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Losing power after 10 minutes of driving

Azazl187

Azazl187

Messages
1,067
Hi all,

I have a strange issue where I seem to lose some mid range torque after about 10 minutes of driving. I tend to only do town driving so it's all stopping and starting, but one thing I've noticed is that when I start driving the acceleration seems sharp and responsive but as I drive this seems to die away after 10 mins or so.

It's not sudden or anything, the car just seems sluggish after its warmed up.

I've just had all 4 calipers professionally refurbished by BCS with all seals replaced, bled and fitted.

I have the standard airbox with a new filter but I'm thinking that due to removing the exhaust heat shield as it rusted up and rattled I'm getting heat soak as it's now summer time. I removed it years ago though so I'm not convinced....

VTEC engages fine and I've just done the valve timings well within spec although I noticed this before I did that.

Any suggestions peeps?
 
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I get that when I'm nearing a service. Doing fluids this weekend.


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Azazl187 said:
I have the standard airbox with a new filter but I'm thinking that due to removing the exhaust heat shield as it rusted up and rattled I'm getting heat soak as it's now summer time. I removed it years ago though so I'm not convinced....
Click to expand...

It certainly sounds heat-related given the time involved, I couldn't cope with the exhaust manifold heat shield off, running the fan for cool air led to warm air entering the cabin, the footwell felt warm, etc. How do you handle it?

Is the inlet pipe leading to the air-box properly connected? Do you have an OBD reader that you could check stats with before and after the sluggishness begins?
 
I'd start with heat soak. Have you been driving it more this year than previous? We have had a lot of 30+ degree days this year.
 
mike.h said:
It certainly sounds heat-related given the time involved, I couldn't cope with the exhaust manifold heat shield off, running the fan for cool air led to warm air entering the cabin, the footwell felt warm, etc. How do you handle it?

Is the inlet pipe leading to the air-box properly connected? Do you have an OBD reader that you could check stats with before and after the sluggishness begins?
Click to expand...

Yea thats what i was thinking. I haven't really noticed a temp changed from before although it was a long time ago. If anything im driving it a bit less these days as i live closer to work, maybe 2000 miles a year.

Everything is connected as it should be so there should be no issues there. I have an ODB reader that connects to my phone and i can get all the info i want from an application. What should i be looking for in particular?
 
Have you had it out on any good runs? Good hour or two of driving? 2,000 miles a year of all town driving is not much good for the engine, she'll be all bunged and the oil full of fuel etc.


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Sounds like a heat soak issue. It's a combination of high summer temps and the town driving. Also the butterfly valve in the throttle body doesn't like stagnant driving. Needs a good blast every now and then.

An oil change and good flush of the coolant system might see you right.
 
OK I'll do an oil change as well as coolant. She goes out for a drive every couple of months so it's not 100% town driving, just most of the time 3 or 4 times a week.

I'll take her out tomorrow for an hour or so regardless. Do you think getting a replacement heat shield for the exhaust is a good idea? I'm thinking of running a cold air feed from the Mugen front splitter hole, through the wheel arch cover and upto the standard air box instead of getting cold air from the front of the engine bay as standard
 
I'd do all of the above mate, a second hand heat shield and a bit of ducting will be cheaper than some of the alternatives!!

When you flush the coolant might be a good idea to catch it in a clear container and check to make sure there's no contamination. And same with the oil if you can.


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I run a standard airbox and exhaust manifold without heatshields and have no issues. Be suprised if it is heatsoak, could understand with an open filter but not a closed airbox.

A good blast and service is a must.
 
OK all good advice guys. Ill get the bits in, do the work and report back. It cant hurt even if it doesnt fix it :smt047
 
Is it after lots of stop start ot2 all the time? It could be brake bind if it's only once it's had time to warm up, though I think you'd notice smoke or heat from a wheel.

Spark plugs been changed recently? Or air filter?

Engine oil and filter won't hurt, but a coolant change isn't going to do anything to do with this fault.

If it's only really around town when it's happening it could be heat soak, but I can't see that being noticeable when you're just pottering around.

I'd clean up the throttle body and idle control valve, change the oil and filter if it's due, change air filter if it's due, double check no brakes are getting overly hot, then take it for a blast and see what happens.

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Also, if you want to check compression, I have a tester you can borrow. Though very unlikely to be that serious!

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I think the suggestion of coolant was based on potential for heat soak, freshen it up a little. And check for contamination in there (head gasket).

From my experience the brake binding makes the car feel down on power every time you move off, even when the car is still cold.

To be fair I also think heat soak would be more of an issue if you're just pottering around town in 25+ ambient with a lot of stop start than if you're blasting about some B roads.


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Then that kinda leaves more evil things, lambdas, MAP sensor, inlet air temp, fuel pump or filter (limiting max pressure). The fun part is working out what the actual values should be for an OBD read. :(

It's all a bit weird that it's only when the car's at operating temp though.

Is it all a problem before VTEC rev-ranges, or only when using VTEC?

Does your check-engine light work (does it illuminate when the key's in the on position prior to starting the engine)?
 
Cheers guys. Ive ordered everything for a oil and coolant change. Oil change is due and coolant hasnt been done in the 32k that ive had the car so I may as well do that.

Brakes are very unlikly to be an issue as had all 4 rebuilt professionally month ago. Thanks for the offer on compression testing Norv, ill take you up on it if this doesnt make a difference
 
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mike.h said:
Then that kinda leaves more evil things, lambdas, MAP sensor, inlet air temp, fuel pump or filter (limiting max pressure). The fun part is working out what the actual values should be for an OBD read. :(

It's all a bit weird that it's only when the car's at operating temp though.

Is it all a problem before VTEC rev-ranges, or only when using VTEC?

Does your check-engine light work (does it illuminate when the key's in the on position prior to starting the engine)?
Click to expand...

Its pre vtec, as far as I can tell vtec works just fine. Yes he engine check light works fine and ive plugged in the reader and there are zero error codes
 
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Norv said:
Also, if you want to check compression, I have a tester you can borrow. Though very unlikely to be that serious!

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Click to expand...

Maybe pop round and take her for a spin next weekend Norv and see what you think?
 
Yeah no worries, can be about sat morning if you need any help. How about the spark plugs, have they been checked/changed in a while?

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