Hi I have recently fitted a completely rebuilt jap spec bigport 4age to my ke20 and I am having trouble with it missing or surging, It happens once the revs get to about 3,200 but only under heavy acceleration, slow acceleration is fine, timing is set properly, it has a good strong spark to all cylinders, the engine check light isn't throwing and codes other than the speed sensor code when I'm cruising at 3,500rpm in 5th (I don't have a speed sensor), the TPS is set correctly, map sensor seams to be working fine, at idle if you give it a quick rev it blows a tiny bit of black smoke, could be running rich? Or maybe just cause its such a sudden rev the ECU doesn't respond quite quick enough? I am running 98 octane, any ideas to help me out its driving me crazy

Thanks heaps

Fastest solution would come from a dyno run with a air/fuel graph.

 

Most educational solution would be from an oxy sensor and an AFmeter. That way you can spend a couple of weeks watching it in all driving situations and work out when it is or isn't rich.

 

You could hunt down the resistances of the sensors involved and check them with a multimeter, that will clear any suspects there.

 

The actual solution from the diagnostics might be harder, a sensor packing up, a poor fuel map, a fuel problem... If the ECU wasn't responding quick enough it would be lean on booting it, rich on lifting off, but I doubt that is the problem. More likely, the ECU reads the quick boot and is programmed to instantly richen it as much as possible. Maybe they need a programmable ECU to run really well.

Ok I have tested lots of stuff and it all seems to be working fine but it still misses, map sensor working fuel pressure is 2.8 bar what ever that is in imperial, the coolant temp sensor reads a resistance of 1.88 when the engine was cold and had not been run all day, then I started the car and it dropped 1 decimal ever 1-2 seconds, by the time is gets to 0 the water is about 40°c, the 2 wires to the temp sensor read, brown wire 0-0.2 resistance with the engine running and the green wire 5-5.25 volts with the engine running, do those readings sound right? If yes than what the hell is going on its doing my head in, could it the the ECU?

Plugs are new too I had to clean all the carbon off but they're fine, ignition system is fine, just running really really rich

One of those is the cold start injector sensor, so maybe that is running it rich.

 

https://www.toymods.org.au/forums/tech-conversions/33404-4age-coolant-temp-sensor-s.html

 

I've got an AE86 manual, but it only lists the resistances for the gauge sender unit, and my Altezza 3SGE manual has similar voltages to what you quoted, but it only has one sensor.

 

The specs for that temp sensor unit are probably online somewhere, if you know who made it.

Edited January 18, 201313 yr by altezzaclub

A mechanic who deals with this sort of stuff said that seemeed right and he will look at it next week and try to sort it out but I'm trying to fix it my self to save a big bill if I can

Any other ideas