Misfire Problems

[Vistaman73]

OK, so my CB has been acting up on me lately. Under light acceleration from a complete stop it misfires a bit but if I get on it, it smooths out. It idles fine. If I am cruising (barely on the gas) at any speed under 40 mph it is a constant misfire and it shakes, if I tap the gas or get on the gas at all it stops if I'm off the gas it stops, anything above 40 mph is fine. Also when revving in park if I slowing apply throttle it is fine but if I blip the throttle I can hear it hesitate/misfire. It's really bugging me. I just replaced my spark plugs and wires and checked for water in the dizzy since I have got water in my engine bay and have had starting issues but never this constant misfire under these certain circumstances. I have 175k on the car and don't think the fuel filter has ever been changed, I'm doing that next. It sat for a whole week in the garage while I was on vacation, it's about 103 here in KS all day so it had time to dry out if that even was the issue, I also left the battery unplugged. One of my old wires had ripped off the metal clip for the spark plug and I thought that was my issue but it wasn't. My buddy said he could smell the gas while riding behind me when it was misfiring. Also I'm getting 21 MPG but I mostly blame that on my major lead foot, what can I say, I'm a teenager. Any help would be greatly appreciated, I pray its just a simple, fast fix or a maintenance thing like the fuel filter. Thanks.

[deevergote]

Does your check engine light ever come on?

[Mishakol129]

Does your check engine light ever come on?

I had misfires but my CEL never came on, what does that mean?

[deevergote]

It could mean anything. The light coming on will help narrow down the issue. The light not coming on doesn't provide nearly as much focus.

Let's keep this on the topic of the OP's car, shall we? His problem and your problem could be completely different issues, and it's rude to make this thread about your car.

[Vistaman73]

My CEL never comes on.

[alb_accord]

disconnect the o2 sensor or the water temp sensor D under the distributor and let us know if the car will run without any of the misfiring.

[Vistaman73]

I went out and started it up in the garage, earlier today and tried to make it misfire by putting the engine under load and applying the gas, no misfire, but it was cold so I let it warm up and bam, misfire. So it seems to run fine for the first minute or so but I was stationary, I can't recall a specific time where I noticed it ran fine while cold but I'm not saying it was always misfiring, just didn't pay enough attention while driving the first mile or so. So I went out and took it for a drive and recorded me driving around in an empty parking lot, don't be afraid to turn up your speakers there are no super loud parts, I just want you to clearly hear the misfire. Tell me what y'all think. Thanks.

http://s1170.photobucket.com/albums/...t=MOV_0550.mp4

[cincy90h22]

Check for vaccuum leaks, dry rotted hoses, etc. Spray intake manifold where it meets the head with carb cleaner. If its leaking the motor will bog down if there is a leaking gasket.

The temp sensor under the distributor is for the gauge, it has no bearing on the ecu. The temp sensor on the thermostat housing is the one you want to unplug. If it is indeed the culprit, you will get a cel, and it will idle higher but should run better. I doubt that is your problem though.

Since you did plugs and wires already you should be good already, as long as your gap is correct (you didnt drop any accidentally did you?) and your wires are securely connected. Ive seen wires come loose at the distributor.

[Vistaman73]

Wires are secure and the plugs were not dropped, I was very careful. I'll check for vacuum leaks tomorrow. Could this be fuel related? I don't think the filter has ever been replaced.

[cincy90h22]

It wouldnt hurt to change your fuel filter, but I dont think its your main problem. If you were starving for fuel it would get worse as rpm/load increases. Have you noticed a decrease in power in the higher rpms, or does it feel normal? Dont compare it to when it misfires, think before it started. If it doesnt do it cold, I would lean more towards an air leak, because you are running full rich at start-up the extra air isnt effecting performance as much. When it goes into closed loop when it warms up, less fuel + air leak = rough run at idle/lower rpms. Higher rpms you wont notice as much.

[Straight Success]

I had this problem. My culprit was a bad map sensor.

Things to check: Distributor, plugs, wires, map sensor.

[cincy90h22]

yes, Map sensor as well.

[Vistaman73]

Power seems to be fine at higher RPMs. I'll definitely check for leaks that sounds like a promising lead, also, how would I check the functionality of my MAP sensor? Are they expensive to replace?

[Vistaman73]

Got some extra info, when my aunt owned the car the CEL was always on because of faulty o2 sensors. they went through 4 american ones, when my dad bought the car he bought a Honda oem o2 sensor and it worked fine since then. Not really important just trying to give info. Don't know how often EGR ports clog up and this car doesn't have a past of EGR problems. But who knows. As the late Carroll Shelby said, "Everything was fine until the Government made us pump the crap going out the exhaust back into the crankcase." LOL

[1991redcoupe]

When mine had a similar problem it turned out to be the o2 sensor.....disconnect and see if problem persists