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idle ok, hit the gass and bogs down

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Hi guys,

got an isse with MY97 Boxster with a MY99 engine.

car started to act like a bad MAF of Fuel Flter problem that i've had before, under normal acceleration it would hesitate or bog down. (previosly that was the extent of it and changing the maf or fule filter fixed it, the problem never worsened before the fix)

This time however, it got worse over just a day or two, to the point now, where it will idle but as soon as the accelerator pedal is moved, even the slightest bit, it bogs down. sometimes, if i shut car off, then restart immeadiately, it will run "ok" but still seems sick.

used Durametric and grabbed these codes....

P0154 (i think this was pre-exsisting)



what i have done so far on Loren's advice from other posts with simillar issues.....

relplaced air filter (was using a K&N), cleaned MAF with MAF cleaner from CRC, checked for vacuum leaks with propane method and brake cleaner method, none found.

if i slightly crack the oil filler cap during idle, i get a significant negative change in idle, if i slightly crack a J-tube hose on intake, i get a significant negative change in idle. there is no smoke at startup.

last night after that work, i took the car for a spin about 1 mile total distance, it seemed ok, heavy accel was ok, idle was good.

this morning i go out to do another test drive and.... crud.... same relativley good idle with bad rev up. i shut off the car, restarted right away and it ran fine while sitting in parking spot, accel good idle good. i shut it off put the engine cover back on, restart and here comes the bog down garbage again, try restarting several times with no success in changeing the engine behaviour.

any idea where i should start looking now?

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Can't help you with the codes but…

Did Loren recommend a K&N filter? My recollection from sometime back is that they really stunk. Could be a real maf killer so full of oil.

Regards, PK

....was using a K&N, re-placed with a Mann

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Looked at the throttle body? If the KN was spewing oil into the intake, the throttle body could be covered with oil (see Pedro's writeup for cleaning instructions).

i will take a look and clean it, couldn't hurt, thanks for the pointer to pedro.

was thinking about this last night.... my duramtric described the p1126 code as a fuel pump relay problem. this does not jive with my manual or the code descriptions here. i didn't think anything of it before because odds are this is just a messup in duramtric, but maybe i'll pull the relay start the car and see what happens. (if this will kill my engine or blow up an orphanage in mexico, please stop me, i will be performing the test at 3:30ish Arizona time today)

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Loren has NEVER recommended a K&N filter to anyone. I am very sure.

to be clear, because some people did not understand what i said about Loren's recommendations and to make sure no one else makes the same mistake...

"what i have done so far on Loren's advice from other posts with similar issues.....

replaced air filter (was using a K&N), ...."

Loren's recommendation was to REPLACE the Air filter. not to get a K&N,

the comment in parenthesis was to show for complete disclosure that i WAS using a K&N BEFORE i did what Loren recommended... replace the Air Filter...., that way readers would know the condition and configuration of the car when symptoms first presented.

now that we've put that to rest...

I replaced the Fuel filter as my hunt continues, car seems to be better but not fixed.

is there a test i can do with durametic that will show in some way the volume / pressure of fuel?

Edited by kedf1
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performed voltage test at fuel pump connector, PASS

unable to perform pressure test,, i dont have the tools

performed fuel volume test, FAIL

i collected maybe 250ml, the fuel spurted out erradicaly, not a steady stream.

if someone would be so kind as to confirm this is a symptom of a bad fuel pump and likely not another component of the fuel system? ( note: i just put in a new fuel filter)

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As long as you don't have a pinched line somewhere from the front to the rear of the car and your measurement was at the fuel rail - then it pretty much has to be the fuel pump.

test was done per bentley manual instructions, at the fuel return line at rear underneath car.

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thanks guys,

i replaced the fuel pump and we are good to go. i think i have been dealing with a underperforming pump for some time as the car feels more spritely and smoother then before the major symptons presented.

so in conclusion...

i had codes P1124 and P1126 due to a lean mixture caused by a failing fuel pump. the pump did not fail outright, it slowly died. the volume test exposed the failing pump.

the car had a "good" idle but sometimes hesitated and stumbled in acceleration, i could drive it for the first day if i was easy on the pedal, the condition did worsen rapidly over less than 50 miles over a few days to the point where idle was affected.

i bought the VDO pump at BAP in Scottsdale for $245 and i replaced the sending unit rubber seal $10

i did not drain the tank completely, i left about half a tank, the issue with that is i had to wear a rubber glove to install the new pump which made holding it and the indexing of it on the lugs a little difficult, but it was easier than using my fluid transfer pump.

i used the hammer and screw driver method for removing the retaining collar, i would have much preferred using the special tool if i could have found one localy.

thanks again, i appreciate the help and insight.

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