Jump to content
SAU Community

Recommended Posts

It is a mostly stock 89 R32 GTR. Basic bolt on mods; intake, zorst, gutted cat, boost is at 1 bar.

Here we go.. I've been having this problem off and on since I bought the car 8 months ago. It misfires below 4k rpm AND there is boost. No boost, no miss. It might be missing above 4k, I just stop feeling and hearing it around that point. It is also running slightly rich. I don't have a wide band so I can't exactly how rich. Idle bounces a little from 850-950.

Since I bought the car I have changed: plugs (twice), fuel filter, ignitor, air filters, turbos (stock R33), all exhaust gaskets, Lambda (O2) sensors, PCV, ECU, some broken vacuum hoses, and all fluids.

The first set of plugs I used were NGK BKR7E. They looked a little sooty after 6 months. I replaced them with NGK BCPR7ES. Tried gapping at 1.0, 0.8, and 0.6. It runs best at 0.8.

No boost leaks. I have cleaned & resoldered the MAFs. TPS measures 0.47v at 0% throttle and 3.96v at 100%. Coils ohm out between 0.8 and 0.9 and I didn't see any cracks them. I swapped coils around and pulled coils one at a time. It doesn't seem to be any one cylinder. I have done a motorvac on it (kind of like running straight injector cleaner).

Every time I cleaned or replaced a part, it helped. But it didn't clear up. I'm at the end of my mechanical ability. What can I do next?

Sorry if this has been covered before. I searched, but everyone else fixed misfires by cleaning the MAFs or closing boost leaks.

Link to comment
https://www.sau.com.au/forums/topic/263156-intermittent-misfire-low-rpm-boost/
Share on other sites

Its a long shot but have you checked the earths, battery terminals and alternator output? Have a look at the ecu plug too, try disconnecting and reconnect making sure the plug goes on nice and square as your tightening it.

Its a long shot but have you checked the earths, battery terminals and alternator output? Have a look at the ecu plug too, try disconnecting and reconnect making sure the plug goes on nice and square as your tightening it.

There is a back wire coming from the main engine loom that earths to the ignitor housing. It ohms out to 0.5. Everything else is good.

I don't see it on the wiring diagrams. Any idea where it goes?

There is a back wire coming from the main engine loom that earths to the ignitor housing. It ohms out to 0.5. Everything else is good.

I don't see it on the wiring diagrams. Any idea where it goes?

Just talking to myself again...

Spoke to an auto-elec. He says that the wire is OK to measure 0.5 because it looks like it provides ground to another device. I'm just reading the resistance of whatever that device is (probably a circuit in the ECU).

Also, he said to replace the batter cables (because it's cheap) and to test the coils and coil loom after the car is warmed up. What an eye opener to talk to someone who really understands electronics.

Any other thoughts?

The main ecu earths are on the the top of the engine, bolts to the top water outlet near injector 1, 2 x 10mm headed bolts. Run another earth cable from there, to the ignitor and back to the battery terminal, keep them all on the same ground.

Pulled another earth wire from battery to ignitor and also jump it down to the aluminum rail that the coils bolt to. Remade some joints that looked questionable. That one wire measured 0. Went for a drive, no improvement.

I borrowed a set of split fire coils. Still no improvement.

I'm still going to get new battery leads, but I don't think my problem is with earths at this point.

So I've been thinking.. Fuel pressure regulator? Leaky injector? Ignition signal from the ECU? CAS?

I'll check all those out next weekend. Anything else I can try?

Update!

Took the car to the parts store to pick up a new fuel pump. Only about 2k away. On the way back she back fired out the exhaust worse than I have ever seen before. Then stalled. I'm only 1/2k away from my house so I start it up and try to limp back. It only gets about 30m and stalls again. This time it won't start again.

Did the obvious: checked connections, battery, fuel, etc. This car is really starting to frustrate me.

Any advice?

Boost leak?? Afm??

No boost leaks, I used one of those pressurized boost leak testers. I will read the FSM an do some diagnostic on the AFMs. Although I have cleaned and resoldered them already.

Got it started and limped back home. I swapped in the new fuel pump. It runs way better. Probably another 5-10kw, but it still misses.

The service manual says the MAF signal wire should be 1.1v at idle. Mine jumps around from 0.92-0.98v. Loom wiring looks good. Are they stuffed?

Stock ECU. I have reset it. No codes either. How do I check my injectors? Just pull them out and look? (Is that a stupid question?>_<

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Thanks Duncan, that's the best info I've read. Furthermore after learning about the PCM programming side controlling the factory boost solenoid, the purpose of the solenoid is to "bleed" boost when pin 25 is earthed, thus allowing spring pressure in the wastegate actuator to overcome diaphragm boost pressure, thus closing or reducing the position of the wastegate flap creating more boost as the turbo is able to spin faster. It's pretty cool to see a designated Pill to do exactly this, would have liked to have seen it with a tiny filter over the end for those moments in vacuum.  The constant bleed pill has now been removed completely from the system and solenoid boost control has been restored once again.   Case closed 😂
    • The wideband reading is meaningless if it's not running. Why are you using shitty old sidefeeds on any engine, let alone a Neo? What manifold and fuel rail are you using to achieve that? Beyond that, can't help you with AEM stuff as I've never been their ECU/CAS combo.
    • Manual boost controllers (where a little of the boost was bled off) were quite common back in the day, because they were cheap and easy. Generally they had a manual adjustment screw rather than being fixed like yours. Down side is they always bleed boost, not just when you want them to so an electronic boost controller that uses a solenoid will have less lag.
    • Hello , im new here and i have A31 home build  RB25det neo stock eng / turbo  aem ems 2 blue connector  aem 3.5 map aem cas disk aem wideband connected to ecu  355 lph pump 550 nismo yellow injectors side feed aftermarket regulator  and won’t start with base aem tuner basic tune eventually flipped cas 180 degree so it triggers on correct stroke not in exhaust cycle  Now it won’t start Wideband reads 10 and 11 at lowest fuel setting  and will share calibrations soon for aem tuner i think something is wrong in aem tuner    please if you have any information, am very grateful         
    • Legend. I ended up finding the facebook account of the owner of the first car i sent but sadly he deactivated the account. I think you’re right in saying it’s some sort of well done custom job. Really appreciate your help anyways.
×
×
  • Create New...