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Marty, European Car Expert
Category: UK Car
Satisfied Customers: 407
Experience:  ASE & Bosch Certified Master Tech. Over 30 years experience.
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I have misfire on my 2003 lexus is300, 280000km I've just

Customer Question

I have misfire on my 2003 lexus is300
JA: How many miles are on the car? Is it a steady misfire? Or random?
Customer: 280000km I've just changed a my own head gasket, spark plugs, coils and wires Im searching the www if the intake cam could be off a tooth
JA: Are you fixing your GS300 yourself? What have you tried so far?
Customer: First we changed the head gasket and radiator.
JA: Anything else you want the mechanic to know before I connect you?
Customer: The head was machined
Submitted: 1 year ago.
Category: UK Car
Expert:  Greg replied 1 year ago.

Hi, I'm Greg (Indy-Tech).
Welcome to JustAnswer. I'm reviewing your question now, and will post back with your reply ASAP.
Rgds Greg.

Expert:  Greg replied 1 year ago.

Please check for any malfunction codes .if the timing is off we will see misfire codes cam / crank codes etc.

Get back to me with any codes if found .


Customer: replied 1 year ago.
When using my obd adapter and torque App, I can read and clean the fault codes.
There is always only one fault code at a time but not always the same:
P0302 misfire cyl no2
P0303 misfire cyl no3
P0305 misfire cyl no5Once I had a flashing CEL, it flashed 14times making a pause, than flashing again.I had to change my head gasket in August.
I changed plugs, coils and wires in mid September (course of misfire).Now im not sure if its the injectors or the vvti or timing belt off
Expert:  Greg replied 1 year ago.

Make . model and engine please and how many miles on the engine .

Why was the head gasket replaced what problem was you having .

Rgds Greg

Customer: replied 1 year ago.
Its a 2003 Lexus IS300 with the 2JZ-GE engine.
275000km that about 170000milesThe head gasket had to be replaced because cyl no5 blew exhaust gas in the waterchannels (leakdown test) and let the old radiator "explode". I've downloaded the needed toyota rapair manuals to remove the head. I had the head machined to be flat again.
After the reinstall with Reinz gasket and bolts the 2JZ-GE run fine for a couple of kilometers. After about 1500km the misfires started to get worse.
I replaced all coils wires and plugs. It run fine for a couple of days, but starting the engine in cold condition needed some extra cranking. After a few days the misfires began again.It misfires when cold and at idle, or when you stand on the brakes while the ATM is in "D". Reving over 2500rpms and no misfires appear. When engine is warm it runs mostly smooth.
Expert:  Greg replied 1 year ago.

Sounds like an intake manifold leak most likely coming from the brake booster check the vacuum line from intake to brake booster .

Then check all vacuum lines and intake manifold gasket for leaks .

check this then pleas eget back to me .

Rgds Greg

Customer: replied 1 year ago.
Hello,I couldn`t find any leaks in the vacuum and all the other intake pipes/manifolds.
I've pressurized the whole system wothout a leak.Anya other hints?
Expert:  Greg replied 1 year ago.

Do a head gasket test you may have a bad gasket .

Who did the repair dealer or service centre.


Customer: replied 1 year ago.
Head gasket test?!? Is thats another Name for "leak down test" or something else?!?I've changed the head gasket on my own, with a little help of my friends.
Downloaded all needed Toyota remove and installation .pdf-documents.Torqued everything to spec.
Used Reinz gasket and bolts, Denso plugs, ngk wires, ...
Expert:  Greg replied 1 year ago.

When you torqued the head how did you do it .

This is a very tricky issue .

Headgasket test by checking Co2 in the coolant .


Customer: replied 1 year ago.
We torqued the head in the correct order, with the correct torque, let em sit a few minutes and turned 90° twice.We also followed the documentation with order and torque and retorque for the camshafts.I do not have any bubbles in the cooling reservoir neither to much pressure on the Radiator hoses.All marks on the Timing belt are lined up, but the used belt feels a Little "loose"
Expert:  Greg replied 1 year ago.

Do a engine compression test and give me the readings for each cylinder .