[1995svtcobra]

Ok guys i need some help. i have a 95 cobra, owned it for 3 years never had much problems with it, great car. its started running horrible a couple weeks ago. i limped it home, it had a lot of vibrations throughout the drive train that I could feel while driving. it was hard to keep running extremely rough at idle and when giving it gas. since having it at home i have changed the plugs, pretty sure the spark plug wires are good, changed the distributor cap, rotor, and cleaned the air filter. No change still running like crap. The motor has a vibration or a shake that you can see while it's running. It will idle but very roughly. today i tried to do a vacuum test to see if i had a leak. I used one of the lines going to the egr valve o get my gauge reading. not sure if that is ok?? tried some of the lines around the throttle body but i could not get a reading. at the egr tube i'm getting about 10 in. Hg. at idle. when you give it gas it will increase to 12-14 in. Hg. from the book that came with the gauge it seems like it could be a number of things. maybe restricted exhaust flow, clogged cats maybe?? any help would be great. i first wondering if you have any ideas. if i can get a accurate reading from the egr vacuum line, or if not which one to use??? do you just unplug the line and plug it into the gauge or do you have to do a "T" connection that way it is still hooked up? never done vacuum testing before so i'm not sure. thanks for any help

[Nice 5.0]

Check for a vacuum leak by spraying around the intake with carb cleaner. You may need to do a compression check. Also how do you know the wires are good. I would have changed plugs and wires first, before everything else. They could be bad. You have to go through a process of elimination.

[93hatch]

pull off the h pipe and try and start it

[1995svtcobra]

I doo\n't think it's the wires because they were replaced a few years ago with a high quality 8mm set. I guess they could have already gone bad, though. Nice 5.0 what will happen if you spray the carb cleaner around the intake? This will tell you if you have a vacuum leak? Let me know never done this before. thanks guys

[Mlx50man]

Originally Posted by 93hatch pull off the h pipe and try and start it

+1 if you have the stock h-pipe with cats, your cats might be plugged.

[vfast]

does it heat up?
the vibration check the harmonic balancer

[americanmuscle90]

You can check the wires w/ a multimeter there should not be more than 10000 ohms of resistance per foot of wire.

First do a good visual inspection checking for obvious problems i.e. fuel and vacuum leaks, and bad connections. Check all of your fluids. Make sure they are in servicable condition. You may find coolant in your oil, you never know. Alot of problems come from overheating, so check the coolant. Test for spark at each cylinder using a spark tester. Check fuel pressure and ensure it is within specs. If you have the ability to retrieve DTCs they can be very helpful. Perform a compression test to check the mechanical soundness of the engine. If a cylinder has low pressure perform a wet compression test to determine if you have bad rings. If the pressure comes up during the wet compression test the rings are bad. If it doesn't come up you have bad valves or blown head gasket.

You have owned the car for 3 years it is not like you just bought it and hve to give it a complete tune up. I would not have rplaced a single part until I found the problem. You are wasting money that could be used for mods instead. DO NOT throw parts at a problem. Use troubleshooting fundamentals to solve a problem. You know an engine needs fuel, spark, air, and compression to operate. You also know it needs to be cooled and have a means of letting the exhaust escape. Start with the process I laid out and I know you will find the problem w/o spend alot of money.

Now if you don't find the problem you need to start testing the sensors, mostly the input sensors to the PCM like the ECT, MAF, IAT/ACT, O2S, MAP, ect. Keep us updated. If you need help you can contact me.