4ZZ-FE 1.4L Corolla misfire p0170

[marshallboi]

Hi all, looking for some help!

Car is a 00-02 1.4L petrol vvt-i Corolla S

It's recently been misfiring (2 severe ones, rest of the time it's a popping sound when under stress), after 2xCEL of fault code p0170 fuel trim, bank 1.

Has also started kangarooing when going uphill, and has a lack of power in general. No smoke yet.

MAF has been cleaned, and it's got new spark plugs and alternator (original one died a week ago) and is still no better.

Any ideas?

TIA

[Bper]

Hi D,A faulty lambda sensor is a common cause of rich fuel mixtures and the P0170 fault code directly points to this. It's a relatively common wear item and replacing it can often resolve the issue. Vacuum leaks are another common issue and can be caused by cracked or loose hoses around the intake manifold, air breather pipes, and vacuum lines. As the P0170 code specifically indicates a problem with fuel trim in bank 1, which is directly related to the oxygen sensor in that bank. A faulty sensor can send incorrect signals to the ECU, causing it to deliver too much fuel.

Vacuum leaks are a common cause of engine performance issues across various cars, and they're relatively easy to diagnose with proper tools. A leak allows unmetered air into the engine, disrupting the air fuel ratio and causing a rich mixture.

The other possibilities like faulty fuel injectors or fuel pressure regulator are less likely to be the initial cause based on your information, although they cannot be entirely ruled out without further investigation.Hope this helps.

[Red_Corolla]

It sounds like possible fuel starvation. I would check the fuel pressure, or take it to someone who has the equipment to do so.

[marshallboi]

10 hours ago, Bper said:

Hi D,A faulty lambda sensor is a common cause of rich fuel mixtures and the P0170 fault code directly points to this. It's a relatively common wear item and replacing it can often resolve the issue. Vacuum leaks are another common issue and can be caused by cracked or loose hoses around the intake manifold, air breather pipes, and vacuum lines. As the P0170 code specifically indicates a problem with fuel trim in bank 1, which is directly related to the oxygen sensor in that bank. A faulty sensor can send incorrect signals to the ECU, causing it to deliver too much fuel.

Vacuum leaks are a common cause of engine performance issues across various cars, and they're relatively easy to diagnose with proper tools. A leak allows unmetered air into the engine, disrupting the air fuel ratio and causing a rich mixture.

The other possibilities like faulty fuel injectors or fuel pressure regulator are less likely to be the initial cause based on your information, although they cannot be entirely ruled out without further investigation. Hope this helps.

Thank you for being so thorough in explaining this!

Is the bank a section that is controlled by an O2 sensor? And so it's likely the engine itself is fine, but the external accessories aren't.

It had been sat for 7 months before I bought it in Feb, so it would make sense some stuff needs replacing!

[marshallboi]

9 hours ago, Red_Corolla said:

It sounds like possible fuel starvation. I would check the fuel pressure, or take it to someone who has the equipment to do so.

I hadn't thought about that.  I don't have the equipment to get it in the air, but I was thinking about checking the fuel filter. (apparently the VVT-i ones are in the actual tank)

Starvation would make sense due to it mainly struggling when going uphill!

[Bper]

Hi D, unless you have the ability and tools to check these possible causes and you have access to another vehicle then i would book it in with a garage. I understand how frustrating it can be along with the potential cost taking to a garage but this problem can be caused by a number of potential issues and they can diagnose these quickly.👍

[Guest]

39 minutes ago, Bper said:

Hi D, unless you have the ability and tools to check these possible causes and you have access to another vehicle then i would book it in with a garage. I understand how frustrating it can be along with the potential cost taking to a garage but this problem can be caused by a number of potential issues and they can diagnose these quickly.👍

I've done what I can, but you're right time to pass the reins over I think. I've got a good mechanic who explains everything thoroughly to me, so I can learn either way. 

Thanks for the help!

[Red_Corolla]

10 hours ago, marshallboi said:

I hadn't thought about that.  I don't have the equipment to get it in the air, but I was thinking about checking the fuel filter. (apparently the VVT-i ones are in the actual tank)

Starvation would make sense due to it mainly struggling when going uphill!

It's normally checked from under the bonnet, at the fuel rail. But needs a gauge and the right fittings to connect it up.

Another approach is to drive the car on a quiet road while monitoring the signal from the first oxygen sensor. The signal should briefly go high to report a rich condition if you suddenly floor it - if it fails to do that then it's a good indication of a lack of fuel, for whatever reason (pump, filter, MAF etc.)

As you suspect, a lot of modern cars don't have a proper filter any more, just a strainer on the pump, which sits in the top of the tank and can sometimes be accessed from under the back seat.

[TonyHSD]

Uphill lack of power is common thing  when we have fuel filter blocked or fuel supply restrictions of some sort. Good suggestion to check on that 👌

[marshallboi]

On 5/31/2024 at 2:18 PM, TonyHSD said:

Uphill lack of power is common thing  when we have fuel filter blocked or fuel supply restrictions of some sort. Good suggestion to check on that 👌

It's just had the fuel filter cleaned out and yeah definitely seems to be running much better. Going to try and park it on a hill facing upwards so all the fuel runs down to back of the tank. If I have trouble, then I'll know where the problem is!