bmfgsxr

i just bought this car last saturday and didnt really hammer on it at all during the test run.
its an 89 lx 5.0, 5 spd. with 3.73's and cat back exhaust.

at idle it sounds pretty good for the most part although every so often it sounds like there is a miss.

where the issue is, is when you bring the revs up over 3000 rpms. whether in nuetral while sitting still, or driving in any gear as the rpms climb it makes a bit of vibration and sounds like its having a tougher time making the revs. im not sure if the vibration is from the motor struggling, or if its the motor vibrating making it seem like its not revving as smoothly. im thinking i should have the motor mounts inspected, possibly the harmonic balancer (although it looked to be in good shape, and didnt show any signs of being out of balance when inspecting the motor). i read that it could possibly be not getting enough fuel in the upper rpms, so i dont know if its clogged or bad injectors or how i would even figure that out. i dont know if the fuel pump could have anything to do with that.

i was told the car had just a tick over 100,000 miles. although im starting to think that its been flipped twice but i could be wrong. also, the previous owner said he did a recent tune up a few months ago and it has a new cap, rotor, and plugs, but he didnt change the wires because he said they were done last winter. also he said he changed the fuel filter. i pulled the cap and it looks clean with no signs of arcing and there is spark going to the cylinders. i did pull the number 5 plug and it looked so clean as if there wasnt much happening in that cylinder.
my cousin is a mechanic and he said that the car didnt seem too bad, maybe just a little tired since it is an 89.

maybe im just expecting more out of this car going from memory, or maybe its because im used to my 03 Lightning, but it should run smoother, and pull a little harder.

any ideas would be appreciated.

gspfunk

Sounds like it could be one of a few things. I'd start w/ the balancer: have someone rev on the engine while your watching it. Look for ANY wobble. Then turn the car off and try moving it w/ your hands. The outer ring can come loose and spin.

I would also check all your plugs and do the KOEO/KOER tests for trouble codes.

Since it is rpm-related (since you said it does it in neutral or in gear, unrelated to speed), you can rule out the drivetrain. This will be something to do w/ the motor.

bmfgsxr

thanks for the input man.. tomorrow im gonna pull all the plugs and inspect them as well.

nice avatar by the way. ive got the same one on another message board only it has a caption that says "what the **** were you thinking"

Raphs50

I currently have almost the exact same problem with my 86 GT, but it only started after I swapped the AOD with a TKO 600 tranny. I have it in the shop right now to have that checked out. If they figure it out I will let you know what the fix was. I think my problem is a balance issue with the new flywheel and clutch assy, but didn't have the time to pull everything back out and troubleshoot myself.

bmfgsxr

keep me posted. this thing recently had a new clutch, pressure plate, and throwout bearing installed maybe they didnt do it correctly?

AdderMk2

time for a tune up.... plugs, wires, cap, rotor, air filter and fuel filter.... start there... THEN go after the expensive stuff

2 kwik

with what adder said I would also look into dist. wear,vacuum leak,engine mounts,and that harmonic balancer ,then move on to check fuel pressure from a weak pump, also look at the coil and coil wire..then do a compression test

hint..next time drive the car like you want,your the one buying it

bmfgsxr

i went through the car pretty good this weekend and it runs stronger for sure, but i still notice a little vibration. im beginning to think it could be the motor mounts, or the balancer because the motor seems to pull alright. however; i did notice that my fuel pump is exceptionally loud. i can hear a loud whine constantly while the car is idling from outside of the vehicle. this makes me think that it may be going bad and not giving good fuel pressure.

my cap and rotor are fairly new and in very good condition. i pulled the drop in k&n filter and cleaned and oiled it. i cleaned the maf, and changed the oil. i also checked to make sure every cylinder was getting spark which they are. motor mounts make the most sense to me at the moment. although like i said the fuel pump makes me curious.

and next time i buy a used car ill be sure to drive it a bit harder. part of the problem here was the guy was over an hour late getting back to his house and by the time i got to inspect the car it was getting dark and, and i was tired, hungry and very impatient.. all bad combo's when looking at a car that is almost 20 years old.. ive been buying new vehicles for so long i guess i was just being a little lazy on inspection. but i was also recommended to the seller by someone i work with so i had a higher level of trust which is also why i didnt inspect as closely as i should have.

thanks for all the help.

hot85fifty

I had the problem too. it was just that one sparkplug boot was not pushed on all the way. It also happened to me when my roller rockers were not adjusted perfectly.

aode08

replace the thing making all that whining noise his buddy, the filter and partner, the strainer. Do that and let us know what you found.

Check inside the tank, see if some baffles are broke loose, if so replace the fuel tank, dont try and weld them back in place.

TAKE THE AIR FILTER BOX HOSE OFF, WHILE ITS DOING THAT, HAVE A BUDDY SPRAY SOME STARTING FLUID, AND SEE IF IT SMOOTHS OUT