[Need Help] Ford Lynx - Engine misfires and stalls at Idle when engine is warm (worst if with A/C)

[Jeh]

Need help po regarding my Ford Lynx 1.6 m/t 2000

Car Info:
1. Engine - EFI with coil packs (no distributor)
2. Transmission - Manual Transmission
3. On-Board Diagnostics - OBD1
4. Stock/Unmodified

Condition/Symptoms:
1. Car idles or runs fine when engine is still cold (with or without aircon). May hatak po yung kotse (even uphill) and walang hesitation or misfire. Upon idle with at least 5 to 10mins engine running, RPM needle is steady at 900 RPM (without aircon) and 850 RPM (with aircon)
2. When engine is already hot (or should I say reached its operating temperature), let’s say 30 minutes running (worst 20 minutes if stuck in traffic), the following will be noticed:
a. Upon idle without aircon on - nagmimisfire from time to time, nagddrop yung needle to the point na almost mag stall na engine and then biglang taas then balik sa 850 to 900 RPM. In short, if without aircon, will misfire but will not stall at idle.
b. Upon idle with aircon - kapag nag engage na yung compressor - after 2 seconds, engine will stall. However, upon starting, nagsstart naman agad engine. In short, with aircon, will misfire and stall at idle.
c. When running/cruising with or without aircon - nagsstumble/jerk po yung makina dahil sa misfire (which I think equivalent sa pagstall kapag naka-idle). In short, if with or without aircon, will misfire/jerk/stumble/hesitates while cruising.
3. When engine is already running for almost 45 minutes to an hour, the above symptoms will worsen noticing the following:
a. Upon idle without aircon - Namamatay makina if hindi nakapress yung gas. In short, if without aircon, will misfire and then stall at idle.
b. ** What I do when naka idle ako, especially if traffic, nakaapak lang ako sa gas para hindi mag stall yung engine.

History of repair/parts replaced to date - Ito na po mga pinalitan kakahanap ng solusyon:
1. Spark plugs - stock - Yung pinagpalitan ko ay brown yung sunog, so I guess maganda ignition system ko.
2. Coil packs - 1 year old - Tried unplugging one coil at a time at nagrereact makina, so I guess working din mga to. I even pointed the coils sa cyclinder head at may spark naman.
3. Fuel pump - new
4. Fuel filter (high pressure and low pressure) - new
5. Air filter - new
6. Thermostat - new (no overheating issue pero pinalitan ko nalang kasi mukhang luma na at sira na rubber grommets
7. Water pump
8. Timing belt and related parts
9. Aircon Belt
10. Alternator Belt
11. Throttle body - newly cleaned
12. MAF Sensor - newly cleaned
13. Knock Sensor - Japan surplus (the old one is already melted)
14. Camshaft Sensor - (replaced last 2005 due to stalling problem)
15. IAC Valve - surplus *

* Now, the latest one replaced was the IAC Valve. This was done just last week, September 10, 2016, in Banawe. I arrived in Banawe (from Makati) na mainit na makina at namamatayan na. Upon changing IAC Valve, hindi na namatayan at idle even with aircon on. We even test drove it. Total running time siguro ng pagtetest is about 3 hrs (note wala masyado pahinga kotse dahil pagkadating ininspect and inayos na kaagad). However, nung umayos yung stalling problem nya, napansin naming na nagmimisfire yung kotse at high RPM (4k and above). They dried diagnosing but to no avail. Nevertheless, satisfied na ako nun kasi di na nagsstall, kaya I called it a day and then umuwi bound for Makati. On my way home, bigla nalang po bumalik yung sakit niya. Parehong pareho padin. Until now, ganun po parin. Di ko na kasi naasikaso ibalik since busy sa work.

Tingin nyo sir, IAC Valve kaya problem? Nakakapagtaka kasi okay naman nung una. Or may iba pang culprit? If other than IAC Valve, ano kaya relation nya sa rineplace na IAC Valve kaya gumana sya nung una. Gusto ko na din sana ipa-scan kaso wala ako makitang nagooffer ng OBD 1 scanner. Syempre, gusto ko din medyo handa ako bago pumunta ulit banawe para di po ako mataga.

Sorry po sa haba. Para kumpleto lang po details. TIA mga sir!

[StockEngine]

Nice and detailed.

How does the engine look from the inside of the oil cap? Is there sludge?

How long does it warm up to operating temperature? 30 minutes?

Hindi namention ang replacement ng oilpump. Baka hindi na sya operating at maximum..

Curiosity. .ano odometer reading 250k?

[Jeh]

Nice and detailed.

How does the engine look from the inside of the oil cap? Is there sludge?

How long does it warm up to operating temperature? 30 minutes?

Hindi namention ang replacement ng oilpump. Baka hindi na sya operating at maximum..

Curiosity. .ano odometer reading 250k?

Sir,

ODO is 200k.

Normally naman po, the temperature needle rises up to almost midde mga 10mins palang. Mas mabilis magrise if upon start kotse eh iddrive agad.

Yung 30 minutes i assumed lang na thats the time talaga na mainit na makina. Consistent po kasi. Parang may timer yung kotse. 20-30 minutes magpapalya na.

I think sa oil po, okay naman. Actually kakachange oil ko lang po to liquimoly with engine flushing. Every year po ako nagpapalit oil. Last year was royal purple. Usual comments ng mga mekaniko eh "maganda pa makina nyo sir", tho di ko alam bakit nila nasasabi yon. Hehe




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[jick.cejoco]

what is the model year of the car? Sounds like ignition problem. Try substituting the ignition coils with known good ones or have the coil waveforms looked at on an oscilloscope(better if you can have the waveform patterns printed or saved electronically for email).

[Jeh]

what is the model year of the car? Sounds like ignition problem. Try substituting the ignition coils with known good ones or have the coil waveforms looked at on an oscilloscope(better if you can have the waveform patterns printed or saved electronically for email).

Thanks sir. Why do you suspect that its the ignition coils? San po shop ang nagooffer ng ganyang service? Thanks!


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[jick.cejoco]

at a higher operating temperature the internal resistance of the ignition coil is also higher. it would be easier for the high voltage to dissipate to the nearest ground path which is the cylinder head versus the spark plug that is exposed to the higher pressure of the compression. electricity is very lazy, it will take a short cut when it can, hence the spark happens at the most convenient location than at the pressurized spark plug gap. what you can do too, in the absence of an oscilloscope is to measure the primary and secondary resistance of the coils. if you have a megger(high voltage insulation tester), is to inject high voltage and see if the spark happens around outside of the coil housing

[Jeh]

at a higher operating temperature the internal resistance of the ignition coil is also higher. it would be easier for the high voltage to dissipate to the nearest ground path which is the cylinder head versus the spark plug that is exposed to the higher pressure of the compression. electricity is very lazy, it will take a short cut when it can, hence the spark happens at the most convenient location than at the pressurized spark plug gap. what you can do too, in the absence of an oscilloscope is to measure the primary and secondary resistance of the coils. if you have a megger(high voltage insulation tester), is to inject high voltage and see if the spark happens around outside of the coil housing

Thanks sir. Very informative. Other than the said testing, i have 2 sets of old coil packs na nakatabi lang sa bahay. Nagpalit ako kasi nung mga nakaraang taon dahil pumapalya, pero hindi pala yun ang culprit. Try ko din kung okay din mga yun.

Curiousity lang is, bakit nung sinalpakan ng ibang IACV gumana sya at di namatayan? Pero kinalaunan, bumalik din sakit.


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[jick.cejoco]

Thanks sir. Very informative. Other than the said testing, i have 2 sets of old coil packs na nakatabi lang sa bahay. Nagpalit ako kasi nung mga nakaraang taon dahil pumapalya, pero hindi pala yun ang culprit. Try ko din kung okay din mga yun.

Curiousity lang is, bakit nung sinalpakan ng ibang IACV gumana sya at di namatayan? Pero kinalaunan, bumalik din sakit.


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that's just it. it wasn't the cause, maybe a coincidence. wrong guess in my opinion. what model year is the car?


the IACV does not cause misfire under normal usage. the most vulnerable is the ignition coil because of heat.

[jick.cejoco]

can you identify your engine? was the car manufactured in the u.s. or europe?

[sirkosero]

Sa lynx ng pinsan ko, turns out it was just faulty high tension wires.

Replaced the high tension wires no more, problem.

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