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Hi, just wanted to ask so see if i can get some advice on where to look or the next step to take in troubleshooting my vehicle.
Problem: need to get the vehicle smogged to register it, but bank 1 and bank 2 are running lean (throwing check engine light) there are some other issues that should be addressed. ill list them, but they shouldent be relevant to this issue.
So the issue is that im getting a lean condition on bank 1 and bank 2. it does not throw the lean condition in idle, so the manifold gaskets are fine. the fuel pressure should be around 55-60 psi key on engine off, mine goes to 50psi. im not sure on running pressure, but at idle it is running around 48 psi. so i would assume that this is causing the lean issue. only occurs between 5-20 mph, and it wont throw a lean condition when im at full throttle or slowing down from full throttle.
The fuel pressure was unstable at idle (bouncing from 46 to 50 psi), so i replaced the fuel pressure regulator, now my idle pressure is solid at 48 psi. another issue i had was the mass air flow sensor. replaced that less than 3k miles ago. had the fuel filter changed when i got the oil done, 3k miles ago. i dont think the pump is bad, because it has been at 48 psi for 2 months, had no trouble starting/idling. and from what ive read, once a fuel pump decides to go bad, its already gone.
Lastly with the vacuum line removed the pressure is at 58 psi.
other issues that ive had that are un-related (i think)
1. EVAP pressure sensor is throwing a high condition (replaced gas cap, did the same thing, sensor is probably bad)
2. a general code about the evap system (might be because of the pressure sensor)
the only thing i can think of is if the fuel pump is just running at a lower pressure. or if there is an issue in my vacuum system that is giving it a lower pressure.
i was looking to buy this vehicle from my parents, but with these issues i cant register it in nevada (previously in idaho). should i continue to trouble shoot this or just look at getting a different vehicle that will pass smog. (have 1000 dollars of new parts into it.)
The pump is not the problem. Doesn't matter if pump is 50-60-70 psi. The pressure is the same at any rpm. Fuel supply is regulated by the pressure regulator. Excess fuel is returned to the tank. Are injectors delivering the amount of fuel as required per RPM by the ECU? If all are equal 5-20 mph [but lean], could be an ECU command problem. Not amount of fuel per se but electric that opens injector. Are all vac hoses in good condition? Any split/crack will cause a problem.
was the fuel filter installed in the correct direction?
You can always disconnect the fuel filter and install a fuel pressure gauge on the line. Get a psi reading. You may have a weak pump and thus way more to just psi reading from the pump. I had a GMC where the fuel pump was weak. The truck had a poppit injector system and it HAD to have 50 psi. I was getting 48 which wasn't enough. Changed the fuel pump. Then I changed the fuel spider cause it was leaking
I had the same issue on my Chevy Tahoe 5.3. I had to have the map sensors replaced.
They're not expensive but.... you have to pull the intake manifold to change them.
I was getting low power and it wouldn't pass smog.
The pump is not the problem. Doesn't matter if pump is 50-60-70 psi. The pressure is the same at any rpm. Fuel supply is regulated by the pressure regulator. Excess fuel is returned to the tank. Are injectors delivering the amount of fuel as required per RPM by the ECU? If all are equal 5-20 mph [but lean], could be an ECU command problem. Not amount of fuel per se but electric that opens injector. Are all vac hoses in good condition? Any split/crack will cause a problem.
im looking at the vacuum system next, was going to take a can of carb cleaner to see if i can find any cracks that are causing an issue, i need to get the book for this suburban though so i know where to look and what lines/connections to test.
I had the same issue on my Chevy Tahoe 5.3. I had to have the map sensors replaced.
They're not expensive but.... you have to pull the intake manifold to change them.
I was getting low power and it wouldn't pass smog.
the intake manifold? from looking up on youtube its on the top rear of the engine (under some shrouds). but you could be right, he might of had a different model. thanks for the advice, ill try to replace the map sensor and see, the suburban has about 300k miles on it and i think most of the sensors havent been replaced since my parents bought it. (about 150k miles ago)
im looking at the vacuum system next, was going to take a can of carb cleaner to see if i can find any cracks that are causing an issue, i need to get the book for this suburban though so i know where to look and what lines/connections to test.
Depending upon where you live, if your library has online access you might be able to use your library card to log in and access all the Chilton repair manuals. Sacramento Public Library - Auto Repair
was the fuel filter installed in the correct direction?
You can always disconnect the fuel filter and install a fuel pressure gauge on the line. Get a psi reading. You may have a weak pump and thus way more to just psi reading from the pump. I had a GMC where the fuel pump was weak. The truck had a poppit injector system and it HAD to have 50 psi. I was getting 48 which wasn't enough. Changed the fuel pump. Then I changed the fuel spider cause it was leaking
i will take another look at the fuel filter. didnt think it could be installed backwards, but you might be right. i haven't had a problem with power or acceleration, so i think im getting enough pressure for the injectors, it just seems to dip down into the range to throw the code at times. since its a v8 suburban i couldn't tell you if i had a leak issue or if that was because i drove it for 10 feet.
i will take another look at the fuel filter. didnt think it could be installed backwards, but you might be right. i haven't had a problem with power or acceleration, so i think im getting enough pressure for the injectors, it just seems to dip down into the range to throw the code at times. since its a v8 suburban i couldn't tell you if i had a leak issue or if that was because i drove it for 10 feet.
I had a 2000 3500 Chevy and the filter was a threaded in and out and it was the same size, the filter had a arrow with word FLOW. It was supposed to be installed with arrow facing forward. My shop used to take cars to Pepboys and they put the filter in backwards. It lacked power.
Not sure if they changed anything in 01 but it's worth a look.
the intake manifold? from looking up on youtube its on the top rear of the engine (under some shrouds). but you could be right, he might of had a different model. thanks for the advice, ill try to replace the map sensor and see, the suburban has about 300k miles on it and i think most of the sensors havent been replaced since my parents bought it. (about 150k miles ago)
You might correct... its the "knock" sensors that you have to pull the intake manifold to get to.
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