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fuel cut on stock 1g, possible boost creep?

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Overkill54321

Probationary Member
15
0
Dec 20, 2010
calgary, AB_Canada
ok so im going to try and include as much info as i can to help with suggestions so this may be a bit long, i have searched all over the forums and found similar problems but not quite mine,

i rescently picked up a 1990 awd dsm with about 200000 miles on it for next to nothing, not sure if its the original motor but im thinking it was not. from what i can see the only mods are a hacked air can, bcs restrictor and stock exhaust with the cat cut out. i have no gauges in the car YET but since i plan on keeping the car pretty much stock as a winter beater i dont want to add more than i need. i have changed plugs, wires, air filter, ran a couple bottles of injector cleaner through it and i run 94 octane only. i flushed the coolant and never see the temp go over the halfway point. i have tightened up alot of loose or missing bolts in the engine bay and exhause and there is no lifter or valve noise so im tending to think this is not a knock issue but if it comes down to it i will install the knock sensor LED. tomorrow ill change out the fuel filter and im wondering if a clogged fuel filter could make it feel like a fuel cut because it cant flow enough?

on the stock boost guage the needle goes almost to full (1.0) even with half throttle and then i feel the fuel cut, first gear feels pretty good until the high rpms but after 1st i can tell for how much boost im getting it is not accelerating even close to what it should. im not sure where the needle should be with stock boost but i am thinking i am getting fuel cut due to boost creep because of the missing cat. would that be enough moding to the exhaust to cause boost creep? i know that porting the o2 housing and wastegate are solutions to this problem but i was hoping to avoid this unless nessisary. i have replaced my vacuum lines but i have not checked things like the wastegate or intercooler for leaks yet, would something like that cause the sysmptons i am experiencing?

are there other possibilities i am overlooking? i had a 92 that just had a boost controller and nothing else on it and it hit fuel cut HARD, when my 1990 hits "fuel cut" it is not as abrupt which made me think it was detecting a knock but maybe it doesnt feel as hard because im not running 16-20psi when i hit the fuel cut.

anyway i hope i didnt overload with non important info.
 
The stock gauge only let's you know there is positive pressure based onan electrical input. You need a real boost gauge to determine boost creep.

Did you change out the fuel filter at all?
 
I would try and get a real boost gauge like Liquidx said. Also too what he said about a fuel filter. You may be experiencing fuel cut because your fuel system can't cycle fuel properly and you will not get the required amount of fuel with a clogged filter.
 
i ordered both the oem fuel filter and a universal fit but i havnt changed it yet, made one attempt quickly but the banjo fitting was on there really good, i was thinking id torch it off, jk LOL

and while the rpms are climbing, it suddenly stops reving or accelerating until i back off the throttle, since the car isnt running good i really havnt been hard on it so this is under medium to moderate throttle only.

oh and the cut happens at almost the exact same place on the factory boost meter every time.

one thing i forgot to ask, with the BOV stock, should i be hearing any kind of noise in between shifts? its not loud like if the tube was off the BOV but it does make a noise
 
That fitting can be a real PITA! Change it out and see how it goes. Don't forget to de pressurize the fuel system before messing with it and wear goggles when you initially take the lines off for a possibility of gasoline spraying out.

A while back, I was changing out the fuel injectors. I unplugged the fuel pump and just kept starting it until it wouldn't start anymore. I thought it was de pressurized. Went and pulled out an injector and got sprayed in the eyes with pressurized gasoline. Not fun.
 
ouch that doesnt sound like fun at all, i will do that tomorrow and see if it makes a difference

ok so update, got in the car today and tried to start it and it started fine despite it being really really cold out, but it choked out right away every time. I pop the hood and start poking around and sure enough the BOV is on loose (like half of the stuff in the engine bay when i bought it :( ) so i tighten it up and car runs great and no fuel cut. anyone having a problem like me i would recomend checking out all possible vacuum leaks.

Thanks for the help!
 
quick question for you does a universal bov leak often?? because its not flanged on its like set screws for a shift knob bought the car that way.... and im experienceing fuel cut problems and bogging sputtering in mid to high rpm range... help??
 
The best thing you can do to answer your question is to do a boost leak test with some very soapy water sprayed on. This will show if you have any leaks that would cause issues. If you need more help with a boost leak test, try searching and if you are still confused... post back and we can help out more.
 
what will a boost leak cause??? bc it sputters around 3krpm till 5500rpm. and it seems like it spools really slowly and not consistantly... like 3k to 3500 is when we start to pull positive pressure.... that seems late to me...
 
what will a boost leak cause??? bc it sputters around 3krpm till 5500rpm. and it seems like it spools really slowly and not consistantly... like 3k to 3500 is when we start to pull positive pressure.... that seems late to me...

Thats what a Boost leak will do
 
k sweet, bc we thought we might have to replace plugs and wires... we will still probly do that just to make sure its being put back together right. ya know. what are the best plugs and wires to pick up?
 
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