Sr20det misfire/hesitation under 4k rpm

[jduke]

Above 4k rpm it rips hard no stuttering/misfire/hesitation, below 4k rpms it does all of that. Swapped a new o2 sensor(oem) and new spark plugs (bkr6e). looked over for boost leaks as well found none. I Just imported the car 90 180sx so im finding all the mods as i dig in. Where should i start next
Here's what i know it has so far.
Swapped to a red top SR
z32 maf
Trust FMIC
Power enterprise turbo
3" turbo back exhaust
Has a different ecu from "Technical shop ADVANCE original SPL ROM MT2000 real time rom emulator map tracer"

[Kingtal0n]

Sounds like a poor signal from the maf. You need a real carefully designed maf plumbing- like the factory- if you want a good signal.

1. you need a reasonable length of tube, preferably with a bend, between the maf and compressor. The larger the maf, the smaller the turbo, the more distance/bends you need. (small turbos and large maf sensors are more likely to generate noisy low resolution signals)

2. you need a recirculated bypass, hanging open during idle (and cruise) to stabilize the maf signal. A closed bypass, like an ssqv, will cause maf signal noise as the compressor chops at the incoming air with nowhere to dispose of it (runs in the surge portion of the map) and this causes noise in your maf hot-wire signal (unless you have a considerable length of tube between the compressor and maf. There are alternatives if you can tune and adjust these variables).

3. Tuning. You can tune around a noisy maf if you are satisfied with poor fueling quality.


A tight control on fueling is ALL about a high resolution maf signal, which means you need to do all of the above, and then take further steps, such as using an appropriate air filter and monitoring the maf signal, making adjustments to your bypass/plumbing to improve that signal.

[koko_S14]

I am having a similar problem with my S14 SR20DET. I've made a list of possibilities; I'm planning to check all these soon when I have the time.

-Fuel pump ground
-Leak @ valve cover gasket
-Bad FPR
-Fault 4th/5th gear sensor
-Timing issue
-TPS issue
-MAF issue(as stated above)
-Clogged fuel filter
-Leaky injector o-rings
-Coilpack issue
-Ignitor mounting
-Knock sensor

This is what I have found online from others in similar situations, so I'm not sure if everything listed is 100% accurate. I'll let you know if I find anything on my end.

[jduke]

Im going to clean the maf and put a new filter see if that helps. If not ill look into redoing the intake setup. Think i may put a new knock sensor and harness in. koko definitely let me if you figure yours out ill be posting in here when it gets sorted out.

[koko_S14]

I did a few more pulls and realized it hesitates past 4000RPMS. I didn't notice before since it's not as noticeable. I think we have different causes of a similar problem, but I'll keep you updated.

[lupathkep]

such as using an appropriate air filter and monitoring the maf signal, making adjustments to your bypass/plumbing to improve that signal.http://goo.gl/0q2uAN

[jduke]

Ok so something new i noticed. At warm up idle jumps around. It res up to about 1500 rpm then slowly drops down to about 700 rpm stutters feels like its gonna die then surges back to 1500 rpm. Also maf is grounded to the chassis. there are bends in the intake pipe to the turbo as well. Bought a new filter as the old one was black. Cleaned maf with crc maf cleaner with no changes.

[koko_S14]

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[koko_S14]

Have you checked the coolant temp sensor? I read that a faulty one can cause you to run rich(i.e. bogging) and to have a fluctuating idle.

[jduke]

I havent yet been busy with work plus that Colorado snow hit so the car is currently an igloo lol. Ill be checking that this weekend. Glad to hear you got yours sorted out.

[jduke]

Alright so i fixed my issue. It was either the knock senor or maf. I replaced the maf with a known working one and i did the knock senor resistor mod. Resistor mod is only short term, like i drove around the block to feel it out and thats it. New OEM knock sensor and wiring specialties harness goes in this week.

[koko_S14]

Good to hear man. I found my #4 coilpack's clip is broken, so it wasn't all the way on the contacts and had a poor connection.