HELP!!! Bucking and Jerking at cruising speed

[88GTStreetRod]

Yah, that's another issue. When I bought the car, I was told it had the cobra mass air conversion. Cobra mass air requires 24lb injectors and 19lbs mass air because the computer is programed to run this way. I upgraded the mass air to a 75mm 19lbs unit sevral months ago when I had my old set up (GT40P Heads and Cobra intake). The car ran fine. I changed the heads and intake leaving the 75mm 19lbs mass air and the car runs like crap. I looked at the computer, could not tell if its cobra or not (Computer code is X3Z) So I bought today a 75mm 24lbs mass air meter. The car idles great now, no more surging or stalling. The bucking is still happening. I have the battery disconected right no, hoping that this may clear the computer. I was gonna try lowering the fuel presure more for a quick ride just to see if that changes anything.

your new mass air meter is calibrated for 24 pound injectors correct?

 

[88GTStreetRod]

What is a TFI? Sorry still learning.

I had a problem with my 5.0L, would buck and jerk at anything but WOT, changed EVERYTHING, starting with the TPS,down to 02 but to no avail, it turned out to be a bad TFI, which usually just have heat soak failure..swapped in an old spare, no more problems...was that ever agrivating..

 

[Pops Fun]

What is a TFI? Sorry still learning.

Iam having a similar problem. My son sent me this Haven't tried it yet.... Let me know if it helps.

http://www.pro-flow.com/tech info/troubleshoot.htm

Steve

 

[88GTStreetRod]

Thanks, I have tried evryone except the Crankcase, I will give that a shot.

Iam having a similar problem. My son sent me this Haven't tried it yet.... Let me know if it helps.

http://www.pro-flow.com/tech info/troubleshoot.htm

Steve

 

[88GTStreetRod]

Anyone have any other ideas? Could the computer be doing this? What about the fuel pump? But if it wear the fuel pump, would'nt it buck and jerk at all speeds?

Thanks, I have tried evryone except the Crankcase, I will give that a shot.

 

[5.0Droptop]

What are your plugs gapped at? I have read many guys with the newer MSD Ignitions run a lesser gap. I have read guys had so many issues with MSD they took it off and put stock ignition on and it fixed it. Sounds like fuel/ignition

 

[5.0Droptop]

The TPS is brand new, do you think I could have a problem with a new one? I will try anything. I have dumped $4K into this car in the last month. If i do not get it running right, I may be forced to light it on fire!

No not likely if the tps is new.
What did you find out about your EEC? is it the cobra or the A9L or A9P ?

 

[88GTStreetRod]

My computer is a X3Z. Any idea what this is?

I went to mustangs unlimuted down the street, had them pull a cobra mass air conversion kit out. The number on the comra was not what I have. I took my car to a speed shop, they tried several different gaps. I also thinks itis a fuel or ignition problem. I repalced MSD, Accel coils, wires rotor, etc. If it were a fuel problem would'nt i see it in other areas other than cruising speeds?

No not likely if the tps is new.
What did you find out about your EEC? is it the cobra or the A9L or A9P ?

 

[5.0Droptop]

X3Z - 93 5.0L Cobra 5-spd

 

[5.0Droptop]

thats all the info I could find on it right now......But that means your 19# maf is ok because the eec will make up the differnce. Have you tried clocking the meter? as in turning it 90* cleaning the wires,

 

[5.0Droptop]

Do you have a code scanner? Have you tried the key on engine running test? This will tell you if its lean or rich and if sensors are not working properly. The engine needs to be fully warmed to operating temp.

 

[88GTStreetRod]

I just found the same infor about the computer. I bought a 24lb 75mm mass air meter Saturday, Installed it and my idle surge and stalling problem went away. Go figure? I found a guy on the internet that has the X3Z computer and runs 24lbs injectors and 24lbs 75mm mass air on his 88 GT. May be the 24lb Mass air is interchangable with the cobra computer? I had a scanner run on it,the only thing that came back was that the Oxygen sensors were contaminated. I think this was from my old heads that were burning oil. The sensors were very white indicating running lean. We bumped up the fuel presure and changed the sensors, no improvement.

Do you have a code scanner? Have you tried the key on engine running test? This will tell you if its lean or rich and if sensors are not working properly. The engine needs to be fully warmed to operating temp.

 

[5.0Droptop]

Did you reset the eec after changing the o2 sensors?

 

[5.0Droptop]

Whatever works I guess.

I just found the same infor about the computer. I bought a 24lb 75mm mass air meter Saturday, Installed it and my idle surge and stalling problem went away. Go figure? I found a guy on the internet that has the X3Z computer and runs 24lbs injectors and 24lbs 75mm mass air on his 88 GT. May be the 24lb Mass air is interchangable with the cobra computer? I had a scanner run on it,the only thing that came back was that the Oxygen sensors were contaminated. I think this was from my old heads that were burning oil. The sensors were very white indicating running lean. We bumped up the fuel presure and changed the sensors, no improvement.

 

[88GTStreetRod]

What will turning the meter do?

thats all the info I could find on it right now......But that means your 19# maf is ok because the eec will make up the differnce. Have you tried clocking the meter? as in turning it 90* cleaning the wires,

 

[5.0Droptop]

What will turning the meter do?

Some times when you put a new meter on you have to clock it ot Turn it to get it to not surge,sometimes this is necessary if you have a CAI kit.