Hey guys, I was just wondering what I would feel/hear/see/smell when I get a misfire in my car. The same with detonation. How did you know that you had a misfire or detonation when it happened to you?

A missfire will sound like a hiccup or a studdering of the engine. You can def feel it when it happens. Detonation will sound like a bunch of BB's or ball bearings being shaken in a tin can. A nasty rattling. You really cant feel detonation, esp light episodes of it. Any moderate detonation on the stock pistons, will crack the ring lands without warning. Our stock pistons can tolerate only very light amounts of detonation, anything more will damage them.

Hmm..how bad are misfires on the engine? I just ordered the missing link but I had MAP sensor related CEL's that caused hiccups like you mentioned whenever I eased into boost. Also what exactly is detonation and the best way to prevent it?

BTW XtremeRS, you're easily one of the most informative members on this board. Thanks :thumbsup

>Hmm..how bad are misfires on the engine? I just ordered the
>missing link but I had MAP sensor related CEL's that caused
>hiccups like you mentioned whenever I eased into boost.

A missfire, when the Air/fuel mix doesnt ignite, really isnt bad on the motor for brief periods at a time. If you keep running the engine with missfires all the time when its running, then I would say thats not the greatest for it. If a cylinder constantly isnt igniting the fuel mixture, then the fuel can wash oil off the cylinder walls, and dillute the oil.



>what exactly is detonation and the best way to prevent it?
>
Detonation is basically when the air/fuel mixture does not ignite properly. Under normal cumbustion, the burn of the fuel mix starts at the spark plug's spark. The flame moves outward in a controlled and smooth manner, burning completly outward. Detonation is when the "end gas" of the air/fuel mix suddenly ignites, soon after the spark plug ignites the front of the mixture. The two flame fronts collide, and put tremendous force on the combustion chamber and all its parts(pistons, rings, ect.) There are many ways to help prevent it. Whenever the temperature of the air/fuel mix goes up, so does the chance of the end gas suddenly igniting(detonation). So anything you can do to lower the temperature of the mix will help prevent it. Running a richer A/F ratio will help cool the mixture down a bit. A more efficient intercooler to cool the intake air will help also. Lower compression pistons will help also. Anytime you raise the boost pressure into the engine, that will also raise the temperature of the Air/fuel mixture. Thats why you run a greater risk of detonation when running more boost. Too advanced ignition timing can also cause detonation. Pulling out a few degrees of timing (making the spark occur a tad bit later in the compression stroke of the piston), will help control it also. Ignition timing is a very big factor to detonation, and controlling it. When the spark occurs earlier in the compression stroke (advaced timing), it increases compression tmperature. When the temp of the air/fuel mix is increased, so is detonation. Advanced ignition timing increased cylinder compression temperature by relating back to Physics. When the spark occurs earlier in the compression stroke of the piston, the spark is igniting the mixture at a point where there is more compression pressure from the piston before it reaches top dead center. The longer it takes for the piston to reach TDC, the lower the compression pressure gets, and thus usually results in lower power output. Advanced timing makes power, but you need to find a happy medium when it comes to detonation. Running higher octane fuel also helps, because the greter the octane rating of the fuel, the less "explosive" the fuel is. There is a great misconception that higher octane fuel gives more power, but that is incorrect. Octane alone is what makes fuel more or less volitile. Hope this makes sense :)

I'll have to raise my hand when we say "cars running like shit toinght?" The whole damn engine shakes it misfires so badly, and if i richen it up, it bogs down, if you lean it out, you hear exhaust pops and it STILL RUNS LIKE SHIT. I wish i could get my car to run decent at night. It's like, when you give it 1/4 throttle, you get no response, if not, you slow down. What is that? Someone help me, its really getting annoying. Am i too rich or too lean??


Jon

1997 Eclipse RS

14.21@101mph 10/4/02

There are a ton of things that can cause a misfire unfortunately. The best thing to do is go down the list as given by the FSM. There's a nice troubleshooting section that will outline your attack for addressing misfire.

For example, I had a REALLY bad misfire about a month ago, that the whole board was trying to help me diagnose. I took on one thing at a time, replacing and checking with a multimeter, the spark plugs, the wires, the coil, the fuel injector terminals, and finally, the fuel injectors. I used a mechanic's stethoscope to listen for the clicking (or the absence of in this case) of the fuel injectors working. It turns out, I had a bad #3 injector.

Start going down your list.

Well after I went turbo and had the misfire I took it to Autozone to have the CEL checked out he said it was related to the MAP sensor and I posted it on here and everybody said the missing link will solve the problem.

i dont think its an injector, but i'll start trobuleshooting it today. it runs like a raped pig under boost.


Jon

1997 Eclipse RS

14.21@101mph 10/4/02

Yes, the missing link should solve that problem..unless your map sensor is broken.

Today i drove it around, and it is the strangest thing i've ever seen. It cycles. It'll start off really shitty, misfiring and barely running,then 5 miles down the road my EGTs will come back up and it'll run smoothly....bout 5 miles later, it's back down running like shit...EGTs are down to 500C at cruise...thats way rich i think. Then, sure enough, they come back up and the car runs smooth...it cycled about 3 times to my girlfrineds house. I'm resetting the ECU to see if that makes a differnece, but my gas mileage sucks ass...half a tank in 2 days!!!

Also, another thing would be my CEL. This morning it started flashing. Usually it's just steadily on. I have NEVER seen it flash before. That scared the piss out of me. Sorry if i'm stealing a post, i dont mean to :)


Jon

1997 Eclipse RS

14.21@101mph 10/4/02

Jon, what FPR are you using? Did you check your fuel pressure when the car was running bad like that? 500 degrees is waaaayyyy to cold for cruising. Sounds like you are putting way to much fuel into the engine. Just check your fuel pressure when the car is doing that. If you have the Cartach FPR, then I need not say any more haha :P

You read my mind. It's at 500 C, i think you realized that. That's usually my idle. If i freerev, it falls down to 450-400C. I've been through half a tank of gas in one day. I've leaned it as far as -10, and i think that's too much when just the other day the car ran fine on -2 lo speed. Maybe i can take it apart and clean it, but i really dont have time. I'll turn the FP down, but i think its sitting around 33-35 idle (couldnt tell when i looked earlier today, fp gauge is kinda nasty). I can't remember because it's been a long time, but i think...someone mentioned that i should disconnect the vacuum line and set the FP. All injectors are firing well, my plugs only have 5000 miles on them, the plug wires are alright, everything is firing well. I reset my ECU, it solved the problem for about 3 minutes, then its back to sputter sputter. I'll go turn down the FP on the damn thing tonight before i drive home and see if it makes a difference.


Jon

1997 Eclipse RS

14.21@101mph 10/4/02

FPR is fine, its functioning just like it should normally. I'm putting things together, check the new theory: i've drained half a tank of gas in 1 day, my car is so rich. Since it is cycling, i am believeing that it is my o2 sensor. It is a factory o2 sensor, it has 130k on it. I just didn't think they went. This could explain the reason my car's running like shit this entire time, just spatially. Anyone else agree??? :thumbsup


Jon

1997 Eclipse RS

14.21@101mph 10/4/02

I don't know. Could be. You really should check the codes. A flashing CEL light is worse than just a regular lit CEL light.


95 Eclipse RS : 5 speed
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

Yeah, but i've had non-functioning o2 sensor as a code for 20,000 miles now. i'm pretty sure that is the problem.


Jon

1997 Eclipse RS

14.21@101mph 10/4/02

Whoa. absolutely amazing. This is the COOLEST mod i've ever done. (mod, haha). My car runs perfect now!!!


Jon

1997 Eclipse RS

14.21@101mph 10/4/02