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she stumbles past 4k... is this limp mode

2K views 21 replies 11 participants last post by  amp 
#1 · (Edited)
she was low on fuel.. drove her to the gas station without boosting..
noticed that she wont go past 4k without stumbling...
after refueling... she took a while to start and thick black smoke was spewing out the exhaust but she started after multiple cranks..
same deal after driving her... wont go past 4k
going to remove the negative on the battery overnight and see what that does... any ideas on what this could be..

one thing to note is that i put on a new rad.. tstat and battery prior to this.. deleted the windshield washer tank...nothing was disturbed during this install
 
#6 ·
update... fuel pressure is @ constant 42psi.. it stumbles past 4-4500 at idle also
When you say constant I'm not sure how you mean that. 42 is good base fuel pressure but it should go up 1 to 1 with boost.
 
#5 · (Edited)
No - it is not limp mode. You will understand if it ever goes into limp mode!!
There could be a number of causes - it could be a fuel issue - something as simple as a filter.
Start with the simple stuff - although there are some serious problems that start this way. Jared at Speed for Sale could describe what we found when I had similar thing happen.... Ended up with a different head and some more stuff!!
 
#7 · (Edited)
... it could be a fuel issue - something as simple as a filter.
Start with the simple stuff - although there are some serious problems that start this way....
going to change fuel filter next... not looking forward to that
22 year old car... yeah i knew what i was getting into.. just hoping its not too serious


When you say constant I'm not sure how you mean that. 42 is good base fuel pressure but it should go up 1 to 1 with boost.
was referring to idle not under load... thinking perhaps it would indicate a clogged system or bad pump if low...
dont have a way to check or log pressure while boosting atm...

changed the plugs last night... gapped .25 ngk bkr7e
took her for a drive in the morning and same deal... pops and bogs past 4500
old plugs are black.. would indicate rich condition
no cracks on coils|boots...
 
#9 ·
was referring to idle not under load... thinking perhaps it would indicate a clogged system or bad pump if low...
dont have a way to check or log pressure while boosting atm...




This would be #1 on my list of things to check. What kind of fuel/ignition management are you running? Anything that can produce some logs would be helpful. Regardless, if you don't have a way to monitor, or at least log the fuel pressure then get one.
 
#11 ·
I had this exact problem on my Evo. Turned out to be a bad IACV AND Coils were on their way out..
You need to find a way to monitor fuel pressure, injector duty cycle, & afr/lambda while under boost.
Otherwise you'll just need to throw parts at it. In which case i'd start by swapping out IACV, the coils, and/or your fuel pump.
But yeh that boost leak test isn't a bad idea either.

Have you noticed any new noises coming from your gas tank, or injector ticking?
Pull the pump and check the coloring on the housing.
 
#15 ·
Sounds like it could something as easy as plugs. Turbo cars tend to foul plugs relatively quick, or the gap could have gotten messed up. Try just a simple tune-up. I have had cars stumble as soon as they hit boost, or once the timing advances the plugs cant keep up. Cheap place to start and youll have to do it eventually anyways.
 
#22 ·
so finally got to do the boost leak test..
she cant hold more than 3lbs of pressure..
the leak seems to be coming from underneath the fuel rail..
my guess is that its the intake mani gasket ... but arent these metal..
have had similar hot start up issues and stumbling with my old honda passport with a failed intake mani gasket..
should have remembered this..
i initially thought the leak was coming from an old line that ran to the bov but they tested ok..
line to fpr is ok too... anything else in that area where it could leak that yall can think of before i tear her down..
 
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