Mods in my sig are a little outdated. Writing this from my phone so please bear with me...
car is a 97 RS v6 auto that I swapped my 383 M6 into. I'm still using the stock RS gauges
and gauge wiring harness. I have had the car running perfect like this for a year now. I put
a 125 shot on a couple of months ago. I just changed my plugs to tr6s for the nitrous. Since
then my car has not been running right. It starts right up and it only has code 33 for map
sensor circuit high which can be caused by the unstable idle. I checked the primaries with
an infared thermometer and 4 6 and 8 stayed at about 115 to 120 degrees. All others were
about 275 to 300 degrees. I have changed all plugs again as well as wires and the opti cap
and rotor and distributor. No change. I put a known good coil and icm on to no avail. I feel like
I'm beating my head against a brick wall. I am going to check fuel pressure and the inj
circuits with a noid light.

Any other suggestions?

Thanks all!

 

I would do a compression test to rule out head gasket. Do you specifically know its one dead cylinder and if so what cylinder is it?

 

Uh yeah..... 4 6 and 8. Like I stated in my first post. Good call on the compression test. Ill try that too.
Why would it blow a head gasket after changing plugs though?
That makes no sense to me. I don't know that they are completely dead yet. But they are the cylinders with
Issues

 

Oops sorry i must have missed that but yeah to me if its that entire side of the motor points me to head gasket if your getting spark and fuel that is. But that strange that it happened after changing plugs.

 

I agree that it could be a blown head gasket... Im just perplexed about the timing of the problems. Literally all I did was change plugs... Problems ever since. Thats a good suggestion on the comp test. I'll try it and see what I get.

 

Keep us posted

 

Will do. Thanks for the input!

ps. Updated my sig....

 

y dont you try swapping plugs again.. if that was the problem.. maybe u got bunk plugs

 

Twice?? I highly doubt it.

Do a leak down test. I think you cracked a piston or 2 or 3. I see engines messed up from nitrous all the time. If it's a dry system, I'll bet money on it. If you ever fired up the nitrous below WOT I'll bet money on that too.

 

Its a wet kit and has been tuned for nitrous. I have forged internals and I have only sprayed it a couple of times. I was planning on taking it to the track so I changed plugs just for added safety. I had tr 55s before. And besides, if it was a cracked piston or two or three, I think I would have notice before changing plugs. A leak down test may still be in order though.

 

It was difficult to read that the problem occurred since you used nitrous or since you replaced the plugs.

We know you're smart enough to have NOT screwed up the plug wires on the same side of the opti?

http://shbox.com/1/opti.jpg

Since you then changed the entire ignition system. No way you could have duplicated the same error right?

So if we remember that all it takes is fuel, spark and compression to fire off a cylinder. You confirmed the spark portion is correct. Albeit the expensive way.

You need to confirm the injectors are spraying correctly. Doesn't matter if you have pressure or injector pulses. Could still be clogged.

So that leaves you with compression and leakdown.