First of all this is in reference to a '98 Type R with about 88,000 miles on it.

Yesterday my check engine light came on and according to the blinking engine light(74) I have a cylinder 4 misfire or a condition that is favorable for a misfire. I then thought ok I'll just get some new spark plugs and spark plug wires for it.

Later on that nite I took it out to get something to eat and I noticed that on start-up my dash lights would flicker for about 2-3 secs until the car settled down into it's idle. I then started driving and I noticed my speedometer was acting a little strange, while I'm applying gas it reads the correct speed(although it oscillates a little bit) but as soon as I take my foot off the accelerator it goes to 0. Apply gas correct speed, foot off of accelerator speed reads 0. All the other gauges appear to be working ok.

I didn't have any other trouble codes, it kept reading a constant 74. So are there 2 non-related problems or is it the same thing causing these 2 problems?

 

Update: Now the speedometer doesn't work at all.

 

I'm betting on two problems... the cylinder 4 misfire and a dying or shorting vehicle speed sensor (which would explain the erratic speedo movement).

 

The main reason I started this thread is that both problems popped up at the same time. I was also thinking couldn't the malfunctioning speed sensor cause the engine misfire(or alleged misfire) because in the couple of test drives I took I've noticed no let down in power or sluggishness in the engine?