Stuttering Before Boost Is Reached?@! Help!

[imprsv]

Hey There,

Got my new engine put in this week, and after a bit of driving around etc i've noticed that sometimes when the revs are low and building up to boost

at about 2500rpm the car stutters a bit and feels like its holding back, then once it gets past there it boogies.

Now, i had a major issue with one of the cams f**king up so one of my old cams was used in the motor as the other was broken, now if the cams were say to be different would this cause the issue? The cams supposably on the new engine were NA ones but im unsure of this as a fact.

The car doesnt really pull hard on 14psi as it used to, it used to throw you back in your seat now the car just seems to pull along the revs?

Also thinking Injectors or fuel pump?

Help! I wanna get this fixed!

Trent

[paulr33]

ask the engine builder

if the engine is only a week old it could be anything and u should tell them straight away to make sure its covered etc

[imprsv]

Ah it was a rebuild motor previously so it has done now 40,000kms

[paulr33]

oh ok sorry - so the engine was just put back in the car?

id say something is loose, like a hose clamp, intercooler pipe work, the air vac lines for the actuator etc - something along those lines?

[BDC70T]

i had similar thing happen on a golf vr6 i owned... found one of the spark plug leads had a slight incision in it and it would amp outside the lead causing it to misfire at low revs... hard to spot though... try check your plugs and leads?

[imprsv]

Yeah i might have to go over my plugs and leads, hopefully its something small

[sik14]

i had the same problem with my 33. i closed up the gap on my plugs a bit and it helped. i ended buying new coil packs and the problem went away. also now i have heaps more torque. sounds like the same prob your having???

[imprsv]

Well its not the gap on the plugs

After a fair bit of reading ive come to the conclusion that its the fuel pump not sending enough to the engine, probably causing it to lean out. The car runs fine when cold but thats when its running rich but as soon as it settles its stuffed.

"Many of you with S13s have probably experienced hesitation on boost which can start to happen when the standard fuel pump is getting old."

I believe thats what my problem is.

Now im estimating that its dangerous to drive the car whilst in this state, i.e fuel pump could break down, or could lean the engine out.

Would i be right saying that?

[BANGN]

it will be dangerous for you to give the motor any reason to demand more fuel yes.. like cracked piston spec. putting around not so much the best thing for you to do man is take it to a dyno and get your air/fuel checked out they will be able to tell u if it is leaning out or not, if so extreemly likely tis the fuel pump

what gap and how much boost are you running? I was running 14 psi and I had a stutter even after I put in a new 040 pump and pulled the gap from 1.1 to .8 and it stopped it

Edited December 30, 2007 by BANGN

[imprsv]

It's def the fuel pump im thinking, i cracked a piston in my old motor couldnt find out why.

Found out why now.

[imprsv]

Car was datalogged today, we found that the timing was out. We also adjusted the teeth so that it was sitting perfectly.

We also changed over to a working CAS which still didnt fix the problem, the timing was jumping around from sitting on 15 to 7/8 up and down. Also tried a few diff coilpacks but we are unsure if they are working correctly.

I'm waiting on my walbro replacement to come back then ill be installing that into the tank see if that fixes the issue, other than that its coil packs/injectors we are thinking.

Anyone able to add some to the situation?

Also, if somone could be nice enuff who lives in the melbournes west to let me borrow there coilpacks for 2 minutes to see if the car runs any better would be appreciated.

For a 180sx SR20 Red Top

Anyone who can help either post or pm me please!

[r33747]

My car does the same sometimes, most likely cause would be either fuel pump or injectors. i have a power fc and when it happens i look at the inj duty and its 100% . It never used to it when i had 550cc in there. Two ways to fix it....

1. Bigger fuel pump, Fuel reg and bigger Injectors and tune.. or

2. Turn the boost down.

[imprsv]

Boost was turned back to stock, same issue still occured.

Its going back to mechanics they can find the problem.

[Mr_GaZZa]

someone in another thread said its o2 sensor!!

can any1 confirm??

got simarly problems...