Hi,
Im writing on behalf of a friend who owns an 89' MA70 7MGTE supra. The car was purchased about 2.5 a half years ago with a number of pre-existing problems. Since the purchase of the the clutch, timing belt, steering rack, centre bearing and a heap of vacuum hosing has had to have been replaced. The car has been modified a small amount and has a GReddy E-Manage Blue piggy back ECU that was fitted with the car. I have connected this to the computer and have the ability to view airflow and ignition maps in real time.
Ever since the car was purchased it has has an extremely irritating and somewhat unsafe problem in that it severely hesitates under acceleration. This usually occurs in first gear and feels similar to if the car was hopping due to bad clutch control or fuel cut. Under higher RPMs the problem doesn't seem to exist. The first thing I checked was the TPS, thinking that it may have been out of calibration. We removed the throttle body and gave it a good clean, making sure that the bore and the butterfly valve were completely clean of any gunk. It may be a good time to mention that the car also has a very poor idle. Sometimes is is extremely smooth, but somewhat high, while other times the RPMs fluctuate quite a bit and the engine even splutters and stalls after a bit quite commonly.
While the throttle body was off and cleaned I began calibrating the TPS, only to find that when the throttle was completely closed the butterfly valve was still open more than it should have been. Thinking that the throttle stop may have been played with i backed it completely off, only to find that the butterfly valve wouldn't close any further under its own spring force. I was stumped. The dashpot wasn't interfering at all and the fact that i could force the butterfly valve to close properly with my hand made me think that the linkage was worn or that the springs were no good. Pretty confused i set the idle screw to stop at the maximum point that the valve would close to and adjusted my TPS to read IDLE at this position.
After doing that I started the car and tested for Engine Error Codes. Previously I had been getting TPS error 42 but that was now gone and no errors were read. I than opened my e-manage support software and calibrated the TPS to read from 0 - 100%. I shut the ignition off hoping that the hesitation would be gone.... only to find that it was still there.
I am now trying to think of possible causes of the problem and why my idle is so rough.
I tried to check the condition of the spark plugs while the intake piping was removed but was unable to remove the boot from the end of the spark plug. The rubber cover on top slipped off and the exposed plastic was too sharp to try and pull off. I feared that pliers or vice grips may have broken the plastic. Is there any special way to removing these as I haven't had issues in other cars. Could spark plugs or spark plug leads be causing these issues? These are my next thing to check and replace.
I also thought that there may be problems with the EGR valve, the fuel filter needs replacing or the fuel injectors are dirty or blocked. I have some seafoam that I may run through the fuel to clean the injectors out. I've just about gone insane trying to help my mate fix this problem and I'm hoping that you guys may be able to provide me with some guidance.
Vacuum leaks are also an obvious thing to check for. I don't believe I have any at the moment, but I'll be checking this further as I'm not completely convinced.
If a video of the issue is needed I am happy to post one.
Thanks in Advance,
Toby
Im writing on behalf of a friend who owns an 89' MA70 7MGTE supra. The car was purchased about 2.5 a half years ago with a number of pre-existing problems. Since the purchase of the the clutch, timing belt, steering rack, centre bearing and a heap of vacuum hosing has had to have been replaced. The car has been modified a small amount and has a GReddy E-Manage Blue piggy back ECU that was fitted with the car. I have connected this to the computer and have the ability to view airflow and ignition maps in real time.
Ever since the car was purchased it has has an extremely irritating and somewhat unsafe problem in that it severely hesitates under acceleration. This usually occurs in first gear and feels similar to if the car was hopping due to bad clutch control or fuel cut. Under higher RPMs the problem doesn't seem to exist. The first thing I checked was the TPS, thinking that it may have been out of calibration. We removed the throttle body and gave it a good clean, making sure that the bore and the butterfly valve were completely clean of any gunk. It may be a good time to mention that the car also has a very poor idle. Sometimes is is extremely smooth, but somewhat high, while other times the RPMs fluctuate quite a bit and the engine even splutters and stalls after a bit quite commonly.
While the throttle body was off and cleaned I began calibrating the TPS, only to find that when the throttle was completely closed the butterfly valve was still open more than it should have been. Thinking that the throttle stop may have been played with i backed it completely off, only to find that the butterfly valve wouldn't close any further under its own spring force. I was stumped. The dashpot wasn't interfering at all and the fact that i could force the butterfly valve to close properly with my hand made me think that the linkage was worn or that the springs were no good. Pretty confused i set the idle screw to stop at the maximum point that the valve would close to and adjusted my TPS to read IDLE at this position.
After doing that I started the car and tested for Engine Error Codes. Previously I had been getting TPS error 42 but that was now gone and no errors were read. I than opened my e-manage support software and calibrated the TPS to read from 0 - 100%. I shut the ignition off hoping that the hesitation would be gone.... only to find that it was still there.
I am now trying to think of possible causes of the problem and why my idle is so rough.
I tried to check the condition of the spark plugs while the intake piping was removed but was unable to remove the boot from the end of the spark plug. The rubber cover on top slipped off and the exposed plastic was too sharp to try and pull off. I feared that pliers or vice grips may have broken the plastic. Is there any special way to removing these as I haven't had issues in other cars. Could spark plugs or spark plug leads be causing these issues? These are my next thing to check and replace.
I also thought that there may be problems with the EGR valve, the fuel filter needs replacing or the fuel injectors are dirty or blocked. I have some seafoam that I may run through the fuel to clean the injectors out. I've just about gone insane trying to help my mate fix this problem and I'm hoping that you guys may be able to provide me with some guidance.
Vacuum leaks are also an obvious thing to check for. I don't believe I have any at the moment, but I'll be checking this further as I'm not completely convinced.
If a video of the issue is needed I am happy to post one.
Thanks in Advance,
Toby