amocat95

I would like to thank you in advance for any assistance provided throughout this thread. I feel I am a pretty good mechanic, but find myself stumped over this misfire.

The truck is a 95.5 Tacoma with a 3.4l engine. The truck feels like it runs fine, but loses power in the upper RPM range, and continues to trigger the check engine light with a Cylinder #2 Misfire. Here is what I have done so far to try and fix the problem.

Spark Plugs (properly gapped)
Wires
Swapped coils (to see if the misfire moved to another cyl)
Seafoam
Fuel Filter
New Fuel Injector for Cylinder 2

Is there a way to test if it is Valve related? What else should I look for?

Thanks Again!

mt_goat

Try a compression test.

delio

I had the same symtom on my 2000 4runner ltd 3.4. just cleaned my throttle body and my MAF with a brake cleanner and the problem went away, cause my after market filter caked my MAF with oil and it wasnt working properly.....anyhow give it a try and see what happens....try the cheapest route first before yjou start changing parts.. let me know k.....have fun

stir_fry_boy

Did you gap the dual grounded electrode spark plugs? If you did, you ruined them. They come gapped properly from the factory. Only use dual grounded electrode spark plugs made by NGK or Denso (numbers in your owners manual) and do not gap them or they are toast.

mt_goat

If he's only getting a code for #2 (P0302) my bet is problem specific to the #2 cylinder. I'd do a compression check. Dual ground plugs are good, but mainly because they last longer with our waste-spark ignition system.

amocat95

Actually I had dual electrode plugs in there that only had 5k on them. Just to see if it was plug related I replaced them with standard style plugs (these are what I gapped) to see if that was the problem first.

Do you know off the top of your head what the compression should be?

Thanks for all of the help!

mt_goat

http://www.ncttora.com/fsm/1996/SIL/...compr/insp.pdf

From this you can see different FSMs: http://www.ncttora.com/fsm/index.html

amocat95

When you had this problem was it just misfiring one one cylinder or random misfires from different cylinders. Thanks for the idea.

amocat95

Thanks for the info. I will try to get outside to check it tomorrow. Not sure if I really want to see the results. Don't want to be doing a head rebuild.

j-money$$$

i had a problem like this not too long ago, snd it ended up being that an injector went bad and caused a valve to strectch. i had to get my valves respaced and as new injector, and it took about $1000 hope this is not the case for you. good luck. i heard from my mechanic that compression should be 125. mine was 25 in the missfiring one

mt_goat

The factory spec is 145-174 psi.

j-money$$$

i was close enough haha

mt_goat

It probably would still run with 125

Dvold

Valve stretch? Can't say I've ever heard that one.

redwilly

Compression test is good, but a cylinder leak down test is more of what you'd be looking for.
The object is to make sure the misfiring cylinder is at TDC on firing stroke and test for pressure leaks.
A faulty valve or component of it will allow air out of the cylinder when theoretically is should be sealed.

amocat95

I finally got some time to check the compression, and the compression on cylinder #2 was excellent at 160psi. I might have to perform the test again as I don't think my wife was keeping it at full throttle while cranking it over.

I'm not sure what to do next, someone mentioned a leakdown test? (never done that before) ....I am not sure if this makes a difference, but everytime I clear the code it takes about 20 miles before the check engine light comes back on.

Anyone want to buy a nice stock 95' Tacoma?

redwilly

In essence a leak down test is a measurement of the cylinders' ability to hold pressure over time.
Compression testing fine for finding a really out there valve or blown out piston rings, but a slightly bad valve is found by leak down testing.
you could rough it by making sure the compression tester seals well and just leaving it to see if the pressure leaks down, but there are variables to doing so that could sway you.
Google or you tube leak down testing for more info.
This seems like your next step.

You said new plugs and/or properly gapped, I would suggest switching the plug to a different cylinder to be sure.

mlombardi

I still have random misfire through all speed ranges in my 98 4runner with the 3.4Liter. Plugs,wires,coil packs are okay. Cleaned the MAF sensor and throttle body and added fuel injector cleaner to gas. Running out of things I can tackle in my garage. Might have to take it to a shop to have them check injectors and compression. engine light blinks on and off when it's vibrating from the misfire. Then sometimes I get in and it will run fine for 10 minutes and all of a sudden it starts to misfire again.

amocat95

I am at a loss on this misfire! My misfire really shows itself in the upper RPM range and was intermitting for a while. I do have a couple of questions for all of the experts....

1. If I disconnect the battery does it really clear the code? Or do I need to use the OBDII tool?

2. Is there a sensor that goes to cylinder to that triggers this code? (could it be bad?)

3. Is there some type of "limp" mode that the computer might be in?

Thanks for all the help......

If I can't figure this out does anyone want a Tacoma for $4000.?

mt_goat

Loose crank bolt maybe: http://www.motor.com/MAGAZINE/Articles/012007_04.html