advice needed

[po7553]

How you guys doing.Im not too good.My 92 300 sl is not doing well.The car idles rough and it seems to have a lot less power on the highway sometime I cant get above 55 on the 95 in Nevada,I replaced the wires 6 months ago and i replaced the coil and dist cap yesterday but it made no difference.The no 5 spark plug seemed wet with gas I assume.So I replaced it and it seemed to make a difference for a short time but it started all over again.It seems to run worse the longer i drive it.I cant really afford to go to the dealer.And I dont know any honest and reasonable shops in the Henderson Nv area.It is my daily driver.Thanks for any guidance.Peter

[coleyjf]

Hi there

If it had been a 107 I would have suspected it might be one of the relays, the OVP (over voltage protection) relay comes to mind !

I assume that the 92 300SL has a "similar" engine and electrics to my 88 3300SL in which case it's worth a look but I've No Idea where they are situated or in fact if you've got one in your later body type but it does sound a bit like that could be the trouble!

That or a blown head gasket!!!!!!

[ctaylor738]

First thing is to borrow a timing light, connect it to #5 wire and make sure #5 is firing. If isn't, you could have a bad wire or boot, even though they're new.

If #5 is firing, and the other plugs look OK, the problem could be the injector. If you want to test this, you can swap #5 injector with another cylinder, and see if the problem moves. You could also just replace #5 and the seal.