Engine troubleshooting - what was wrong with my engine

Опубликовано: 16 Октябрь 2024
на канале: driving 4 answers

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Here is the link you need that I keep mentioning in the video: http://www.driving4answers.com/troubl...

Engines often don't run, especially after a tear down and rebuild. After I rebuilt my engine I couldn't get it to run right. There was misfiring and low power. This called for some step by step engine troubleshooting to find out what is wrong with my engine.

I realized this might be useful for a lot of people, especially with older engines, when they decided to troubleshoot their engine on their own. So here are some of the first things to look at when trying to figure out what's wrong with your engine:

Spark plugs
Spark plugs are great bang-for-back item in terms of diagnosis. They are super easy to remove and can tell you a lot about what might be wrong with your internal combustion bundle of joy.
In the link above there's little chart that can help you diagnose your spark plugs in case they don't look normal.

Fuel pressure
Fuel pressure can go out of spec because of any of the following: leaky injector o-rings, faulty injectors, dying fuel pump. Fuel pressure is also relatively easy to check. Fuel pressure for a 4age 16v should be 38 to 44 psi (265-304 kPa).
In the link above there are detailed instruction on how to check your fuel pressure on a Toyota 4AGE 16v

Air Flow meter
If everything checks out fuel wise I would take a look at the Airflow meter next. Checking it out is super simple, just rip out a multi-meter and measure the resistances. Make sure you are measuring using the correct resistance setting and also make sure you're multimeter is zeroed in case it's an analog one. Zero it in by touching the probes together and turning the knob until the dial hits zero. Zero in for the resistance setting you will be using. In the link above are workshop manual pages with detailed airflow meter specs to look for when measuring on your Toyota 4age 16v.

Throttle body position sensor (TPS)
Same deal as the Air flow meter. Get out the multimeter and test. You need a thickness gauge for this part too. This can be done on the car but its a lot easier if you actually take the throttle body off.
In the link above are workshop manual pages with detailed TPS specs to look for when measuring on your Toyota 4age 16v.

Ignition timing
Correct ignition timing is critical for making power and running right. ignition timing determines when spark occurs in relation to the position of the piston. In case its wrong you can have incomplete combustion, knocking and other stuff you don't want. Ignition timing is checked with a timing light. In case of the 4a-ge the procedure is as follows:
Make sure engine is at operating temperature
Attach timing light (watch video below to see how)
Connect diagnostic plugs E1 and T
Fire up engine
Point timing light at timing marks.
Timing needs to be 10 degrees before top dead center (BDTC) i.e. advanced for the 4A-GE 16v

Cam timing
Cam timing is not to be confused with igniton timing. Cam timing determines the position of your camshafts in relation to the position of your pistons. How do you check cam timing? Easy. Camshaft pulleys and crankshaft pulleys all have TDC marks on them that need to align with TDC marks on things right behind them. Cam pulleys align against the backing plate, crankshaft pulley aligns with the bottom timing cover (corolla 4age) or with the pointer needle (MR2 4age) and the timing belt sprocket aligns with a mark on the oil pump (you need to remove crank pulley and timing cover to see this).
Lift up your car, remove the passanger side-rear wheel, remove the top timing cover, rotate engine by hand until crank pulley is at tdc. In case any of your cam timing pulleys is not at tdc your cam timing is off and that will make your engine run like poop.

What was wrong in my case?
MY timing belt skipped a tooth. How did I find out? By looking at my cam timing. When I put my crank pulley at TDC neither off my cam pulleys was at TDC. This clearly told me something was off here.
What failed? A 30 year old tensioner pulley spring couldn't do its job. I could not tighten the tensioner pulley sufficiently and my belt would skipped a tooth. I tried it twice and twice it skipped. Solution? Got rid of it, pushed tensioner pulley in manually and tightened it down. Worked like a charm. A whole nother car now.
Yay! Some sort of road trip needs to happen soon.

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