Less torque/power when warmed up?

[Interceptor]

I noticed that my car loses torque/power while getting warmer - when cold, I drive it between 2000 and 3000 rpm and it has satisfying amounts of torque, BUT when the engine is at working temperature, it seems like it lost it's elasticity. It doesn't seem that strong anymore. Engine temp. sensor? Vacuum leak? O2 sensor? Too much stuff to change just to rule out the possibilities. I hope someone can give me some pointers before I become desperate and spend half of my salary just to change 9 working parts and 1 that failed :)

[Bill R.]

your not running a high grade premium, then your knock sensors are going to really retard the timing when its warmed up to eliminate pinging and knocking.





I noticed that my car loses torque/power while getting warmer - when cold, I drive it between 2000 and 3000 rpm and it has satisfying amounts of torque, BUT when the engine is at working temperature, it seems like it lost it's elasticity. It doesn't seem that strong anymore. Engine temp. sensor? Vacuum leak? O2 sensor? Too much stuff to change just to rule out the possibilities. I hope someone can give me some pointers before I become desperate and spend half of my salary just to change 9 working parts and 1 that failed :)

[Interceptor]

your not running a high grade premium, then your knock sensors are going to really retard the timing when its warmed up to eliminate pinging and knocking.
I am using 95 RON fuel as MarkD suggested. I don't think my car has knock sensors since it doesn't have VANOS - or am I wrong?

[Bill R.]

1
I am using 95 RON fuel as MarkD suggested. I don't think my car has knock sensors since it doesn't have VANOS - or am I wrong?

[MarkD]

I am using 95 RON fuel as MarkD suggested. I don't think my car has knock sensors since it doesn't have VANOS - or am I wrong?

You don't have knock sensors and VANOS. When did your problems start?
How many km's on the motor?

How long have you had that O2 sensor in there?
(if more than 50K km's, it may be time for a new one)

How is the fuel consumption? Has it decreased? An old O2 sensor usally causes the mixture to run on the rich side.

There can be many things that will cause your problem, as you mentioned.

Try swapping parts like the coolant temp. sensor and MAF from a friend's car if possible.

My guess is that the motor is running a bit lean after warming up. Look for intake air leaks by using an unlit propane torch with the valve just slightly open, and moving it around the intake area while the motor is idling. If it changes the idle speed, you have an intake leak.

MarkD

[Interceptor]

You don't have knock sensors and VANOS. When did your problems start?
It started a few months ago, before I bought the chip. My mechanic changed 5 injectors and the situation improved significantly, but it's not yet "the real thing"


How many km's on the motor?
Cca. 240000 km.


How long have you had that O2 sensor in there?
(if more than 50K km's, it may be time for a new one)
This one is 8 months old.


How is the fuel consumption? Has it decreased? An old O2 sensor usally causes the mixture to run on the rich side.
Fuel consumption is higher than normal - around 13/14 mpg around town.


There can be many things that will cause your problem, as you mentioned.

Try swapping parts like the coolant temp. sensor and MAF from a friend's car if possible.

My guess is that the motor is running a bit lean after warming up. Look for intake air leaks by using an unlit propane torch with the valve just slightly open, and moving it around the intake area while the motor is idling. If it changes the idle speed, you have an intake leak.

MarkD
I don't have any tools and/or experience in that sort of business :(

[Robin-535im]

I don't have any tools and/or experience in that sort of business :(
Hey, it's just flammable gas - you're a man, what more training do you need? :)

My 535 pulls harder when cold, I've always considered it a function of air density getting to the cylinders. The engine bay gets pretty hot, and the intake manifold is painted black, absorbing all it can.

My car definitely has good days and bad days, and usually the colder it is the better. Is it a big difference on your car, like before-and-after-an-EAT kind of difference, or is it only the kind of thing an enthusiast would notice?

[MarkD]

It started a few months ago, before I bought the chip. My mechanic changed 5 injectors and the situation improved significantly, but it's not yet "the real thing"


Cca. 240000 km.


This one is 8 months old.


Fuel consumption is higher than normal - around 13/14 mpg around town.


I don't have any tools and/or experience in that sort of business :(


13 - 14 mpg? That's terrible. I'd expect at least 20 mpg. (and probably higher, even around town)

A coolant temp sensor could not be expensive, you can just buy a new one and have the mechanic install it. I bet it's a $25 USD part.
At the price of fuel where you live, you can afford to change lots of parts to fix this problem as you'll get it back in savings.

Maybe your fuel pressure regulator is bad, try swapping that also. Again, with the bad mileage you are seeing, you should just take it to a mechanic as your burning off your cash with the high fuel consumption!

Isn't gas at least $3.00 USD a liter where you live?

Here are prices from May, 2004:
http://money.cnn.com/pf/features/lists/global_gasprices/price.html


Nation City Price
UK TEESIDE $5.64
HONG KONG HONG KONG $5.62
UK MILFORD HAVEN $5.56
UK READING $5.56
UK NORWICH $5.54
GERMANY FRANKFURT $5.29
DENMARK COPENHAGEN $5.08
NORWAY STAVANGER $5.07
NORWAY OSLO $4.93
ITALY ROME $4.86
TURKEY ISTANBUL $4.85
PORTUGAL LISBON $4.80
KOREA SEOUL $4.71
SWITZERLAND GENEVA $4.56
KOREA KOJE/OKPO $4.53
AUSTRIA VIENNA $4.50
CROATIA ZAGREB $4.32
JAPAN TOKYO $3.84
AUSTRALIA SYDNEY $2.63
CAMBODIA PHNOM PENH $2.57
TAIWAN TAIPEI $2.47
GEORGIA TBILISI $2.31
LAOS VIENTIANE $1.66
THAILAND BANGKOK $1.60
CHINA TIANJIN $1.54
CHINA SHANGHAI $1.48
RUSSIA MOSCOW $1.45
KAZAKHSTAN ALMATY $1.36
KAZAKHSTAN ATYRAU $1.35
TAJIKISTAN DUSHANBE $1.32
AZERBAIJAN BAKU $1.15
VENEZUELA CARACAS $0.14


Ok, guys, I won't be on the forum for a while, I'm going to drive to Venezuela!
:D

MarkD

[Interceptor]

13 - 14 mpg? That's terrible. I'd expect at least 20 mpg. (and probably higher, even around town)

A coolant temp sensor could not be expensive, you can just buy a new one and have the mechanic install it. I bet it's a $25 USD part.
At the price of fuel where you live, you can afford to change lots of parts to fix this problem as you'll get it back in savings.

Maybe your fuel pressure regulator is bad, try swapping that also. Again, with the bad mileage you are seeing, you should just take it to a mechanic as your burning off your cash with the high fuel consumption!

Isn't gas at least $3.00 USD a liter where you live?

Actually, it's US$ 1.25 a liter. We have the cheapest fuel in the region (Italy, Austria, Hungary and other countries around us have higher prices).

Regarding the coolant temp. sensor, I will try starting with that and see what happens.

Thanks for all the info!


Ok, guys, I won't be on the forum for a while, I'm going to drive to Venezuela!
:D
I wish you a pleasant trip and return home safely! :)

[Interceptor]

Hey, it's just flammable gas - you're a man, what more training do you need? :)
You're right, I'm a man, what else do I need?! :) OK, my spirits are up :)


My 535 pulls harder when cold, I've always considered it a function of air density getting to the cylinders. The engine bay gets pretty hot, and the intake manifold is painted black, absorbing all it can.
Actually, when the engine is cold, material of which it's made of is tighter giving it higher compression - that is why you shouldn't drive it hard until it reaches working temp.


My car definitely has good days and bad days, and usually the colder it is the better. Is it a big difference on your car, like before-and-after-an-EAT kind of difference, or is it only the kind of thing an enthusiast would notice?
Well, it's not a HUGE difference but it's noticable - well, I notice it, since I commute daily.

[632 Regal]

Interesting concept

"Actually, when the engine is cold, material of which it's made of is tighter giving it higher compression - that is why you shouldn't drive it hard until it reaches working temp."

[MarkD]

Actually, it's US$ 1.25 a liter. We have the cheapest fuel in the region (Italy, Austria, Hungary and other countries around us have higher prices).

Regarding the coolant temp. sensor, I will try starting with that and see what happens.

Thanks for all the info!


I wish you a pleasant trip and return home safely! :)

I assume you know I was just joking, I said that as the gas in Caracas is almost free. (0.14 per liter)

Mark

[Bill R.]

Robin was much closer to correct with his idea that the manifold was cooler and the charge was denser because of this... but one of the main reasons is that the fuel mixture is intentionally set richer during warmup by the dme since fuel doesn't ignite as easily in a cold motor, its richer to help it to ignite and the timing curve is more advanced when cold also.It will tolerate more advance when cold without detonation






Interesting concept

"Actually, when the engine is cold, material of which it's made of is tighter giving it higher compression - that is why you shouldn't drive it hard until it reaches working temp."

[Interceptor]

Robin was much closer to correct with his idea that the manifold was cooler and the charge was denser because of this... but one of the main reasons is that the fuel mixture is intentionally set richer during warmup by the dme since fuel doesn't ignite as easily in a cold motor, its richer to help it to ignite and the timing curve is more advanced when cold also.It will tolerate more advance when cold without detonation
Hm, then why shouldn't one drive it's car hard when cold? If there's no difference in mechanical friction, why is it possible to ruin the engine with high rpms at that time?

[Interceptor]

I assume you know I was just joking, I said that as the gas in Caracas is almost free. (0.14 per liter)
OK, I did some more research and it seems that the engine has a slight misfire when at working temp. This does not happen when cold. Also, I'm experiencing coolant loss (and it's still relatively mild here) - around half a liter per 2000 km. But, I don't see any leaks! Headgasket? Maybe there's a coolant/air leak due to a bad headgasket? It doesn't leak oil anymore, after the oil pan and oil sensor gaskets were changed.

[Rory535i]

Hm, then why shouldn't one drive it's car hard when cold? If there's no difference in mechanical friction, why is it possible to ruin the engine with high rpms at that time?

When u drive the car from startup there's not as much oil circulating the engine because while it has been sitting since last being driven, all the oil drains back down to the sump from the various parts of the engine. As a result of this u are more likely to do damage to it when it's cold by over revving it because the pistons, cam, crank etc don't have enough lubrication. I think the M3's redline is lower when the car is cold and as it warms up the red line increases??

[Matt P]

M5 owners shouldn't go over 4000 RPMs until oil is fully warmed up.

The coolant will reach operating temp in just a couple minutes, while it may take 10-15 minutes (or more) for the oil to reach 90 degrees (centigrade). Premature redline can lead to *expensive* engine damage.

This is not the case with the M50 or M30 obviously, as those enignes are not quite as stressed.