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lag under full boost

notchy

notchy

New member
View attachment 10106Hey all, so my 02 gtp started laggin out or sputtering while in full boost a few months ago. It runs perfect besides that. If I let off the throttle slightly when it starts to "miss" it is fine, I just cant lay in to it fully. Last week it threw a code P0420.. lol... which is numerous possibilities. I have aftermarket exhaust, which is how i bought the car a year ago. I have since replaced the oxygen sensor , but it didnt quite thread in properly to the new exhaust, probably need to clean the threads from slight rust perhaps? I do have a small coolant leak visible right on the gasket on intake a half inch from the injector port. There has been condensation on the oil filler snorkel every time I take the cap off, and occasionally , some slight yellow sludge which im assuming is a wee coolant leak from that intake manifold into the oil. Which could explain the code.

bla bla bla, anyways my question is what to do for this lag and power hiccup at full throttle? I will fix my oxy sensor and thread it in to full depth and do more inspections but thought i would throw this one on the forum for help.

thanks all.
Notchy.
 


P0420 code is the cat. Aftermarket cats are known to throw codes. Your bogging issue indicates that your cat may b clogged.
 
she smells fine, and ya probably factory cat, ill look tonight. so delete cat or replace with higher flow etc?
 
with coolant showing up by the injector, its time for lim gaskets as well. that would be the only place it can come from.

just did mine the other day, its fun. not really but its easy enough to change.

10106d1353084638-lag-under-full-boost-photogtp2.jpg
 


hey all, so... upon inspecting further, hell ya its time for new gaskets. Also when i removed the pcv valve it was so gummed up im surprised if any air got through it. The boost lag out is gone until it gums up again in the pcv. Time to open her up and clean er out, i may as well do lifters while im in there??? so a new question is, best gasket brand... Fel-pro? ive heard
 
make sure you get the metal lower intake gaskets. i got ac delco's from rock auto. then used a felpro sc gasket, its called a upper plenum gasket, just so you can find it easier. hell the auto zone guy had no clue till i told him what to search for.


the lifters, id leave alone, unless your are ticking like mad.
 
don't know if i should chime in, but about a year ago, my car was lagging/sputtering at wot/full boost and i found i had a plugged cat...

i decided to cut it out and haven't had any sputtering since at wot/full boost!

i do believe that the plugged cat lead to the demise of my crankshaft positioning sensor and my computer pulling a code p0336...

this sputtering at full boost/wot was one of the initial signs of something being wrong with my car...

just sayin...

and i hope it all works out for you.
 
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thanks i have heard that too. So without the cat does the rear 02 sensor still work proper, is that sensor more of a heat related one?
 
no, i don't think it would work properly after having your cat cut off and a straight pipe put in (i think this is where you'd have to get a 02sensor delete, or something like that)... in my case, i believe my cat was taken off and gutted and then re-installed, so there is still a place for the 02 sensor. so far, i haven't got a code for the cat, but only time will tell. i did get a CEL months ago, which i thought could be because of this very reason, but when i took my car to the mechanic's this past week to get the crankshaft positioning sensor done, he never mentioned anything about the car pulling any type of "cat" code... so, i really don't know.

all i know is i'm not planning on selling this vehicle for quite a while as i like driving it, so i'm not worried about any such codes unless it would cause severe damage to it, but my mechanic didn't mention anything like that either??? but, why would he... lol

when he had my car all done he gave me the fouled crankshaft positioning sensor and i asked if there was any way to "test" it to see if it was still good or bad... he said there wasn't, so i just left it at that.

now i know i've driven atleast 30 miles, the car has reached the same level on the temp guage, and the car hasn't pulled any check engine lights/stalled/sputtered/backfired or what have you, so i'm thankful and hopefully this worked! my mechanic seemed to think it did fix the problem. he scanned my car while i waited when i dropped it off, and then when i went home i researched the code here to find out about changing this particular sensor and for what reasons, symptoms, etc... i called him back and informed him of what i found (kinda like doing the leg work for him and then he just had to do the work with his tools/shop/etc...).

i wish i could tell you more, but this is just what happened to me and so far so good. it wasn't that expensive and supposedly the only problem is taking the harmonic balancer off (you need a special puller for the job) to get at the sensor. good luck with yours and definitely let us/everyone know how you make out. that's exactly why i looked here first to try and find the solution! hopefully i did!

:)
 


i will let you all know how it turns out. my gaskets are on order and should be here soon. Now i just gotta convince a buddy or fam member of using their garage for the day so i dont freeze my ass off in the prairies. lol.

A big thanks to all of you who posted, what a great world we still live in. cheers.
 
well, it all worked out great. All gaskets replaced, all fluids changed ( that needed to be ) only problem was misfire when I started her back up.... long story short , after some trouble shooting and eliminating possibility of bad plug, wire, injector... it turns out you should plug in all 6 injectors not just five of them ... smrt!
 
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