Thread: In need of some help. B13 has unstable/rough idle, hesitation, etc

I am going to give some back story on my situation.

My brother bought the car working about 6.5 years ago. See thread if interested http://www.sr20-forum.com/members-rides/19072-project-shoebox-91-ser.html . The car was left motor removed and dissembled. It sat that way for about 2 years. Then he purchased a motor from a person on the forum. Installed that but never started it. I bought the car in pieces and after a total of 6 years I got it running again. Then my problems began

The car has had bad hesitation in the mid range, unstable, rough idle, regardless if the motor was hot of cold. Bad mileage about 215 to a tank. If I drove the car like a middle aged woman it would be ok, anything over 35% throttle or so and it would hesitate, and clear up and hesitate and clear up. Felt like someone was pulling on the ebrake while driving. It only died on me 3 times while driving in the 2 months or so its been on the road always staring right back up, until today.

Here is what I have done to try and diag and/or repair the issue

empty old fuel from tank
replace rubber fuel lines at tank and in engine bay
replace fuel filter 300zx
New copper plugs
Replaced all grounds with 4 gauge wire
regrounded maf
better ground for o2
checked maf voltage - OK
checked tps BAD 4.00v open or closed no change
Reset the ecu numerous times
All egr is gone and properly sealed.
All Vacuum lines replaced
New Intake Manifold gaskets
All old egr plugs are plugged
No vacuum leaks. checked visually, with carb cleaner and by pinching pcv line
Checked Iacv and cold start valve. Both function correctly
Cleaned both valves
Performed Comp test 165-175 on all four

Issues still existed

My other brother also on this forum has a 92 ser that is down for a head swap. His ran fine so I borrowed some known working parts to help test with

Installed his
Maf
TPS
Plug wires
distrib cap
iacv
cold start valve

Car ran better idled smoother but not perfect. His TPS Voltage and Maf voltage was correct. Set TPS to 3.98 at full open. Withe the tps connected the car would buck and lurch when attempting to drive. Completely undriveable. It would buck so hard it my head nearly hit the steering wheel and when it lurched it chirped the tires. With the tps disconnected it ran good. not as peppy as it should be but it would go all the way through the rpm range with no hesitation, idled ok. For the first time I could get on the car and it ran good. I drove the car for about 20min came home and let it idle for about 10 min. It had a slight miss but held a stable idle at about 850rpm. This was on Sunday. Today I plan on taking it to work, I start it, let it idle for about 5 mins. Idles high at about 1200. I back out accelerate easily shift into second at about 20mph. The car hesitates bad I hear a slight backfire, but very small. car dies and wont start at all. cranks and cranks but nothing. I hear the fuel pump priming.

When I get home from work I pull the plugs. They all look good. wet from fuel but thats to be expected from trying to start it. I installed the plugs into the wires and had my wife turn the car over. They all sparked.

I am at a complete loss. I have been researching and researching threads and trying different solutions but havent resolved the issue. Its time to tap out and ask for help. sorry its long but I wanted to get all the important info laid out

I am in south spring hill fl, if anyone is will to come over to help I can provide food, drink, or cash if desired. I just need to get this car running

i had this problems too, what I did :

- Replaced the spark plug cables
- Replaced all vacuumn hoses, especially those with hairpin curves, makes sure use use xtra large size and no bent on the corners
- cleaned injectors
- Adjusted Fuel Regulator to 5bar

Once a while if I WOT, the engine dies if I directly let go the throttle.

This can be solve by replacing a standalone ecu WITHOUT the MAF sensor, coz alot of nissan MAF aged and causes idling problem too

I take it you have an adjustable fpr. I dont think you can adjust the stock one. Everything else I have tried with the exception of the fpr

maybe the FPR is faulty, or your fuel filter......these small things can be a culprit too

It kind of sounds like your O2 sensor could be dead. Although I think you may have a few issues. It sounds like your TPS is obviously also toast. You could have a dying fuel pump as well.

When an SR20 dies with a small "pop" sound like you've heard, 95% of the time the coil-to-distributor high voltage line has popped off of the coil and just needs to be put back on. If that wasn't your problem, then I'm suspecting the fuel pump finally died. You should test the fuel pressure if you can. I know you say you hear it priming, but it could still be bad. If it's not that, move on to testing the injectors. And start to think about it maybe being a CAS or ECU issue.

Get yourself a good TPS on the car that you can keep on there. Then spread the contacts out inside the coil-to-distributor wire and zip-tie it down onto the coil to prevent it from popping off. Then maybe get a new or known good O2 sensor in there and test the fuel pressure.

Let us know how it does after that.

Did you check the engine coolant temp sensor?
http://www.sr20-forum.com/general-sr20/24921-coolant-temperature-sensor.html#post320991
http://www.sr20-forum.com/general-sr20/25565-stock-sr20-stalling-during-idle.html#post329361

forgot to mention I i did a full block and heater core flush with a new t-stat and both ecu and gauge sensors

I know my tps is bad my brothers tested good voltage wise and his car ran fine before he took it down. I also took and installed his Fuel rail with injectors. (I assume the fpr is built into the rail) So both of those should be known working parts.

I did a quick push test on the coil when it left me stranded but it didnt help. Its an aftermarket coil to dizzy wire so that could be an issue in itself.

So my to do list right now is:

order a fuel pressure gauge
zip tie coil lead
test injectors (I assume you mean resistance)

I have an o2 sensor used but known to work. Some one stripped the one currently in the header real good so I need a chase to align the threads
Doing research it seems a safc was installed So I will check for broken or exposed wires.

What is CAS?

unplugging o2 sensor while the car was running didnt affect anything. Could that be sign of a bad o2

Is there a way to test to see if the igniter or the coil maybe bad

I have been tried 2 fuel filters one 300zx and one being a factory size. Both drained visually clear fluid and no change was noticed when swapping them

And/or have someone crank the engine with the rail/injectors out of the intake manifold, spraying onto rags to see if one is not firing or weak.
Refrain from smoking during this test.

Cam Angle Sensor. It is inside the distributor housing, but is basically unrelated to the function of the distributor. It just happens to share the same shaft. It gives the ECU crank and cam angle data using an optical beam and a wheel with tiny holes in it. Sometimes oil leaks into them and causes issues.

Yes, but is probably not a definitive test.


Do a similar test as I describe for the injectors... Remove all plugs from the engine, but keep them hooked up and ground them to something. Pull the fuel pump fuse, and have someone crank the engine preferably while it is dark out and watch for strong blue sparks in the correct order. Video record it and watch it back if you want to make sure.
Do not perform this test at the same time as the injector test.