Mechanics

MISFIRE

1992 Honda Accord • 455,000 miles

I had rebuilt my motor 3 months ago (took block to resurface and honed cylinders, head completely rebuilt/ new seals, rings, rod bearings) and re-assembled. (Note-it has all new trans & motor mounts) and been noticing for a while that my #3 cylinder plug wire changes motor reaction very little when pulled out. Seems to not fasten tightly so replaced wires and plug itself and same thing. Probelm occuring is that I could hear car misfire ahd have that funny odor from exhaust after car is shut off. Also every morning does not idle properly at start up (normal I belive is at around 1500rpm) and my car idles first at around 800rpm, I tap the gas and it drops down to 100 then back up to 800, then about a minute idles up to about 1200-1500 rpm until warmed then drops to normal 700 rpm idle but when this happens, engine shakes like crazy that the stering wheel is vibrating badly most of the time (time to time shakes very little). Valves have not been adjusted but not sure if this could be the problem. Also another note timing belt broke and I had replaced both but this problem existed even prior and still the same after. Could this be a result of a bad idle or fast idle control valve? Or something else?

thanks.
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Steveal01
April 25, 2013.




If your timing belt broke you may have bent valves. Take a compression test. #3 may be low the check fuel pressure should be 40-47 with vacuum disconnected and 30-38 connected. Also valves should be adjusted otherwise valve may not be closing properly.

Hmac300
Apr 25, 2013.
I will have those checked out. Also note: 1) This problem ocurred even prior to the belt breaking
2) At idle when fan or some eletrical use (window switch) RPM drops down quickly then back to normal (voltage drop)
3) Only at #3 spark plug boot where it sit on valve cover (covers spark plug tunnel) seems to be darkening (valve cover was painted white so noticable discoloration). Seems to be running hotter than other plugs I think). 1, 2 & 4 not even darkening.

Tiny
Steveal01
Apr 25, 2013.
Check that plug wire boot for leakage or replace it
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Hmac300
Apr 25, 2013.
Well, I finally got to checking these items and done the following: 1) valve adjustment, which dramatically improved my mileage
2) replaced the spark plug wires
3) compression test: #1 - 170
#2-168
#3-90
#4-180

Obviously, I doubt the rings are bad because they are brand new approx. 1000 miles, or the valves on #3 got bent when the timing belt broke. I believe this is the culprit. The numbers are somewhat a little separated but not too bad and I think this is the reason why the car was shaking so bad. What do you think.

Tiny
Steveal01
May 11, 2013.
Yup you bent a valve, that is probably the cause of the misfire.

Hmac300
May 12, 2013.
OK so I removed the head and on each port, did a leak test and found the leak, replaced bent valve. Re-checked all my timing line up (crank @ t.D.C, front balancer mark lined up, rear balancer locked in position with mark at approx. 5-o'clock, and cam marked up with marks matched with surface of head), re-checked timing after initial warm up, runs fine but car still slightly shakes on idle when in gear. All 4 mounts are in new condition (but mechanic told me that they have to be installed a precise way otherwise they wil not function properly and cause the shakes). I am not sure how true this is as I replaced each one at a time and can only install one way, there is no (or not much ) slack to adjust to bolt down. I also checked the idle air control valve and it is reading at peak 15 ohms at time to 16, I think this could be my next culprit. What do you suspect? (Note-no longer misfires, now idles properly at initial start up, when fans now kick in, not much of electrical drag that the car no longer seem to want to shut off like before).

Tiny
Steveal01
May 20, 2013.
Try cleaning the throttle plate and iac hole first instead of replacing it it shold read 8-15 ohms though so it sounds ok You could have a bad plug or wire and i'd drive it first for a bit before doing anything.

Hmac300
May 20, 2013.
I have cleaned the throttle body & plate & IAC prior but will re-check those and drive a little as you suggest. I had installed new plugs and wires but the wires are autozone brand and don't like them much as I feel they don't seat well. I will drive a little and possible upgrade wires to NGK. Thanks

Tiny
Steveal01
May 20, 2013.

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