Low RPM hesitation/stutter on acceleration

S

suchamoneypit

Greenie N00B Member
Greenie Member
EDIT: Problem solved, both my HPFP housings were bad. New HPFP housing solved the problem. More detailed explanation in a response posted below.

Hey everyone, been pulling my hair on this one. Here's the scenario. Car is running fine (2011 speed3), for 1.5 years. I buy brand new Corksport HPFP internals, and another used HPFP. So I have the one on my car, and this spare. I clean up, polish, and install the Corksport internals on this used HPFP, to swap with the one on my car.

I take off my HPFP my car has been using, and install the "new" one with the corksport internals. My car now has hesitation, sometimes severely, when accelerating around 3000rpm and below. Right after I take this turn, my throttle pedal position is consistent, but you see the car stutter (and can see it on the tachometer). In logs, this is shown as load increasing to around .8-.9, but fuel pressure staying at ~85psi. When the car "recovers" and starts to accelerate normally, the fuel pressure shoots up to the proper ~1800psi. Once the car is at proper pressure, It drive normally, and I can take normal WOT logs that don't have any issues.

So I take my spill valve off my known-good HPFP, and install it in the "new" used HPFP with my corksport internals, thinking its a bad spill valve.

Still does it, so now I take my old working HPFP, reinstall its known working spill valve back, along with my brand new Corksport internals. So Im using my confirmed working HPFP setup, with brand new corksport internals. Car still has the problem.

I now replace my fuel relief valve with a brand new one. Still have the problem.

TL;DR
-confirmed working HPFP spill valve + HPFP housing, brand new Corksport HPFP internals
-brand new fuel relief valve
-hesitation on acceleration ~3000rpm and below
-shows in logs as requested throttle going up, load going up to .8-.9, but fuel pressure staying at ~85psi.
-Video of it in action
-data logs attached to post

Anyone know what the problem could be? And why installing new HPFP internals could prompt this problem?
 

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Uploaded a how to for ya that I took a few years back

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EDIT: NVM. saw you replaced the relief valve. Hmmm back to thinking...
 
The_big_dill said:
Very strange indeed. What did you remove in the process of installing the pump?
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I only disconnected some PCV lines, and my intake, so it should be pretty isolated to the HPFP housing (and even then, I replaced the fuel relief valve). I wouldn't think a problem like this would be a problem at the fuel tank level like the in-take fuel pump, I haven't replaced anything there, but I'm not an expert.
 
suchamoneypit said:
I only disconnected some PCV lines, and my intake, so it should be pretty isolated to the HPFP housing (and even then, I replaced the fuel relief valve). I wouldn't think a problem like this would be a problem at the fuel tank level like the in-take fuel pump, I haven't replaced anything there, but I'm not an expert.
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Based on what I am reading, you tried every combination of parts except the original HPFP internals.

I know its a pain, but I would put the old HPFP internals back in to be 100% certain its not a parts problem.
 
Sho said:
Uploaded a how to for ya that I took a few years back


EDIT: NVM. saw you replaced the relief valve. Hmmm back to thinking...
Click to expand...
The_big_dill said:
Based on what I am reading, you tried every combination of parts except the original HPFP internals.

I know its a pain, but I would put the old HPFP internals back in to be 100% certain its not a parts problem.
Click to expand...

So this adventure has continued, my car still has the hesitation/stuttering and with P0089. I may make a new post, but my car still stutters and I have done the following:

-replaced spill valve (off ebay good condition used HPFP)
-replaced fuel relief valve (brand new)
-replaced fuel rail pressure sensor (pulled from speed3 partout, another from amazon)
-replaced in tank fuel pump (brand new Aeromotive stealth)
-replaced HPFP housing (used in good condition from ebay)
-swapped between Corksport (brand new) and Autotech HPFP internals(previously in my car)

The only thing that I can think of is by some insane probability that my working HPFP pump went bad from sitting 3-4 weeks before I did the HPFP internals install, AND the used good condition HPFP off ebay is also bad. This would mean spending like $330+ for a new HPFP but I think that wouldn't solve the problem given the swaps I've done and the nature of the problem. If anyone has some ideas I'd love the hear them.

Note: I also did thorough testing to verify this issue is not a boost leak, along with all new intake gaskets and boost tubes. Its also gotten new properly gapped spark plugs.
 
I would swap the hpfp back over to see if it's something with the install of the corksport internals
 
Easter Bunny said:
I would swap the hpfp back over to see if it's something with the install of the corksport internals
Click to expand...

I did. I tried two different HPFP housings, each with CS internals and Autotech internals (so 4 different setups tested). Autotech internals were confirmed working and in my car previously. CS were brand new.
 
I'm not trained in this at all, and it could be my comment is just my ignorance showing. Could it be that the used fuel rail pressure sensor which you picked up is faulty? Looking through the logs, it looks like either your sensor is inaccurate, or your stutter could be the engine trying to protect itself as the car is in boost, and your fuel pressure is still far too low.

Also, I had a shudder for awhile, which turned out to be my O2 sensor.
 
Jeff0500 said:
I'm not trained in this at all, and it could be my comment is just my ignorance showing. Could it be that the used fuel rail pressure sensor which you picked up is faulty? Looking through the logs, it looks like either your sensor is inaccurate, or your stutter could be the engine trying to protect itself as the car is in boost, and your fuel pressure is still far too low.

Also, I had a shudder for awhile, which turned out to be my O2 sensor.
Click to expand...

I actually picked up two separate fuel rail pressure sensors on top of the one in the car , and the issue persists when using all 3 sensors.

I'm no expert either , but I don't think it's an o2 sensor , why would the car operate fine above 3000rpm everytime ? I think it would be weird for the o2 sensor to be a problem only <3000rpm and not throw any o2 sensor related codes.
 
Update: Problem solved

Before I tried this, I also started see fuel rail pressure drop to ~1400psi during WOT, this prompted me to start swapping around HPFP internals and housings.

I got a working VCM II and Mazda IDS working, and followed the dealer steps to troubleshoot my P0089 CEL. The steps told me to verify whether at idle a pressure sensor read 3MPa (megapascal). I was logging pressures of only 500KPa (kilopascal). Recommended steps were to replace the HPFP housing, and if not fixed, then the fuel rail itself (which I highly doubted was the problem). So I replaced it.

It was the HPFP housing. This means both of the HPFP housings I had are bad, which I did think of before, but thought highly improbable. After swapping between my Autotech and Corksport internals, I saw the exact same issue on both (hesitation and pressure drop at WOT). I bought a brand new HPFP from a dealership ($340), swapped it on with OEM internals (and down-tuned the car for them), and the car immediately started up and ran perfect. No hesitation whatsoever and no fuel pressure drop at WOT, verified over ~30 min of driving and 3 WOT data logs. I then swapped my Corksport internals onto the the brand new HPFP housing, and the car continued to run perfect, with zero hesitation, and no pressure drop at WOT, verified on 4 WOT logs and 30-45 min of driving.

Going back at my previous logs I took using Versatuner, me only idling at ~70psi, or my fuel tank pressure from the in-tank pump, this should have been an indicator to me the problem lied with the HPFP housing itself. 70psi is ~500KPa so I should have been able to figure it out just by using Versatuner and referring to the workshop manual that the Housing was the problem. Lessons learned. I ended up breaking my hard fuel line from the HPFP to the fuel rail and replaced that too, and I have completed 8+ HPFP installs. I'm pretty much a master assembling/disassembling the engine bay and I know an incredible amount on the entire fuel system of the car.
 
Glad it's working finally for you! I'd be asking for a refund on that used hpfp assembly that should have been "working".
 
Awafrican said:
Glad it's working finally for you! I'd be asking for a refund on that used hpfp assembly that should have been "working".
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Unfortunately since it took me ~3+ months to get this resolved I am well past the refund window for it. I only paid like $100 for it. Lesson learned, don't try and save money and be cheap on such an important component. I'll save it to scavenge certain (working) parts off in case I ever need them.
 
By HPFP "Housing", do you mean the actually HPFP itself, as opposed to the internals?

Glad you found some resolution with this. It's an odd failure mode though, and not one that I've typically heard of with these cars. HPFP failure is exceedingly rare.
 
MacheteJames said:
By HPFP "Housing", do you mean the actually HPFP itself, as opposed to the internals?

Glad you found some resolution with this. It's an odd failure mode though, and not one that I've typically heard of with these cars. HPFP failure is exceedingly rare.
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Correct , I'm talking about the HPFP housing itself, not internals. Even the mazda dealer told me they dont see many of those pumps sold, but failure is possible.
 
suchamoneypit said:
Correct , I'm talking about the HPFP housing itself, not internals. Even the mazda dealer told me they dont see many of those pumps sold, but failure is possible.
Click to expand...
I'm glad that you were able to find the solution.
While it is frustrating as hell while you are going through it, I find that these are the issues that end up teaching/familiarizing us with so much of the car. Plus, it must have felt great to both find the solution, and realize that you had fixed it.

What about the housing was fouled? Was there a fuel smell in the engine bay?
 
suchamoneypit said:
Correct , I'm talking about the HPFP housing itself, not internals. Even the mazda dealer told me they dont see many of those pumps sold, but failure is possible.
Click to expand...

hey OP, I seem to be having this same issue after a recent engine swap. Drives just fine 95% of the time but it seems like making a low speed left turn always triggers fuel pressure to plummet to 50ish PSI, only to immediately recover after about 2-3sec.
Did the HPFP housing show any indication of failure or wear? I’m having all these same issues, even after a hpfp rebuild. So frustrating
 
In a similar boat as well and would like to know what about the housing can even go bad, along with any signs that might point out a defective one.
 
I'm having a similar issue as OP and the last two posters. My car is a completely stock early 2007 car with 109k miles. I had P0192 and fixed it with a new FP sensor. When I got my car back from the mechanic, it had a weird noise. From the inside of the car (with the door closed) it sounds like either some high pressure air hitting a metal chamber or tube, or something rumbling. From the outside of the car it almost sounds like a slipping belt. It's worst when the car is cold, and I don't know if it only happens below 3k rpm or I just can't hear it above that. With the hood open, the sound seems to be coming from either the HPFP toward the back, or from the wastegate actuator area of the turbo.

I had brought the car in mostly to get oil consumption looked at. Roger Beasley had told me the turbo was leaking oil. This independent mechanic found that #3 cylinder had oil control issues. I know they took TMIC off and enough to look at the turbo (they said it looks fine other than the oil it accumulates from #3 cyl). They also took the spark plugs off to do compression testing and bore scoping.

The car's power is fine and driveability is fine...until you go make a turn. It's worst/easier on left turns, but I can make it happen on a right turn. It acts like a rev limiter (but at 3k rpm). I don't get a traction control light and it doesn't feel like the torque limiter function when turning. After finding this thread, it sure seems like it could be the HPFP.

The main point of all this is to ask if the HPFP is known to make strange noises when it's failing? It does also seem to tick very loudly when running.
 
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