Trying to hunt down the problem

4

4everun22

New member
I've had my 4runner for over a year now and my problem is getting worse every day. Ever since I got it the first problem is the long cranking. I've researched and replaced parts. No luck. Not a huge issue, seems to be normal to cranks 4 or 5 times. But then it started to have a multiple cylinder random misfire. P0300 everytime I start it for 5 to 15 seconds then it runs great. No other codes but this one. I've replaced fuel pump, fuel filter, injectors, pressure regulator, plugs, wires, pcv, both o2 sensors, cleaned every inch of my intake system and sensors with all new gaskets, checked for vacuum leaks and burnt wires. Still having the problem. I'm at a loss. My mechanic friend told me it could be the timing? Jumped a tooth and after it goes into a closed loop it corrects itself? Not sure if this would cause this problem but I have all the parts to do this I've just been dreading doing it myself. If anyone has any input please share. Thanks!
 
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Symptoms may include:
the engine may be harder to start
the engine may stumble / stumble, and/or hesitate
other symptoms may also be present
Causes
A code P0300 may mean that one or more of the following has happened:

Faulty spark plugs or wires
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector(s)
Burned exhaust valve
Faulty catalytic converter(s)
Stuck/blocked EGR valve / passages
Faulty camshaft position sensor
Defective computer

Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.
 
MStudt said:
Symptoms may include:
the engine may be harder to start
the engine may stumble / stumble, and/or hesitate
other symptoms may also be present
Causes
A code P0300 may mean that one or more of the following has happened:

Faulty spark plugs or wires
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector(s)
Burned exhaust valve
Faulty catalytic converter(s)
Stuck/blocked EGR valve / passages
Faulty camshaft position sensor
Defective computer

Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.
Click to expand...


All that has been checked or replaced. Also there is no egr
 
4everun22 said:
I've had my 4runner for over a year now and my problem is getting worse every day. Ever since I got it the first problem is the long cranking. I've researched and replaced parts. No luck. Not a huge issue, seems to be normal to cranks 4 or 5 times. But then it started to have a multiple cylinder random misfire. P0300 everytime I start it for 5 to 15 seconds then it runs great. No other codes but this one. I've replaced fuel pump, fuel filter, injectors, pressure regulator, plugs, wires, pcv, both o2 sensors, cleaned every inch of my intake system and sensors with all new gaskets, checked for vacuum leaks and burnt wires. Still having the problem. I'm at a loss. My mechanic friend told me it could be the timing? Jumped a tooth and after it goes into a closed loop it corrects itself? Not sure if this would cause this problem but I have all the parts to do this I've just been dreading doing it myself. If anyone has any input please share. Thanks!
Click to expand...

I can't think of much you haven't done but your friend isn't much of a mechanic. Skipping a tooth affects valve timing, not ignition timing. The ECM controls ignition timing but has no way to affect valve timing. What he said makes no sense.

If you are worried about valve timing you can pull back the upper cover (slide the coolant hose clamp back, don't take off hose) and check without dismantling everything. Set crank pulley to 0° and then check marks on cam pulleys.

Since you are out of options I'd say do a compression check. Might point to something. I don't see where you have done anything to the cam and crank position sensors. Those can definitely mess up starting if there is a problem.
 
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I had this problem on a different 4runner and it ended up being a coil pack. Replaced it with a toyota one, all is well. The one in there was brand new but from a parts store.
 
TheDurk said:
I can't think of much you haven't done but your friend isn't much of a mechanic. Skipping a tooth affects valve timing, not ignition timing. The ECM controls ignition timing but has no way to affect valve timing. What he said makes no sense.

If you are worried about valve timing you can pull back the upper cover (slide the coolant hose clamp back, don't take off hose) and check without dismantling everything. Set crank pulley to 0° and then check marks on cam pulleys.

Since you are out of options I'd say do a compression check. Might point to something. I don't see where you have done anything to the cam and crank position sensors. Those can definitely mess up starting if there is a problem.
Click to expand...

Exactly what I said and asked. He was confident it wasn't the crank sensor. I tested the resistance but can't find the specs anywhere. It was 2.27 which seemed faulty to me but again idk what is supposed to be. Cam sensor was 1.14ish I don't remember. That was what I was going to do next
 
4everun22 said:
I've tested them and they are working. Plus wouldn't it effect certain cylinders not all? Hard to believe all 3 went out
Click to expand...

Yeah, hard to believe all three went out, but not an impossibility! How did you test them? resistance measurements on coils aren't always 100% as a leak might be occurring at higher voltages than what you're testing at.

Ignition control module? Do you have access to an oscilloscope to check the signal?
 
I_bRAD said:
Yeah, hard to believe all three went out, but not an impossibility! How did you test them? resistance measurements on coils aren't always 100% as a leak might be occurring at higher voltages than what you're testing at.

Ignition control module? Do you have access to an oscilloscope to check the signal?
Click to expand...

A coil failure would give me different codes referring to the cylinders attached. This had been a year with nothing but ransom multiple cylinder misfire p0300
 
How does it start when the truck is at operating temp? Could be a long shot but you could have a faulty coolant temp sensor. Just an idea.
 
TheDurk said:
I can't think of much you haven't done but your friend isn't much of a mechanic. Skipping a tooth affects valve timing, not ignition timing. The ECM controls ignition timing but has no way to affect valve timing. What he said makes no sense.

If you are worried about valve timing you can pull back the upper cover (slide the coolant hose clamp back, don't take off hose) and check without dismantling everything. Set crank pulley to 0° and then check marks on cam pulleys.

Since you are out of options I'd say do a compression check. Might point to something. I don't see where you have done anything to the cam and crank position sensors. Those can definitely mess up starting if there is a problem.
Click to expand...

I've actually owned two vehicles over the years that had valve timing issues (an old Mazda 323 with a stripped keyway on the crank, and a 2nd Gen 4Runner) and both of those got harder to start when the problem started happening. There were other symptoms as well, such as reduced power and horrible fuel economy.

Since the timing belt on 3rd Gens lasts so long I'd say it's a long shot that that's what the problem is here, but I'd definitely pull the timing belt cover, bring the crank around to the TDC mark, and see where the pulleys are at. It's too easy to rule this out and then move on to something else.

The compression check will fail if the valve timing is off enough, so I'd want to make sure it's right before pulling plugs.
 
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