Datsun Roadster Forum-311s.org

hello everyone,

just wanted to ask if any has had this problem with their SR20 swaps. the car starts fine with no issues, but once as i drive i press on the gas going on a straight,downhill,uphill road and engine starts to bog's for a while and goes away. There are times when the car does not bog while driving and drives normally then it would bog randomly so i tried various things like holding the clutch down and letting off the gas (thinking maybe its fuel issue) and press it again and hope the bog stops but doesn't after awhile, I've tried shifting it to neutral and see what happens(thinking it's a fuel issue again) and nothing happens still bogs and goes away. There are times when i do try these things it would work but still happens. I've also tried pressing the gas pedal deeper while it bogs and doesn't help much but i did notice the engine sounds/feel like it cuts off.
things i have tried to troubleshoot:
Check and changed MAF nothing wrong with that, made a little wind shield screen for the air filter in the front nothing changed too much, changed the fuel pump and nothing wrong, checked and scan for leak's nothing came up, checked and added new grounds nothing wrong with that.
I've had a few people suggested i could possibly have an ECU problem and some would say it could also be a fuel delivery issue. i'm just trying to narrow things down on this before i start purchasing parts i may need. Hope you guys can share your input on my issue. Thanks in advance.

It is pretty rare to have a ECU issue considering it runs, I would plug Consult in and make sure your TPS (throttle position sensor) is reading correct.
FSM will have the values you need to see. If that looks good I would then consider sending your injectors cleaned or replacing your injectors as we have seen several issues with them sticking and giving weird symptoms. Hope it helps

I’ve used mr injector to test, clean, and provide a a final flow test for my injectors. Less than $20 per injector plus shipping. Fast turn around. Also when you check consult readouts, you might want to make sure that your temperature sensors are working so the ecu knows how to adjust for temperature.

I'm experiencing a similar problem. Starts and runs great from cold. After driving for awhile, shutting off for an hour or so, engine will buck and miss for a short time then clears up and runs great. I've replaced fuel pump, filter, and injectors with no change with issue. I'm buying the Nissan Data Scan software to load on my lap top to hopefully find the issue. FWIW Pat

With the wet fuel pump ,a metal flake that makes it thru the screen to the strong magnet ,causes problems like that .
Also slight miss align of the intake tubes /manifolds will cause a dead spot 97 Galant mitsu had a TSB on it ,just a 1/16 " could caused it to stall on the highway ( I know hard to believe ,but mitsu was right)
Does it have a 2 stage / variable venturi intake? Most in that era did ,they can cause it

It does sound like a fuel delivery issue, I've been there before swapping fuel pumps and filters. You can check the TPS pretty easily with a multimeter if you have one 5v comes from ECU to the TPS and a reduced voltage goes back based on the position of the throttle / resister. with engine on (doesn't have to be started ) you should get around 0.4 to 0.5v (centre pin to ground, 3 pin plug? don't have an SR in front of me) and about 4.5v when you pull the throttle all the way open. or pull the plug and the resistance should go from 1k to 10k (ish). You should be able to confirm this with google.
From memory I put in a small fuel pressure gauge to check the lines. I had a petrol tank that was corroded and clogging the pipes. idle was fine but any load the engine bogged down and no power. The car was not being used so this was the excuse to pull it a part for a frame off resto [ongoing]. If you don't have a CONSULT cable yet these are good.
https://www.plmsdevelopments.com/index.php/consult-cables

thanks for the input guys i will get to this asap.

If you know someone with a wideband, throw that on there and log a run. Then you'll at least know of it's a lean or rich bog (probably lean). then start working back from there. Also absolutely confirm that you whole ignition system is in perfect order( wires, plugs, cap, etc). Do the midnight test under the hood and look for fireworks. Then it's down to a good scan tool with logging to see where things are going afoul.

Sometimes these things are a be-och to nail down. I still have an issue my self with an SR20DET startup blubber.

Good Luck
Regards,
Steve

Are you using premium gas ? Because no one else is , not many
And it can be , a year old , or has water in it
Pump it out and try lower grade

I had troubles with my s15 swap . i had data scan and i had troubles holding tune , the idle was terrible on cold start . Once it was warm it would idle good some times and other times it would be shake .tps voltage i had to run .08vdc just to get in to idle mode . I contacted jk tuning in carlise Pa . I got a b13 ecu with nismotronics sa board and had it tuned there . I couldn't be happier . You should look in to it . because it has a data logger that can hold your file . Then send it j-k via email and changes can be made and sent back to you and you can upload it Or you can blue tooth connection installed and can be real time log . good luck .

update:car finally runs smooth. Took out the injectors not knowing they were dirty and i was able replaced them also installed an aftermarket FPR that i had laying around for awhile. Thanks to all for the input

OGFAIRLADY wrote: ↑Mon Aug 31, 2020 5:24 am update:car finally runs smooth. Took out the injectors not knowing they were dirty and i was able replaced them also installed an aftermarket FPR that i had laying around for awhile. Thanks to all for the input

What's an FPR? Fuel pressure regulator?

Yes, Fpr is fuel pressure regulator.