back firing on high rpm

[ibk]

ok i my cb7 got a h22a swap on it but when i drive it back fires on high rpm and sometimes when i switch on the car it idles very low and eventually turn off need help! i've check the dizzy and spark plug wires and spark plug.

[thepowderblue]

Do you have a misfire ?
I would check your timing.eletrical and mechanical.

[dj_ender]

ok i my cb7 got a h22a swap on it but when i drive it back fires on high rpm and sometimes when i switch on the car it idles very low and eventually turn off need help! i've check the dizzy and spark plug wires and spark plug.

this may not be your issue but my girls cd5 would do this if I rev'd pretty high and it was because there was a hole in the exhaust at the first bend, most likely due to water rotting it out. I know it was due to the hole because as soon as I replaced the pipe it went away. Like I said, might not be your issue but it could be. More than likely thepowderblue is right, check your timing. Also while the car is running run your hands over all of the spark plug wire connections, even then dizzy, dont worry the shock isn't a lot AND it wont shock you unless theres a break in your cables. But if you get shocked your wires are leaking the spark in them to the block, change them.

[batever]

I would not recommend putting your hands on the spark plug leads when the car is running. never done it, maybe the shock is mild, but not going to do it either. Dj ender, are you serious? Is this something you guys do where you are? I'm curious.


***side note*****
BTW, as a point of interest, if you are going to let yourself get shocked, it's better to get shocked when touching a the electrical source with your right hand, and with your left hand not touching anything. That's because (unless you are unusual, anatomically) your heart is on the left side of your torso and the electricity will travel through your right arm and down the right side of your torso (shortest path) to the ground. If you are touching electrical ground with your left hand, then the electriciy will travel through the heart region. BAD. For this reason, if you are working on an electrical circuit or even a phone circuit and there's a chance that power could be restored through it while you are working, it's better to do it one handed with your right hand, with your other hand in your pocket, in general.

My brother in law works as a high voltage lineman electrical transmission lineman and he was initiated into the brotherhood back in the day /they used to initiate new linemen into the job by their supervising partner having them touch (I think he actually said, "grab onto "onto the high voltage line on the tower with their right hand (i believe). This was on a big tower, not on the little street transmission lines.
Management got rid of that practice within the last 10 years. Can't imagine why. I'll have to ask him to retell this story.

****end of side note*****

it's worth it to check your ignition timing with a timing light and make sure you are within 2 degrees of 15 deg BTDC (somewhere between 17 deg BTDC amd 13 deg BTDC. Ideally, put it right at 15 deg BTDC since you are having this problem. I'm not thinking this part totally through, but I seem to recall it is an issue with this kind of problem. I believe for this issue you would rather be slightly advanced than slightly retarded, in your ignition timing, but I can't remember why exactly in full.

The misfire is likely because the fuel air mixture is getting too lean at the given cylinder temperature and compression level. Now why is that happening at high rpms only? The ECU is supposed to prevent this by controlling the injector pulse width (length of time the fuel injector runs) top make sure there is a safe margin of extra fuel in the fuel/air mixture at all rpms and engine loads. (this extra fuel helps cool the cylinder and prevent spontaneous misfiring, because a given air fuel mixture will ignite without spark if it reaches a certain temperature, a temperature which we try to avoid when running our cars. The ECU tries to avoid this using a program and lots of data points put into it at the factory). If you have a partially clogged injector then i think that could cause this problem, which would show up first at high rpms. Primarily because the injector won't deliver as much fuel as the program thinks it will (I THINK. I stand to potentially be corrected here).

Also, Becuase more fuel is combusting in the engine in general in a given time period (more ignitions per second) that increases general cylinder heat. That by itself, or perhaps combined with a dropoff in fuel delivery in one cylinder, might be enough to create conditions for an off-time fuel mixture ignition due to the cylinder temperature being high enough to ignite an overlean mixture.

You could also have an oxygen sensor going bad. If it's not reading the O2 level correctly, and the ECU thinks there is more free O2 in the exhaust than there is, then the ECU will lean off the mixture slightly, resulting in an OVERLEAN condition.

I'm not sure if this is a normal failure mode for the O2 sensor though. You might want to check into that. I suspect the normal failure mode is an underread of oxygen, not an overread. But I'll leave that for you to check.

Last but not least, if you have scaling in your cooling chambers, that decreases the amount of heat that the cooling system can pull away from the cylinders, which contributes to the overheated condition that can cause misfiring.

OR if you have a cooling gallery obstruction in the wrong part of the engine, or an oil gallery obstruction.

Really last but not least, if your oil pump is failing to pump enough oil to the head, the oil flow might be insufficient to transfer enough heat from the head. Same thing with your water pump.

Good luck. That's a lot to think about.

[dj_ender]

Yeah its not the ideal way to check for a break in the cables, but its cheap and effective. Oh and it is pretty mild, a lot less than sticking your finger in a lamp socket.

[JBradley500]

Yeah its not the ideal way to check for a break in the cables, but its cheap and effective. Oh and it is pretty mild, a lot less than sticking your finger in a lamp socket.

i wouldn't recommend it if you're running a high powered ignition system or a magneto. that would probably burn the short and curlies right off of your manhood.

[dj_ender]

Lol, yeah that's true.

[batever]

Yeah its not the ideal way to check for a break in the cables, but its cheap and effective. Oh and it is pretty mild, a lot less than sticking your finger in a lamp socket.

Ok well then if i''m ever in a desperate situation and need to know, I'll keep that in mind. Makes sesne that it is mild compared to house current because the shocks out of the ignition system, while high voltage, are intermittent and extremely short in duration, plus probably fairly limited in their overall peak current level. the system only provides enough voltage to create a spark across the spark plug gap, and likely provides only enough overall power, with a margin of safety, to create an adequate spark size/level during that spark jump.

[dj_ender]

Ok well then if i''m ever in a desperate situation and need to know, I'll keep that in mind. Makes sesne that it is mild compared to house current because the shocks out of the ignition system, while high voltage, are intermittent and extremely short in duration, plus probably fairly limited in their overall peak current level. the system only provides enough voltage to create a spark across the spark plug gap, and likely provides only enough overall power, with a margin of safety, to create an adequate spark size/level during that spark jump.

I feel stupid after reading that post...

[batever]

I feel stupid after reading that post...

sometimes i think i think too much! LOL. but i'm sure it has saved my health/ life on a number of occasions. Especially when working around heavy objects jacked up off the ground, and electricity.

It's good to know when someone has actual practical experienceof, say, getting shocked by a spark plug lead, for example....adds to my total store of knowledge. So, thanks!

[dj_ender]

sometimes i think i think too much! lol

It's all good

[batever]

Oh, and IBK, do you have the right ECU for the h22? I'm not sure but I would imagine it needs different programming than the F22, hence, a different ECU. Problems due to that might not show up in an obvious way except at either high engine load or high rpms. I'd check that out first before doing anything else. If you have the wrong ECU for your engine then that needs to be swapped out before anything else.

And, as DJ Ender says, also rule out an exhaust leak, particularly one at the down pipe. Have someone clap their hand over the tailpipe and off, over the tailpipe and off , while you look at the downpipe area and also the whole exhaust for exhaust coming out of places where it shouldn't come out.

[dj_ender]

I found out about our issue when I was cleaning out the engine with Seafoam. It started backfiring and I started freaking out, looked under the car and saw a huge hole at the first bend under the gas tank.