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Registered: May 2003
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A symptoms needs a diagnosis
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Mon, 24 October 2005 12:05
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hey there,
I have a 4ac engine in my sprinter and it has been running well for the last 4 years or so. Anyways recently when i rev the car past 2500rpm or a bit higher the car startes the shutter and I feel a huge loss in power. This occurs when accelerating conservatively and when its pushed a bit harder. Any sugestions on what it could be? Possible Carby from what others have said
Thanks for the help
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Location: tallahassee FL usOFa
Registered: May 2002
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Re: A symptoms needs a diagnosis
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Mon, 24 October 2005 14:24
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what's the compression?
what do the spark plugs look like & how old & how many miles on them, and the plug wires?
was anything done BEFORE this started happening?
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Registered: May 2003
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Re: A symptoms needs a diagnosis
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Mon, 24 October 2005 21:44
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No nothing was done before this. It just started to occur lightly to the point when u can really notice the power loss and the shuttering of the car/engine above 2500 rpm.
Im not sure what the compression is but Ill check it out at a mech today
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Location: London
Registered: July 2004
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Re: A symptoms needs a diagnosis
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Mon, 24 October 2005 21:53
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Could be coil too?
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Registered: May 2003
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Re: A symptoms needs a diagnosis
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Mon, 24 October 2005 22:00
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Whats a coil sorry?
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Location: London
Registered: July 2004
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Location: Sydney
Registered: September 2004
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Re: A symptoms needs a diagnosis
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Tue, 25 October 2005 08:42
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general rule of thumb with diagnosis is:
First check Electrics i.e. plugs, coil, leads, cap, rotor button, dizzy
Then fuel i.e. carbie, fuel pump (if applicable), filter, leaks in the lines
Then mechanical i.e. compression, leak down, sticking valves, unusual noises, blown head gasket etc.
the reason for this is most that is the order of most likely faults to least likely...
In addition, the basics an engine needs to run is:
Air
fuel
compression
spark
the above order will let you determine which of these is not doing its job....
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Registered: May 2003
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Re: A symptoms needs a diagnosis
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Tue, 01 November 2005 12:09
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Hey,
The engine just recieved an major service and everything was fine . Although once i filled up with a full tank of optimax last tuesday my engine started to rumble (like a wrx) on acceleration and it was unsmooth with alot of jerking. On idle, the engine is still sound rough and the engine is idling like it is going to stall but isn;t if that make sense.
Could my engine need a carby tune and service or is my engine just had its time.
Thanks
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Location: Canberra
Registered: July 2005
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Re: A symptoms needs a diagnosis
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Wed, 02 November 2005 02:54
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the rumbling says to me that it would be missing. The most likely cause is ignition, so give your HT leads, dizzy cap, plugs and coil a check. Corrosion is bad.
Another possibility is the compression could be gooorne on one of the cylinders. While it is not the best guide in the world, the oil consumption is a good guide. Are you blowing lots of white smoke?
Less likely (if it is inconsistent) is the carb.
As said above, chase the electrics first.
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Registered: May 2003
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Re: A symptoms needs a diagnosis
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Wed, 02 November 2005 04:31
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HT leads, dizzy cap, plugs and coil a check was replaced during the service so I doubt that is the problem. Possibly compression has gone down in one of the cycliners since power levels are dramatically losted
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Location: Adelaide
Registered: June 2003
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Re: A symptoms needs a diagnosis
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Wed, 02 November 2005 05:03
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If the symptoms started after you filled up with petrol, you might have got a shitty batch of petrol.
Shell are good for that.
We've had this before.
It clogs up your fuel filter.
The more fuel the car requires, the more shit it will runas the lines are partially clogged.
Hence the rev problem.
Check to see if your idle mixture screw is grotty and your fuel filter.
Get rid of the fuel that is in your tank and swap it for something BP, they are usually good.
Change your fuel filter before you start the engine on the new fuel.
You will most likely have to change the filter again soon after, as the crud that was in the hoses will now flow into your new filter.
Another option might be your ignition timing, if it is over advanced it can run like shit.
Check to see that the vacuum advance is working by sucking on the tube and seeing if anything moves inside your dizzy (take the cap off first). Things should move.
These things should be checked in addition to the electrical stuff that the other guys said.
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Location: brisbane
Registered: September 2005
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Re: A symptoms needs a diagnosis
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Wed, 02 November 2005 06:08
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also check to make sure ur jets are flowin proper in the carb
i took mine off, and when it got put back on she idled like a ho, and died on revs
i advanced the timing to get it to a mate who is a mechanic, and on the way she almost died up a hill so i planted it and dropped to first, hit the redline and she was fine. machanic said it was likely a bit of shit in the jet
its worth a look as the filter mite have missed somethin
~andrew~
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Location: Brisbane
Registered: July 2005
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Re: A symptoms needs a diagnosis
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Wed, 02 November 2005 06:54
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You posted on Tues 1.11 that last tuesday 25.10 was when you filled up and car and it had been serviced before this already yeah?
You started this thread on the 24th so your car must have had this problem BEFORE the fuel went in???
It also means you must have had a major service just before your problem??? What date was service and how long did you have normal driving for before this issue?
There are usually few coincidences i find. Rather than think "HT leads, dizzy cap, plugs and coil a check was replaced during the service so I doubt that is the problem" i would be thinkin the opposite, they were all touched recently so which one could be the problem?
From what you have described it sounds like you could have a problem that is localised to one cylinder, or else its the cleanliness of your fuel system.
To eliminate a cylinder specific problem, with the engine running, pull one HT lead off, note the difference at idle (hopefully it wont stall) and at a small amount of revs compared with before you pulled it off. Repeat this for each cylinder. If one causes less of a drop than the others, then it wasnt running properly with the lead on - bad lead, plug, connection, compression...
It can take a keen ear but its an easy test which will have you looking in the right place whether it ends up being a cylinder or your fuel.
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Location: Tamworth
Registered: August 2004
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Re: A symptoms needs a diagnosis
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Wed, 02 November 2005 07:24
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i found a chewing gum wraper in my fuel tank the other day!
Blow backwards through ur fuel lines into the tank and then see if the car runs any different for a moment.
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I supported Toymods
Location: Perth
Registered: October 2003
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I supported Toymods
Location: Perth
Registered: October 2003
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Re: A symptoms needs a diagnosis
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Wed, 02 November 2005 08:10
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When I had my 4AC something like this happened but on the primary jet in the carbi. This meant I had to rev its head off for it to drive smoothly so the second jet would function as well. A combination of fuel filter, changed a few times cause of a shit batch of petrol from some shit place, distributor points, leads and carbi.
1) Replace fuel filter
2) Replace Leads / Spark plugs
3) Get the points changed in your Distributor and have the timing readjusted.
By now you should be experiencing a smoother ride by now, if not..
4) Carbi Cleaner. Clean out the Carbi with Throttle Body / Carbi Cleaner. You will have to take the Black filter box of to do this. Also reeving the engine then holding your hand over the inlet of the carbi can help, and holding the accelerator down just after you put your hand over, use a rag but don't let it get sucked in, for safety. By doing this it floods the engine, and just before it dies take your hand of. This can remove crap and free sticky valves/jets up etc.
After I changed all these the 4ac was ready for some action, and it ran particularly well !
I hope this can help you with your problems.
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Location: Seated
Registered: November 2005
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Re: A symptoms needs a diagnosis
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Wed, 02 November 2005 10:27
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Have you actually pulled the plugs out to check if their ok?
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Registered: May 2003
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Location: brisbane
Registered: September 2005
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Re: A symptoms needs a diagnosis
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Sat, 05 November 2005 01:44
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