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94 CX with DX motor - rpm drop then suddenly pick up accelerating

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Old 09-27-2010, 01:42 PM
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Default 94 CX with DX motor - rpm drop then suddenly pick up accelerating

my car is a 94 cx with a dx motor 150000miles
has about 180000miles now
my car used to run fine until now

when i start my car cold its fine
when i go to the store or out of the car and come back when i start my car the rpm runs really high like 2.5 rpm but that's when the engine is already hot and not cold
sometimes when the engine is hot and i start the car it is fine and rpm is normal but that's
a 1 out of 10.
so the problem is when at 2.5 rpm it seems like its running rich or something but the main problem is when i put my foot on the accelerator pedal(at idle or in gear) the rpm suddenly drops down about .5 rpm and seems like its lost power then suddenly rpm goes up and seems normal. this only happen when im in first gear trying to pick up speed again from a stop or light. you drive it around for like 10-15 min then when at idle the rpm is normal again
@ 700 RPM and when i accelerate it is back to normal
also when this problem occurs i get it to second or third gear and floor it the car will stall and seems like it gonna shut off on me

i thought it was the o2 sensor failing on me but ive replaced that and its still there

if anyone has had this problem or knows how to fix it please help me out
thanks

Last edited by beginmyhonda; 09-27-2010 at 01:44 PM. Reason: forgot to add more detail
Old 09-27-2010, 05:34 PM
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Default Re: rpm drop then suddenly picks up when trying to accelerate

Any CEL codes?
Old 09-28-2010, 06:54 AM
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Default Re: 94 CX with DX motor - rpm drop then suddenly pick up accelerating

no CEL at all
Old 09-28-2010, 07:16 AM
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Default Re: 94 CX with DX motor - rpm drop then suddenly pick up accelerating

Originally Posted by beginmyhonda
no CEL at all
what is the reason?
Old 09-28-2010, 08:02 AM
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Default Re: 94 CX with DX motor - rpm drop then suddenly pick up accelerating

When you turn the key from off to ON(II), does the CEL turn on and then off after 2 seconds? Or does it remain on steady?
Old 09-28-2010, 08:35 AM
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Default Re: 94 CX with DX motor - rpm drop then suddenly pick up accelerating

Originally Posted by RonJ@HT
When you turn the key from off to ON(II), does the CEL turn on and then off after 2 seconds? Or does it remain on steady?
it goes off after 2 seconds
Old 09-28-2010, 08:36 AM
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Default Re: 94 CX with DX motor - rpm drop then suddenly pick up accelerating

Originally Posted by FranklinWalker
what is the reason?
for what?
Old 09-28-2010, 08:38 AM
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Default Re: 94 CX with DX motor - rpm drop then suddenly pick up accelerating

When were the plugs, wires, cap, and rotor last replaced? Have you checked the ignition timing with a timing gun?
Old 09-28-2010, 08:43 AM
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Default Re: 94 CX with DX motor - rpm drop then suddenly pick up accelerating

check these;

-IACV (very possible for your high idle)
-TPS (also possible for your high idle and the sudden drop to .5k rpm when accelerating)
-MAP sensor (could be the problem for the sudden drop in rpm)
-Faulty wiring (a sensor listed may have come loose or gotten torn recently)

after you check all those, then it means your engines bad and you should just scrap the whole car as is!
Old 09-28-2010, 08:44 AM
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Default Re: 94 CX with DX motor - rpm drop then suddenly pick up accelerating

also what ronj@ht posted
Old 09-28-2010, 10:06 AM
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Default Re: 94 CX with DX motor - rpm drop then suddenly pick up accelerating

Originally Posted by RonJ@HT
When were the plugs, wires, cap, and rotor last replaced? Have you checked the ignition timing with a timing gun?
plugs and wires have been replaced since last oil change
plug gap already set too
timing is within spec
havent messed with the cap or rotor though


Originally Posted by Boost>NA
check these;

-IACV (very possible for your high idle)
-TPS (also possible for your high idle and the sudden drop to .5k rpm when accelerating)
-MAP sensor (could be the problem for the sudden drop in rpm)
-Faulty wiring (a sensor listed may have come loose or gotten torn recently)

after you check all those, then it means your engines bad and you should just scrap the whole car as is!
i was thinking maybe one of those sensors too but i have forgotten the spec voltage it measures


but my idle is fine when its running good and doesnt go up or down like most i heard of
Old 09-28-2010, 11:34 AM
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Default Re: 94 CX with DX motor - rpm drop then suddenly pick up accelerating

maybe clean your IACV??
Old 09-28-2010, 12:54 PM
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Default Re: 94 CX with DX motor - rpm drop then suddenly pick up accelerating

Originally Posted by bubbaparks2121
maybe clean your IACV??
the one that connects to the throttle body or the one behind the intake manifold?
Old 09-28-2010, 01:20 PM
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Default Re: 94 CX with DX motor - rpm drop then suddenly pick up accelerating

Just curious, when you did the swap what intake/exhaust manifold did you use? What ECU? Which injectors? May be unrelated but just curious
Old 09-28-2010, 01:30 PM
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Default Re: 94 CX with DX motor - rpm drop then suddenly pick up accelerating

Originally Posted by beginmyhonda
the one that connects to the throttle body or the one behind the intake manifold?
behind the intake manifold
Old 09-28-2010, 03:22 PM
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Default Re: 94 CX with DX motor - rpm drop then suddenly pick up accelerating

Originally Posted by HondaPartsHero
Just curious, when you did the swap what intake/exhaust manifold did you use? What ECU? Which injectors? May be unrelated but just curious
i did complete swap all stock nothing changed
the problem occured after i have driven it 30k miles which is now

Originally Posted by bubbaparks2121
behind the intake manifold
ok thanks
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