Misfires, rough idle, shaking

Tiny
ACORN8
  • MEMBER
  • 2000 TOYOTA 4RUNNER
  • 3.4L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 314,000 MILES
Am I getting ripped off? Third Gen. Toyota 4Runner misfires, rough idle, shaking (details below)

My car was running just fine a year ago, when I went to a highly rated (Yelp and Google Maps reviews) independent shop because I noticed the red brake light on my dash coming on sometimes. They fixed it by tightening something, no charge, but also talked me into doing a tune-up (oil and air filter change and replaced spark plugs and wires - $350.00).

Ever since that day, my car has been shaking upon startup, while accelerating and while sitting at stoplights, but shaking goes away at cruising speed. Check engine light is also on. (What could they have done to my car to cause this problem?)

I immediately took it back, and they said “oh, it turns out we put a defective part, but we replaced it with a new one”. No difference – problem still there.

I took it back, they pulled codes P0300, P0303, P0306 (random misfires). They replaced wires under warranty, replaced radiator cap, and swapped ignition coils to test misfire. Maybe put one new ignition coil. (I paid $180). Also suggested I add Techron to my tank next time I fill up. Did that, twice, floored it while accelerating through two tanks of gas. No difference – problem still there.

Went back again, they pulled codes P0300 and P0304. Replaced 1 spark plug. (No charge). No difference – problem still there.

Had Auto Zone pull codes P0300, P0301, P0303, P0304 and P0420 (Catalyst System Efficiency Below Threshold – Bank 1).

Had problem diagnosed at Toyota dealership (they’re the experts on Toyota's, right?) – They wanted $2,000 to replace fuel injectors and $150 to diagnose “excessive coolant loss”. Also suggested another tune-up for $170 because they “Found engine to run rough” – well Duh – that’s why I came to you and I told you I had a tune-up 6 months ago! (Paid $140 for diagnosis and left).

Went back to independent shop, pulled codes P0300, P0301, P0306. They replaced fuel filter and did Air Intake Decarbonization Service – BG. (Paid $280.00). No difference – problem still there.

Went back again – now they want to replace fuel injectors, seal kit and intake plenum gasket – quote is $733.00 plus tax.

My own research on the net suggests ignition coils may be the problem? (A much cheaper fix). I already replaced the Mass Airflow Sensor a few years ago.

I want to trust these guys – they seem like good guys, but it seems to me no coincidence that the misfire/rough idle problem started immediately after they did their tune-up, and now I’ve given these guys over $800.00 and the problem has not been fixed, and they want another $733.00 plus tax…

Obviously it’s an old car and every part is getting old - I figure I can afford to replace parts as they fail – but I can’t afford to replace every part on the freakin’ car in a wild goose chase to fix a problem – shouldn’t they have been able to diagnose this and fix it correctly by now for much less money? Doesn’t it seem like maybe they caused the problem in the first place in order to sell me all this service? Shouldn’t they refund me what I’ve paid so far so I can afford to replace the ignition coils and/or fuel injectors and finally be done with this problem?

What should I do? What would you do? Thank you in advance for your advice.

Year 2000 ("third generation") 4Runner, SR5 2WD, 183-hp, 3.4-liter, V-6 engine, regular gas, 19 MPG (combined), fuel-injection, non-interference, four speed automatic w/OD ECT transmission, California emissions, 314,000 miles.
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Tuesday, September 10th, 2019 AT 9:31 PM

10 Replies

Tiny
SCGRANTURISMO
  • EXPERT
Hello,

I understand that chasing gremlins around with driveability issues can be very, very, very frustrating. Random misfires can be caused by a lot of things, so we will be running down a list of things, the most likely culprits to the least until we come across the problem, or problems, okay. I know you're probably fed up with the whole thing and looking for somewhere to buy a stick of dynamite, but please, have a little patience and we will get everything worked out. Okay, so let's check on the health of the engine real quick with a compression test. This will give us clues to the health of the piston rings, valves, and head gasket of the engine, rule out internal engine failures and is fairly cheap and simple to do. You will need to have a compression gauge, which can be purchased at any auto parts store for around $20.00 or rented by just leaving a refundable deposit. Here is a link describing how to do a compression test below:

https://www.2carpros.com/articles/how-to-test-engine-compression

Please go through this guide and report back with the readings on all 6 cylinders and we will go from there.

Thanks,
Alex
2CarPros
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Wednesday, September 11th, 2019 AT 3:14 AM
Tiny
ACORN8
  • MEMBER
Okay, thanks so much Alex - will do and get back to you.
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Wednesday, September 11th, 2019 AT 7:46 PM
Tiny
ACORN8
  • MEMBER
Alex, okay, did the compression test (dry test), readings were as follows:
Cylinder 1 - 180
Cylinder 2 - 180
Cylinder 3 - 175
Cylinder 4 - 160
Cylinder 5 - 180
Cylinder 6 - 175

What do you think?
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Sunday, September 15th, 2019 AT 8:10 PM
Tiny
SCGRANTURISMO
  • EXPERT
Hello again,

They all look good to me. Pretty strong actually. Cylinder 4 so/so but still very good readings as a whole. Okay, now that we know it's nothing internal causing these random misfires, normally I would go the ignition system, i.e. spark plugs, plug wires, ignition coil(s), but the problem with that here, is that you are having misfires on all of your cylinders at random times with no rhyme or reason to it. That would lead me to an air intake or vacuum leak. Next lets check to make sure no unmetered air is getting introduced into the engine, i.e. let's check the intake manifold gasket. Okay, so a vacuum leak and unmetered air is described as any air entering the air intake system up to the engine's combustion chambers that enters past the Mass Air Flow sensor(MAF). Since you are experiencing multiple random misfires this is the likely culprit. It would also produce rough idle and low speed driveability concerns and would smooth out at higher speeds because of the volume of air being ingested by the engine. Down below is a link explaining how to test for a vacuum leak. Please pay close attention to the intake manifold gasket area.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

I have also included an exploded diagram of the intake manifold and associated parts in the diagrams down below to help you. Please get back to us with what you find out, and we can go from there.

Thanks,
Alex
2CarPros
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Monday, September 16th, 2019 AT 1:28 AM
Tiny
ACORN8
  • MEMBER
Thank you - very encouraging! Will get back to you.
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Monday, September 16th, 2019 AT 10:33 AM
Tiny
ACORN8
  • MEMBER
Well. Sure enough, leaks all over the place - upper and lower intake manifold gasket, PCV valve, vacuum hoses.

That is, if I trust these guys (went to a totally new shop for this one). The problem is, just like in dentistry and medicine, they have a vested interest in finding something wrong so they can "fix" it and make more money. And yes, I avoid dentists and doctors like the plague now - especially since hearing that only 1/3 of treatments actually benefit the patient; another third actually do more harm than good, and the final third have mixed results or no effect. This is borne out by my own experience and that of others I know. It's also true that members of certain religious groups that shun most medical treatment have the same life expectancy as the rest of us - actually a bit longer, if I recall correctly.

There really should be a doctors/dentists/mechanics who only do diagnostics, and don't give any recommendation on where to go for treatment/repair. Then and only then could you really trust the diagnosis. Right?

They quoted $1,100.00 to fix the leaks. Ugh. Your thoughts?
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Tuesday, September 17th, 2019 AT 9:06 PM
Tiny
SCGRANTURISMO
  • EXPERT
Hello again,

If you want we can fix it. I can tell you exactly how to do the diagnostics and give you step by step directions on what to do. It can all be done in 1/2 a days time with basic tools. The parts will probably cost around $50.00 or south of that. Please get back to us with what you want to do.

Thanks,
Alex
2CarPros
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Tuesday, September 17th, 2019 AT 9:20 PM
Tiny
ACORN8
  • MEMBER
That would be so helpful - it's amazing how much money I could save!
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Thursday, September 19th, 2019 AT 8:35 PM
Tiny
SCGRANTURISMO
  • EXPERT
Hello again,

Okay, so in the diagrams down below I have included the step by step instructions for the removal of the intake manifold on your vehicle. This is an excerpt from the instructions on how to removal the cylinder head(s) on your vehicle. Toyota decided to combine the two together as you would need to remove the intake manifold to remove the cylinder head(s). The installation is going to be the reverse of the removal. I have included general diagrams for the first few diagrams. The torque specs are going to be for the intake manifold bolts. Basically on these bolts start tightening in the middle of the manifold and work out to the outside alternating sides as you go. Think about it as flattening out a table cloth, you put your hands in the middle and take the wrinkles out by smoothing it with your hands out the edges. Same concept. Don't overthink things. Be systematic and deliberate hear. A helpful piece of advice, have a cleared off table nearby with ziptop sandwich baggies a sharpie marker nearby. Whenever a components comes off set it neatly on the table top and place all of the fasteners(bolts/screws) in a sandwich baggie, zipped up so none get lost, and mark what they go to with a sharpie and place them next to that component. You will save an enormous amount of time and will make reassembly much, much, much, much easier. For the intake manifold gasket itself I would recommend buying Fel Pro Gaskets, and get a small tube of black RTV sealant(Permatex) and put a small amount on each corner of the intake manifold gasket to "tack" it down and hold it in place if there are no dowels to hold it in place on the engine. As far as torquing down the bolts, follow the torque specs, but remember do not over tighten. Less is more here. Just enough to snug it down. Please go through the guide and let us know how it turns out, or if you have any other questions or concerns, please, don't hesitate to ask.

Thanks,
Alex
2CarPros
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Friday, September 20th, 2019 AT 6:37 PM
Tiny
ACORN8
  • MEMBER
Alex,
I haven't gotten around to this yet, but I want to thank you in advance for your kind help!
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Monday, September 23rd, 2019 AT 8:19 PM

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