revs up to 4K then cuts/jerks

[97t4mitsu]

i just recently installed a turbo on my car, along with a few other items, injectors, cams, bigger TB, and it has done nothing but lead me to trouble. the biggest problem i am concerned with right now, is that my car WILL NOT rev over 4,000 RPM. No matter if i'm in gear driving or in neutral idling.

if i'm in gear, driving obviously, it will not go over, the second it hits 4K it cuts and shakes/jerks violently until i shift up or let off the gas. the only way i can get it to go over, is to downshift and it'll hit around 5 or 6 and just slow down, and if i give it gas it still shakes the same. one thing i notice is on my air/fuel, it drops VERY rapidly from rich to lean at about 3900-4000 and the second it starts to drop, just a few bars, it does it again. i'm thinking this could this be fuel cut because of the turbo...but i'm only pushing 8 pounds right now. thanks for the help guys

 

[Blitzeclips]

i just recently installed a turbo on my car, along with a few other items, injectors, cams, bigger TB, and it has done nothing but lead me to trouble. the biggest problem i am concerned with right now, is that my car WILL NOT rev over 4,000 RPM. No matter if i'm in gear driving or in neutral idling.

if i'm in gear, driving obviously, it will not go over, the second it hits 4K it cuts and shakes/jerks violently until i shift up or let off the gas. the only way i can get it to go over, is to downshift and it'll hit around 5 or 6 and just slow down, and if i give it gas it still shakes the same. one thing i notice is on my air/fuel, it drops VERY rapidly from rich to lean at about 3900-4000 and the second it starts to drop, just a few bars, it does it again. i'm thinking this could this be fuel cut because of the turbo...but i'm only pushing 8 pounds right now. thanks for the help guys

Do you have a FCD?
If not, do a search on it and you will see what I am reffering to..

 

[BigRand]

PM the moderator VelocitàPaola, he makes Fuel Cut Defenders (FCD) for our applicaition.

 

[Locke]

are the cams aligned properly? and if you installed a big cam, did you get the springs/retainers for them as well? i put a lunati 480 grind in a SBC and the degreeing chart kept slipping, first run I couldnt get it over 4500. redegree'd it, and got it to 6500.

 

[97t4mitsu]

first, i've got some crower stage 2's but i'm pretty sure the cams are degreed properly, i had a local machine shop do those so i didn't mess anything up. and i also mated them with some titanium springs/retainers.
second, just took out my SAFC II, and rewired my map sensor back up, and it redlined for a couple seconds when i first turned it on, then i drove it, and now it's doing the same thing.
and third, no, i don't have a fcd, will look into it though.

 

[420a-t]

yeah man you need to get an fcd asap. you'll be able to drive your car, but it will run like poop. i just had the same problem with mine where i had my fcd working but the wire i spliced into for the power for the fcd (windshield wiper) kept popping the fuse for it.

btw, how many 420a guys are there in utah? i cant seem to find anyone here...

 

[BigRand]

yeah fcd is your problem.

It'll redline because its not going to see boost with no load, but sure enough put a load on her nad she'll do it everytime. Map sensor just doesn't like to see a positive reading (anything over 5volts). So just pick one up, wire it in, and you'll be boosting all day everyday in no time.

 

[TheCykotik1]

sounds like the timings off to me. i had that happen after i did my timing belt and found out i didnt have the timing set right. also when u put on the turbo did you use a missing link on the map sensor?

 

[jreese86]

If his problem is fuel cut, wouldn't it be avisable to do a thorough boost leak check, and turn the boost down? That would be the simplest check here.

 

[TheCykotik1]

dont think its boost leak. no MAF on 420a.

 

[VelocitàPaola]

sounds like a timing issue to me. that happened on my car at 4000 after i did the timing belt and didnt have it aligned right. also did u use a missing link to keep the MAP sensor in check?

If his problem is fuel cut, wouldn't it be avisable to do a thorough boost leak check, and turn the boost down? That would be the simplest check here.

No and no. His problem isn't timing, and this isn't a factory turbo car... A boost leak won't necessarily cause fuel cut in 420As like it causes in 4G63s. That's because a boost leak in 4G63s looses metered air (measured at the intake), whereas a boost leak in 420As looses air that won't be accounted for until the intake manifold.

Get an FCD, that's your problem. PM me for details.

 

[DGajre777]

No and no. His problem isn't timing, and this isn't a factory turbo car... A boost leak won't necessarily cause fuel cut in 420As like it causes in 4G63s. That's because a boost leak in 4G63s looses metered air (measured at the intake), whereas a boost leak in 420As looses air that won't be accounted for until the intake manifold.

Get an FCD, that's your problem. PM me for details.

Interesting... we all learn something new everyday.

 

[4UH8ERS]

Interesting... we all learn something new everyday.

metering in the form of MAF compared to MAP it will all make sense to you one day.

 

[TheCykotik1]

what exactly does a fuel cut defender do to prevent fuel cut?? alter a few sensors or what?

 

[DSMcrazy3]

Limits the amount of voltage sent to the ECU from the MAP sensor. Once the ECU sees too much from the MAP(I can't think of the exact #, I'm sure someone has it) the ECU will freak out and think something is wrong, cutting the fuel supply.