Bucking at full throttle? what do I do
 

I installed the greddy turbo system and very carefully searched the forum for installation(to make sure I did it right) and problems. but I dont' see anyone else with this problem.

car
1992 1.6
greddy turbo and intercooler.

thats it
here is the problem.

the car runs fine idles fin and everything all they way up to 4000rpm.

once I step on the gas (floor it) past 4000rpm the car startes to jerk like riding a wild bull. (yes really that bad, and yes I have ridden a bull before). any ideas what is going on? or a link to where on this forum someone else had this problem?

my thought was not enough fuel, but then again I know nothing about cars.

Please help me.

Did this just start happening? How long have you owned the car?

I had a garage rebuild the engine. the engine ran perfect until I put in the greddy.

I put 400miles on the greddy to break it in then took it out today to run it and this happened

and I put about 20,000 on the car after the rebuild

Install a saddle and hang on!!!!!!!!!!!!


Double check all your piping clamps- a blown off pipe might cause it), and spark plugs, loss of spark would cause it.
What plugs and gap are you running? Could be flameout??

running ngk ir 35 gap checked all the pipes and tubes and connections and everything

the bucking is so bad there is no way I would be able to control anything

Make sure the AFPR is hooked up correctly. I think this can happen if you have the lines reversed. This is happening just as you are entering boost right?

When it happens can you see a black cloud of smoke belched from the exhaust? Did you do a check of the stock fuel pump to make sure it was healthy? New fuel filter?

I had the stock fuel pump checked I put in an another inline fuel pump and put in a new fuel filter.

i checked the afpr lines and they are hooked up according to the manuel and I did a seached and they are also as stated in one of the instalaiton posts on here

any other ideas?

What fuel pump, what AFPR and how much boost? Do you know what your fuel pressures are?

zex inline fuel booster

the vortec thing that comes with greddy

and no I don't know

stock boost so i assume 5 but i get like 1-2 psi (if I am lucky) and it starts bucking

You are probly overfueling your system with that zex booster. Take it out! The stock fuel pump produces enough fuel for the greddy kit up to about 6psi.

Sounds like when you hit the Rev limiter on an NA, has the Rev limiter been droped to 4k?

How in the world could that happen with just a basic greddy kit?

how does it happen I have no idea I am dumb when it comes to cars.


could it be the slipping (clutch grabing and releasing)?

just curious because when it happens the car revs high then jerks and sone on

I bet you $5 your fuel lines to the FMU are backwards or wrong.

The line from the back of the fuel rail (firewall) runs into the offset fitting of the FMU. Then the center fitting runs backs to the hardline.
The line to the front of the fuel rail (radiator) should still be connected straight to the other hard line.

if it's not the fuel lines, i would consider the injectors. sounds like you are losing one as the load/demand increases.

overly rich, or too lean. I would get some NGK ZFR6f-11 plugs and gap them down to .028 to make sure spark isnt getting blown out. I still think its a fuel issue though.

Look on my pages under two sections ... Greddy Install and Vortech AFPR. Can run a complete check on the fuel system to include the AFPR in about 10 minutes. Can decide if that is the problem or not.

did you check your timing? try setting your base timing to 6 degrees.

Do you have any other items added that you haven't told us about? Emanage? Bipes? WI? anything that would cut your ignition in error?

is the gap suposed to be .35 or .28

no other items

yes the vortech is connected properly
yes I had a mechanice change the timing too

Can you take a picture of the whole installation and post it? Maybe we will see something.

yeah I'll try asap

And i want to thank everybody for taking the time to help me out

are the gap in my plugs suposed to be .35 or .28

Suggest starting at .035, and if you like to tinker gradually keep enlarging in small increments. The stock gapping is .044, but that may be too wide for the spark to arc thru the higher pressure during boost.

I will be away from the computer for the next day, but what I wanted to look for in the pictures was any hose on the intake side of the turbo that might be collapsing and cutting off the airflow, then opening, and closing again.

Its that stupid fuel pressure regulator that comes with the kit, same thing happend to me. you have the fuel lines mixed up. Rev2Red wrote this to me when I posted the same question on miata.net. He said "Go over the FMU and make sure the lines are correct. It should be tapped into the return line. So the line comming off the far end of the fuel rail (firewall) should be going into the offset fitting on the FMU. Then the center fitting should be going back the the hard line." and bam!!! my car was hauling ass!

I was just wondering if his problem was ever figured out. I have a drop in power at 4100 that comes back on about 4800 but thats a totally different issue but just for curiosity sake I'm wondering if it's related. I run my gaps at .028

-LAZ

At about 4000 RPM, you are probably going to open loop on the ECU. If you are not running an O2 clamp, you probably have pretty high fuel pressure at that point when the ECU moves from trying to maintain Stoich with the oxygen sensor to a preprogrammed map. This extra fuel can cause a lack of power until your engine brings the AFR up as the RPM's (and fuel requirement) increases.

I'm boosting 6psi by about 3000 and the air/fuel meter is sweeping away. At 4000 it drops off the scale red till about 4500-5000 then it goes into green and the power comes back. Between 4000 and 4500/5000 I'm running on borrowed time. :sadwavey: bye bye pistons if I can't sove this. Explain the egr clamp? What exactly is that? I'll have the AEM EMS in about a month but untill then is there a "quick fix" that might help?

-LAZ

EGR? wtf am I thinking. o2 clamp.
sorry.

-LAZ

An O2 clamp sends a phoney lean signal to the ECU as you enter boost so that the ECU tries to add more fuel to compensate for it. It only operates until the ECU goes to open loop, then it has no effect.

What pump are you running? Sounds more like a lack of fuel being available there.

you and like ten others were having the same problem and it seemed to help. (btw I'm Rev2Red over there)

I'd like to know if chowder fixed the problem....:confused:

That could be your problem right there if you already checked your fueling as suggested. That stubby short spark may not be long enough for complete or consistant combustion.

I don't think it would be the plugs. Incomplete combustion should read rich on the gauge then wouldn't it? But it's easy enough to try. What gap is suggested? Just to verify... The fuel into the regulator is on the side and the outlet (return) is on the bottom? I think I tried it both ways with no noticable change. Read: "same problem" My fuel pump is OEM and dead-head pressure is about 80-85 psi depending if the car is running or not. Ironiclly it's higher while running. I would think the pressure would be a bit lower being that the engine is using fuel but it could be due to the voltage being higher while running.