Hey, new to forum. Picked up a really clean low mile gs300. Has just one issue. I’ve changed all coils, plugs, wires. Cleaned throttle body, cleaned maf. Start car and no code, start driving, code pops up. What’s next step? Compression check? Vvt solinoid? Injectors? Any advise would be appreciated. Thanks

 

Ayyo, did you check the proper order for the spark plug wires? I just recently picked up a GS300 too, and it didn't run because it had the coil feed wires unplugged on two cylinders which gave me a P1300 code, which shut the fuel off. After I got that fixed, I had misfires on cylinders 1 and 5. I was confused, thought it might be the plugs and the wires, then realized that I was getting spark AND fuel. Thats when I realized that the cylinder 6 coil had a wire running to cylinder 5, and cylinder 2 coil had a wire running to cylinder one. Seriously. I put the cylinder 6 coil wire down to cylinder 1, and the Cylinder 2 coil wire to cylinder 5 (the way its supposed to be), and she ran like a dream. Just a little input, not sure if that is your problem or anything.

 

Read the code

 

I'll bite.
What code was it?

🍿

 

Codes were p0300, 301,302. Changed everything to new. Firing order 6-1,2-5,4-3 runs fine at idle , drive pops on

 

The P0301 code means that the cylinder 1 is misfiring or is randomly misfiring. Start by checking for intake leaks and if no leaks are found the next step is to replace the spark plugs on cylinder 1.
The P0302 code means that the cylinder 2 is misfiring or is randomly misfiring. Start by checking for intake leaks and if no leaks are found the next step is to replace the spark plugs on cylinder 2.

I seem to remember there being a common mistake people make when reassembling after replacing the coil wires on the 2JZ-GE. I would go over every step again. Generally, if a problem starts appearing after you've fixed something, the issue is human error at some point along the way.

 

We are missing a lot of information here. Why was the work performed? Was the car misfiring or having issues when purchased? Or only after replacing the plugs? If the later, I'd suspect coil connector damage or some other human error with going back together. If it was having issues before. Then yes, things like compression tests are in order.

Now going from checking for intake leaks to replacing spark plugs misses a great many steps.. In a perfect world with proper diagnosis one should be able to pinpoint the issue without replacing parts until it's solved. Besides, he stated he replaced the plugs already. For a P0300 code, I generally ignore the individual cylinder misfire codes unless there is a clear dead misfire on one or more. P0300 means that all cyls are misfiring from a common issue and it will eventually throw a P0301 2 3 4 5 and 6. So indeed, starting with the air box and back to the throttle, check for leaks, holes, disconnected lines, clamps etc. MAF seal/ cleanliness/ connection. Throttle cleanliness next in line. Once all is rechecked you would go into data from the sensors and fuel trims etc. But since the normal person doesn't have that capability, you'd go into cyl by cyl parts swapping and testing. Say for example cyl 1 is misfiring more than the others. You can swap the plug with another cyl to see if it follows the plug. If so you replace the plug. If not, you swap the coil, same thing, if the misfire moves you replace it, then the injector, and on and on with any cyl continually giving trouble. Doing a compression test is easier than injector swapping so I'd do that before going much farther.
However, if there is no clear one or two cyls misfiring and they are all having the symptom, you need to be looking at things common to all cylinders. Swapping parts between cyls wont make a difference. Fuel trims are necessary in this case. You have a MAF, Throttle, O2 sensors, and less important ones that all control how the engine works. All of these need to be monitored for their voltages and waveforms. We would need more information on whats happening with this car before being able to help. Way too many things cause misfires.

 

Thanks for all replies, but car was bought with the problem. It had multiple codes when I scanned it. Cleared codes, drove fine, rescanned it. Only 3 codes came back. 300,301,302. So I figured I just do a complete tuneup, changed oil, coils plugs, wires. The car does have a cold air intake (previous owner) don’t have stock box. I’ve checked the best I can for vacuum leaks and hoses. It does have a few places on intake and other places where they’ve capped off lines? Not sure about the cai?it doesn’t seem to have the same lines as stock box. Like stock box has 3-4 vacuum lines, cai has only 2? Car only has 134k and doesn’t leak or burn anything, seems to run fine at higher speeds. Only really noticed at stop or idle..I’ve driven car about 60-70 miles since replacing parts. No other codes but,300,301,302. Cylinder 1 is a plug, 2 is a coil. Everything is new. Should I try to swap plug and coil again?

 

And a little confused? Since 1-6 are connected and 2-5? Why do only 1,2 missfire? Seems if 1 missfire it would affect 6? And so forth?

 

valves out of adjustment? I read somewhere these engines should be checked at 120-140k miles.

 

What about vvt solinoid? How much resistance should it have? Best way to test it? I ordered another one just to be sure? Would bad vvt cause missfire? Also tested most injectors, around 13.7 across the board. So guess not injectors. Cam sensor? As far as vacuum leaks, if I tear down and pull intake , replace gaskets would that be the most likely place to leak?

 

Ok since last post. I now replaced all fuel injectors with denso. Replaced intake gaskets. Car starts on a dime and runs smooth. After coils, plugs, wires. Throttle body cleaning. I guess no1 injector was clogged. Resistance was fine, pulse was fine but seems to be gone now. Has power, good acceleration idles decent. But when we drove about 30 miles, check engine light flashed 3 times and went out? Didn’t effect car at all. Drove home. No check engine light on but scanned anyway. P0300,301? I don’t feel a miss or anything. Way better than before I changed everything. Possible it’s a hard stored code and my reader doesn’t really erase it? Just turns off light? I’m really confused. Thanks

 

Flashed? Then turned off?
Hmmm, I think that would freak me out worse than if it flashed then stayed lit.
If it "fixed itself" that sounds like possibky it's an electrical thing.

Perhaps clear all codes and see if it pops back up. I remember a guy at another forum a while back chasing a similar issue on a Honda engine and it was an electrical connector to one of the injectors that was the problem.

 

Ok this morning went out and started car. Fired right up.seems to idle fine. Check engine light came on, flashed and went out? I’m very confused. Car runs and drives great but not sure what’s going on and can it be trusted? I’ve tried my best to check wiring and leaks and I’m lost now. Any ideas? Thanks

 

Ok so I think I got miss fixed. Not sure? Car runs fine now but every once in a while it still will flash and go back out(check engine light)? And now another issue..... cooling fans run all the time. Checked relays, radiator never had switch installed just plug hanging there. So bought new switch. Removed plug and not much antifreeze came out? Some but didn’t pour out. Is that normal? And fans still run constantly.