Lifeless or Flat Spot

P

Phil-E30

Active member
Afternoon all,

Apologies for my lack of contributions lately, new job in London has taken a lot of time off me!

Driving the car this weekend, the one niggling issue remains the flat spot or hesitancy in acceleration in first/second gear. A good example is if lights change before I get to them, I drop it to second and even if I put my foot to the floor, there is a moment of nothingness before the car comes to life. Something isn't quite right.

Reflash of DME seems to make little/no impact apparently, so what are the issues/areas I should consider looking at? Bearing in mind I only get a couple of days at home a week, it would be nice to know what I need to ask people to look at.

Thanks, as always! :thumbsup:
 
I would start by doing what I'm going to do in the next few days and give the whole air intake/manifold a complete clean out, including ICV and go from there. It's cheap and should be fairly simple DIY with the right tools. A lot of people have done this (focussing especially on the ICV) with good results. See how that works and go from there as then your probably going to have to start spending money on replacing certain sensors/parts that the cost of which mounts up pretty quick! You should be aware no-one appears to have a definite solution for this so you could end up throwing a lot of money replacing stuff for little/no gain, depends how far you want to go with it and how much it bothers you really....
 
As above, the ICV seems to be the most common solution, people have reported sustained improvement due to cleaning (over 5k miles), potentially not permanent, and I'm not sure if anybody has taken the step to replace the ICV as yet?

Not suffering with it personally, but seems a fairly common issue so like to keep an eye on any solutions (which seem to have been a long time coming).
 
Indeed, the ICV does appear to be a significant factor. I had brought a new ICV but on the advice of James at Redish Motorsport I took it back to BMW for a refund as at £255 a new one is a last resort really. As a part that literally has a butterfly valve that is either open or closed its hard to see why it would fail, apart from getting gummed up but then a good clean should sort that. And it wouldn't explain why some people get the problem and others don't which suggests there must be more to it. Cleaning it is a good start point though.
I'll post my results next week, might do a DIY write up if I get the time as I go along.
 
If there are no fault codes and there's nothing obviously wrong, then I'd start with an "Italian Tune up". Let the car have a play at high revs even if that means you're just doing 60mph in 2nd gear when you could be in 5th. Get the engine nice and warm to burn of the deposits on the internals from cruising. It will also help the ECU to set it fuel trims.
 
exdos said:
If there are no fault codes and there's nothing obviously wrong, then I'd start with an "Italian Tune up". Let the car have a play at high revs even if that means you're just doing 60mph in 2nd gear when you could be in 5th. Get the engine nice and warm to burn of the deposits on the internals from cruising. It will also help the ECU to set it fuel trims.
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My kind of tuning. :driving: :thumbsup:
 
buzyg said:
exdos said:
If there are no fault codes and there's nothing obviously wrong, then I'd start with an "Italian Tune up". Let the car have a play at high revs even if that means you're just doing 60mph in 2nd gear when you could be in 5th. Get the engine nice and warm to burn of the deposits on the internals from cruising. It will also help the ECU to set it fuel trims.
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My kind of tuning. :driving: :thumbsup:
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Indeed. Might do this just for fun even though there's not any need :lol:
 
I was looking at the piston removed from a Rotax kart engine yesterday, and despite that engine running at over 13,000rpm, there were still carbon deposits and varnishing on the end and sides, so you can imagine what an engine revving most of the time at, say, 3,000rpm might look like after a while.
 
Exodus, what's a good procedure for an Italian tune up.

Warm the car up to operating temps, then give the engine a good spanking. Is it good to say leave it revving highly at say 7k revs for a few minutes, or up and down the Rev range.

Obviously a good sporty drive would do the job, but if one was trying to give it an Italian tune up, how long in time should one take.

I don't have any symptons, but interested to know about how long it would take to burn any deposits off.
 
Rob, I think the procedure depends on where you live and the access that you have to appropriate roads to do some spirited driving, but essentially, you want to get the oil/engine up to working temperature then use 2nd and 3rd gears as much as possible so that you're near the redline in 2nd and around mid revs in 3rd. You can stay around the 60mph mark so not speeding doing this. :wink: If you're on the twisties you can make lots of downshifts into 2nd approaching bends, which will keep the engine revs high and then accelerate to the redline and then change to 3rd. It's also good practice for heel & toe and rev-matching technique. About 10 to 15 minutes of this will get the engine nice and warm and then see how things are afterwards. If you can give the car some high revs every time it goes out, it all helps to keep everything working well.
 
I think an Italian tune up sounds like the first port of call then :lol: :thumbsup:

I am also going to do the intake/ICV clean too though.

Cheers for the responses! :thumbsup:
 
Great advice Exodus.

Yeah I have been told before you should try and get to the redline each time you drive it. I normally do once it's warm as I don't do short trips in it!
 
I find I rarely have to get anywhere near the red line to have fun, but man when you do get there - the noise 8)

Sounds like an early Saturday morning task next weekend before a wash :driving:
 
Bing said:
I find I rarely have to get anywhere near the red line to have fun, but man when you do get there - the noise 8)

Sounds like an early Saturday morning task next weekend before a wash :driving:
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PVR will have all your roads coned off next weekend too stop you thrashing it :rofl: :rofl:
 
Phil-E30 said:
I think an Italian tune up sounds like the first port of call then :lol: :thumbsup:

I am also going to do the intake/ICV clean too though.

Cheers for the responses! :thumbsup:
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very interesting post, like the itu idea, thats a pretty normal part of a trip out ! any pics of location of icv, and best method of cleaning it.? many thanks :thumbsup:
 
I would also like to support the last poster's request for pictures or guides for ICV location and cleaning. Italian tune up will now become a regular occurrence :thumbsup: :driving:
 
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