need help please with a running problem??

Lon

Lon

Banned
its a 88 gt 5.0 all stock.heres what its doing,the idle gos up and down(900 to 400 rpms) everytime on start up,even when its warm.no matter what speed im at 20 30 or 40 mph,if i hold it there it acts like it wants to miss or buck on me till i hit the gas about half way down then its fine.when it acts up like that and i push the gas half way or to the floor to get it to stop it will pop through the intake once in a while and when i let it idle too long the rpms will go up and down and sometimes the rpms will stay around 1200 and when that happens ill turn the car off and restart it and the idle gos to normal(900)after it stops going up and down.i noticed when i put it to the floor(wot)it dont pull like it should and sometimes it kicks in like its running on 6 cyls and the other 2 kick in.its like a v6 on nos but you never know when the nos is going to kick in.parts replaced=fuel pump reg,full tuneup,fuel filter,timing chain and every gasket on the motor,Parts cleaned= egr,iac,tb.car has 33 psi of fuel press at idle, jumps up to 40 when i hit the gas and its at 41 with the vac line off.it ran the same way be 4 i replaced all the parts:pissed: .anyone??
 
Have you checked your throttle position sensor?? your egr valve & solenoid could be staying open causing your idle hunt. What is your timing set at??
 
Vacuum leak letting in air, perhaps a bad line. IAC gone bad, computer can't actuate the coil properly (you can check it with a multimeter).
 
chuckycaprice said:
Have you checked your throttle position sensor?? your egr valve & solenoid could be staying open causing your idle hunt. What is your timing set at??
Click to expand...
the timing is good.i checked and cleaned all the sensors and they seem fine.i might have a bad injector but im not sure.if someone car drive it for me and tell me there input that wil be cool.
 
Hmm, could very well be a couple of clogged injectors. Fuel pressure seems right. You've checked the plugs and wires. What size injectors?
 
not too framiliar with the setup or access to the injector plugs. But do a drop test on the injectors while its running shitty.

Start one by one pulling the plug off the injector and listening, feeling, hearing a miss. If it runns shittier with that injector cut off, then that injector is probably fine. But if you run accross one that doesnt change when u pull power from it, this tells you that that injector is malfunctioning.

You can also do this drop-test with your ignition. Pulling Plug wires off of the plugs one by one, and listening for a miss.

IMO i dont think this is your problem. It sounds like you have an internal engine problem, like a intake valve leaking. This pressure difference in your intake could be fooling the MAP.

Have u checked compression and cylinder leak-down?
 
As stated earlier the EGR could be hanging open. Cleaning it won't help. Check the TPS with a multimeter. It should show about .9 volts at closed throttle. Open the throttle slowly and the voltage should steadily increase to almost 5 volts. If it jumps up and down at all it is bad.
 
82bird said:
not too framiliar with the setup or access to the injector plugs. But do a drop test on the injectors while its running shitty.

Start one by one pulling the plug off the injector and listening, feeling, hearing a miss. If it runns shittier with that injector cut off, then that injector is probably fine. But if you run accross one that doesnt change when u pull power from it, this tells you that that injector is malfunctioning.

You can also do this drop-test with your ignition. Pulling Plug wires off of the plugs one by one, and listening for a miss.

IMO i dont think this is your problem. It sounds like you have an internal engine problem, like a intake valve leaking. This pressure difference in your intake could be fooling the MAP.

Have u checked compression and cylinder leak-down?
Click to expand...
this is a new motor,it runs the same way the other motor ran so its not the motor.the car has 73,000 on it now.the motor that is in it has under 70,000 on it.i drove the car i got the motor out of(the guy put a 4 bolt 347 in his car after i paid for it).when it was in his car it had no problems at all.verry smooth runner.now that i think of it,i didnt get the intake(just the short block).so i think im going to need injectors.
 
You must log in or register to reply here.
Back
Top