I have an NA-T 95 SC300. It has a misfire at idle and throughout the RPM range. I'm having trouble locating the cause of it.
It has new injectors, plugs, wires, cap, rotor, and I just smoke tested it for vacuum leaks and repaired the two I found. There is currently no CEL's on. I have the 2 main 02 Sensors wired up fine without the 3rd. Other than that it's your basic NA-T setup. Does anyone have any tips on sensors or other areas I could check. The head and headgasket only have about 2500 miles on them and a compression test showed good numbers across the board. The misfire only started just recently.

 

Are you using stock ECU?

 

As far as I know it's a stock ECU unless the previous owner swapped it. I'll look into checking that out.
I plan on doing a compression test in the morning. The head is new with under 2000 miles on it so I don't believe it could be the issue and it drives well. I want to rule it out however and it's the only thing I can think of.

 

Compression test showed good but I noticed when I pulled my #6 plug that it looked brand new. I tested the injector with a noid light and received lights and received spark from the #6 wire. Looking like it's a bad injector even though they only have a few miles on them. Gonna order a replacement and I'll update.

 

Have you checked your bov? Put your hand firmly over the valve and see if it sucks your hand in at all.

EDIT: didn't read last comment. Sorry.

 

I did check the BOV, the spring appears to have good pressure thanks!

 

have you checked for vacuum leaks?

christian

 

Yes. I've smoke tested it and only found two leaks. An injector, and the turbo inlet. I fixed both. The injector just had a crack in the gasket.

 

if its on the stock ecu try resetting the ecu.

 

I have reset the ECU a few times now for different reasons. It hasn't helped.

I replaced the injector and it ran great fro 5 seconds then started doing the same thing again. Now I've noticed if I mess with the #6 injector wiring while running the car keeps dying, like it's grounding out. I'm trying to find a wiring diagram to troubleshoot from there.

 

This may be a pretty basic question, but how do you reset your ECU? Is your idling intermittent? I am having idling issues as well, but mine are intermittent. I have tried to trouble shoot this and had my mechanic replace way too many components for this to be continuing. So far I've replace the ignition coil, wires and plugs. I also replaced my MAS airflow sensor with a used one and started getting a check engine light for that around when my idling problems started. Could this have anything to do with 02 sensors going bad? My sister was having idling issues and the 02 sensors were blowing codes. When she had them replaced she said that fixed the issue. Any thoughts?

 

I'd suspect the o2 sensors.

Resetting the ECU is very simple. Disconnect the negative battery terminal and leave it for 20 or so minutes. Plug it back in.

 

I just take it off for like 20 seconds and that does the trick.

Canman44 start a thread and be as detailed as possible sc300 or 400, mileage, previous maintenance, like have the o2's ever been changed that you know and issues you are having. whats wrong with the idle exactly. chances are we can point you to what the problem is faster than a mechanic as we deal with these cars constantly and know their trouble areas.

 

Thanks for the suggestion. I'll start a new thread on this one and see if anyone has had this type of issue due to 02 sensors. Didn't mean to hijack this one.