Misfire codes

[Josho]

Vehicle: 1999 Toyota 4Runner SR5 2wd Auto.
Codes: p0300 p0301 p0302 p0303 p0304 p0305 p0171

Prior to the codes it ran sluggish, with no noticeable misfire but definite loss of power. And it would idle rough-ish, not terribly bad though. Those codes showed up and that's when the noticeable misfire began. I have not driven it since.

Things I have done: Replaced MAF, TPS, plugs, wires, cleaned TB and IAC. I removed the catalytic converter and it made no difference. Here's the problem, I'm tired of throwing money and time at this thing. Any trouble shooting suggestions?

 

[LittleCaesar]

When is the last time the timing belt has been changed?

 

[Buckaroo]

Vehicle: 1999 Toyota 4Runner SR5 2wd Auto.
Codes: p0300 p0301 p0302 p0303 p0304 p0305 p0171

Prior to the codes it ran sluggish, with no noticeable misfire but definite loss of power. And it would idle rough-ish, not terribly bad though. Those codes showed up and that's when the noticeable misfire began. I have not driven it since.

Things I have done: Replaced MAF, TPS, plugs, wires, cleaned TB and IAC. I removed the catalytic converter and it made no difference. Here's the problem, I'm tired of throwing money and time at this thing. Any trouble shooting suggestions?

Multi-cylinder misfire with lean condition. Not something cylinder specific like injectors or ignition coils. Check O2 sensor response, fuel pump/filter pressure & flow, entry of un-metered air, vacuum leak, PCV valve. These are things I would go after. Test to verify issue....don't just replace expensive parts.

Buckaroo

 

[catrains]

on a vehicle this old you did not spend much for those parts and given the age a good thing to do.

The way to narrow this down is not to guess on part changing. having a $200 scan tool that can read the diagnostic sensor data this can be repaired more accurately.

then checking fuel pressure and any vacuum lines for any cracks is required . any leaks after the maf on the piping to the Throttle body.

tooo lean not enough fuel so its miss firing.

A/F ... O2 sensors probably not it. but if they have over 130K miles they are worn out they get sluggish on the response to the oxygen in the exhaust gases.

diagnostic scan tool is needed ..then post what the readings are.

 

[Josho]

I picked up a compression and fuel pressure tester. I'll post results shortly.

 

[Josho]

I pulled the plugs out that I recently replaced. They are NGK BKR5EGP plugs gapped at .035. Do these need to be gapped at .044??

 

[Josho]

Compression test results.

Cylinder - Psi

1 - 210
2- 210
3 - 200
4 - 210
5 - 195
6 - 210

Seems within spec to me. All plug tips were white. So, to me, it's looking like a fuel related issue. I have a fuel pressure tester but it looks like I need to get an adapter seems how this particular model didn't come with a pressure valve.