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P0171 ad P0174 codes

6K views 3 replies 3 participants last post by  FJ@llDAY08 
#1 ·
Well, for the past month and a half I've been dealing with an acceleration issue. Under hard acceleration, such as driving on the highway, going up hills, or towing, I'd noticed that the truck really struggles and hesitates. It's really noticeable on the highway when accelerating up hills. It feels like someone is tapping the brakes. Really annoying.

The first thing we did was to clean the MAF sensor, replace spark plugs, and replaced the air filter. It still did it. So we replaced the MAF sensor last week.
It still did it. So it's obviously not the MAF sensor. Luckily they will take back the MAF sensor and give me a credit towards the real issue. My mechanic put his computer in the truck and went for a good drive. He got the truck up to about 3500 rpm. Once he hit there, the fuel pump pressure dropped to 0. Once he took his foot off the accelerator, the fuel pressure came back. So the fuel pump is buggered. He dropped the tank. The filter sock was black with crud and this weird clay/sand stuff on it that rubs off. He said he had never seen a fuel pump/filter act or look like this. He checked the fuel tank out and it is spotless. Fuel is clean and no gunk on the bottom of the tank. So no idea where this stuff came from. I do travel on logging roads quite a bit to go to lakes to do some fishing. So maybe dust from the roads got in the tank? Apparently the fuel pump in the tank comes on every night to check for leaks and my FJ had no codes pending for a fuel system leak. So he has no explaination as to how it got in the tank.

So he is going to replace the whole assembly, as he's not comfortable putting any of it back in. Either am I. Up here in Canada it's quite an expensive part. I was quoted $700 for the assembly. Luckily I get back the $325 I already paid for the MAF sensor. He's going to send a write up to Toyota Canada so they have it on file. He also took the other techs at Toyota for a drive to show them the symptoms so that if they ever have another truck come in displaying the same symptoms, they know what to look for.

Just thought I'd share what was dicovered while troubleshooting the 2 codes my truck spat out. By the way, I have a 2007 FJ with 155,000 kilometers or 96,000 miles.

Cheers,
FF
 
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#2 ·
I believe you have the same fuel tank unit as the US trucks do where the fuel filter is inside the tank.

If that is the case, yep you likely have a clogged filter. My Tacoma the filter would start to clog at 30,000 miles. The first time I replaced the entire tank unit at more than $600. The second time it happened I developed the URD Fuel Pump/Filter Upgrade Kit.

Underdog Racing Development

The kit modifies the tank unit to accept a high flow fuel pump and converts it to use an external easy to change fuel filter and it is way cheaper than a new tank unit from Toyota.

The fuel pump does not turn on in the middle of the night. What is going on there is a system that checks for vapor leaks in the fuel system. It is a small air pump that fires up and pressurizes the fuel system and then shuts off. The ECU then monitors how long it takes for the pressure to drop. That is how it can determine if there is a vapor leak in the system or not.


G
 
#3 ·
Very interesting. I now have the truck back and there is no more problem. He said the bottom of the housing had a thick layer of a mud like substance. Once it dried, he said it was rock hard. I did have the whole unit replaced. Part was $708 CAD + labor. Came in just shy of $1400 CAD. Crazy!! Just for a fuel pump. I will definitely look in to this if I decide to keep my FJ and not upgrade to a new Tundra.

PS. I already have your URD sleeve kit installed in my clutch. Took my chirp away and saved me from replacing the bellhousing for a 5th time, as the quill was quite scored. I also had the TSB parts installed at the same time. I'm hoping to get 2 more years out of this truck before it's time to buy something new.
 
#4 ·
Well, for the past month and a half I've been dealing with an acceleration issue. Under hard acceleration, such as driving on the highway, going up hills, or towing, I'd noticed that the truck really struggles and hesitates. It's really noticeable on the highway when accelerating up hills. It feels like someone is tapping the brakes. Really annoying.

The first thing we did was to clean the MAF sensor, replace spark plugs, and replaced the air filter. It still did it. So we replaced the MAF sensor last week.
It still did it. So it's obviously not the MAF sensor. Luckily they will take back the MAF sensor and give me a credit towards the real issue. My mechanic put his computer in the truck and went for a good drive. He got the truck up to about 3500 rpm. Once he hit there, the fuel pump pressure dropped to 0. Once he took his foot off the accelerator, the fuel pressure came back. So the fuel pump is buggered. He dropped the tank. The filter sock was black with crud and this weird clay/sand stuff on it that rubs off. He said he had never seen a fuel pump/filter act or look like this. He checked the fuel tank out and it is spotless. Fuel is clean and no gunk on the bottom of the tank. So no idea where this stuff came from. I do travel on logging roads quite a bit to go to lakes to do some fishing. So maybe dust from the roads got in the tank? Apparently the fuel pump in the tank comes on every night to check for leaks and my FJ had no codes pending for a fuel system leak. So he has no explaination as to how it got in the tank.

So he is going to replace the whole assembly, as he's not comfortable putting any of it back in. Either am I. Up here in Canada it's quite an expensive part. I was quoted $700 for the assembly. Luckily I get back the $325 I already paid for the MAF sensor. He's going to send a write up to Toyota Canada so they have it on file. He also took the other techs at Toyota for a drive to show them the symptoms so that if they ever have another truck come in displaying the same symptoms, they know what to look for.

Just thought I'd share what was dicovered while troubleshooting the 2 codes my truck spat out. By the way, I have a 2007 FJ with 155,000 kilometers or 96,000 miles.

Cheers,
FF
I realize this thread is old. But I really wanted to thank fishinfiend for posting his experience. I’ve been struggling with the same problem he had for almost three years now. I’ve gone through 3 MAFs because I kept getting CEL for it. Smoke tested for vacuum leaks. Even bought a whole new intake. Among other things such as spark plugs, filters, etc. I would still always have the same hesitation in 4th and 5th, like someone was tapping the brakes. I searched the Internet high and low and could never find anyone with the same issue. The other day my truck popped the codes p0171 and p0174. I researched and found this thread. I immediately replaced the fuel pump and filter and viola!!! Problem solved! So thank you thank and thank you again!
 
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