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Old 29-11-2005, 10:03 PM   #1
EVOlution
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Intake problem - flat spot - need help

G'day, I just bought a secondhand Mazda Astina 1992 BG twin cam 1.8L (I think it's a 1.8), I have fitted a pod filter and still have a "flat spot" from idle when you accelerate.
If you are sitting in neutral and you give it a rev, it hesitates for a second then it revs, it's like a dead accelerator pump in a carby setup.
So, my question is - has anyone ever had this problem and if so, did you fix it and how was it fixed, what had to be replaced etc.
I am guessing I may need a new AFM as the pod did stuff all for the flat spot but it goes a little better once it's revving.
It's not a bad little car but this flat spot is really noticeable.
Any help would be appreciated, thanks in advance.
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Old 29-11-2005, 11:09 PM   #2
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I just thought it was normal. I have it on my standard turbo setup just as you put the
foot down a little drop and then flies. I have changed at seperate points ECU, AFM
and the car its in to same result.
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Old 30-11-2005, 06:32 AM   #3
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That would be normal on most turbo cars I would have thought. Mine is not turbo unfortunately. I fitted a pod filter because the standard air box is deformed and won't seal that the end under the AFM and so it leaks past the filter. I thought the leak might have had something to do with the flat spot but it is still the same with the new pod.
It is really bad, the car almost stalls, it's like someone is pulling the coil lead out then putting it back in - it is that bad.
I will talk to Mazda when I go to buy the new front window strips and see how much it would cost for a full tune up.
I would rather try to get help here and fix it myself but it's gotta be done quick. I'll keep looking until I have to go to Mazda.
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Old 30-11-2005, 11:33 AM   #4
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Not a turbo thing same motor running a haltech doesn't have the drop. Mine is not
nearly stall bad just a little hesitation then revs. You did have this before you put
on the pod correct it may be time to give the throttle body a good clean see if that
helps especially the bottom IAC section
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Old 30-11-2005, 12:24 PM   #5
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It actually sounds a bit like anti-pollution problems. Have you checked to make sure all vacuum lines are hooked up and not leaking?
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Old 30-11-2005, 12:39 PM   #6
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I'd suspect it's the idle control valve (IAC) thats located on the throttle body, as has been mentioned a few times in other posts by people with smilar problems. Just a maybe though
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Old 30-11-2005, 03:48 PM   #7
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I was thinking IAC too but in another post it was asked if the idle goes up or down when air-con is turned on - the idle goes up when I turn on the air-con so I would have thought the IAC was working ok.
I might rip off the throttle and give it a clean and check all the polution control hoses while I'm there..... Mazda want to charge me $101 per hour to look at it I will try my best to fix it myself then if either I kill it or can't fix it I will go to Mazda unless anyone can recommend a good mechanic in sydney western suburbs, around Parramatta area?
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Old 30-11-2005, 05:28 PM   #8
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Quote:
Originally Posted by Rupewrecht
I'd suspect it's the idle control valve (IAC) thats located on the throttle body, as has been mentioned a few times in other posts by people with smilar problems. Just a maybe though
Damn, I was gonna say that....
Give it a service, replace the plugs, check inside the dizzy cap for corrosion, maybe replace the plug leads. My first guess would be ignition.
Else maybe a bottle of fuel injector cleaner next tank and a treatment of Subaru upper engine cleaner (available only from Subaru spare parts dept.).
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Old 30-11-2005, 07:14 PM   #9
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yeh if ur gonna try injector cleaner,my mechanic says it doesnt really do nething.but if theres like sumthin in ur fuel like dirt or bit of water fill ur car atleast half a tank and poor about a quarter-half a bottle of metho in n it will clean ur fuel n lines.
but yeh double check that theres no air leaking out ur intake pipe.
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Old 30-11-2005, 07:51 PM   #10
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yeh if ur gonna try injector cleaner,my mechanic says it doesnt really do nething.but if theres like sumthin in ur fuel like dirt or bit of water fill ur car atleast half a tank and poor about a quarter-half a bottle of metho in n it will clean ur fuel n lines.
but yeh double check that theres no air leaking out ur intake pipe.
Yeah like a mechanic will promote a fix in a bottle, it puts him out of a job. It is worth a try. Pulling injectors is a pain of a job, trust me I've done it twice this week and will do it again once I have new 'O' rings for 'em
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Old 30-11-2005, 08:10 PM   #11
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Hmmm, doesn't look like a big job to pull the injectors on this engine, might rip 'em out and run 'em on the machine for a leak and pressure test.
As for metho in the fuel - no way, not good to do on fuel injected cars, especially if they have active knock sensing and multiple EGO sensors. Try putting that percentage mixture of metho in a direct injection engine hahahaha.
Anyway, I'll get into the throttle body this weekend if I'm not rallying (I'm a professional navigator, just sold my daily driver Lancer rally car to buy a normal car to run around in..... and I went and got the Astina with it's problems )
I am right this very minute taking a break from my HID & stereo & air horns install. Would anyone be interested in a HID how-to???? I took a few photos while I worked on it.
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