Title is not clear. What I mean is my 2001 Camry 5SFE has a random cylinder misfire. Research online suggests checking the function of many things that should, in theory, have their own code if there is a problem with them such as O2 sensor, fuel pump etc. Most sources that describe various causes of random cylinder misfire don't start with the obvious....do you even have a code saying the component is faulty? My question is do these codes often not appear and so I should be checking resistance, pressures etc to see if they are causing the Random Misfire code?

My OBD did display, briefly, something about emissions but there was no actual code with that. It's gone and I can't find it?? Now the random cylinder misfire is on.

117K miles on my Camry. Light was blinking a block from home so I made it to my driveway. I've replaced: Valve cover gasket and spark tube gaskets, Intake manifold gasket, EGR gasket, throttle body gasket, cleaned carbon off throttle body, fuel injectors, ignition coils, spark plugs, wires. I cleaned carbon off of intake manifold plenum, I scoped into the engine and saw very little carbon, I applied vacuum to EGR valve and that stalled engine so thats good. I removed fuel filter and added gas, shook it, seems fine no crud comes out, clean gas flows straight through etc.

I need to check MAP sensor resistance, fuel pressure (but again....shouldn't I have codes hinting this may be an issue?)
I did cursory inspection of vacuum lines and need to do this better.
I did not do compression test yet, waiting for a solid long-reach fitting to get down in there. I will do combustion gas test at radiator which does not bubble at all while car is running btw.
Any thoughts are much appreciated. I know very little about cars btw, this has all been youtube and research online.
Thank you everyone!

 

The light blinking means there is a gross misfire that will damage the emissions converter. This misfire is causing the fuel/air ratio to be too rich and this extra fuel now burning will overheat the converter. Don't drive the car when the light is blinking.

What were the specific codes? Did any of the misfire codes specify a cylinder number? If specific codes state with that cylinder.

Yes, you need to check the individual systems for pressure, resistance, etc.

Many systems have their own code but some do not. There is no code for low/high fuel pressure, fuel flow. bad fuel pump, injector problems. The fuel system is monitored indirectly via the A/F-O/2 sensors that respond to fuel mixture. Same with injectors and ign coils. An ign misfire caused by ign problems can result in the misfire code(s). Sometimes there is a misfire code(s) and also other codes.

MAP sensor itself seldom fails but do check the vacuum hose and connection to engine. Compression seldom is a problem. A blown head gasket can cause issues but misfire may not be one of this. Try to remember if the you needed to add coolant on a regular basis.

Common issues for misfire are are bad spark plug(s), plug wire(s), ign coil, injector stuck open/leaking. Sometimes there is a bad A/F-O2 sensor that for some reason doesn't set a code for this sensor.

A scanner you can provide get real time info for the engine various sensors which might help in diagnosis.

 

Thanks for the reply and sorry for the delay...dealing with various issues on top of the Camry.
Codes have cleared but I question it. I made a newbie mistake initially and did not manually clear them after I did all the major stuff. I continued to tinker, unplugging sensors to inspect and seeing new codes appear related to MAP and intake air sensor. Numerous start ups, long idles, head scratching. Eventually I wised up and cleared them manually. Idling in driveway and then test drives up/down the street with OBD hooked up resulted in Cylinder 1 misfire, then Cylinder 2 misfire and then random Misfire codes (on the OBD but no engine light??) I then drove around with a fuel pressure gauge hooked up and noted it was about 50 even when floored it. And it held at 45 for 15 minutes after I cut engine. Then all codes disappeared and I got "No engine DTCs" or something. But I never cleared them so is that normal? Was my car just working out kinks from previous malfunction and that's why the misfire returned, only to disappear on its own? We'll see if it holds. Greatly appreciate the help!

 

A misfire and blinking check light is serious as it can cause the converter to burn up. As such doubt the system is just working things out.

There can be a misfire then immediate check light, then everything goes back to normal. If the chassis wiring to the ign coils is OK, would look at ign coils starting to fail.

The fuel pressure should be 44-50 psi engine running. Engine off fuel pressure should be 21 psi or more after 5 minutes. Your readings indicate fuel system is OK. , .

The computer is constantly running self checks on systems. For most systems if the problem goes away and the self check passes the codes will go away also.

Speculating the ign coils cold be bad. Perhaps now reacting engine heat, who knows.

Suggest as stated look for wiring issues, arcing of the coils bodies, cracks, ign wire issues, issues, etc.

Check resistance between secondary high tension terminals of the coils. Should be 9.7-16.7K ohms cold and 12.4-19.6K ohms hot.