HPFP drop at 5k rpms wot (auto tech)

Jordan lewis

Jordan lewis

Greenie N00B Member
Car started doing this recently,when wot everything is smooth until I hit 5k rpms then fuel pressure drops to 700psi or less,I’ve changed relief valve,injector seals,cleaned internals,replaced and gapped spark plugs and still can’t seem to figure out the problem.Internals looked great no scoring or scuffing.Olny thing I can think of now is taking apart the spill valve and cleaning it. Does anyone have anymore ideas?
 
Sounds like limp mode, which is usually a cracked or loose coupler or pipe somewhere in your plumbing post turbo. Your car tries to make boost, loses that boost immediately, and the ECU detects something is very wrong and shuts everything down to prevent damage. I had something like that once when I had a coupler pop loose from the intercooler.


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Solarsurge said:
Sounds like limp mode, which is usually a cracked or loose coupler or pipe somewhere in your plumbing post turbo. Your car tries to make boost, loses that boost immediately, and the ECU detects something is very wrong and shuts everything down to prevent damage. I had something like that once when I had a coupler pop loose from the intercooler.


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That could be true,but I’ve sent my tuner my logs and he says it’s weird cause everything looks completely normal except the fuel pressure drop at 5k rpms
 
Solarsurge said:
Sounds like limp mode, which is usually a cracked or loose coupler or pipe somewhere in your plumbing post turbo. Your car tries to make boost, loses that boost immediately, and the ECU detects something is very wrong and shuts everything down to prevent damage. I had something like that once when I had a coupler pop loose from the intercooler.


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Here’s my logs
 

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It’s really hard to read a log without knowing a little more about the setup. Either way, your tuner should know way more about your map since he is tuning it. But something is obviously not working correctly. All the “odd” fuel pressure drops I’ve seen were either relief valve, dying in tank pump failing to keep up with the demand of the HPFP, or boost issues. First I would always inspect hoses. Never assume things are connected. Any time you have problems, your first instinct should be to assume something came disconnected or broke and look it over visually. From there, if nothing obvious is disconnected or broken, I would do a cold KOEO fuel pressure check. It should be around 60psi. If it’s in the 40s it’s likely a failing in tank pump. Fuel pressure only cuts like that when it runs out of fuel, the measured values for air or fuel fall out of range of what the ECU is expecting or you have an ignition problem.

Edit: Probably should also mention that it’s a very good practice to start looking wherever you did the last thing you did before the problem. If you just change the spark plugs, you should check the spark plugs. People have had issues with brand new plugs cracking. You never know till you look.


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Last edited:
Solarsurge said:
It’s really hard to read a log without knowing a little more about the setup. Either way, your tuner should know way more about your map since he is tuning it. But something is obviously not working correctly. All the “odd” fuel pressure drops I’ve seen were either relief valve, dying in tank pump failing to keep up with the demand of the HPFP, or boost issues. First I would always inspect hoses. Never assume things are connected. Any time you have problems, your first instinct should be to assume something came disconnected or broke and look it over visually. From there, if nothing obvious is disconnected or broken, I would do a cold KOEO fuel pressure check. It should be around 60psi. If it’s in the 40s it’s likely a failing in tank pump. Fuel pressure only cuts like that when it runs out of fuel, the measured values for air or fuel fall out of range of what the ECU is expecting or you have an ignition problem.

Edit: Probably should also mention that it’s a very good practice to start looking wherever you did the last thing you did before the problem. If you just change the spark plugs, you should check the spark plugs. People have had issues with brand new plugs cracking. You never know till you look.


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Haha all these problems started when I took off quickly from a stop and missed 2nd??? And it bounced off the limiter twice then I got it back into 2nd and it did the sputtering. But went away for 2 days then came back and has been back since.And I still drive the car everyday,but I can’t go fast or it’ll drop in pressure and sputter.Thats when I started changing stuff to fix the problem,I’m not sure what could be causing this.And The fuel pressure cold is usally 58psi-61psi
 
Does your engine oil smell distinctively like gasoline?

I don't mean a faint smell, but definitely as if you mixed oil and gas like half and half.
 
Have you checked the plug on your fuel pressure sensor on the rail? I had it where it was just loose enough to work haphazardly and cause lot of issues.
 
Checked hpfp voltage while driving and it’s reading 0v but still drives like normal until I try to hit boost at 5k rpms.Unplugged it and car immediately died
 
Jordan lewis said:
Checked hpfp voltage while driving and it’s reading 0v but still drives like normal until I try to hit boost at 5k rpms.Unplugged it and car immediately died
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Check your grounds, harnesses, fuses and relays. It’s also a good idea to take a small wire brush to the contacts and give them a shot of electrical contact cleaner just for good measure. Any time you see 0v on anything, it’s a pretty good indication there’s bad contact. Check the pins, too. Sometimes those pins do get bent or break off if they’re not seated properly before you push that connector in.


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Jordan lewis said:
Checked hpfp voltage while driving and it’s reading 0v but still drives like normal until I try to hit boost at 5k rpms.Unplugged it and car immediately died
Click to expand...


Had any luck on resolving this? I had similar issue. Replace relief valve and went away for like two weeks. Same thing i missed 2nd gear then it happened. Two weeks later a similar thing happened and missed going to 3rd. (Driver error i know) After that i cruised car home and it had same symptoms I had the first time. I’m thinking to swap pumps with someone and try that. Then look at in tank pump etc. Any other suggestions. My pressure drops to like 100s though not 600-700 like yours.
 
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