Code Help! P0301, P0171, Pending P0300

D

DWilliam

Member
2002 with 140k. No symptoms, but it has the codes above. So far I’ve done:

Fuel pump, check valve, plugs, wires, coil on cylinder 1, timing belt, water pump, thermostat, VSV valves. Cleaned MAF sensor and throttle body.

I plan on doing the hose leak test with carb cleaner to see if I can trace a vacuum leak. Is there anything else I should look for? I assumed the misfire on 1 was a bad coil so that’s why I did the plugs, wires, and replaced that coil. Truck seems to run fine and doesn’t have any issues.
 
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The P300 is random multiple missfires. Probably from the P171 system too lean code. Look for cracks in the rubber intake trunk.

What is your warmed up idle rpm?

What is your MAF reading with a warmed up idle?

How old is your fuel filter?

Any exhaust leaks?


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19963.4lsr5 said:
The P300 is random multiple missfires. Probably from the P171 system too lean code. Look for cracks in the rubber intake trunk.

What is your warmed up idle rpm?

What is your MAF reading with a warmed up idle?

How old is your fuel filter?

Any exhaust leaks?


Sent from my iPhone using Tapatalk
Click to expand...

Getting around to updating this. MAF sensor and throttle body were cleaned. Coil replaced on cylinder 1. All new plugs and wires. Still have the codes. My reader says MAF is 0.50 lb/min and fuel rate is 0.33 gal/hr at idle

The big black hose that the MAF sensor is on is looking a little old, do you know the part number for that? The one that also hooks to the throttle body.

Anything else I can troubleshoot with this? I just want the damn CEL off. I’ve put 10 grand into this thing in less than a year.
 

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I'd be tempted by those price differences too - I say if the amazon seller offers 100% refund and paid shipping both ways - study the seller pics comparing to yours and if it seems to match go for it. Luck.
 
Changed out that black plastic piece, still have the codes. Any other ideas?

What should I throw at it next? The misfire makes me think it’s an injector but I have no idea.

Also I noticed that when I try to “floor it” there’s a very noticeable hesitation and pause before any real RPM jump.
 
I have been taking my time with a Cylinder 1 misfire code (only occurs on warm restart). You can feel it stumble. I thought I had solved it but it returned. It'll run perfectly for hours on end under all conditions until I kill the engine. Then I need to pop the hood and wait 30-40 mins. I've done pretty much everything you have done and did a compression test for peace of mind. I grabbed a cheap tester online and all were well within spec. I have a full set of MotorWest injectors, gaskets, banjo crush washers, etc., on deck.....good luck with yours!

Timmy's injector video: https://youtu.be/N-lhZIWOkyU
 
Endlessblockades said:
I have been taking my time with a Cylinder 1 misfire code (only occurs on warm restart). You can feel it stumble. I thought I had solved it but it returned. It'll run perfectly for hours on end under all conditions until I kill the engine. Then I need to pop the hood and wait 30-40 mins. I've done pretty much everything you have done and did a compression test for peace of mind. I grabbed a cheap tester online and all were well within spec.
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Are you getting a P0171 also? This sounds nearly the same as what mine's doing.
 
4BoiRunna said:
Are you getting a P0171 also? This sounds nearly the same as what mine's doing.
Click to expand...

I did see that one a couple of times during the misfire issue. It never came back once I did the injectors. I might have seen it twice over a 1 month period (I was driving it a little as possible).
 
I was in the same boat as you [MENTION=751428]DWilliam[/MENTION] few years back.After all the trouble shooting, replaced the #1 injector with an oem and have put about 100k miles on it with no issues since.
 
spartacus said:
I was in the same boat as you [MENTION=751428]DWilliam[/MENTION] few years back.After all the trouble shooting, replaced the #1 injector with an oem and have put about 100k miles on it with no issues since.
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Thanks! Same codes? Did you have the little hesitation when giving it gas after filling up the tank? Any other symptoms?
 
DWilliam said:
Thanks! Same codes? Did you have the little hesitation when giving it gas after filling up the tank? Any other symptoms?
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MIne always had the problems when heat soaked. After every troubleshooting session just when I thought I had the it fixed, it re-emerged.
 
spartacus said:
MIne always had the problems when heat soaked. After every troubleshooting session just when I thought I had the it fixed, it re-emerged.
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Same here. If i could go back in time I would heed the advice from people on this forum who suggested I bite the bullet and get a full set of MotorWest Performance tuned refurbed Denso injectors with o-rings and seals preinstalled, banjo washers, and plenum gaskets and be done with chasing fuel delivery gremlins. Sure I'm happy to have new coil packs, plugs, wires, a clean MAF sensor, an Airaid intake and peace of mind knowing I have good compression on all cylinders, but I spent a lot more time and money getting to the end result - a warm restart without a CEL and a bad combustion stumble :)
 
Endlessblockades said:
Same here. If i could go back in time I would heed the advice from people on this forum who suggested I bite the bullet and get a full set of MotorWest Performance tuned refurbed Denso injectors with o-rings and seals preinstalled, banjo washers, and plenum gaskets and be done with chasing fuel delivery gremlins. Sure I'm happy to have new coil packs, plugs, wires, a clean MAF sensor, an Airaid intake and peace of mind knowing I have good compression on all cylinders, but I spent a lot more time and money getting to the end result - a warm restart without a CEL and a bad combustion stumble :)
Click to expand...

I’m going to have my mechanic do the injector install. Should I do the plenum gasket as well? If so, do you have a part number? (2002). Anything else while he’s in there?
 
DWilliam said:
I’m going to have my mechanic do the injector install. Should I do the plenum gasket as well? If so, do you have a part number? (2002). Anything else while he’s in there?
Click to expand...

The plenum gaskets are a pair and should be replaced. The fuel rail (Banjo) crush washers need to be replaced at the same time. I had a throttle body gasket but I didn't use it. i got all the parts together from MotorWest so I'm not sure what the toyota P/N would be but the gasket MFG was Reinz Mahle or something like that.
 
Endlessblockades said:
The plenum gaskets are a pair and should be replaced. The fuel rail (Banjo) crush washers need to be replaced at the same time. I had a throttle body gasket but I didn't use it. i got all the parts together from MotorWest so I'm not sure what the toyota P/N would be but the gasket MFG was Reinz Mahle or something like that.
Click to expand...

Thanks. I didn’t realize they had the gasket and crush washers too.
 
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