Intermittent Long cranking times before firing

Vehicle data: 12/07 Honda Accord, 2.4 L DOHC, auto transmission.

Approximately 2 or 3 times a week there will be extended cranking time before firing. These extended times are about 3 or 4 times normal cranking time before firing. With some of these extended cranking times the yellow engine light comes on. This light will go out after a day or 2.

On 2 occasions the car went into "limp home mode". In this condition the car would struggle to achieve 40 km/h and have very little power. This condition occurred the first time after extended cranking. The 2nd occasion was whilst driving: the engine started normally but at about 30 km/h power was lost and a maximum speed of 30 to 40 km/h was all that could be achieved.

Diagnostic scan results: P0339 CKP sensor circuit intermittent interruption; P0302 misfire #2 cylinder; P0303 misfire #3 cylinder; P0300 random misfire; anti-lock brake code- 83-13 ECM/PCM relation failure.

In an attempt to solve this issue I have changed the CKP sensor, changed the in tank fuel filter, drained and cleaned the fuel tank and tested fuel pressure. As codes were thrown up for number 2 and number 3 cylinders, coils and plugs were swapped with 1 and 4 cylinders. All these measures have not resolved the extended cranking times. And we are waiting for the vehicle to go into its 3rd "limp home mode".

After this work was carried out I consulted a Honda dealer with vehicle specific diagnostics. The vehicle was off the road at the dealer for a week and a half with no resolution as the fault conditions that existed in the vehicle on arrival disappeared after about 4 days and for the remaining time the vehicle functioned normally. The Honda technician was working through a checklist and when that checklist failed to fix the problem the next stage was to get from Honda Australia a test ECU. But they could not tell me when this would be available and didn't seem very interested in pursuing the problem further. They said if I brought the vehicle back they could only do what they had done previously that was unsuccessful. In addition to that they seem to blame the age of the vehicle and what put me off even further was when they said I wasn't a regular customer. So I felt quite abandoned.

During their investigation they failed to: check the CKP sensor wiring for continuity back to the ECU; did not check the waveform or the amplitude of the hall effect CKP sensor output nor did they check the plug connections at the back of the ECU. That seems to me to be a major failure in diagnostics given the problem was intermittent.

At this stage I am wondering whether there are any other sensors that combine with the CKP sensor to get the engine to fire normally. There could be a deterioration or an intermittent fault on one or more of these.

I really hope you can shed some light on this problem.

John

But the car runs fine when the car isn't having this problem yeah? If so it sounds like the ecu but others should know more.


A faulty or misaligned ckp will cause random misfire..

Thanks beeza.
Car runs well other than when it goes into "limp home mode". The CKP is positively located.
My next move is to put an oscilloscope on the output of the CKP to check the wave form and amplitude.
Also the Honda diagnostics recorded 353 and 193 misfire cycle B and 3 and 0 CKP noise on 2 separate tests.

Have you checked the electrical grounds? And ecu connection?

Thanks for your reply. Thanks for mentioning the earth points or grounding points. I have not checked those as yet.
However, I have removed the 3 multi pin connectors from the back of the ECU and cleaned them with contact cleaner but they were quite clean anyway.
Since my last post, I have connected 3 wires from the CKP sensor to the ECU. This was to eliminate any possibility of a wiring fault between the sensor and the ECU. But there is probably only been a slight improvement that is possibly not as many extended cranking times and probably of a slightly shorter duration for the long ones.

Have you any idea how many are thing all grounding points the there are in the Honda Accord?

Thanks again for taking the time to reply.

John

There's 2 grounding points,

Battery to chassis

Engine block to chassis

I replaced my grounding points with aftermarket years and years ago.

Thanks again for your reply Fredoops,

Could you please clarify what you mean by replacing your grounding points with after market items please?

Did the cables need replacing and if so what did you find wrong with them? Or did you just replace the lugs on each end of the cables?

I'd be interested to know what caused you to replace the grounding points. Was it due to corrosion or some other factor?

Thanks again,
John

Fredoops explained to us that he replaced his cables with larger cables. He mentioned that he replaced the chassis to battery cable to 4 awg cable (nearly twice as thick (from 20mm2 to 35 mm2). There are 2 chassis to engine cable, one near the engine mount and one under the air box (harder to see and access). Fredoops changed the one close to the right engine mount.

Yeah after some time, some corrosion takes place and the resistance gets too high. You can buy an original cable from Honda (I'm sure it's not too expensive) or better still to replace with bigger cables especially if you have aftermarket accessories (head unit, subwoofer, etc...).

Thanks Fredoops and Martin77. I'll Check out my cables.

John

Hopefully your ECU has not taken a sh#t