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upnorthguy

2.5 V6 engine running rough

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Bought a '95 Mystique 2.5L and it is running rough. Changed the sparkplugs and found that the front 3 looked good but the back 3 were not so good. one was coated in oil (I think it is oil. definitely not gas). one was black. and the 3rd was a little corroded up on the top (the metal part above the insulator).

 

I'm not sure what my next step is. I changed the air and fuel filters and now the plugs. Haven't pulled the new plugs to see what they look like but it didn't seem to help how it is running.

 

Should I change the plug wires, distributor cap, check the engine codes, take it to a mechanic ...? Don't really want to spend too much money but it is costing me too much in fuel to run it like this. $35 to fill and only 250-300 km.

 

I really appreciate all your help with this.

 

I should also ask about one other thing. When the transmission (automatic) shifts from first to second it seems to make a sort of clunk. Will that be transmission or possibly engine mounts? Thanks again.

 

Greg from Alberta

Edited by upnorthguy

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A couple of things here.

 

You didn't say what the mileage was but if it is over 80K it could be the fuel injectors. Generally speaking, the fuel injectors need to be serviced at about that point. Bad plug wires, bad plugs and dirty or bad fuel injectors all have the same symptom. Around here we have a place called Dr. Injector that will flow check, sonically clean and then flow check (again) the injectors. A lot cheaper than buying them new. You also get a new o-rings and some "special" grease back with them. Costs about 35 bucks each. Injectors are easy to do and if your injectors need attention than you probably need to clean the throttle body too. Buy the special cleaner and make sure the TPS (throttle position sensor) is on the other side of the room when you do the cleaning. The back of the throttle body (and that's what gets dirty) is coated with Teflon (I think that's what it is) and the special cleaner is kind to it as opposed to cleaning solvent or something.

 

As for plugs, I have been advised by a damn good mechanic to stay away from the Platinum plugs and do Iridium instead. He was telling me that he's had problems with Platinums missing with not a lot of mileage on them so he's gone to Iridium plugs. I did Iridiums on my SVT and they work great.

 

Consider these two things normal maintenance.

 

Report back.

 

Bought a '95 Mystique 2.5L and it is running rough. Changed the sparkplugs and found that the front 3 looked good but the back 3 were not so good. one was coated in oil (I think it is oil. definitely not gas). one was black. and the 3rd was a little corroded up on the top (the metal part above the insulator).

 

I'm not sure what my next step is. I changed the air and fuel filters and now the plugs. Haven't pulled the new plugs to see what they look like but it didn't seem to help how it is running.

 

Should I change the plug wires, distributor cap, check the engine codes, take it to a mechanic ...? Don't really want to spend too much money but it is costing me too much in fuel to run it like this. $35 to fill and only 250-300 km.

 

I really appreciate all your help with this.

 

I should also ask about one other thing. When the transmission (automatic) shifts from first to second it seems to make a sort of clunk. Will that be transmission or possibly engine mounts? Thanks again.

 

Greg from Alberta

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