[TheRoad64]

I have a 93 Formula, and it has a problem which I and a couple of shops have been unable to solve.

First things first, the car is unmodified, due to the fact that I cannot afford anything, plus it has 162k on the odo. In spite of this, I am the 2nd owner of the car, and it is cherry. Dealer maintained its whole life. Almost perfect inside and out.

The car has developed a misfire in two cylinders on the right side of the engine. It misses throughout the entire RPM band, badly. It isnt throwing any codes which confounds me.

A tuneup was performed less than two months before it started acting up, including a completely new opti. I have replaced coil and O2 sensors.
The shop has performed a compression test which was within acceptable limits.

However, the passenger side exhaust manifold does have a crack beneath the heat shield. Could this be causing the problem? People have theorized bent valves, blown head gasket, and a host of other things. I have the car parked since I'm joining the Air Force, and have given up for the time being.

 

[1970judge]

The cracked manifold can def do that to your car. Also check your pcv system for leaks.

 

[Chris 96 WS6]

Yeah I would definitely fix that manifold...exhaust leaks that close to the head can cause funky symptoms.

 

[F-Bobby]

yeah definately get that manifold fixed. i dont think its a head gasket cause you would be losing coolant, if it was a bent valve you prolly would hear it. too bad the car isnt obd2 , there are so many neat tests you can perform with a Tech 2 that can help you narrow down the problem.

 

[MotorBreathLT1]

sounds like a good excuse to get some Jet Hot LT's

 

[Vendetta]

sounds like a good excuse to get some Jet Hot LT's

or Kooks LT1s

 

[1970judge]

In deed.

 

[Fastbird]

Yeah, definitely take the cracked exhaust manifold out of the equation and then see how the car reacts. That cracked manifold is basically drawing in air into the exhaust upstream of the oxygen sensor and is most likely causing very false lean signals to be sent from the O2 up to the PCM, which in turn will richen things up. And hit up the link in my sig seeing as how you're a 93 guy also.

 

[harvickgm]

man, you need to fix the exhaust before anything. different backpressure on different cylinders can cause a misfire. but listen to fastbird and check out our sigs. and meet us there. lots of help from other 93 owners

 

[Lifeisgood]

yea if its the smallest crack that would def. hit that 02's sensor, but since its not and obd2 car it wont throw a code for that. if that is not the problem start looking else where, maybe a couple of inj. going bad. check the resistance on those inj. but the best thing to start with is that crack
good luck