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Power loss when ambient temp rises over 28-30 Deg. Celsius

3693 Views 11 Replies 5 Participants Last post by  ojobson
Dear C-Max Owners, Mechanics, Engineers, Technicians, Experts,

I am a new man here.
We have try to find the reason by many way, but no results!
Please help Me to find it! I am so dissapointed because i am not able to utilize the power resource of my 1,8 CSDB petrol engine.
So My ca( r )n is a Focus C-Max 1.8 CSDB, Petrol, 2004.
When the weather is colder, under 28 degree C. everything OK. But if the temp rises over 28-30, and the engne get operation temperature, the engine forgets to give me its hosres to work. I feel fear when i need to climb on a hill road. Especially when the car is full of my family, and we need AC too. In this conditions the car totally out of the power, and it becomes very very difficult to start from stationary. Like 80 HP for 1600 kg. (instead of 120 HP)

About the symptom:
If the ambient temp rises over 28-30, and i push the pedal little more agressively, i hear unusual noise simultaneously with the engine sound, (according to my mechanic like the engine unable to suck the air), and from that moment the car get out of its power. From that moment I know, that i need to make lighter my foot.... The problem becomes constantly presented from that FIRST moment. It goes if the temp is falled down under 28-30 Celsius.
If the weather get colder the horses come back to make me feel ok, eigter in same day or same trip whitout a stop. There is a very tight transition range, time etc... between becaming good to bad, or becaming bad to good operation.

-20 to 24 deg C. Very good performance.

24 to 28 deg C. Little power loss.

over 28 - 30 deg C. No power.

What we try already:
- MAP changed.
- Valve gaps checked(cold, warm). Perfect.
- Timing ok. New chain and guides.
- Lambda ok.
- Cat. Ok.
- Butterfly ok and cleaned. Potentiometer(s) are ok. Pedal also.
- Vacuum and pipes are ok.
- IMRC and swirl flaps are ok. (Brand new solenoids)
- Theoretically everyting looks good. The "correction values" are also OK when we monitored with ODBII reader. So there is no fake or bad values by any sensors.
- Oil and coolant level ok. Oil quality and visco ok. No oil consumption.
- No extra fuel consumption.
- KAM reset done. 2x

There was a piston ring replacing and head upgrading 5 months ago, because the engine ate the oil. 2 liter/1000km.
but now is perfect.
Ther was a coolant sytem leakage 3 times in 1 month 3 months ago, because irresponsible and bad quality repair. (O -ring replacement close to the inner radiator.)
The head temp never gone over the trip-, treshold limit but the 75% of the full amount of coolant gone each time.

There are no (were not) DTC-s.

I can use ODB reader, HS-MS mode too.
I monitored many parameters for many days, but there are no differences between the normal and the faulty operations. I focused on the butterfly control, the temperatures (IAT, head, cooland, ambient.) and ignition angles. The intake air temp by the time stabibized 40+/- 5 celsius over ambient constantly. Is this normal? Example after a hour drive: IAT-78 deg C, Ambient: 33 deg C., Coolant: 93 deg C., Head: 113 deg C.

There are no missfires, or lambda error. No reach or lean mixture. Results of the Catalyst and EGR selfdiagnostics also OK.

So there is a huge problem which comes with the ambient temperature rise and goes with the temperature fall.

It comes with the ambient rise only.

About the ECU:
Module type: ESU-121
Firmware version: v.15(14.12.2004)
Firmware number: UHDCAJ7

Maybe firmware update could solve the problem?

Ohh, i bought this car in last september in the autumn season so i have no infomation about last summer, hot season...

If You have any suggession, do not hesitate to share with me!

Maybe PID-s to monitor? Special drive condition or drive behavior to monitor?

A complete log about a trip. O2, Temps, Driving behaviors, etc...

Best regards,
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Hi again!

I could exlude some potential parts.

Catalyst, EGR, AC pump, Injectors, ign. coils.

It seems that the problem about the intake manifold. I am before changing the complete part.

I hope you have suggestions about the intake manifold, swirl and reso changer flaps... Is that possible that the vacuum motor of the flaps are clogging? IMRC solenoids are good.

Do you know what are the symptomes of the error of the swirl problem, and what are the symptomes of the reso changer flaps problem?

Is there winter now here, so the car is pretty good.


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My car is bad again. It is summer. I could change the parts one by one, but i am out of my budget.

I and my mechanics really do not know what is the exact reason. :(

Last time I change the complete intake manifold without any result... :(
Hi There!

The weather in Hungary is extremely hot now. In the last 1.5 years i heard some rattle, tinkle noise some time.

But now, ambient is about 40c, IAT about 75-85!!! celsius(sensor is ok). The engine is rattling and tinkling very often. The performance is about 65 -75 HP. AC impossible.

My friends opened my eyes! Hey Dude this engine is running in detonatig "mode" :). Oh sh&#t.

It seems that somewhy the intake air, the mixture and we think that the cylhead temps are also higher than should be and it cause detonating burn. With my slow OBD I can not monitor&log surely(fast) the timing advance. It seems that some time the timing is step back 10-20 deg, when the noise is coming up.

We thing that the EGR is completaly closed, or clogging. Tried to clean but there is a huge coolant pipe front of the bolt. :(

By another our theory the crankcase pressure is high and the PCV always open and force hot gas into the intake sction. But the engine was reconditioned (new rings, etc..) So it should be impossible to allow gas down to the crankcase...

The head ventilation is also should be ok. New valveseals(sorry i do not know the exact name)...

There is another theory. EGR is not closing properly, catalyst are choked and the exhausted gas is forced back to the intake section thorough the EGR....

I will use octane 100 petrol till got money to change EGR. I hope this help.

Unfortunately my mechanic do not help me. "It is to long time to do diagnosis"....blabla

I want a garage, oscilloscope, jack, and nobody touch my car anymore.

Do you agree with one of our theory?
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There is the 3rd summer is on its way. The problem is still there.

Engine overhaulled already. Compression ok, valve gaps are ok, cam timing ok.

I replaced:

injectors, O2 upstream, sparks, coils, egr, complete intake man, with PWM coils, thermostate, camshaft pos sensor, crankshaft pos sensor.

This winter was very good.

But now the problem starts appear again.

Over 15 celcius the car loss its power. Compare to the winter performace it is 70-65% of itself now.

IAT is 60-80 celsius on summer. Do you think it is normal?

How the air get this temp on the 1 meter long intake channels?

Sensor is after the PCV (crank) inlet points of intake manifold. Maybe the PCV stucks open, or the oil overheated, and the gasses at the crankshaft are too hot?

Catalyst clogged? But why only on summer?

New components

- intake manifold, with vacuum PWM valves...

- EGR valve

- O2 sensor (upstream)

- injectors,

- sparks

- coils......................................

nobody can, want to help me...
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I also have this issue, but the problem isn't quite as bad. Warm days there is a noticeable power drop and also a hesitation (about 2500rpm) when accelerating hard.

I think it's either:

Malfunctioning throttle body

PCV valve stuck open

EGR stuck open

At the moment it needs 4 new tyres, three new bushes, a bearing and a new exhaust so I don't think I will have time to replace anything else right now...!
Intake air temperature is wildly wrong. If anything, it should be cooler than ambient. Can you clean/change the IAT sensor? This seems likely to be the problem, especially given your remarks about previous engine work.

Would also be worth checking all connections and wiring to the sensor.
Dear Emmedem, have you sorted out your problems? My car has the same symptoms. When ambient temp is high, after engine has warmed up for good, it looses half of its power.
Hi There!

This is the fifth summer season.

My car is still bad. Finally, I get used to it.

Summer needs difference driving behavior.

Many friends told me, sell it now!

Honestly: This car is not bad, I only need to change oil, filters and some part around the wheels in the last 2 years.... (no, there was a crank pcv pipe leak)

Nothing else. Lot of friends, who sad sell this shit...., has wv and other miracle German and Italian cars, what need to go garage every months....

So i like this "shit" with its every known issues, i forgive it to her and try to live with it. Waiting for winter every summer, to the power come back, and enjoy that months.

Aircon works, can make heat, i change oil and filter every 10.000 km, and pray for long lifetime for the Shity C. Maximilian....

If you got the reasons, please share with me!

good luck!

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One more think.

I changed IAT sensor. (integrated pressure and temp sensor)

Temp was the same.

I make small electronics to simulate the IAT signal and i did give "fake" temp to the ECU. The given temp was around the ambient every time.

Nothing change.......

Maybe design error....
My wife's car did the same - I never got to the bottom of it. It also drank a lot of oil. I sold it in April when it started to become too unreliable.

Amazed you have stuck with it for so long!
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