Bad Idle & Front Suspension Issues

tgrans21

Registered User
Quick Background: 95 SC - 5spd - ~90k miles on engine. Prev. owner (as of a year ago) did some modification to this engine, not extensive, but enough. 10% OD pulley, double intercooler, new intake plenum, raised top, 3.73 gears, 1.5" lower, custom exahust, 17" cobras, etc. I gave all that because to a point I believe his work is the culprit for a few probs.

Alright, I've currently got a few problems with my engine. When driving at any point, right from startup cold or hot; when I engage the tranny and it mates with the engine I hear a grinding type noise coming from the back of the engine and/or tranny. When I disengage the engine from tranny I continue to hear this grinding noise, but its decreasing. If I sit the car still and spike the throttle and let the engine come back down on its down to normal idle I can hear the grinding still and it dissapates with the engine speed. Ive played with it some and it seems to be connected to the accelerator. I only say that because when I am not using the accelerator the noise isnt there. When I press the accelerator and speed up, the noise is blatantly obvious. Only after I get to about 2500+ does the engine speed drown out the noise. When coming down from high rpms it sounds like bigger chunks of gunk and when at lower rpms (or without boost and in vacuum) little grainy chunks of gunk. I still get boost, and the car still goes, but I am afraid to press the engine hard to gain any good speed in traffic because of this sound, last thing I want to do is blow my tranny or have to replace the lower half of my motor.

Another problem is my idle. Im willing to blame the spark plugs because I havent changed them or the wires yet from purchase a year ago but Id like to know for sure. I start the car up in the mornings (some colder than others) and let it warm up. After about 2 minutes of decent idle time, going from 1500 to 1000 and idling, the car begins to choke... it sits at 700 for about 15 seconds before it struggles for life at 300 and then rocks and dies. If started back up it will immediately return to normal 2min idle before stooping to another awful death. After driving the car for a while and letting it coast it will idle around 1300 and stay. But if the engine is idling too long it will choke and stumble, making drive-thru almost impossible without deafening the guy on the other end of that speaker while trying to nurse my car back from a stumbling idle.

Next on the list is my front suspension. Newest concern is a creek or crack noise from my passenger side wheel area after moving from a dead stop. Just sounds like weight is suddenly being lifted off of that area and it wants to pop. My biggest concern with the suspension is my driver-side. When slowing down dramatically (ie: interstate off-ramps, sudden stoplight, etc) the driver-side begins rattling/shaking, like something is hitting the wall, and it sounds heavy. Ive yet to take the tire off and start moving parts around, I believe that maybe the caliper is not tightened down all the way, or worse one of the joints is loose and ready to pop. No noises when driving, just when slowing down suddenly and even when turning. Mostly when making a left-hand turn.

Also Ive got a code 51 coming from my airbag light, telling me that my fuse is blown in the diagnostic module due to intermittent ground. If somebody could point me to a) where that diagnositc module can be found in the car, and b) what its going to take to find that intermittent ground I would be very grateful.

As far as the idle is concerned Ive already let the computer relearn its idle process a few times, incase its been my driving. Next to do is change the plugs and wires and get a new air filter. That seems to be the most I can do for the time being. As far as the shaking of the driver-side wheel I dont know what to do other than check the calipers and shocks for vibration.

If anymore information is needed to make a diagnosis feel free to ask as Ill be here until its solved. I appreciate all help given greatly. I am morethan willing to do all of the work myself (unless wiser not to) -- And also I was curious to know: The previous owner droppd this car down a little too low for my taste as when I pass a speedbump I scrape the underside of my car horribly, what would it take to get my car back up a little? Either back to stock or just enough to pass a speedbump I dont mind. Again, thanks greatly for all help!

Ted
 
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I would think that your suspension issues are the most pressing. It sounds like something is amiss in the front suspension, for sure. You can test the condition of the wheel bearings and tie rods by simply putting the wheel off the ground (follow proper safety procedures) and checking for play left-right (tie rods or bearings) and up-down (bearings). It could also be your sway bar end links (grab the link and try to twist it with your hand - if it twists without a lot of effort, it's bad. You can also test your outer tie rod ends the same way.). Now, if it is a balljoint, that could be harder to diagnose. I think you have to unload the suspension by jacking up the lower control arm and then test the lower balljoint for play. Also, if any of the boots (balljoint, tie rod end, sway bar end link) look bad, that is a real good clue as to what may be worn out. (It could also be worn out bushings - like strut rod or control arm bushings. If they look shriveled up or you can cause some play at that joint, that's not good.)

As for your idle, it sounds like an electronic (computer or sensor) problem. Maybe your ECT sensor or O2s?
 
Thanks much. Ive got to get it up on stands later today after work, hopefully find the culprit. Need to hit up the local autozone for the code reader too eh? Not sure if its related though maybe- my vacuum is under 20 in most cases. When I turn the car on it is fine but after just a few minutes of driving when I dont put any pressure on it it drops to what looks like -22 and takes a bit of pressure to get to boost. Im not quite sure of how to go about checking for vacuum leaks, what are the most common vacuum problem areas? All that I know to check is the vacuum hose on the back of the inlet and it seems fine. Thanks for the help.

Ted
 
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