[NIX]

Doing some maintenance, some questions raised. I replaced cap rotor and wires and planned to replace the plugs. The engine seems to idle on 5 cilinders. At higher RPM's it purs like it's supposed to. Plug no. 5 was a bit black, the rest was OK. I also think the shop gave me the wrong Plugs so I didn't replace them (of course I didn't check at the shop). It seems I have the plugs for a post '91 i6. I didn't it would matter, but these Champion RC12LYC's project way further into the combustion chamber then the RC9YC's i'm supposed to use for an '88 i6. It seems they almost reach the pistons.

1. Could the black No.5 plug be caused by a bad injector (peeing instead of spraying)? Plugs are only 1 year old and used for about 10.000 miles.

2. Can I put these post '91 plugs without any risk in my '88 lowport or should I change them for the recommended ones?

Thanks (I hope).

 

[Guest]

As the '91 had an "H/O" motor, so I'd say no. The heads were different and so were the ports on the Intake/Exhaust manifolds. Besides, as cheap as spark plugs are, compaired to most everything you'll spend for a good tune up, why even risk it? If you're getting blackened plugs after 10,000 miles, you've likley gotten either a ring or valve seal issues or a bad injector. For my $$$, slap in some reasonable plugs (gapped to the right specs) and change your old 02 sensor. I gained about 2 MPG this week and can actually "feel" better idle and throttle response, just from putting in a new Bosch premium 02 sensor. As a matter of fact, having Bosch plugs, wires, injectors, and 02 sensor, all work together, like OEM intended. I replaced all my injectors prior to the hollidays and have seen improvement there too. If you're still getting blackened plugs after that, it's mechanical, not electrical....

 

[NIX]

Just the info I needed. Thanks.

 

[3946]

Run some good fuel injector cleaner through your fuel system also to remove any varnish that may be in the system. Many people use Marvel Mystery oil in their gas regularly to keep the whole system clean and also remove valve deposits.

 

[NIX]

Did that just before I changed the rotor, cap and wires. With no result, so I started suspecting the injector. Thanks anyway.