i have a 94 interga HMO LS swap w/ nitrous. one night i hit nitrous and i lost a cylinder( 4 to be exact). i have tried and tried to figure the problem out, i have had numerous people look at my car and no one can figure the problem out. i put new plugs/ wires/ injectors/ dizzy/ tried a different ECU checked timing and its all good. i have fuel and spark to the cylinder and i do not have a broken or bent rod and there is no hole in piston. but for some reason when you pull the wire on cyl 4 it acts like it was never connected. it sounds like a subaru and it constantly back firing. any more questions that might help diagnose it i will answer. someone please help.

 

HAve you ckecked compression in cylinder four? A leakdown test would be better. You could have a burned exhaust valve on cylinder 4.

 

Ditto the above^^^
Burnt exhaust valve would be my guess, if the valve is not seating properly it would explain the backfiring.

Wet or dry system?
What is your nitrous shot?
When is it "sprayed", manually or automatically, if automatically at what RPM, or is it a WOT? 94

 

ita a wet 50 shot and its on a manual full throttle switch. i have never herd of a burt valve but i was just told today maybe it could be a bent valve? and how does a leak down test work is it the same as a compression test. sorry im from a town where the import thing is really weak so i got no one to help me

 

if i had to guess i would agree with burnt valve. bent? doubtful. that would mean the valve would have had to contact the piston.

 

You said that you have spark and fuel to the cylinder, so it's most likely compression.
If you have an air compressor then you can make or buy a leak down tester; I used the diagram in this link and it works great:

http://vmaxoutlaw.com/tech/leakdown_tester.htm

A compression tester would tell you if you had a total loss of compression, which is what you would be interested in knowing. You can get one for about $20 from autozone or advance auto parts. Because this happened when you were spraying it's probably the valve or piston ring. Was your car tuned for nitrous? If not I would say 99% it's a compression loss.

 

I agree with burnt valve, nitrous going lean is pretty much a cuttin torch in ur combustion chamber and itl fry a valve in a millisecond. Maybe u should reconsider the placement of ur fogger nozzle, thats assuming uv follow manufacturer recommendations on the jet sizing. Compression test will confirm and the tester can b had at advance auto for like 25 bucks

 

its not tuned for nitrous i did not get the chance to before i did whatever it is i did. i dont think i damaged the piston or rings it does not smoke at all and does not have any blow by. its a really small shot. just a 50. as soon as i get it running good again i have a friend that can tune so i am going to have him tune it for nitrous

 

50 shot wet, why wet?
Where and how is extra fuel injected?
What type, [make and model] of system do you have?
Is fuel pressure monitored by the nitrous system?

I run a 75 shot dry, [ZEX], auto spray @ WOT and above 5000RPM, I have been running the system for 7 years in a 94 Teg, both drag and autocross without any problems.
I agree with Sr420Det if your spraying and mix goes lean, stuff will burn.

A compression and leak-down test are needed. 94

 

yep and a tune wont help anything when ur running a wet kit. The fact remains that ur manifold is a dry intake manifold and is not meant to flow fuel (wet) only air. Not saying ur bound to have problems (cause i never have) but there is always a chance of distribution of the fuel being way off. Take the head off, replace the valve (i did mine in my livingroom with my bare hands and the help of a buddy), reinstall, and keep spraying. Make sure ur fogger nozzle is right in the middle of the intake tract and 6 inches from the throttle opening.

 

the extra fuel is T'ed off the main fuel line to run into a solinoid and the nitrous solinoid and gas solinoid open at the same time and two lines run into one nozzle that is the best way i can answer your question and its a nitrous express kit. and i really wana pull my head off but the car is the only thing i have to drive right now i blew the rear end in my truck so as soon as i get the head gasket and studs i will pull my head off. i hav another head to throw in it as soon as i get the parts i need.

 

I didnt ask any questions