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

**jick.cejoco** · September 16th, 2016 03:53 PM

stop guessing around.
try swapping the ignition coils with know good ones first. if you can borrow from somebody for testing do that first. the policy in my shop is to always blame the computer first(sic). these ignition coils were so miniaturized that they were designed to last five years. if you go beyond five years, it is a bonus.

**Jeh** · September 16th, 2016 03:57 PM

Originally Posted by oj88

Just throwing this out...

I think the clue here is that, the engine appears to run better when cold than when hot.

Simply put, when the engine is cold, the ECM goes into open loop. It means that it will ignore the O2 sensor and use the preset air-fuel table stored in the ECM program. This program is usually biased towards a 'rich' A/F mixture. Once the engine warms up (as dictated by the coolant temp sensor), it goes into closed loop and air-fuel mixture is computed based on the measurements provided by the different onboard sensors, including the O2 sensor.

If the O2 sensor is faulty and isn't providing the correct output, it will usually cause a CEL. However, it may be possible that the ECM is still seeing the sensor to be within the acceptable parameters based on its programming, but in reality, is already giving out erroneous signals.

Thank sir. Tried inspecting the exhaust system of the car and it seems walang o2 sensor. Is this possible? Tried calling mazford, fordland and fordmaster in banawe and they told me that only the 2.0 (rs) has an o2 sensor.

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**niky** · September 16th, 2016 03:58 PM

You can check the strength of your vacuum by unplugging one of the hoses and checking for suction. If it's okay when cold, I doubt it's a simple vacuum issue.

Since your IACV and knock sensor are surplus, I'd look there. Though a knock sensor problem would result in running issues rather than idle.

Most likely the surplus IACV is just not up to snuff. Idle issues often start there.

I'd also check the PCV system, just in case, to see if there's an issue there. That one can also cause issues when hot.

-

You're correct that the Cam Position Sensor issue results simply in stalling. And yes, the non-RS Lynxes do not have O2 sensors. Since our OBD ports are weird (neither OBDI nor II), you'd need to go to a specialist with the right connector to diagnose. Check up on FCP for places that have it. AFAIK, PowerTorq and Speedlab both have the right connector, but if they're too far away from you, best ask around where else this can be done.

Impressed that you've ticked off all the boxes on what's not wrong. ;) I'm also tracking a running issue with my Number Two Lynx, and I've got vacuum lines plugged with old spark plugs and fuel return lines (oh, by the way, check the Fuel Return valve... see if the running changes when you disconnect the electrical supply to the actuator) clamed with vise grips and I'm still stumped... Hahaha... might have to pull the fuel pump to check the filter soon.

**Jeh** · September 16th, 2016 03:58 PM

Originally Posted by jick.cejoco

stop guessing around.
try swapping the ignition coils with know good ones first. if you can borrow from somebody for testing do that first. the policy in my shop is to always blame the computer first(sic). these ignition coils were so miniaturized that they were designed to last five years. if you go beyond five years, it is a bonus.

Noted sir. Will try replacing the coils. I could not recall exactly pero parang replacement lang din coil packs ko. Thanks.

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**niky** · September 16th, 2016 04:26 PM

Originally Posted by Jeh

Noted sir. Will try replacing the coils. I could not recall exactly pero parang replacement lang din coil packs ko. Thanks.

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Coil pack issues should result in rough running, as one or two cylinders will not be getting enough spark. Does the car stumble or hesitate at low rpm?

**Jeh** · September 16th, 2016 04:35 PM

Originally Posted by niky

You can check the strength of your vacuum by unplugging one of the hoses and checking for suction. If it's okay when cold, I doubt it's a simple vacuum issue.

Since your IACV and knock sensor are surplus, I'd look there. Though a knock sensor problem would result in running issues rather than idle.

Most likely the surplus IACV is just not up to snuff. Idle issues often start there.

I'd also check the PCV system, just in case, to see if there's an issue there. That one can also cause issues when hot.

-

You're correct that the Cam Position Sensor issue results simply in stalling. And yes, the non-RS Lynxes do not have O2 sensors. Since our OBD ports are weird (neither OBDI nor II), you'd need to go to a specialist with the right connector to diagnose. Check up on FCP for places that have it. AFAIK, PowerTorq and Speedlab both have the right connector, but if they're too far away from you, best ask around where else this can be done.

Impressed that you've ticked off all the boxes on what's not wrong. ;) I'm also tracking a running issue with my Number Two Lynx, and I've got vacuum lines plugged with old spark plugs and fuel return lines (oh, by the way, check the Fuel Return valve... see if the running changes when you disconnect the electrical supply to the actuator) clamed with vise grips and I'm still stumped... Hahaha... might have to pull the fuel pump to check the filter soon.

Thanks sir niky. Already checked with powertorq, kina sir kiper pero la na OBD1 scanning. Di ko pa nattry mag inquire speedlab.

I'll try again to source out for another IACV. Checking on local suppliers, order basis po sya. And ginto, hehe. Last qoutation sakin is 14.5k.

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**Jeh** · September 16th, 2016 04:37 PM

Originally Posted by niky

Coil pack issues should result in rough running, as one or two cylinders will not be getting enough spark. Does the car stumble or hesitate at low rpm?

If mainit na, like running for 30 minutes, the car will stumble/misfire/jerk. On idle magmimisfire yun, 1 in every 20 seconds siguro. If i-on aircon pagnagengage compressor, magstall na.

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**Jeh** · September 16th, 2016 04:40 PM

Originally Posted by Jeh

If mainit na, like running for 30 minutes, the car will stumble/misfire/jerk. On idle magmimisfire yun, 1 in every 20 seconds siguro. If i-on aircon pagnagengage compressor, magstall na.

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Question re: the coil packs

My high tension wire na nakakabit sa coil pack diba po. If nag fail ung coil pack, necessary bang sira din yung htw? Thanks

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**niky** · September 16th, 2016 04:45 PM

14.5k for IACV? Ginto! Are you talking directly to Mazford ba?

Originally Posted by Jeh

If mainit na, like running for 30 minutes, the car will stumble/misfire/jerk. On idle magmimisfire yun, 1 in every 20 seconds siguro. If i-on aircon pagnagengage compressor, magstall na.

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Okay. So look at the coil packs nga talaga.

Originally Posted by Jeh

Question re: the coil packs

My high tension wire na nakakabit sa coil pack diba po. If nag fail ung coil pack, necessary bang sira din yung htw? Thanks

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Not necessarily.

**Jeh** · September 17th, 2016 10:29 PM

Mga sir. Eto lumabas na trouble codes.

What does this mean? Advisable bang bili agad ako maf? Or is it possible stored trouble code lang ito kasi nung hinahanap culprit eh tinanggal namin once ung MAF sensor.

After kasi iclear yung code at scan ulit, wala na lumabas na trouble codes.

Possible ba na ung stalling problem ko hindi din madetect thru trouble codes?

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