c.stenson1

hi, i have a question for all those guru`s out there. i have a 93 twin turbo that runs fine when driven slow, i can get it all the way round past 8 on the rev metre, but as soon as i give it some gas i have the biggets stumble, almost throwing me out of the window followed by the biggest back fire you ever did hear. there is next to no boost on the turbo meter i have installed, it used to go round to 14 psi, the pipe is on ok at both ends from the meter. i have changed all the ground cables, new plugs, new leads, chaned a few solanoid valves which had broken, had a diognostic check found the fuel pump relay might be faulty so changed that, i also changed the ckeck valves with the viton ones from dale all with no change. my car is completely stock, could a high fuel pressure be to blame, i have ran out of ideas of where to go next, can any one advise please, please, please. cheer phil.

BlueTII

Sounds like you are having a MAP sensor issue.

dpeak

Sounds like you blew/cracked a boost hose or maybe limp mode.
1.Make sure all your pipes are well connected and in good condition.
2.Is your check engine light on? If so, pull the codes and post them. Disconnect the battery for a few minutes to reset the ECU, drive it and see if it exhibits the same problems.
3.Oh..... make sure the Boost sensor hose is connected.
4. Check ignition coils.

Is it only breaking up under load or does it break up while your sitting still too?

c.stenson1

i forgot to mention i have checked all the rats nest little vaccum pipes under the uim, and all the ic hoses all ok now, there is no light on the dash but i have done the battery off and tap the brake pedal to reset the ecu. i had it plugged in for the diagnosis and after the fuel pump code we never got another code. it is ok sitting still and driving carefully its only under load i get thrown out the window and deafend. where is the boost sender and hose and how can i check the ignition.

Marc01

I'm having very similiar problems, as soon as my car gets out of vacuum it stumbles and boggs down. If I keep the car at full throttle it'll stop gaining rpm and start bucking violently. It was bucking below idle a little, I adjusted my TPS and made sure the connector for it was snuggly in place and that fixed it in the vacuum range. I'm still searching for a problem in the vacuum nest. Getting some vacuum line today to reconnect some solenoids (it started raining on me yesterday). I've replaced the lines with restrictor pills with the manual boost control after finding the pills were long gone. I'm starting to wonder about the map sensor. It is connected right, but there must be some way to test it. Nobody around here has a FD, so there won't be any quick swap and check. The only thing I can think of is to order a new map sensor, plug it in, if it doesn't fix it, return it, if it does keep it... Maybe go to a GM sensor to save money, plus upgrade. When going to a GM 3 bar map sensor do you need to replace anything on the harness or computer?

c.stenson1

just beed out to check the square black thing on the top right the fire wall near the brakes (i think its map sensor), anyway the black valve going to it, i can blown through it both ways is this right. oh and what is the tps and where is it.

Marc01

its not a check valve! Its a gas filter. You should be able to blow through it both ways. Your map sensor wouldn't ever be right if it was a check valve, it'd just hold the highest pressure it had seen in there. The tps is right across from the map sensor. Mounted to the throttle body between the TB and the firewall. It can be quite difficult to get to. I adjusted mine by taking off the UIM (I had it off anyway), plugging it in, and connecting the ground. Gave me a LOT more room to play with it.

BobfisH

sounds like spark plugs, i had the same problem and a few other members have had it too.

Ignore the fact your spark plugs are 1k miles old (if they are!) mine went faulty after a week...

c.stenson1

thanks for the help, i will try the spark plugs again, but do you think my spark could be weak and need an ignition amp to help it, could my fuel pressure be to high or mixture and that is blowing the spark out or could it be another solanoid valve that i havent checked yet if so which one. i have the custom solanoids coming from america off a group buy but at the back of my mind i dont think they will solve my problem, any thoughts.

rotary

marco i think your in limp mode. this means your metering oil pump is bad or a related part is. it is expencive brand new i advise a used one if this is the prob. are you having a check engine code?

Marc01

I don't want to steal this thread, I have my own somewhere down the list. But no, no codes. I don't think its limp mode because I get full boost above 4500 rpm. And it wouldn't make sense for it to be spark plugs, as spark plugs would get worse with more pressure and higher rpm ... right? Mine have ... 100 miles at most on them.

Integrals

damn this is my exact problem to. I noticed my gas filter was in backwards, i wonder if the pressure sensor is fucked...

turboIIrotary

iTrader: (9)

are these cars stock....i had a similar problem with my fc everytime i got right out of vacuum it started bucking...i then bought a downpipe and it was fixed so my cat was clogged.

Integrals

mine is stock but is Decatt'ed