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Go Back   Madabout Kitcars Forum > Mad Build Area > Marlin 5exi builds

Marlin 5exi builds Calling all you sexi builders....sorry 5exi builders, show us your progress.

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  #1  
Old 31st December 2007, 10:32
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Default Engine playing up…. 1 week to SVA…. Damn!

Dear all,

As sods law would have it, 1 week prior to my SVA my engine has decided to start playing up – manifesting as a miss-fire.

I’ve been pretty thorough checking for faults, and I haven’t yet solved the problem.

The miss-fire isn’t bad, just a slightly lumpy idle, and minor occasional pops when holding the revs at “fast idle” (circa 2k rpm).

I’ve checked the following so far:

Plugs – look perfectly healthy – no fouling with oil, fuel, or carbon.
Engine coolant temp – ECU shows a sensible reading of ~ 80 Celsius.
Inlet air temp – was registering ~ 8 Celsius yesterday afternoon.
Cam & Crank sensor fine.
Lambda – 12v (actually 13.5v…) supply to heater is fine, and the output appears to be swinging merrily.
Fuel pressure – dead on 50 psi, with no fluctuations.
MAP sensor – sensible vacuum figures for idle.

The only slightly quirky figure I can see from the ECU logs, is the closed loop short term fuel trim, which is at about -7%. My suspicion is that this is causing the engine to run a bit lean, causing the miss-fires. If the fuel trim is the issue, then the only culpable sensor is the lambda sensor.

As a “time is running out” measure I’m going to bung a new lambda on this evening, and hope that remedies the situation. However, in case it doesn’t I’m wondering if there’s anything I might have overlooked….? Can anyone think of something I’ve missed?

Cheers,

John.
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  #2  
Old 31st December 2007, 15:17
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John

I have to say my mechnic days were 25+ years ago, and then all these sensors ect were unheard of, if I were looking at this problem though then, I would be looking at at changing the plugs and leads as a starter for 10, then a slight air leak,

Is the fuel new, or has it been siting in the car for a long time, something worth a thought.

Although it should be unlikely on a modern engine, but sticking valves could cause a similar issue, although I sincerely hope there not.

Aside of that, could the hondata unit be causing issues.

Best of luck.

Steve
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  #3  
Old 31st December 2007, 17:55
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Make sure all your injectors are working.
You can check by placing a long screwdriver blade on each injector in turn and holding the handle to your ear. You can hear them clicking away if working normally.
I had one on stick shut on my BMW engine and it appeared just like a mis-fire.

A sharp tap on the side with a large screwdriver got it going.
Worth a check?

Peter
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  #4  
Old 31st December 2007, 19:25
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Sorted!

The short term fuel trim being down at -7% was definitely the right lead to pursue - new lambda sensor on, a few blasts up the driveway (neighbours must think I'm odd) to get some fuel through, and the fuel trim is now dithering between 0 and -2%. Crucially the miss-fire has gone.

Curious!

Thanks for the suggestions guys.
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Old 1st January 2008, 09:00
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Talking

John

Well done, always a good feeling when things work out.

Steve
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  #6  
Old 2nd January 2008, 12:21
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Glad you fixed it.

All the best for the SVA
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  #7  
Old 5th January 2008, 21:54
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Default Sva

Jon


When is your SVA appointment?

Do you need any assistance Taunton end to drink the Champagne or dry the hanky?



eaa53
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Old 6th January 2008, 00:38
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John,

It's 8am on the 7th. I expect to fail (it'll blatantly do this on something I've overlooked), but hope to pass (small chance I suspect).

I can't say I'm entirely happy with the state in which I'm going to present the car; there are some "rough edges" which annoy me, but I'm taking the approach that it's best to have a crack at the SVA, and see what happens. I could go on for months improving what I feel to be sub-standard, only to fail on something seemingly obscure.

It's a shame the weather forecast is looking pretty poor, as I was hoping to drive the car to and from the test to get a feel for the car, bed the brakes in, and quite simply because it'd be fun! Looks more likely I'll be dragging the car there on a trailer now though.

Cheers,

John.
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Old 6th January 2008, 08:20
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Hi good luck on the 9th.

Have a look here what mine failed on.

http://www.madabout-kitcars.com/foru...ead.php?t=1199

Steve went to the same test centre as me. Changed "u" clamp etc. Passed first time. Which I think is rare.
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  #10  
Old 6th January 2008, 10:22
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Cheers John.

I fitted a different NS steering rack clamp, as the Marlin supplied one didn't make it to the nyloc end of the nut.

Wheels - I've not been jazzed to get some rover steels, so wheel projection might be an issue - I'll have to wait and see on that one. I reckon the body is flush with the wheel..... but it's not my opinion that counts!

Doors - no doors, so one less area of concern!

It'll be interesting to see what the comment is about my seatbelts. I'm using Lotus Elise seats, thus the seat belt anchors through the seat frame.

Weather has cleared here a bit since yesterday, so maybe I will get to drive it! The car is currently filthy from driveway testing, so I'd best do something about that.

Cheers,

John.


EDIT>>>>

BU**ER - Certain to fail, as windscreen just cracked! Damn it!
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  #11  
Old 6th January 2008, 13:48
5EXi girl 5EXi girl is offline
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Default good luck for tomorrow

Hi John

Just happen to notice your SVA is tomorrow so thought we would send you our best wishes today. If you have any problems that you are not happy with during your exam, do ring. We have just put a 5EXi through all ok :-)

Terry & mark
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  #12  
Old 6th January 2008, 15:03
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John

Best wishes, just enjoy the day as well, I found it really intersting seeing and being part of the checks.

Steve
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  #13  
Old 6th January 2008, 15:17
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Cheers all.

Here are some pictures, including the lovely crack in the windscreen. I'll give 2p to the first person to work out how I did it!







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