2JZ-GE misfire/stutter - gets worse in the rain

[70XIN]

Hey guys,

Girlfriends' JZA80 N/A supra has a little annoying problem. Basically, the car has a horrible hesitation/stutter if you try and keep it at a constant amount of revs for more than a few seconds. Also, if you accelerate (for example, in 4th gear from 2000revs) it will stutter and complain for a bit anywhere from 2000-3500, then take off fine.

Driving around the hills the car is perfect, cruising is not. She also thinks the problem might be getting worse in the rain.

Parts replaced over the last 6 months:
- Alternator (used)
- Battery
- Iridium plugs were replaced with cheapo coppers (this appeared to make things better, for a bit)
- Ignition leads
- Fuel pump and filter
- Other used O2 sensors were tested

Ignition timing is definitely right (confirmed with timing gun), and shorting the diagnostic terminals doesn't flash any error codes.

Any help or ideas would be great, thanks Seamus.

[70XIN]

Also, the car has 135,000km's, and had it's full major service a year or two back.

[cambelt]

Hi
Sounds like rotor button or cap , seen a few denso rotors fail lately
Dave

[The Godfather]

could be as simple as a blocked fuel filter maybe... just a suggestion, maybe a bad batch of fuel, or a shitty servo she keeps going to and is constantly getting bad fuel

[LeeRoy]

Hi
Sounds like rotor button or cap , seen a few denso rotors fail lately
Dave

I vote this.

High humidity (eg rain) will make it easier for a spark to jump and this can cause misfires etc.

If you accelerate in 4th at low RPM this is creates high load, and it's more lilely to misfire when under such load.

[70XIN]

Sorry for the late reply, i've been waiting for parts

Unfortunately it's still not fixed. We have tried and installed a new dizzy cap, rotor, and ignition leads. Spark plugs looked absolutely perfect (like new) so i left them alone.

We also found the radiator cap had shat itself and the spring/seal etc were nowhere to be seen.

Any thoughts anyone?

[70XIN]

Oh and the car idles fairly low (700ish .. maybe less), and still stutters on low "cruise" throttle or if you immediately get on it. .. still revs to redline like a champ though once it's done hiccuping around ~3500rpm.

[2jzhilux]

I have converted my hilux daily to 2jzge and it idles quite low as well, almost to the point where it wants to stall although i havent hooked up the ELS wire yet so that should help, maybe check to see if you have power to the els pin of the ecu when the demister/taillights are turned on.

I wonder if its possible it has a small leak in the cooling system into the combustion chamber?
Maybe try a cylinder leakage test.
Have you also checked the map sensor hose is on the correct port, i fucked this up once and it took a while to work it out.

[Wizzard]

Also do you have access to a friend with a 2JZ-GE supra, try swapping the ecu to test that out. Also try swapping the igniter to rule that out.

[George]

70XIN
have you tried another ignition coil? I would vote for inspection with oscilloscope and capacitive probe, this would show everything ignition-related.

Personally I believe that the problem is around ignition system, but I would suggest to check fuel system just for the case. One of the first things to do is to check fuel pressure before injectors. The test must be performed under heavy load (which is the main trick), then if your pressure drops noticeably - that's it.

Another test is to make the engine enter extremely rich failsafe - disconnect map/maf (haven't seen non-vvti 2jz's so I'm not sure what you have there). Intake air leak and sensor malfunction may cause the engine to run lean. Extreme values of long-time fuel trim (if you have access to obd1 scanner) would point to this kind of problem. Also check vacuum line from intake manifold to fuel pressure regulator.