Do a compression test, all 6 cyliners and then report back with the readings and we will go into it from there.

 

Google's cool:

http://www.google.com/search?hl=en&q=leakdown+test

Basically you pull the plugs, pump air into the cylinder and see if it leaks...

 

just had the exact same problem with one of our 4Runners and it was a bad fuel injector, had replaced been good ever since

 

Did your runner run fine until the the engine got to normal operating temp, or did it misfire the entire time? I just had all fuel injectors serviced, replacing 2 bad injectors. I hope it would not be the case however it is easier to replace than a head gasket or a valve job. Let me know.

 

Did you ever run a compression test yet? or leakdown?

I can't imagine having that many fuel injectors go bad, maybe leaky o-rings though.

 

not yet. hoping this weekend. let you guys know asap.

 

the car seemed to idle fine when not in gear but when we would put it in gear it would get rough and shake , it would hesistate when accelerating but then seemed to smooth out once we got up to speed. it was kinda weird

 

I am getting the misfire in my 99 Taco (2.7) when at idle, the shaking is getting worse. I replaced the plugs, pcv, air filter, vacuum lines and out in a can of techron fuel treatment in the tank to no avail. I ordered a set of ngk wires. After that, I guess I will have to check the injectors and coils. No CELS though.

 

ok everyone, i haven't had a chance to do the compression test. I do have a question though. Should I do a test on a cold engine or should i let the engine run a bit first? Also, I noticed the the roughness only occurrs between idle and about 2500rpms. After that it smooths out. I don't know if this makes any difference or not. i will do a compression test tomorrow though and post my results. Just tlet me know if I should do it on a cold or warm engine.

 

NGK wires? Dealer probably has them in stock. OE wires are the best around. They dont pull apart and leave the end on the plug and will last 3 times as long as aftermarket and only cost a little more. But I think you are on the right track. I'd suspect wires myself.

 

Ok, here are my results.

1. 155 2. 160
3. 150 4. 150
5. 160 6. 155.

Today I reset the codes. I switched the 1 and 3 coil pack. The cel is still the same, P303. Also whe I tried to start her today, the idle was below 500rpms and just died right away. So when I started her again I gave some gas and she would run. Is normal idle around 500 rpms? Again as a reminder, spark plugs and wires were changed with oem from dealer. Fuel injectors were serviced and 2 were replaced. The injectors were cleanedand new o-rings andd gaskets were replaced. So anyone got any ideas what my problem is?

 

Other possibilities are a dirty throttle body/IACV, a bad engine or tranny mount, or maybe an O2 sensor since I am only getting 15 MPG...or a bad battery.

 

Compression numbers are not that far apart...the normal RPM should be posted in your VECI sticker under the hood.

 

Mine usually idles around 700. 3.4L V6

 

yeah i think that is what normally idles at, but now it's 500 or less.

 

Have you chacked all vacuum lines for leaks?

 

I didn't find any leaks anywhere. I was messing with as many hoses i could find.

 

Well it looks like the compression numbers all look good so that is good.

The way to check for vacuum leaks is using a bit of carb cleaner on the hoses, where the hoses connect and the fuel injectors. If there an unmetered air leak, then the engine will respond to the carb cleaner being used (ie you'll hear the difference in the idle RPMs). It is also a very dangerous method because it is flamable so you need to have a hose handy to extinguish any flames which might occur from accidental ignition.

Finding leaks:
http://www.asashop.org/autoinc/may/TECH2TEC.HTM

 

Thanks, I'll look into soon. I will update with results.

 

I was wondering would a vacuum leak cause only one cylinder to misfire? Also, what are some causes for a drop in idle? I also forgot to mention, that just before having the low idle starting problem, I went to a friends house and parked on the driveway. When I put her in park, the idle jumped up to about 1500rpms. I pulled off the driveway back onto the street and the idle came back down. I don't recall that ever happening before. It seems like I am generating more problems. just as a recap.

Cylinder 3 misfire.
compression ok
low idle on start and dies (new problem)
timing belt good.
fuel injector serviced, orings and gasket replaced
new denso spark plugs *dealer
new plug wires *dealer.

still need to do a vacuum check, anything else you guys can think of for me to check?