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Discussion Starter · #1 ·
Greetings from Slovenia!

Accent 2004 1.3l SOHC

I have a problem, when i slowly accelerate my car shakes (car stumbles but it stil accelerates normaly, it is similar like misfire) from 1500rpm to 2200rpm (just in this area, higher revs is all normal).
No trouble codes is found, car works great, i just have this problem.

When i am driving in 5th gear at 2200 rpm it you can feel that shaking operation it is small but it is annoying.

I have changed:
- air filter
- gas filter
- spark plugs 10k miles ago.
- Spark cables

I changed also TP sensor, MAP sensor, i check for vacuum leaks, in fuel tank for bad connection of fuel pump.

I am out of ideas. Can it be that my fuel pressure regulator is faulty or maybe injector (mechanical), bad ground connection.

Car runs great at idle, it goes over 100mph without any problems, great millage. Just that shaking is very annoying.
I went to a dealer no trouble code, everything is ok. Yeah wright.
Please give me any suggestion what i can look for. It seem it is something mechanical, but i don't know what.
Please help.

Thanks

Bostjan
 

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Does it work properly at full throttle between 1500 and 2200? Also, take out the plugs and replace them with NGK G power plugs. They have a small diameter center electrode. Gap them 5 thousands UNDER the recommended gap. This will insure that you are getting the proper spark. I had a lot of part throttle problems on my 99 Accent until I did this. I don't really think that the coil packs put out enough voltage to fire the plugs properly.
 

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Discussion Starter · #3 ·
Hi!
Thanks for the reply. I tried changing spark plugs with original ones brand NEW, bougt them today. Not even a small diference.

When i press full throttle the car accelerates normaly just between 1500 and 2200 rpm is not smooth it shakes like somebody would take the spark for a fraction of a second away. I am not experiencing eny power loss.

I also tried today changing both ignition coils - no difference .
Then i unpluged (one at the time) EVAP and PCV valve, then i unpluged O2 sensor bank 1 - no diference.
If you unplug 02 sensor bank 1 the computer takes a reference point to make mixture of air/fuel
I have also checket all ground connections they are all OK.

I am still thinking of fuel pressure regulator, but how to test it?

I am thinking if it was injector (mechanical fault) i would have problem at idle running poorly on 3 cylindres if it was constantly closed then poor acceleration, or other case, running rich, smell of petrol in exaust, it would run good on high revs if injector would be open. Am i wrong?

Hope for new ideas?
 

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If you had low fuel pressure it would get worse at high RPM with full throttle. I would have someone read the ECU when the engine is missing and check the long and short term fuel trim values. They should be out of range if the fuel pressure is incorrect. It is easy enough to buy a fuel pressure gauge and see if the pressure changes when the engine starts to miss.
 

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You have to admit if you have low fuel pressure the short term trim will show it as the ECM tries to compensate for the problem.
 

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Discussion Starter · #8 ·
Hi!
I do not understand what you mean to say with this. For diagnostic tools i have available Launch Diagun (me and my 3 friends bought it together).

Witch parameters must i look for?

Is this normal, at idle when i press throttle and i am looking injection times for all 4 cylinders and first says 4.5 ms other three 10.2 ms i repeat that several times and on cylinder 1 and 4 the times change between 4.5 ms to 10.2 ms.
Cylinders two and three are constant at 10.2 ms.
 

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All of the injector times should be the same and should change with engine load. If you can get a friend to read the tool while you are driving, check that all the injector times are the same and change as you press down on the pedal and the engine puts out more power. Make sure that you check the times in that 1500 to 2200 range that you are having trouble with and compare the readings with rpm values where the engine is working properly.
 

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Discussion Starter · #10 ·
Hey too all!

Last week i changed all 4 injectiors and surprise no difference at all. CRAP, back to the beginning.

I have to check more electrical connectors, or can it be, that my speed sensor on the transmission is failing?

And one more question, where i get the RPM reading (on instrument cluster) from? Is it from alternator?
 

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that sucks, u need to stop buying **** and isolate this problem.... i know this may sound dumb but have u done a compression test on all cyl's? if u dont know how ill tell you exactly what to do.... but if one injector says 4.5ms.......... id look into that maybe u need a ECU, i know its very unlikely but they can do dumb stuff when they fail, and a low ms would maybe cause a misfire at lower rpm.

lol the only time i ever had this problem with my car at 1500-2200 like u said, was when 1 of my spark plugs had a tiny crack in the white insulation.
 

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Discussion Starter · #12 ·
Hi!

Thanks for the reply. Just for the record, luckaly i got a frend, he ownes a auto junkyard, so i try it then i buy it.

Compression test is OK.
 
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