2002 MR2 Roadster. 1ZZ-FE, misfire and low idle when hot.

So i ran a backpressure test with the correct tool. 0 psi backpressure, all connections were tight and secure and the guage moves under snap throttle but not very high. I have however just pulled an ignition coil and plugged it into a spark tester (dont know the right name), the spark was wispy thin and mostly orange in colour. Could this be a weak spark?

Ok, no restriction then. Watch one of Paul's videos on spark testing with a test light.

Nissan Technician

kamiwolf0893 wrote: The precats look like one main cat from a glance but with the heat shield removed, each bank has its own precat. There's a main catalyst further down

Good to know! My mistake.

As Tutti suggested do a spark test with incandescent light when engine is misfiring. You can also do a quick cylinder drop test by unplugging the coils 1 by 1. Think it's important to find direction here. Do you have a scope?

Unfortunately I don't have a scope. I tried unplugging the coils one at a time but the car just shuts off. So I lifted them off the spark plug one by one, theyre all firing. I tried putting the ignition coils in the freezer for 30 minutes and reinstalling them. With the engine still somewhat warm this temporarily fixed the misfire. The spark also appeared stronger on my test tool. I couldnt find the specific video you were talking about but did find a tutorial on how to use the adjustable spark tester. Tried multiple ground points too just incase and still a very weak spark. I'll try it again under incandescent light and see if its any clearer. The car ran fine from a cold start this morning but started misfiring again when it reached operating temperature, what would you recommend at this point?

A spark tester is fine that's what they're made for right I'll post a video where Paul is testing spark with an incandescent test light. It's not a COP design but principle is the same. Watch around 7 minutes into the video.
A scope would've been nice. Makes life a lot easier. Good investment if you ask me.
Just to be clear you've done all your testing when the engine runs rough or misfires right? I assume there are no misfire counters in your datalist. PIDS are probably limited.

So I lifted them off the spark plug one by one, theyre all firing.

Did your engine rpm change on all cylinders when lifting the coils?

Yeah, all tests done with the engine hot. Have checked compression also, that's 180psi across all cylinders. I'll check that video out, thanks for linking me engine rpm was affected whilst lifting each coil. Definitely no dead ones, I noticed the resistance for the primary (i think) circuit had dropped a few thousand ohms when the engine was hot. Am not sure if that indicates a short in the coil? Difficult to really tell whats going on with the multimeter as there isn't any service specs to reference to. Also there's no PID for cylinder misfire count, it'd be really useful to have that. It runs fairly decent on a cold start, sometimes misfires and sometimes doesn't. It's worse on hot days, and much worse when the engine has been running at higher speeds (i.e the highway), feels almost like a dead miss. Pulled coils one by one whilst it was like this and they all had equal effect on the engine.

Also, do you have a link for an affordable scope? Probably only gonna use it on occasion if I do get one. Can see why you say it's a useful tool

You can't get to primary on these coils. Transistor's inside the coil. You have a power, ground, trigger and feedback signal. Personally I don't measure secondary resistance. Not saying you can't. But I like to see the voltage pattern and current waveform on my scope. Voltage might be tricky with a paddle probe cause some of these coils are highly insulated.
Anyways. Let's make a list to keep track here.
*good spark (still needs to be verified)
*fuel pressure
*compression
*intake vacuum
*no backpressure
*O2 operation and working cat
*ECT, MAF, IAT...
*Injectors
*Mechanical timing
*Vacuum leaks
*EVAP
*PCV
You've gone through all this right? Quite a lot Feel bad for you man.

Is your scan tool bidirectional? If so perform an actuator test for the VVT. I'd like to know if it stalls. You can also unplug your OCV see what it does. Normally nothing. I've seen maybe 1 of these engines that throw a P1349 and eventually changed the valve or cam phaser. These can stick. But don't change anything so far.

kamiwolf0893 wrote: Also, do you have a link for an affordable scope? Probably only gonna use it on occasion if I do get one. Can see why you say it's a useful tool

You can check out our diagnostic tool section on the forum. Lots of info. I hear a lot of positive feedback on the Uscope. It's only 1 channel but very handy.

This is the basic kit. There's also a master kit.

www.aeswave.com/uScope-Basic-Kit-p9621.html

So the only thing I haven't checked in that list is fuel pressure so far, had replaced the EVAP solenoid, it's not the original OEM part and has smaller ports but never considered that to be a problem. Made sure it was sealed anyway and it fits the Toyota plug, it was meant to be an EVAP solenoid for the Celica with the same engine. Have sprayed water in various places on the engine bay and sealed all vacuum leaks I can find, used hose clamps to make sure all pipes are sealed tight. Tried plugging all vacuum hoses and this made no difference. Am not entirely sure why plugging the PCV hose made my fuel trims positive. Although the engine still runs rough like this. Have an oil catch can installed with bronze filter, I don't think it's sucking up oil vapors although I could be wrong. Had fitted a new PCV valve just as a what-if measure and tried the old one also, they've made no difference. Injectors are new, the engine runs different with these. They were supposedly brand new Denso injectors, from inspection they look fine also. Resistance looks good also and within spec. Tested the MAF for resistance, just within resistance spec. I always wondered about the engine temp sensor, although it gives consistent sensible readings on the car computer. The engine is scalding hot to the touch but I assume all engines are like that. Operating temp it goes no higher than 93c. Had checked the mechanical timing the other day, looks to be in spec. Unfortunately my scan tool is my laptop with an elm 327 cable, EOBD Facile doesn't have bidirection control either, I remember the car threw a 4 digit error code probably 8 months ago but honestly can't remember what this code was. I was thinking of checking the VVT filter's condition, I've seen it's possible to clean it with some brake clean. Have cleaned the idle air control valve a few months ago too and installed a new OEM gasket in that. Would have thought I'd have hit the nail on the head by now so to speak. Have made a smoke tester out of a fog machine, couldn't see any smoke leaking out anywhere, have replaced all brake servo rubber lines and clamped them, tested them by spraying water on them, all new EVAP rubber hoses too. Checked all ground points and cleaned them up too. Feel like this is an ignition related misfire but can't be entirely sure. I'll have a look for a decent scan tool, although I'm not sure what PID's Toyota has that I'm not getting on the EOBD Facile.

OCV?

You've done an awful lot of work on this car. Actually I was just making a list to keep track of everything. Keeps me from scrolling through posts.
I would be careful with changing parts that are not original or Chinese crap. You could be chasing your tail.
OCV is the oil control valve that regulates the oil flow to the cam phaser on the intake.

Ah okay. Yeah I know, it's gotten to the point of frustration now. Have got another car with known good coils I can test my spark tester tool on. It definitely looked weak and looked stronger with a cold ignition coil. Not by much but a little. I'll check that valve out, it's in a bit of an awkward place in the engine bay but I may be able to reach the bolt holding it in. I know it's one thing I haven't checked, had ran some flush in the oil when I got the car before putting some decent quality oil in. The car's felt wheezy for a while and has a bunch of hesitation when I push the throttle to the floor. The throttle is just cable driven, have tried an idle relearn as well, that didn't help either. Ignition timing is bouncing around at idle as well as engine load. It can't harm to check the VVT solenoid anyway.

I fixed the issue with the misfiring and low idle. It turned out to be bad ignition coils. Got a new set of Hella branded ones today and the car runs a whole load better. The only problem is now is that I still have rich fuel trims and a slight roughness to the idle quality. Removing the PCV hose from the valve and plugging it brought the trims back to normal, although I know this isn't a practical way to run the engine. What also helped with trims was undoing the oil filler cap. The blowby coming from the oil filler cap feels excessive, although I'm certain whether it is or not. Where should I go from here? could it be valve stem seals? I tested compression and got 180-185 psi a cylinder so surely not stuck piston rings? car doesn't seem to burn oil although the oil I drained out after 6 months smelt of fuel. Thanks, Adam

Great! Another example of covering the basics first is So you did an oil change after replacing the coils? Keep in mind that the engine was dumping fuel in the exhaust but also some of it in the oil pan. PCV sucks up the fuel vapors causing a richer mixture.

I haven't changed the oil yet no. Although last week I put the best quality oil in I could find and haven't driven the car more than probably 50 miles since, new oil filter too. The misfire was nearly gone earlier when it was warm outside, but now it's maybe a couple of degrees celcius outside the car is shaking quite badly. It's slightly better when the engine warms up, very strange how temperature affects this problem

So I plugged the PCV hose again today and it appears that the trims aren't changing now. However I did test my o2 sensor heaters (had seen scannerdanner test them) and noticed I got no reading from the heater wires. Tried in various configs and couldn't seem to get any reading. Tried the sensor out the manifold, key on engine off so the sensor got live power to the heater (checked there was a feed to the o2 heater element by this point). So now I'm thinking perhaps the o2 sensors are giving a bad reading. Which would explain why taking them out the manifold, putting them back in affected the misfire. Is it possible to just get any decent branded 4 wire sensor and splice it in to the original wiring? I can see there's denso sensors available for my car but they're quite pricey. Many thanks, Adam