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Bad acceleration and hard starting once warmed up
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Steve2234
New User
Nov 14, 2011, 3:53 AM
Post #1 of 4
(2121 views)
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Bad acceleration and hard starting once warmed up
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I have a Nissan bluebird 1993 with a SR20DE. The engine starts perfectly when cold, Once warmed up it seems to have a problem starting. It will rev up to the normal rev and then instantly drop down to say 250 the fluctuate a little until it reaches 750rpm again. Also when driving. I notice when it is cold it's acceleration is much better and when it's cold it starts perfectly. I have replaced leads, the MAF and also the throttle position sensor and it has gotten a little bit better. I have also cleaned the injectors too. I have left the battery off for some time thinking it will reset everything, but nothing has worked so far. I thought it might possibly be the oxygen sensor, but I have no idea, if someone could help me it would be most appreciated
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Nov 14, 2011, 4:19 AM
Post #2 of 4
(2108 views)
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Re: Bad acceleration and hard starting once warmed up
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You just lost chance of getting codes leaving battery disconnected. Tossing parts until you stumble on a problem is an expensive approach.
Is it running rich (you could probably smell it at tail-pipe) when warm?
I'd be testing catalytic converter for poor flow and coolant temp sensor with wiring connections that determines how much fuel to deliver. Vacuum leaks in the picture also and other items,
T
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Steve2234
New User
Nov 19, 2011, 1:52 AM
Post #3 of 4
(2040 views)
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Re: Bad acceleration and hard starting once warmed up
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Ok i just bought myself a computer diagnostic thing. Whats the best software to use to diagnose problems?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Nov 19, 2011, 2:38 AM
Post #4 of 4
(2033 views)
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Re: Bad acceleration and hard starting once warmed up
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If clear instructions on interpretation of what it comes up with didn't come with what you bought it's chiefly useless to me anyway. Vehicles do get different specs depending on expected country of destination. Probably not a lot of if any software but just a small book and counting blinks of a "check engine light" or something like it.
General on readings for this old of a vehicle and may not apply to this one. The blinks are interpreted to a #. First series and last series if anything is just verifying that it's communicating, then on to any info, if any that's stored. This now 19ish year old car is NOT monitoring all that much compared to newer vehicles.
By description this seems like an exhaust restriction. Computer of 1993 might not pick up on that and any results are still really only telling you area of a problem.
The most common (if so) exhaust restriction is the catalytic converter. The bigger question is if that is the trouble is if it was/is the cause of this behaviour or the result of another problem. At the age now will take some judgement on your part.
A couple ways to test for exhaust restrictions.
1. Loosen an exhaust part before converter and if the problem of power and starting is restored strongly suggests plugged up converter. If that trick is attempted beware of where hot exhaust may go and burn something you don't want it to.
2. With a "T" and vacuum gauge to the actual manifold vacuum such that item it serves still gets vacuum too should read about 18Hg at idle and about the same at 2,000 RPMs without load. If much lower at the higher RPMs it's struggling to pass thru exhaust but where isn't clear yet.
I may be steering you in the wrong direction but some testing to at least rule that out would be nice. Yes, have witnessed restrictions that allow more flow when cold, then tighten up when warm - all were converters with cars that had them at all.
Test away. Try hard to pin point the trouble so you don't waste good parts,
T
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