Dutch0ven

Hopefully someone can help me! I bought a 2000 gs300 a few months ago and the previous owner seemed like he was pretty upfront about any issues it may have. At the time it ran fine except a small hesitation around 3,000rpms. Over time it go worse and now the car doesn’t run at all. When I turn the engine over it starts but dies almost immediately. If I give it gas to keep it running it will rev but it’s really delayed and almost seems like you have to put the pedal to the floor to get it to react. It also makes almost a popping noise coming from the engine bay when I give it gas.

the car has about 180,000 miles. I thought at first it was a vacuum leak and replaced the entire intake as well as the MAF sensor, PCV valve, and the vacuum control valve. I also replaced a bad O2 sensor. When I got the car it also had a P0171 code that has since been cleared because I had the battery disconnected to replace the MAF. The previous owner mentioned he replaced the fuel pump as well.

If anyone can guide me as to what I should try next I would greatly appreciate it. Should I take the fuel pump out and make sure it’s installed and running correctly? Could it be back spark plugs or fuel injectors? What can I do to troubleshoot this car and get it running. I’m getting desperate and it’s getting expensive just throwing parts at the car.

I have a ODB reader and can run diagnostics but I don’t know what I’m looking at. Any help is greatly appreciated. Thanks in advance.

jettate

I had clogged exhaust from honeycomb in cats coming apart and clogging the exhaust system. It would start, but the higher the rpm's the less power it had. Wonder if yours is completely clogged.

Dutch0ven

interesting. So you just unbolted your headers and exhaust and cleaned it all out? Never even thought about this.

Frankn

If you unplug both of your pre cat O2 sensors on your headers you will open up some flow, do that and see if it runs

jettate

I replaced my cats from Rock Auto, Midas installed them and then deleted my 3rd unmonitored cat. They were hollow when they came off the car. Not sure how I was passing inspection.

Frankn

Replaced them previously or its fixed via the new cats?

CurlyG

P0171 means the engine is running too lean. If the MAF and O2 sensors are reading correctly, you likely have an air intake leak. Unmeasured air, leaking in downstream of the MAF sensor, will cause a lean condition.

A fuel delivery problem can also cause this problem, however I recommend checking for intake leaks first. If you have even a tiny intake leak, the engine will never run %100 smooth.

If you can get the engine to run, you should fist get some engine data by monitoring the short and long term fuel trim values, using a OBDII reader app like Torque. You can also use these values to validate whether or not you have fixed the problem (in more detail than just, "it runs now!"). Google what short and long term fuel trims mean, if you don't already know.

My GS400 had a leaky intake manifold gasket, which was causing similar issues. The only way I was able to find the leak was to smoke test the intake. I tried everything else, before finding the real cause of the leak. I bought a smoke test machine off amazon for about $100, and it has been well worth the investment, as it found both the IM gasket leak, and also found an Evap leak on top of the fuel tank (a plastic fuel vent on top of the tank had cracked). I also installed a completely new factory intake, replaced the rock-hard PCV grommet and valve, and all of the evap lines, which were good investments, but did nothing to stop the major intake leak (hidden under the IM).
I occasionally check the long term fuel trims to see if the values are still within normal operating range.

You can also (carefully!) spray starter fluid around your IM while the engine is running. If the starter fluid enters the intake through a leak, the engine speed should increase, indicating where the leak may be.

Do you smell gas while starting the engine? Are there any other CEL's/codes?

jettate

I replaced the cats brand new from Rock Auto 399. 250 for install. Fixed via brand new cats and exhaust clean out. I ordered Tanabe Medallion for it. Once that comes in, I will have brand new cats and exhaust.

KyleH

iTrader: (1)

You mentioned in your initial post you have an OBD2 code reader and can pull the diagnostics. Please do this and report back. You also reported a code P0171. Based on a quick google this is a lean condition. If the only code you have is a P0171, I would suspect your fuel pump is failing, given the accompanying issue you're having of the car hardly being able to start and run at all. But before you go there, pull all the codes and report back.

Dutch0ven

this was all great information. Thanks for taking the time to reply. I’ve already replaced the entire intake piping up to the manifold as well as any cracked or damaged vacuum lines, pcv, and vacuum control valve. I really don’t think it’s a vacuum leak at this point. And YES, I do smell gas when starting the car. No other codes at all… it was just p0171 and p0161. I’ve replaced the bad O2 sensor for p0161.

Dutch0ven

Hi Kyle, thanks for taking the time to reply. The only 2 codes it was throwing was p0161 and p0171. The first code was for a bank 2 sensor O2 sensor I replaced recently. It didn’t have any positive effect on fixing the car issue.

KyleH

iTrader: (1)

If it were me, I would find a way to measure the fuel pressure at the rail. I would expect an auto parts store would have one. You should see about 43psi of pressure when cranking the car. If you see a number much lower than that, I would suspect you have a fuel pump problem. For the car to not even start, it's a pretty severe problem you have on your hands - likely not a minor vacuum leak, a faulty O2, or even MAF, since I'm guessing here afterall. However, fuel pumps at this age are not that uncommon to fail.

dwoods801

Most of these cars lack the shraider valve to check the pressure at the fuel rail. I know none of the GS300’s have a port with the shraider valve. Many of the V8’s will have a pop up indicator on top of the regulator to show its pressurized to 43psi and ready for business. But not all have this either. But I found an excellent way to check the fuel pressure at the fuel rail on any of our 2GS cars. If you unbolt the fuel line from the regulator which is mounted on the end of the fuel rail. U want to pull the fuel pump fuse and crank it over to release any pressure then unbolt the fuel line. Get a 2 liter measuring jug, or u could just use an old bleach bottle, but something that holds at least a gallon of liquid and not a milk jug or anything that gas is going to eat right thru. Replace the fuel pump fuse. And have someone crank it over for 30 seconds, a good pump is going to flow about a gallon a minute, so in 30 seconds u should have a 1/2 gallon or about 1.5 liters. If it’s weak, your not going to get anywhere near half a gallon in 30 seconds and if it’s good, your going to be worried about over filling the gallon jug if you give it the full 30 seconds. If u are doing this on an Aristo with dual pumps or something unique, u can usually find the correct flow rate and determine how much is should pump for 30 seconds and adjust the formula accordingly. But this is pretty easy to do and the best way to measure rail fuel pressure if you don’t have a way to measure it with a standard fuel pressure gauge. I will snap a few pictures of the regulator and it’s indicator on my car, and add them to this post when I get a chance.

dwoods801

Depending on how how long the CEL was on before the car stopped running, it should have had a big jump in LT fuel trim % on both banks, if only 1 bank has a high % then it’s a vacuum leak or something and unlikely a fuel pump. And if you can view rhe freeze frame info from your obd scanner. Not all scanners have this feature. But this info can usually point to the problem. If it’s a vacuum leak, then it’s going to be a bigger issue at lower rpm’s, when a weak fuel pump would be able to keep up better, as the rpm’s rise, the fuel starvation would get worse so it points to a fuel pressure issue. If the problem is worse at lower rpm’s then a vacuum leak is more likely. You lose vacuum pressure is rpm’s rise , so a vacuum leak doesn’t suck in as much air at higher rpm’s. Also the size of leak won’t change so at higher rpm’s the extra air gets spread over many more ignition cycles. So if you have a vacuum leak, the car will run crappy at low rpm’s and basically like normal at higher revs. And vice versa if it’s a fuel problem. Also the upstream O2 sensors can help identify other culprits. If it’s a bad sensor or something then the O2 sensors will recognize if it’s actually running lean or rich and won’t correlate to the long term fuel trims. If you have a bad O2 sensor you’ll see a difference from bank to bank, and usually they have a self diagnostic test built in and create a specific DTC if there is a problem.
I smoke machine can be very handy when trying to find a hidden vacuum leak, you just need want to pinpoint your likely problem so u know what to look for. And a P0171 code can be very frustrating.
Most vehicles will run fine until they quit starting without ever tipping u off with CEL, and that’s usually a bad fuel pump, but the Denso fuel pumps seem to get weak before total failure and the only symptom is a P0171 code.
When you have a dead car and just a P0171 code, like the OP, it’s almost certainly a bad fuel pump