOoo BUKAKE!!

[johngriff]

do you have access to an infared thermometer?


Warm the car all the way up, and check the temp of each coil pack on the white top of the coil (they are like this for this reason). Record your findings. Do a hot lap around the block, bring it back, check again.

If you notice high inconsistencies in temperature, or temps OVER 145F that coil pack or its associated wiring is bad.

The MBC might also be to blame, i would try disconnecting it and test the car using straight wastegate connected, you may be spiking and have a guage that is not reacting fast enough.

Did you set your base timing correctly? This is done with a timing light, and the tps sensor disconected @ idle. Make sure your idle is between 900-1050rpm when setting the base timing. I like 14deg base timing.

Is all of your coil pack wiring intact and in good shape? This is a very common problem from the connectors getting overworked and shearing the wiring on them.

[Max_PSi]

Sounds like the MBC, I had break up pretty often, and not RPM specific because the MBC wouldn't hold boost steady. The ECU would just bug out and I'd get break up all the time.

I have the Greddy Profec B installed and have not had on problem with break up since.

I also have an S14 SR too.

[s14unimog]

since my symptoms are EXTREAMLY similar, I'm paying attention to this thread. I have an SBC-iD and it still does it on mine. I never get spiking either.

changing the ECU temp sensor tonight once the car cools down.

[DrIvEsldEwAyS]

check the coils for cracks, mine was doing that and one of my coils was cracked

[s14unimog]

did the ECU's temp sensor tonight, didn't fix mine.

coil packs tomorrow

[Z U L8R]

i'd rather pop in an o2 sensor (denso part #234-3098) than pay $400 for new coil packs......you could always borrow a friend's just to test though.. ^_^

[Sileighty_85]

Check CAS Timing, Igniton Curve probably Fubar

[s14unimog]

did timing on mine as well as reset the CAS by pulling it and reinstalling it correctly with the VC off.