Hello everyone! I did a valley cover job on a Lexus isf 2008

things I replaced
valve cover gaskets
spark plugs
coils
oil pressure sensor
Camshaft sensor b
new manifold gaskets
Injector fuel pressure pumps
injectors all 8 of them
knock sensors all of them

and I’m still getting cylinder 1 misfire

things I did

Switched The spark plug from cylinder 2 to 1 still misfire from cylinder 1

switched coils.. still misfire from cylinder 1

I got new injectors p0303 and p0300 went away after new injectors… still misfire from cylinder 1

compression test cylinder 1 was NOT low

all relays are good

I’m not getting any codes from other sensors..like MAF and sensors like that..

checked voltage and ohms on the injector connectors..all read the same..

checked each injector with my scanner by turning off and on.. they all where turning on and off but I notice that when turning fuel injector 1.. it didn’t feel no difference when being off or on compared to the other injectors .. as I would turn off the other injectors you can feel the engine die down but for some reason injector 1 did not feel like it was dying down the same as the other injectors

also when I got the car it was not misfiring and the car came to my shop with every single spark plug covered in oil.. and dried coolant everywhere around the valley cover and around the connectors of knock sensors and injectors car also came in with o2 sensor code and knock sensor codes.. which got fixed I’m not getting knock sensor codes and p0303 and p0300 anymore… ONLY p0301

yet once replacing all those parts the car is only throwing p0301 along with traction control light and it’s throwing it on limp mode.. and it doesn’t show no overheating.. but it sure does feel really hot after a few minutes of running.. owner did a water pump job not sure if he did a thermostat also.. but it doesnt show on the dash gauge that the temperature is rising.. stays around where it should be.
But either way car did not come in with cylinder 1 misfire and being on limp mode..

 

No one can help? Or give insight

 

Only things I'm seeing from reading around that haven't been tried are

• a full leak down test
• verifying there's not a fuel filter issue
• directly checking the O2 sensors as one being off could lead to an issue with fuel delivery though doubtful it would affect only one cylinder and that no code for it would be going off
• a crankshaft position sensor issue, though that too should be throwing a code if it's faulty
• verifying there's not a head gasket integrity issue

 

There are 16 injectors, not 8. Is the port injector on #1 known to be good? Was it damaged when the manifold was removed? If you put the manifold down with the port injectors in place, you could damage the pintle easily.

Here's the list of possible problem areas for P0301 with the most likely single cylinder issues highlighted:



The troubleshooting guide for this DTC in TIS is pretty detailed and covers all of the possibilities listed here. Also, it's possible the ECM is the problem. I just finished troubleshooting a GS F with a wideband O2 sensor issue, and the root cause is definitely the ECM.

 

Thank you for your response it really helps me narrow things!!.. I’m going to verify the highlighted points by this week. I’m aware there’s 16… and those are good I check them.. and they are doing what they are supposed to do..and for the o2.. car came in with that code already and it wasn’t throwing it on limp mode.. even with a o2 light on.. it shouldn’t be throwing it on limp.. if I’m correct?

 

Misfires put you in limp mode pretty instantly. AMHIK.