Author Topic: Hello guys I need help please  (Read 3407 times)

cris

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Re: Hello guys I need help please
« Reply #15 on: June 29, 2022, 03:36:12 PM »
Hello
So I rerouted the wire for the crankshaft position sensor and avoided the coil pack wire and had no result.
I noticed something else, went out to do another engine ref test to see if I can replicate the unusual  revs read, so the car sat in 30 degrees Celsius  from morning to the afternoon, I did the test around 2 PM, didn't get the unusual revs, but the rpm went (while idling) from 1000-1500-2000-2500 and then dropped suddenly and the engine stalled, started the engine again with the same result about 4 times more, after that it started to run normal. My question is would that point towards a evap system problem?

CRC

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Re: Hello guys I need help please
« Reply #16 on: June 29, 2022, 05:57:07 PM »
http://www.hondafitjazz.com/manual/A00/HTML/98/SAA2E98K72100081924FAAT00.HTML

I don't know much about the evaporative emissions control system, other than the fact that there's a solenoid with two hoses attached on the top of the throttle body.

The Haynes manual stresses that these hoses should be leak free.

The link above should take you to a test routine page. Clicking on the small icons will show the graphic.

CRC

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Re: Hello guys I need help please
« Reply #17 on: June 29, 2022, 07:39:20 PM »
Reading up on the evaporative emissions system, it's hard to see how it could cause any running issues.

Effectively, the fuel tank "breather" is connected to a charcoal filled canister, mounted at the rear of the engine. This canister has a vacuum operated diaphragm that can open and control gas flow through the charcoal canister.

The purpose of this canister is to absorb fuel vapor that naturally evaporates off the fuel. To enable this fuel to be removed, there is a solenoid valve mounted on top of the throttle body, and when this is energised, it allows engine vacuum to open the canister diaphragm valve to allowed the stored fuel in the the charcoal to be pulled out and burnt in the engine.

Apparently, this only happens when the engine is above 70C, and it's unclear whether the solenoid valve then stays open all the time when above 70C.

The P0443 fault indicates a problem with the solenoid valve, but it's unclear how the ECU would know, unless it has a method of monitoring current flow on that output.

Apparently there is a pressure / vacuum relief valve built into the filler cap in case the evap system fails, but that puzzles me as well. I'd always assumed that the "pffffft" noise when undoing the filler cap was positive pressure inside the tank escaping, but the action of the evap system would suggest that it is, in fact, a negative pressure (vacuum) in the tank - which you wouldn't think would be good for a pump to pull from.

So, what could happen to the evap system to stop it operating? Well obviously the solenoid valve could fail to open, but that wouldn't be a problem to the engine as it runs quite happily without it when below 70C, so I would doubt if the engine would notice if it had failed.

Do check the rubber vacuum lines on it though, as a split would allow unmetered air into the engine and that can cause a few issues.

embee

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Re: Hello guys I need help please
« Reply #18 on: July 01, 2022, 12:05:21 PM »
This is not really any help to the OP, but just a couple of comments on evap loss systems.

Fuel tanks generally run at a slight positive pressure which helps reduce the amount of vapour given off by the fuel in the tank and also helps suppress vapour locking in fuel pumps. The pressure is self-generated by the vapour itself.
 Above a certain pressure vapour is allowed to exit to the carbon can. The carbon often used to be charcoal produced from coconut shells which naturally has a very porous structure hence a very large effective surface area, I don't know what today's carbon is like. HC molecules will attach themselves to the activated charcoal surface but are relatively easily removed again by the introduction of air (with low HC concentration, the HC migrates from high to low concentration areas). Evap loss regulations essentially require (by interpretation) that there is no "break-through" of HC vapour, i.e. the can is able to adsorb all the vapour a tank of fuel can generate under test conditions as specified. Obviously the actual amount of vapour depends on how much fresh fuel is introduced and the volatility, the ambient temperature and return fuel temp etc. Modern fuel injection moved to "return-less" where there was no fuel sent back from the engine bay to the tank, which always took heat into the tank and caused more vapour.
The system allows air to flow through the can from atmosphere (not via the tank) and into the low pressure inlet manifold via some sort of control system while the engine is running. This is known as "purge". The vapour is consumed by the engine and does not escape to atmosphere.
Earliest simplest systems used a "gated orifice", a drilling just upstream of the closed throttle edge which gets exposed to the inlet manifold low pressure when the throttle is opened slightly. These systems were effectively passive with no real control system so purge rates were not controllable according to can loading.
Purge systems evolved using variable duty cycle solenoid valves so the ECU could use a feedback loop to increase purge when the can was heavily loaded and reduce it when lightly loaded by looking at the effect purge had on the engine fuelling feedback stystem. If when opening the purge valve the mixture went rich according to the exhaust oxygen/lambda sensor it knew it was heavily loaded, if it went lean it was lightly loaded and the purge strategy could be adapted to suit.
There are checks within the system to ensure that the purge is working, various methods can be used. Electrical checks can be done on solenoid valves, but typically the effect of changing purge signals can be monitored to deduce that it is indeed working.

As for the OP, I doubt the purge system is the cause of the sort of effects reported.
HTH a bit.

CRC

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Re: Hello guys I need help please
« Reply #19 on: July 01, 2022, 02:46:57 PM »
That's excellent information. Thankyou.

CRC

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Re: Hello guys I need help please
« Reply #20 on: July 02, 2022, 12:16:15 PM »
Chris, just a thought ..... what do your two temperature sensors show on the obd reader.

Just wondering if the symptoms could occur if the ECU believes that the engine temperature is very cold ( when it's actually fully warm) and richens up the mixture accordingly (like pulling out a manual choke on an old engine).

This could cause a lot of issues similar to those you're reporting.

Also, if water is going low in the system, this can result in odd temperature readings as the probe regularly goes from water to air and back again.

cris

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Re: Hello guys I need help please
« Reply #21 on: July 18, 2022, 01:18:34 PM »
Hello.
So I checked the temperature sensor and it works fine, also the reading is good.
I found a big crack in the throttle rubber gasket that sits between air filter housing and the throttle body, I will replace it and see if it helps.
Also the throttle position sensor reading (with OBDII) at idle is a steady 9.41% and 90.30% fully open, this readings are when the car is cold.  After warm-up, the reading jumps from 9.41% to 9.81% back and forth, at 12.55% it jumps to 13.00% back and forth, after about 20% the reading holds nice and steady and throttle fully opened it sometimes reads 85.30% or 90.30% not always the same.  Could this be a clue to my dilemma? I checked the cable it has good signal, I checked the sensor while backprobing and the signal was steady even while lightly tapping it, I didn’t manage to test backprobing while the engine I running or hot (the air filter box is in the way) I could backprobe while running if you guys think it would be relevant. I also noticed that while misfiring is happening the throttle position sensor reading drops. My mechanic said this was normal but my intuition would tell me otherwise, most posts about ‘’jumpy readings’’ say that these are symptoms of a bad TPS? Would a jump of arround 0.5% be considered normal and why the sudden drop of TPS signal doesnt trigger a code?

CRC

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Re: Hello guys I need help please
« Reply #22 on: July 19, 2022, 03:28:33 PM »
According to the Haynes manual, there are two types of throttle control on these engines.

Both use the throttle cable from the pedal to operate a quadrant on the throttle body.

The non electronic version operates a normal, mechanical butterfly flap, with the flap position being reported back to the ECU by the TPS.

The electronic version seems to have an electrically operated flap, with the TPS just sensing the quadrant position and the ECU operating the flap accordingly.

Whichever type you have, you really don't want to find a fault as both are incorporated in the throttle body, and Haynes suggests that a new throttle body is the only repair option in the event of a sensor or actuator failure.

You would almost certainly be seeing specific codes if that was the case.

Air leaks is a good thing to investigate. Has your mechanic done a smoke test?


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