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e series 5.0 occasional flat spot under 2500rpm 

 

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 Post subject: e series 5.0 occasional flat spot under 2500rpm
Posted: Sat Mar 29, 2014 1:11 am 
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Ok guys this problem is not unique to me only... couple of mates have said theirs does the same thing..

So what happens is when U take off from the lights sometimes (but not always) it lacks power... not massively but noticeably... it lasts till around 2500 or 2800 then its like a switch is flicked and it gains back full power...

I have also had an ef 6 cyl that used to do this...

It can happen hot or cold...

I'm thinking its the same problem I had with the 6...I never worked that one out either...

Its either pulling timing out or leaning out or maybe even going too rich... who knows...

I'm suspecting o2...but I have a feeling my mate changed those on his and it made no difference..

 

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 Post subject: Re: e series 5.0 occasional flat spot under 2500rpm
Posted: Sat Mar 29, 2014 2:23 am 
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I have the same problem with my na lane but its because of diff gears once I get some 3.45 diff gears it should go away. Might be your problem.

 

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 Post subject: Re: e series 5.0 occasional flat spot under 2500rpm
Posted: Sat Mar 29, 2014 2:26 am 
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Nah...I know what U mean but this only does it sometimes...

 

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 Post subject: Re: e series 5.0 occasional flat spot under 2500rpm
Posted: Sat Mar 29, 2014 2:58 am 
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Okay so every now and again it will run fine and take off well? Maybe worn rotor stud the bit the rotor button goes on. Just take the cap off and give it a wiggle to see if it has any play. I doubt its the problem but maybe be contributing to it possibly dirty injectors or dodgy ones.

 

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 Post subject: Re: e series 5.0 occasional flat spot under 2500rpm
Posted: Sat Mar 29, 2014 8:29 am 
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Theres a pile of things that could be. Maf Issues (Clean it with MAF Cleaner), TPS, Fuel, and O2 Sensors come to mind pretty quickly.

Nigel
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 Post subject: Re: e series 5.0 occasional flat spot under 2500rpm
Posted: Sat Apr 19, 2014 3:02 am 
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Every typical thing has been replaced first with second hand parts and then new ones...o2s...maf...ecu...

Im actually starting to think its a software issue..

 

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 Post subject: Re: e series 5.0 occasional flat spot under 2500rpm
Posted: Sat Apr 19, 2014 8:42 am 
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Have you checked the O2 sensor ground at the back of the engine?

Following on from that, are you sure that no coolant is leaking out of the EGR Spacer into the Manifold?

Check the Engine earth at front of the block as well.

On all of them there should be less than .1v from (engine to battery, engine to body, O2 earth to Engine)
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 Post subject: Re: e series 5.0 occasional flat spot under 2500rpm
Posted: Sun Apr 27, 2014 11:43 pm 
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{USERNAME} wrote:
Have you checked the O2 sensor ground at the back of the engine?

Following on from that, are you sure that no coolant is leaking out of the EGR Spacer into the Manifold?

Check the Engine earth at front of the block as well.

On all of them there should be less than .1v from (engine to battery, engine to body, O2 earth to Engine)


Can you tell me more about this? Maybe a link to a thread that covers issues and remedies? Cheers

 

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 Post subject: Re: e series 5.0 occasional flat spot under 2500rpm
Posted: Mon Apr 28, 2014 7:33 am 
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Nope - I dont know of any threads on these. These are what Id follow up.

The O2 sensor earth is at the back of the manifold, usually near #8 cylinder (inlet Manifold)
The Engine Earth is near #1 cylinder, behind the Alternator, and goes to Battery via the body

Sorry thats all I have time for
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 Post subject: Re: e series 5.0 occasional flat spot under 2500rpm
Posted: Mon Apr 28, 2014 1:01 pm 
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Check base timing.
Mine's an I6 but I was having issues with this quite bad just recently, and decided I needed to do further inspections after my supercharger implosion episode.

Turns out it was retarded by about 5 deg (guesstimate since there's no indicators)

Adjusted it, reset ECU, and it has been sweet ever since.


I don't know e-series v8's but if they use a 3-wire O2 like the I6, then check main earth strap too.
I found I was losing 0.5v under full electrical load just at the crimped lug at the block.

 

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 Post subject: Re: e series 5.0 occasional flat spot under 2500rpm
Posted: Thu Aug 28, 2014 8:35 pm 
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UPDATE : Ive worked out this is an ecu tune issue, despite car being stock...

basically on a 5.0lt 2 mian things determine when Open loop is started...its TPS WOT breakpoint and load...

So what can happen is the ecu is under WOT TPS voltage but still under a fair bit of load...there is delay going from CL to OL...so if u happen to be idling and in CL and then take off at slightly inder WOT breakpoint the ecu will wait approx 2 seconds to go OL...

 

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 Post subject: Re: e series 5.0 occasional flat spot under 2500rpm
Posted: Thu Aug 28, 2014 9:16 pm 
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Thats Partially true, but if your O2 Readings are off because of a bad earth, then your mixtures are usually too lean in the first place, so when you put the boot in there is an abscence of power until the ECU decides to go open loop. Then, when it does go open loop, its mixtures arent right. You'll actually notice that it probably goes open loop when you throw your foot down, and the 2 second delay is when the ECU starts correcting the mixtures and bringing them back into line.

Most O2 sensors in E series are way past their use by date : They get old, and slow.
Most E Series also have earth problems, causing the O2 readings to be way off.

Nigel
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