Honda Accord 2002 F18B2 jerking/rough idle

[Mantas]

Hello, and excuse me for my english in advance. The car is 2002 Honda Accord 1.8l, engine code is F18B2. The problem is, that my car jerks/hesitates when I fully depress gas pedal and then floor it. It does not matter if the engine is cold or hot. The car violently jerks a few times, then accelerates normally. It happens at any rpm. It is more felt in low gears, less in high gears. Another thing is, that when i try to keep constant speed in low gears (1-st ant 2-nd at 1000-2500rpm) it hesitates and it’s hard to drive in traffic jams, because i have to use the clutch very often. Idle is a bit rough, engine seems to misfire from time to time. When cruising at high speed nothing wrong is felt. Also if changing gears very softly and not accelerating hard everything is almost o.k., almost no jerking/hesitation is felt. CE (MIL) light is NOT on. Changed: air filter, fuel filter, plugs NGK, wires NGK, cap/rotor/coil, then tried another distributor from salvage yard. Nothing changed. Cleaned EGR valve and ports. Did put in the new O2 sensor (NTK). Did the valve adjustment. PCV valve is O.K. Tried disconect any sensor that is present in this engine (TPS, MAP, IACV, IAB, EGR, KS, so on), reset the ECU/PCM, then test drive – nothing changes or gets worse. Cleaned IACV. TPS reads 0.5V at closed throttle and 4.5V at WOT. Voltage transition is smooth. Tried another MAP sensor. No luck. Engine idle rpm ‘s are OK, they do not jump around. Compression in all cylinders is 14.5-15bars. No white smoke, coolant level is constant. Eats some oil, but the eating rate is constant and it allways ate some oil. Ground wires to the engine are cleaned and ok. No vacuum leaks I did found. Maybe somebody here knows the solution?

Topic

[Mantas]

Well, not 100% the same, engine runs a bit worse with TPS unplugged (idle speed gets higher, etc.), but it does not affect bucking and rough idle at all

[Mantas]

Can this be because of clogged intake manifold? EGR passages and holes into IM were blocked with carbon, i cleaned that, but maybe there’s much more to clean inside IM runners and this causes problems? Is that common on hondas? It’s not so simple to take entire IM off and clean it, but maybe it’s worth to give it a try?

[EricTheCarGuy]

A clogged intake manifold is EXTREMELY rare. Think about it, gasoline is a solvent. It can clean things up pretty good. That said, EGR is only active under load. It should never be active at idle. It would be very unlikely that clogged EGR passages could cause a problem like that.

I just had a thought. Have you checked the timing belt? If it’s loose or the balance shafts are not in time, it can cause issues with engine performance. It might be worth checking if you haven’t already.

[Mantas]

Been there, done that. Timing belt is in good condition, not loose, mechanical timing is right. Timing is controlled only by ECU, distributor does not rotate. CYP/TDC/CKP sensors resistances are within specs, no CEL. Can timing be still bad? Possibly timing can be too advanced on moments of sudden acceleration, I even have sensor logs the moments of bucking, including timing advance numbers, but i can’t say if timing that ECU chooses to set is right or not at these moments. As I understand right input from many various sensors is important for ECU to set the right timing. Maybe some sensor can be “half bad” and sends wrong data, but not enough “wrong” to set a CEL? On idle timing is 12 degrees – as it should be (OBD2 scantool shows that, not a timing light, but i’m pretty sure this data is true). One thing I’m sure of – sparkplug in 2-nd cylinder ir much whiter that the other three, take a look: http://i39.tinypic.com/2vxlqu0.jpg and this is most probably the core of the problem. Probably 2-nd cylinder gets leaner mixture because of something (no vacuum leak I can find) or it has some machanical issue (but shows good compression – 13.5 bars (195PSI)). Don’t know where to look and what to do…

[Mantas]

Here is an attached file (TrackLog-2014-Jan-08_20-49-55.csv). It can be viewed by a free CSV viewer o Microsoft Exel. It contains STFT, LTFT, MAP, TPS, timing advance and RPM data. What I did was I drove a car pushing it tu buck/jerk – suddenly accelerate hard and then release gas. Maybe somebody can comment that data?

STFT LTFT MAP(kPA) TPS (%) Timing adv. RPM

-0.78125 0 28 – – 9.01960754 11.5 754
-0.78125 0 28 – – 9.01960754 11.5 754
-0.78125 0 28 – – 9.01960754 11.5 754
-0.78125 0 28 – – 9.01960754 11.5 754
-0.78125 0 28 – – 9.01960754 11.5 754
-0.78125 0 28 – – 9.01960754 11.5 754
-0.78125 0 28 – – 9.01960754 11.5 754
-0.78125 0 28 – – 9.01960754 11.5 754
-0.78125 0 28 – – 9.01960754 11.5 754
-0.78125 0 28 – – 9.01960754 11.5 754
-0.78125 0 28 – – 9.01960754 11.5 754
-0.78125 0 27 – – 9.01960754 11.5 754
-0.78125 0 27 – – 9.01960754 11.5 754
-0.78125 0 27 – – 9.01960754 11.5 754
-0.78125 0 27 – – 9.01960754 11.5 754
-0.78125 0 27 – – 9.01960754 11.5 743.5
-0.78125 0 27 – – 9.01960754 11.5 743.5
-2.34375 0 27 – – 9.01960754 11.5 743.5
-2.34375 0 27 – – 9.01960754 11.5 743.5
-2.34375 0 27 – – 9.01960754 12 743.5
-2.34375 0 27 – – 9.01960754 12 743.5
-2.34375 0 27 – – 9.01960754 12 743.5
-2.34375 0 27 – – 9.01960754 12 743.5
-2.34375 0 27 – – 9.01960754 12 743.5
-2.34375 0 27 – – 9.01960754 12 743.5
-2.34375 0 27 – – 9.01960754 12 743.5
-2.34375 0 27 – – 9.01960754 12 743.5
-2.34375 0 28 – – 9.01960754 12 743.5
-2.34375 0 28 – – 9.01960754 12 743.5
-2.34375 0 28 – – 9.01960754 12 738.25
-3.90625 0 28 – – 9.01960754 12 738.25
-3.90625 0 28 – – 9.01960754 12 738.25
-3.90625 0 28 – – 9.01960754 13.5 738.25
-3.90625 0 28 – – 9.01960754 13.5 738.25
-3.90625 0 28 – – 9.01960754 13.5 738.25
-3.90625 0 28 – – 9.01960754 13.5 738.25
-3.90625 0 28 – – 9.01960754 13.5 738.25
-3.90625 0 28 – – 9.01960754 13.5 738.25
-3.90625 0 28 – – 9.01960754 13.5 738.25
-3.90625 0 28 – – 9.01960754 13.5 751.5
-3.90625 0 28 – – 9.01960754 13.5 751.5
-3.125 0 28 – – 9.01960754 13.5 751.5
-3.125 0 28 – – 9.01960754 11.5 751.5
-3.125 0 28 – – 9.01960754 11.5 751.5
-3.125 0 28 – – 9.01960754 11.5 751.5
-3.125 0 28 – – 9.01960754 11.5 751.5
-3.125 0 28 – – 9.01960754 11.5 751.5
-3.125 0 28 – – 9.01960754 11.5 751.5
-3.125 0 29 – – 9.01960754 11.5 751.5
-3.125 0 29 – – 9.01960754 11.5 751.5
-3.125 0 29 – – 9.01960754 11.5 751.5
-2.34375 0 29 – – 9.01960754 11.5 751.5
-2.34375 0 29 – – 9.01960754 11.5 751.5
-2.34375 0 29 – – 9.01960754 11.5 751.5
-2.34375 0 29 – – 9.01960754 11.5 751.5
-2.34375 0 29 – – 9.01960754 11.5 751.5
-2.34375 0 29 – – 9.01960754 11.5 751.5
-2.34375 0 29 – – 9.01960754 11.5 751.5
-2.34375 0 28 – – 9.01960754 11.5 751.5
-2.34375 0 28 – – 9.01960754 11.5 751.5
-2.34375 0 28 – – 9.01960754 11.5 743.75
-2.34375 0 28 – – 9.01960754 11.5 743.75
-1.5625 0 28 – – 9.01960754 11.5 743.75
-1.5625 0 28 – – 9.01960754 11 743.75
-1.5625 0 28 – – 9.01960754 11 743.75
-1.5625 0 28 – – 9.01960754 11 743.75
-1.5625 0 28 – – 9.01960754 11 743.75
-1.5625 -0.78125 28 – – 9.01960754 11 743.75
-1.5625 -0.78125 28 – – 9.01960754 11 743.75
-1.5625 -0.78125 31 – – 9.01960754 11 743.75
-1.5625 -0.78125 31 – – 9.01960754 11 753.75
-1.5625 -0.78125 31 – – 9.01960754 11 753.75
1.5625 -0.78125 31 – – 9.01960754 11 753.75
1.5625 -0.78125 31 – – 9.01960754 11 753.75
1.5625 -0.78125 31 – – 9.01960754 19.5 753.75
1.5625 -0.78125 31 – – 9.01960754 19.5 753.75
1.5625 -0.78125 31 – – 15.68627453 19.5 753.75
1.5625 -0.78125 31 – – 15.68627453 19.5 753.75
1.5625 -0.78125 31 – – 15.68627453 19.5 753.75
1.5625 -0.78125 43 – – 15.68627453 19.5 753.75
1.5625 -0.78125 43 – – 15.68627453 19.5 753.75
1.5625 -0.78125 43 – – 15.68627453 19.5 1883.25
1.5625 -0.78125 43 – – 15.68627453 19.5 1883.25
2.34375 -0.78125 43 – – 15.68627453 19.5 1883.25
2.34375 -0.78125 43 – – 15.68627453 28.5 1883.25
2.34375 -0.78125 43 – – 15.68627453 28.5 1883.25
2.34375 -0.78125 43 – – 16.07843208 28.5 1883.25
2.34375 -0.78125 43 – – 16.07843208 28.5 1883.25
2.34375 -0.78125 43 – – 16.07843208 28.5 1883.25
2.34375 -0.78125 43 – – 16.07843208 28.5 1883.25
2.34375 -0.78125 43 – – 16.07843208 28.5 1883.25
2.34375 -0.78125 43 – – 16.07843208 28.5 1633.25
2.34375 -0.78125 43 – – 16.07843208 28.5 1633.25
10.9375 -0.78125 43 – – 16.07843208 28.5 1633.25
10.9375 -0.78125 43 – – 16.07843208 25.5 1633.25
10.9375 -0.78125 43 – – 16.07843208 25.5 1633.25
10.9375 -0.78125 43 – – 16.47058868 25.5 1633.25
10.9375 -0.78125 43 – – 16.47058868 25.5 1633.25
10.9375 -0.78125 43 – – 16.47058868 25.5 1633.25
10.9375 -0.78125 50 – – 16.47058868 25.5 1633.25
10.9375 -0.78125 50 – – 16.47058868 25.5 1633.25
10.9375 -0.78125 50 – – 16.47058868 25.5 1436.75
10.9375 -0.78125 50 – – 16.47058868 25.5 1436.75
7.8125 -0.78125 50 – – 16.47058868 25.5 1436.75
7.8125 -0.78125 50 – – 16.47058868 25.5 1436.75
7.8125 -0.78125 50 – – 16.47058868 22.5 1436.75
7.8125 -0.78125 50 – – 16.47058868 22.5 1436.75
7.8125 -0.78125 50 – – 16.47058868 22.5 1436.75
7.8125 -0.78125 50 – – 16.47058868 22.5 1436.75
7.8125 -0.78125 50 – – 16.47058868 22.5 1436.75
7.8125 -0.78125 55 – – 16.47058868 22.5 1436.75
7.8125 -0.78125 55 – – 16.47058868 22.5 1554
7.8125 -0.78125 55 – – 16.47058868 22.5 1554
0.78125 -0.78125 55 – – 16.47058868 22.5 1554
0.78125 -0.78125 55 – – 16.47058868 22.5 1554
0.78125 -0.78125 55 – – 16.47058868 26 1554
0.78125 -0.78125 55 – – 16.47058868 26 1554
0.78125 -0.78125 55 – – 16.47058868 26 1554
0.78125 -0.78125 55 – – 16.47058868 26 1554
0.78125 -0.78125 55 – – 16.47058868 26 1554
0.78125 -0.78125 47 – – 16.47058868 26 1554
0.78125 -0.78125 47 – – 16.47058868 26 1554
0.78125 -0.78125 47 – – 16.47058868 26 1964.25
14.0625 -0.78125 47 – – 16.47058868 26 1964.25
14.0625 -0.78125 47 – – 16.47058868 26 1964.25
14.0625 -0.78125 47 – – 16.47058868 27.5 1964.25
14.0625 -0.78125 47 – – 16.47058868 27.5 1964.25
14.0625 -0.78125 47 – – 9.01960754 27.5 1964.25
14.0625 -0.78125 47 – – 9.01960754 27.5 1964.25
14.0625 -0.78125 47 – – 9.01960754 27.5 1964.25
14.0625 -0.78125 19 – – 9.01960754 27.5 1964.25
14.0625 -0.78125 19 – – 9.01960754 27.5 1964.25
14.0625 -0.78125 19 – – 9.01960754 27.5 2071.75
14.0625 -0.78125 19 – – 9.01960754 27.5 2071.75
0 -0.78125 19 – – 9.01960754 27.5 2071.75
0 -0.78125 19 – – 9.01960754 27 2071.75
0 -0.78125 19 – – 9.01960754 27 2071.75
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0 -0.78125 19 – – 9.01960754 27 2071.75
0 -0.78125 16 – – 9.01960754 27 2071.75
0 -0.78125 16 – – 9.01960754 27 2071.75
0 -0.78125 16 – – 9.01960754 27 1662.75
0 -0.78125 16 – – 9.01960754 27 1662.75
17.968 -0.78125 16 – – 9.01960754 27 1662.75
17.968 -0.78125 16 – – 9.01960754 27 1662.75
17.968 -0.78125 16 – – 9.01960754 8.5 1662.75
17.968 -0.78125 16 – – 42.35294342 8.5 1662.75
17.968 -0.78125 16 – – 42.35294342 8.5 1662.75
17.968 -0.78125 16 – – 42.35294342 8.5 1662.75
17.968 -0.78125 16 – – 42.35294342 8.5 1662.75
17.968 -0.78125 90 – – 42.35294342 8.5 1662.75
17.968 -0.78125 90 – – 42.35294342 8.5 2612.25
17.968 -0.78125 90 – – 42.35294342 8.5 2612.25
8.5937 -0.78125 90 – – 42.35294342 8.5 2612.25
8.5937 -0.78125 90 – – 42.35294342 8.5 2612.25
8.5937 -0.78125 90 – – 42.35294342 36 2612.25
8.5937 -0.78125 90 – – 42.35294342 36 2612.25
8.5937 -0.78125 90 – – 9.01960754 36 2612.25
8.5937 -0.78125 90 – – 9.01960754 36 2612.25
8.5937 -0.78125 90 – – 9.01960754 36 2612.25
8.5937 -0.78125 14 – – 9.01960754 36 2612.25
8.5937 -0.78125 14 – – 9.01960754 36 2612.25
8.5937 -0.78125 14 – – 9.01960754 36 2326.25
8.5937 -0.78125 14 – – 9.01960754 36 2326.25
0 -0.78125 14 – – 9.01960754 36 2326.25
0 -0.78125 14 – – 9.01960754 26.5 2326.25
0 -0.78125 14 – – 9.01960754 26.5 2326.25
0 -0.78125 14 – – 9.01960754 26.5 2326.25
0 -0.78125 14 – – 9.01960754 26.5 2326.25
0 -0.78125 14 – – 9.01960754 26.5 2326.25
0 -0.78125 17 – – 9.01960754 26.5 2326.25
0 -0.78125 17 – – 9.01960754 26.5 2326.25
0 -0.78125 17 – – 9.01960754 26.5 2145.75
0 -0.78125 17 – – 9.01960754 26.5 2145.75
17.1875 -0.78125 17 – – 9.01960754 26.5 2145.75
17.1875 -0.78125 17 – – 9.01960754 15 2145.75
17.1875 -0.78125 17 – – 9.01960754 15 2145.75
17.1875 -0.78125 17 – – 19.6078434 15 2145.75
17.1875 -0.78125 17 – – 19.6078434 15 2145.75
17.1875 -0.78125 17 – – 19.6078434 15 2145.75
17.1875 -0.78125 17 – – 19.6078434 15 2145.75
17.1875 -0.78125 20 – – 19.6078434 15 2145.75
17.1875 -0.78125 20 – – 19.6078434 15 2145.75
17.1875 -0.78125 20 – – 19.6078434 15 2628.75
12.5 -0.78125 20 – – 19.6078434 15 2628.75
12.5 -0.78125 20 – – 19.6078434 15 2628.75
12.5 -0.78125 20 – – 19.6078434 26.5 2628.75
12.5 -0.78125 20 – – 19.6078434 26.5 2628.75
12.5 -0.78125 20 – – 9.01960754 26.5 2628.75
12.5 -0.78125 20 – – 9.01960754 26.5 2628.75
12.5 -0.78125 20 – – 9.01960754 26.5 2628.75
12.5 -0.78125 12 – – 9.01960754 26.5 2628.75
12.5 -0.78125 12 – – 9.01960754 26.5 2628.75
12.5 -0.78125 12 – – 9.01960754 26.5 2255.5
12.5 -0.78125 12 – – 9.01960754 26.5 2255.5
0 -0.78125 12 – – 9.01960754 26.5 2255.5
0 -0.78125 12 – – 9.01960754 27 2255.5
0 -0.78125 12 – – 9.01960754 27 2255.5
0 -0.78125 12 – – 18.4313736 27 2255.5
0 -0.78125 12 – – 18.4313736 27 2255.5
0 -0.78125 12 – – 18.4313736 27 2255.5
0 -0.78125 12 – – 18.4313736 27 2255.5
0 -0.78125 83 – – 18.4313736 27 2255.5
0 -0.78125 83 – – 18.4313736 27 2255.5
0 -0.78125 83 – – 18.4313736 27 2505
13.2812 -0.78125 83 – – 18.4313736 27 2505
13.2812 -0.78125 83 – – 18.4313736 27 2505
13.2812 -0.78125 83 – – 18.4313736 36 2505
13.2812 -0.78125 83 – – 18.4313736 36 2505
13.2812 -0.78125 83 – – 9.01960754 36 2505
13.2812 -0.78125 83 – – 9.01960754 36 2505
13.2812 -0.78125 83 – – 9.01960754 36 2505
13.2812 -0.78125 13 – – 9.01960754 36 2505
13.2812 -0.78125 13 – – 9.01960754 36 2505
13.2812 -0.78125 13 – – 9.01960754 36 2580.75
0 -0.78125 13 – – 9.01960754 36 2580.75
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0 -0.78125 13 – – 9.01960754 15 2580.75
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0 -0.78125 15 – – 9.01960754 15 2580.75
0 -0.78125 15 – – 9.01960754 15 2580.75
0 -0.78125 15 – – 9.01960754 15 2232.75
0 -0.78125 15 – – 9.01960754 15 2232.75
20.3125 -0.78125 15 – – 9.01960754 15 2232.75
20.3125 -0.78125 15 – – 9.01960754 15 2232.75
20.3125 -0.78125 15 – – 9.01960754 18.5 2232.75
20.3125 -0.78125 15 – – 24.31372643 18.5 2232.75
20.3125 -0.78125 15 – – 24.31372643 18.5 2232.75
20.3125 -0.78125 15 – – 24.31372643 18.5 2232.75
20.3125 -0.78125 15 – – 24.31372643 18.5 2232.75
20.3125 -0.78125 67 – – 24.31372643 18.5 2232.75
20.3125 -0.78125 67 – – 24.31372643 18.5 2232.75
20.3125 -0.78125 67 – – 24.31372643 18.5 2943.25
7.03125 -0.78125 67 – – 24.31372643 18.5 2943.25
7.03125 -0.78125 67 – – 24.31372643 18.5 2943.25
7.03125 -0.78125 67 – – 24.31372643 36.5 2943.25
7.03125 -0.78125 67 – – 24.31372643 36.5 2943.25
7.03125 -0.78125 67 – – 9.01960754 36.5 2943.25
7.03125 -0.78125 67 – – 9.01960754 36.5 2943.25
7.03125 -0.78125 67 – – 9.01960754 36.5 2943.25
7.03125 -0.78125 12 – – 9.01960754 36.5 2943.25
7.03125 -0.78125 12 – – 9.01960754 36.5 2943.25
7.03125 -0.78125 12 – – 9.01960754 36.5 2617.75
7.03125 -0.78125 12 – – 9.01960754 36.5 2617.75
0 -0.78125 12 – – 9.01960754 36.5 2617.75
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0 -0.78125 17 – – 9.01960754 15 2617.75
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17.9687 -0.78125 17 – – 9.01960754 15 2222
17.9687 -0.78125 17 – – 9.01960754 15 2222
17.9687 -0.78125 17 – – 9.01960754 11 2222
17.9687 -0.78125 17 – – 9.01960754 11 2222
17.9687 -0.78125 17 – – 27.45098114 11 2222
17.9687 -0.78125 17 – – 27.45098114 11 2222
17.9687 -0.78125 17 – – 27.45098114 11 2222
17.9687 -0.78125 76 – – 27.45098114 11 2222
17.9687 -0.78125 76 – – 27.45098114 11 2222
17.9687 -0.78125 76 – – 27.45098114 11 3073.75
17.9687 -0.78125 76 – – 27.45098114 11 3073.75
8.59375 -0.78125 76 – – 27.45098114 11 3073.75
8.59375 -0.78125 76 – – 27.45098114 11 3073.75
8.59375 -0.78125 76 – – 27.45098114 36.5 3073.75
8.59375 -0.78125 76 – – 9.01960754 36.5 3073.75
8.59375 -0.78125 76 – – 9.01960754 36.5 3073.75
8.59375 -0.78125 76 – – 9.01960754 36.5 3073.75
8.59375 -0.78125 76 – – 9.01960754 36.5 3073.75
8.59375 -0.78125 12 – – 9.01960754 36.5 3073.75
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8.59375 -0.78125 12 – – 9.01960754 36.5 2889
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18.75 -0.78125 15 – – 9.01960754 20.5 2436.5
18.75 -0.78125 15 – – 9.01960754 20.5 2436.5
18.75 -0.78125 15 – – 25.49019623 20.5 2436.5
18.75 -0.78125 15 – – 25.49019623 20.5 2436.5
18.75 -0.78125 15 – – 25.49019623 20.5 2436.5
18.75 -0.78125 15 – – 25.49019623 20.5 2436.5
18.75 -0.78125 70 – – 25.49019623 20.5 2436.5
18.75 -0.78125 70 – – 25.49019623 20.5 3145.75
18.75 -0.78125 70 – – 25.49019623 20.5 3145.75
10.1562 -0.78125 70 – – 25.49019623 20.5 3145.75
10.1562 -0.78125 70 – – 25.49019623 20.5 3145.75
10.1562 -0.78125 70 – – 25.49019623 37.5 3145.75
10.1562 -0.78125 70 – – 9.01960754 37.5 3145.75
10.1562 -0.78125 70 – – 9.01960754 37.5 3145.75
10.1562 -0.78125 70 – – 9.01960754 37.5 3145.75
10.1562 -0.78125 70 – – 9.01960754 37.5 3145.75
10.1562 -0.78125 12 – – 9.01960754 37.5 3145.75
10.1562 -0.78125 12 – – 9.01960754 37.5 3145.75
10.1562 -0.78125 12 – – 9.01960754 37.5 3091.5
0 -0.78125 12 – – 9.01960754 37.5 3091.5
0 -0.78125 12 – – 9.01960754 37.5 3091.5
0 -0.78125 12 – – 9.01960754 15 3091.5
0 -0.78125 12 – – 9.01960754 15 3091.5
0 -0.78125 12 – – 9.01960754 15 3091.5
0 -0.78125 12 – – 9.01960754 15 3091.5
0 -0.78125 12 – – 9.01960754 15 3091.5
0 -0.78125 12 – – 9.01960754 15 3091.5
0 -0.78125 12 – – 9.01960754 15 3091.5
0 -0.78125 12 – – 9.01960754 15 2713.25
0 -0.78125 12 – – 9.01960754 15 2713.25
17.9687 -0.78125 12 – – 9.01960754 15 2713.25
17.9687 -0.78125 12 – – 9.01960754 30 2713.25
17.9687 -0.78125 12 – – 9.01960754 30 2713.25
17.9687 -0.78125 12 – – 25.09803963 30 2713.25
17.9687 -0.78125 12 – – 25.09803963 30 2713.25
17.9687 -0.78125 12 – – 25.09803963 30 2713.25
17.9687 -0.78125 12 – – 25.09803963 30 2713.25
17.9687 -0.78125 67 – – 25.09803963 30 2713.25

[Mantas]

As I understand, everytime I release and then hit the gas, ECU sharply retards timing (from let’s say 27 degrees BTDC to 8.5 degrees BTDC) and STFT gets very high – up to 20 and the car bucks/jerks. What could be the cause?

[EricTheCarGuy]

I would table the timing theory for now. If you know the belt is correct and not loose, I would leave it at that.

Just out of curiosity, have you checked compression? If not, it might be worth checking.

[Mantas]

Cyl. 1 – 203PSI (14BARS)
Cyl. 2 – 195PSI (13.5BARS)
Cyl. 3 – 203PSI (14BARS)
Cyl. 4 – 210PSI (14.5BARS)

Manual states, that difference between cylinders can be up to 2 bars (29PSI) so it’s up to spec I quess. Tested on hot and cold engine, results were the same.

[Mantas]

So, any other ideas on where to look and what to do?

[Mantas]

Maybe somebody can suggest what else to check?

[college man]

Two things to try. remove the injectors leaving them in the fuel
rail.crank the engine and watch the injectors spray fuel. Try pulling
the FPR vac line and cap it. take the car for a ride. see if things improve.
You could have a clogged/restricted injector.

[Mantas]

Well, injectors do spray fuel. FPR vacuum line does not have a smell of it. Tried to remove FRP’s vac line, cap it and drive. No improvement, rough idle and bucking are still there. Removing spark plug wires one by one at idle seems to add the same amount of engine shaking.

[Mantas]

Maybe a clogged cat can cause that bucking on acceleration/rough idle/loss of power/increased fuel consumption problems? I’ve tried to unscrew O2 sensor (pre cat) and test drive, but nothing changed. But maybe a hole, created by unscrewed pre cat O2 sensor is not big enough to make a difference? Pre cat O2 sensor voltage fluctuates all the time (0.1-0.9V) when driving at constant speed, and O2 sensor after cat shows “rich” (0.8-0.9V) which is good, I suppose, and shows that cat is working – at least to some degree. But maybe it still can be clogged? Engine burns oil a bit, so I quess there is such possibility that cat is clogged

[Mantas]

Cat is not clogged… I’m completely stuck. Any new ideas anyone?

[EricTheCarGuy]

It’s not likely to be a sensor or something like that. Especially if you don’t have a check engine light for one. You say the timing is ‘correct’ but did you actually check the balance shaft position? As I said, if the balance shaft is out of time you will have a vibration during engine operation near 2500 rpm. I’ve seen it many times.

I don’t think it has anything to do with the injectors either. It’s not common for Honda’s to have injector or fuel delivery issues.

You do have a bit of a difference between cylinder #2 and #4 on your compression readings. I know it’s in spec but anything that throws the engine out of balance such as low compression on one or more cylinders, can contribute to rough running.

I think your issue is something basic. Possibly mechanical. Intake manifold gasket also comes to mind. I’ve seen that cause these issues a time or 2 as well.

My point is stick to the basics and the evidence. I would avoid complicated theories that involve sensors that you don’t have any indication are bad.

Please keep us updated.

[Author]

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