[Jarett]

Also it’s possible an abs/speed sensor may be causing our problem. As well as a clutch position sensor but that’s a long shot

 

[Jgray2016]

So high fuel trims can either be (after all the parts we replaced and no difference) an exhaust leak( car idles perfectly with front o2 unplugged, so confusing), a vacuum or internal vacuum leak(pcv, evap), or physical engine timing( which I think could be the problem honestly knowing techs at ford), sensors are usually pretty good at setting a code if they go bad so I don’t think that’s the problem considering it idles perfectly with no wideband. The car is capable of idling and driving fine with no wideband so I’m thinking a short or electrical issue to do with the wideband or something could also be the problem…

Does yours also do the thing where idle drops to like 500/550, then recovers to 800, sometimes when you come to a junction or traffic lights and A/C is on?

Mine does that, and also does the random 1500 revs idle with no A/C on sometimes

 

[Jgray2016]

also... i did do a smoke test on the exhaust system, and about everywhere I could stick it. but no leaks anywhere

 

[Jgray2016]

Can you check your fuse box in the engine please? Found out mine is all gunked up. Scared to pull any out incase they snap

 

[Jarett]

Can you check your fuse box in the engine please? Found out mine is all gunked up. Scared to pull any out incase they snap

Yea mine does all of the same idle things

 

[Jarett]

Yea mine does all of the same idle things

I pulled and checked all the fuses and cleaned them no difference…

 

[Jarett]

Can you check your fuse box in the engine please? Found out mine is all gunked up. Scared to pull any out incase they snap

Had coolent spew down the side of my car from the cap, now I’m worried I have a bad head gasket…

 

[Jgray2016]

Had coolent spew down the side of my car from the cap, now I’m worried I have a bad head gasket…

Hmm. Not good. Have you checked for the little brass nib to see if correct gasket is there? Tbh on mine, I've had the car since 8k miles in April 2020, and it's now at 63k miles. I reckon if my head gasket was messed up, it would have went by now haha

This guy covers it

 

[Jarett]

Hmm. Not good. Have you checked for the little brass nib to see if correct gasket is there? Tbh on mine, I've had the car since 8k miles in April 2020, and it's now at 63k miles. I reckon if my head gasket was messed up, it would have went by now haha

This guy covers it

Yea I checked when I bought it has the updated gasket

 

[axelr]

Wow, two years of idle surge? The one and only way idle could surge is because there is a small air ingress after the throttle.

I’d remove the intake manifold, check it for cracks, and change the seals.

There is one seal between the throttle body and the manifold, and four seals between the manifold and the head. Get new ones.

There is also a connection from the crankcase breather that is behind the manifold which has a o-ring, the connection from the gas tank evaporating system on the left side, and a o-ring around the MAP sensor.

It will takes two hours give or take to perform all this. This is imo the basic 101 before looking as sensors, fuses and what not.

 

[Jgray2016]

Wow, two years of idle surge? The one and only way idle could surge is because there is a small air ingress after the throttle.

I’d remove the intake manifold, check it for cracks, and change the seals.

There is one seal between the throttle body and the manifold, and four seals between the manifold and the head. Get new ones.

There is also a connection from the crankcase breather that is behind the manifold which has a o-ring, the connection from the gas tank evaporating system on the left side, and a o-ring around the MAP sensor.

It will takes two hours give or take to perform all this. This is imo the basic 101 before looking as sensors, fuses and what not.

Thanks. I did do a smoke test almost everywhere I could think of, but nothing leaked any smoke so discounted any air leaks. Still worth doing would you say?

 

[axelr]

Thanks. I did do a smoke test almost everywhere I could think of, but nothing leaked any smoke so discounted any air leaks. Still worth doing would you say?

Honestly I’d start from that. I’m not sure how effective is a smoke test if the problem is an air ingress under low pressure when idling with the throttle closed. If you fill the intake with smoke there is no guarantees the leak is bi-directional or that you can create enough of a pressure differential against the atmosphere to leak smoke. Changing the seals is not a long job, not difficult, and not costly, so, since you tried everything else, I’d do that now. The gaskets are $25 + $8.80 and the manifold itself (if cracked) is $102 so nothing crazy. For the small o-rings (map sensor and crankcase breather) you can buy a set of Viton o-rings of various sizes from Amazon, something like that or similar, once you know the sizes you need. Viton is heat, fuel and oil resistant so it’s the right stuff for automotive applications.

 

[Barroux]

Honestly I’d start from that. I’m not sure how effective is a smoke test if the problem is an air ingress under low pressure when idling with the throttle closed. If you fill the intake with smoke there is no guarantees the leak is bi-directional or that you can create enough of a pressure differential against the atmosphere to leak smoke. Changing the seals is not a long job, not difficult, and not costly, so, since you tried everything else, I’d do that now. The gaskets are $25 + $8.80 and the manifold itself (if cracked) is $102 so nothing crazy. For the small o-rings (map sensor and crankcase breather) you can buy a set of Viton o-rings of various sizes from Amazon, something like that or similar, once you know the sizes you need. Viton is heat, fuel and oil resistant so it’s the right stuff for automotive applications.

View attachment 364128

Not meaning to hijack the thread but can you let me know where you found the intake manifold for 102$?

I snapped the purge valve nipple in half replacing the purge valve (totally my fault) and waiting on parts today for a temporary fix. I might need to replace the manifold…

 

[Max]

Not meaning to hijack the thread but can you let me know where you found the intake manifold for 102$?

I snapped the purge valve nipple in half replacing the purge valve (totally my fault) and waiting on parts today for a temporary fix. I might need to replace the manifold…

Do you mean CJ5Z-9424-E ?
66 USD at Tasca

2013-2019 Ford Intake Manifold CJ5Z-9424-E | TascaParts.com

2013-2019 Ford part # CJ5Z-9424-E - Intake Manifold

www.tascaparts.com

 

[Barroux]

Do you mean CJ5Z-9424-E ?
66 USD at Tasca

2013-2019 Ford Intake Manifold CJ5Z-9424-E | TascaParts.com

2013-2019 Ford part # CJ5Z-9424-E - Intake Manifold

www.tascaparts.com

Thanks that is exactly it! I’m amazed it’s not another RS specific part that costs 5x more than the base trim part! 66$ is a steal I was ready to take a much bigger hit on this one or posting a WTB thread in the classifieds!

Back on topic now and sorry for the interruption!

 

[axelr]

Thanks that is exactly it! I’m amazed it’s not another RS specific part that costs 5x more than the base trim part! 66$ is a steal I was ready to take a much bigger hit on this one or posting a WTB thread in the classifieds!

Back on topic now and sorry for the interruption!

$102 is the price on parts.ford.com with free 2-day FedEx to your door. As you saw you can find it cheaper but those folks will charge for the shipping and it will typically take longer to ship too as they won’t have it in stock.

 

[Jgray2016]

Honestly I’d start from that. I’m not sure how effective is a smoke test if the problem is an air ingress under low pressure when idling with the throttle closed. If you fill the intake with smoke there is no guarantees the leak is bi-directional or that you can create enough of a pressure differential against the atmosphere to leak smoke. Changing the seals is not a long job, not difficult, and not costly, so, since you tried everything else, I’d do that now. The gaskets are $25 + $8.80 and the manifold itself (if cracked) is $102 so nothing crazy. For the small o-rings (map sensor and crankcase breather) you can buy a set of Viton o-rings of various sizes from Amazon, something like that or similar, once you know the sizes you need. Viton is heat, fuel and oil resistant so it’s the right stuff for automotive applications.

View attachment 364128

awaiting Ford coming back to me on availability for the gaskets etc. meanwhile, I did a datalog of WOT in 3rd gear.

AFR results are particularly interesting, seems I'm running mega lean at some points... AFR = 29 when demanded is 13

So must be an air leak on exhaust or intake for sure.... but also I've ran the car for 55k miles whilst running lean. oh no.

3rd gear WOT - Copy.xlsx

3rd gear WOT time(ms),AAT_V(V),AAT(°C),ADPT1_F,AF_MOD11,APP(%),APP1(V),APP2(V),APP_D(%),APP_E(%),BARO(kPa),BARO_V(V),BBP_CORR(kPa),BBP_MES(kPa),CAC_T(°C),CANVENT_F,CHT2(°C),CHT2_V(V),CMP1_EXH_F,CMP1_INTK_F 10228,1.82,2,No Fault,No,19,1.42,0.72,28.24,14.12,97,3.86,92.5,92.5,0,No Fault,94,3.58,...

docs.google.com

 

[wegiel]

@Jgray2016 something new I have simillar problem with my ST

 

[FastFocus]

I've recently started having this issue on my 2016 RS, around 65,000 miles. I did already have the headgasket warranty work done back in 2017. I'm running the mountune stage 1 tune if that's at all relevant.

My revs surge pretty aggressively at idle but it's intermittent. Sometimes the idle feels perfectly normal, and sometimes it oscillates between 500 - 800 RPM. It also can happen both at cold start or after the engine is at temperature. I've looked at the logs for STFT and LTFT, STFT looks flatlined at 0 and LTFT is at 28.12. Looking back through the thread I'm unsure if these FT values indicate a fuel rail replacement is needed or not.

Are there are traces I should be looking at in the logs to give some clues here?

2016 Focus RS Surging Idle Datalog

Other than this the car seems to run perfectly fine under throttle. Just occasional dips in the idle RPM when coming to a stop and this surging.

Thanks!

 

[FastFocus]

I've recently started having this issue on my 2016 RS, around 65,000 miles. I did already have the headgasket warranty work done back in 2017. I'm running the mountune stage 1 tune if that's at all relevant.

My revs surge pretty aggressively at idle but it's intermittent. Sometimes the idle feels perfectly normal, and sometimes it oscillates between 500 - 800 RPM. It also can happen both at cold start or after the engine is at temperature. I've looked at the logs for STFT and LTFT, STFT looks flatlined at 0 and LTFT is at 28.12. Looking back through the thread I'm unsure if these FT values indicate a fuel rail replacement is needed or not.

Are there are traces I should be looking at in the logs to give some clues here?
View attachment 364666
2016 Focus RS Surging Idle Datalog

Other than this the car seems to run perfectly fine under throttle. Just occasional dips in the idle RPM when coming to a stop and this surging.

Thanks!

An update a few days after this post, my car had the same symptoms of revs surging and idle and then stalled. I then got the following error messages:

• P0171 System Too Lean (Bank 1)
• P08B2
• P1548 Engine Air Filter Restriction
• P2195 bank 1 sensor 1 is too lean

Looking at the post for P08B2 error code I see someone resolved that by swapping the battery. I still have the same battery for when I got the car new in 2016...lol. So I think my next steps are clean the air filter / check to blockage or leaks, swap to a new battery/check grounding, and maybe check the MAF sensor? Does anyone else recommend other troubleshooting steps here? I'm out of the country for work for a bit which gives me time to get any replacement parts now

Thanks
-FastFocus