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MDWhite
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Mar 23, 2015, 12:38 PM
Post #1 of 19
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Too much power too soon
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2004 Hyundai Accent 1.6 DOHC. Has way too much power for accelerator position. Make it difficult to drive in traffic. (has 5-sp. man) Check Engine light not on, no computer codes. Just did a little experiment on hwy. -- cruising at steady 60mph, pedal down abt 10%, increase to 20% and held it. Got up to 85mph and was still accelerating slowly when I backed off. Something must be opening the throttle besides my right foot it seems to me. What could be doing this ??
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Discretesignals
Ultimate Carjunky
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Mar 23, 2015, 2:00 PM
Post #2 of 19
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Re: Too much power too soon
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Probably would be a good idea to have your mechanic take it for a ride to see exactly what your concern is.
Make sure that your floor mat isn't making contact with your accelerator pedal.
This throttle body is cable operated, so inspect the cables for damage or fraying. Make sure the throttle opens and closes without binding. A dirty throttle bore or sticking plate can cause jack rabbit starts. You could clean the throttle and bore with a tooth brush and cleaner to see if that helps out.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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MDWhite
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Mar 25, 2015, 4:52 PM
Post #3 of 19
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Re: Too much power too soon
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Thank you for your response. No, nothing sticking (that would likely cause idle problems) but your comments got me looking at that area and I found the throttle cable adjusting/lock nuts very loose. Got these this adjusted and properly tightened and that helped a lot. Still think the engine is out of spec though -- probably some clown has toyed with the computer at some point (I just bought this used). How would I determine if this is the case ?? I don't know much about these things, but have heard many cars, even an economy car like this have available aftermarket computer mods. I would like to get thisw back to stock.
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Discretesignals
Ultimate Carjunky
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Mar 25, 2015, 6:19 PM
Post #4 of 19
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Re: Too much power too soon
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Not sure what you mean by clowning with the computer. If for some reason they were able to alter the software in the computer, they would have either have flashed the EEPROM with some sort of modified calibration or would have piggy backed some sort of performance chip. I highly doubt it, but the only way you would be able to tell is by inspecting the PCM harness and looking for a piggy back or connecting up a high end scan tool and looking at the calibration number of the software flashed into the PCM.
Just curious, but have you had your mechanic take it for a spin?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Mar 25, 2015, 6:20 PM)
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MDWhite
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Mar 27, 2015, 7:27 PM
Post #5 of 19
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Re: Too much power too soon
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I believe there is a whole industry devoted to doing just those kinds of things with car computers, actually. But still seems like something else is controlling the throttle at times of acceleration. There is no way this is as stock. If that were the case very very few of them would have ever sold. I pretty much have full power at 1/3 accelerator. It ramps up very very quickly above abt 2000 rpm (or less) starting at abt 20% pedal. Makes it very hard to modulate precisely, esp. when dropping the clutch. Have driven over 1.5 million miles in man. trans cars so know what to expect.
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Discretesignals
Ultimate Carjunky
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Mar 27, 2015, 7:51 PM
Post #6 of 19
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Re: Too much power too soon
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Curious, but if you hold the accelerator pedal at 1/3 what is the position of the throttle blade?
You could loosen the throttle cable nut and then have someone hold the pedal to the floor. Then adjust the cable nut till the throttle blade just touches the wide open throttle position . That would probably set the cable correctly.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Mar 27, 2015, 7:58 PM)
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MDWhite
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Mar 31, 2015, 1:12 PM
Post #7 of 19
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Re: Too much power too soon
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I opened up the intake there to see if everything was OK and it seems to be. Interestingly there is a passage that bypasses the throttle valve that apparently is there for idle. If it is blocked the engine quickly dies, though it seems much wider (abt 1/2 in diameter) than I think would be needed to support idle. Someone suggested a throttle position sensor might be at fault here, I might try that. I should say that the engine does vary somewhat in its behavior (both when dropping the clutch and in general) in that it does not ramp up in power so wildly as I described and acts more normally with a gradual progression of power, though most of the time it is the former.
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Discretesignals
Ultimate Carjunky
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Mar 31, 2015, 4:39 PM
Post #8 of 19
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Re: Too much power too soon
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You could have a TPS issue, but a faulty TPS would cause hesitation, stumbling, and possible idle issues. You can sweep the TPS with a volt meter or lab scope to see if it has any dead spots. Not a common failure item.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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MDWhite
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Apr 22, 2015, 11:05 AM
Post #9 of 19
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Re: Too much power too soon
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Have two new things to report. First, I disconnected, cleaned, and reconnected a bunch of engine sensors (though none seemed particularly dirty or corroded) with engine off. Upon starting and running, I noticed a difference right away. It was much more driveable than before, though still not quite right. Just now the crazy power ramp-up happened a bit further down in the throttle, and was now probably a bit less rapid. Also picked up a good 2-3 mpg from this too. (I waited until I had gone through 3 tankfuls of gas to ascertain this. After the first subsequent fillup I thought the gauge must have been stuck.) But like I said still not really right. And then I went to change the sparkplugs recently I found my suspicions about the computer were correct. It has definitely been messed with. It is not firing the coils in stock order (and whoever put the wires on knew the right order to put them) I was lucky I noticed this before I got too far and lost this info. So this is where it stands now. Any further thoughts will be appreciated.
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Hammer Time
Ultimate Carjunky
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Apr 22, 2015, 11:39 AM
Post #10 of 19
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Re: Too much power too soon
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So, you're saying that the firing order was wrong all along and that caused you to have too much power too soon?
Were the wires connected to the wrong coil or just the wrong pole on a single coil?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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MDWhite
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Apr 24, 2015, 5:16 PM
Post #11 of 19
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Re: Too much power too soon
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No, of course not. It is because someone knew which coils (which are marked with the cylinder No.) went to which cylinders (now NOT the No. on the coil) that it wasn't (isn't) misfiring (in which case the car would have been inoperable). My point is the change in order is evidence of a computer reprogramming, which of course included many other modifications.
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Hammer Time
Ultimate Carjunky
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Apr 24, 2015, 5:19 PM
Post #12 of 19
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Re: Too much power too soon
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I don't know what you're smoking but you need to put the pipe down.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Discretesignals
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Apr 24, 2015, 6:25 PM
Post #13 of 19
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Re: Too much power too soon
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I'm confused. The firing order of that engine is going to be 1-3-4-2. That is built into the engine mechanically. Changing the software in the engine controller isn't going to change the mechanical design of the engine.
You can swap 1 and 4 or 2 and 3 plug wires, but you probably won't detect any difference in the running of the engine.
Not only does the spark have to occur in the correct firing order, but the valve timing and pistons' positions also determine the firing order in which combustion events occur:
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Apr 24, 2015, 6:36 PM)
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MDWhite
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Apr 25, 2015, 2:50 PM
Post #14 of 19
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Re: Too much power too soon
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Maybe I am assuming too much here. I assume a coil is only fired when needed, based on the signal from the camshaft pos. sensor (as processed and routed by the computer and its programming). Maybe they fire twice per cycle ? I don't know. Tell me. If you did what you described with an older car with a distributor it would be practically undriveable (in fact people have seriously damaged engines by misrouting the HT wires).
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Discretesignals
Ultimate Carjunky
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Apr 25, 2015, 3:06 PM
Post #15 of 19
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Re: Too much power too soon
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On your system, which is called a waste spark, each coil is fired twice in 720 degrees of crank rotation. This means that each cylinder will get a spark while its piston is near top dead center on both the exhaust and compression strokes.
Cylinders that share the same ignition coil are called companion cylinders. That means when one cylinder is coming up on compression stroke its companion is coming up on the exhaust stroke.
The engine computer determines when to fire the coil based on crankshaft position and speed which is provided by the crank shaft position sensor. The computer will also modify the ignition timing based on throttle position, engine load, engine temperature, and etc.
Your right, having spark plug wires switched on distributor systems can cause misfires and melt catalysts, but the engine would perform so badly you'd be a fool to drive on something like that.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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MDWhite
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Jun 28, 2015, 12:55 PM
Post #16 of 19
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Re: Too much power too soon
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Well I finally realized what is going on here. It is so obvious I don't know why I didn't see it sooner. The intake (the throttle valve I inspected before) is way too large for the engine size. Not any modification, just the way it was made. Overengineered idiocy (like firing spark plugs twice as often as needed). So they can claim say 5 HP more at like 5500 rpm or something (which I could drive the vehicle 100K mi and never use once) the low end is tough to control like it is, at least with the manual trans. Doesn't help that the car has some sort of a racing clutch in it either. I realized that in carbureted trim this engine (it is a descendent of the Mitsubishi 1600cc engine that debuted in the 1970 Dodge Colt) would like a 32x34 mm barrel arrangement with maybe half the cross sectional area this intake has. So of course when I have the pedal down about a third if the way the engine has nearly full power, at least at normal driving rpm's. Still I otherwise like the car, it has good performance and now in the warm weather driving it carefully I get abt 40mpg, which is what I got it for.
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Hammer Time
Ultimate Carjunky
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Jun 28, 2015, 4:20 PM
Post #17 of 19
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Re: Too much power too soon
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That's ridiculous. You've been watching too many cartoons.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Discretesignals
Ultimate Carjunky
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Jun 28, 2015, 6:21 PM
Post #18 of 19
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Re: Too much power too soon
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Unless the engine has been modified by someone, that throttle body and induction system is going to be designed to fit that engine by the manufacture. Maybe your trying to compare it to an old carbed engine that isn't as responsive.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Jun 28, 2015, 6:22 PM)
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MDWhite
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Jul 10, 2015, 1:43 PM
Post #19 of 19
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Re: Too much power too soon
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Yes, thanks for your reply. There is definitely some truth to that, but frankly I don't think it was just that much of a priority. What is it, 90% of cars are automatics now or something like that ? (at least in US). I just couldn't see how the engine was getting that much air, and now I know. Bear in mind this throttle, which is over 50mm in diameter, has TWICE the cross-sectional area of two 25mm chokes that the engine would typically be drawing through in carbed trim. It had been years since I held a carburetor in my hands and I kind of forgot what they were like. But the greatest difference between this engine and the older ones I mentioned is the 4V cylinder head this one has (I would count that as an even bigger difference than the fuel injection vs. carburetion) . They would be remiss if they didn't adapt induction in other ways to take advantage of this, I know. I would like to drive this in automatic trim, that would be really nice I think now (I would not have said that about an older small car). Thats what this is really designed for, I think. Though it wouldn't have been that hard to, say, have the throttle cable wrap on a cam instead of on a simple cylinder to give a variable opening rate in the manual trans cars. And at pedal down they would have the throttle open so they could get that final peak of power. Now I was told when I got the car that it had had a recent clutch replacement and I didn't have any trouble believing that. Very touchy, very grabby. I thought this would fade with use and it really hasn't. I should have mentioned that it is practically impossible to start the car on a hill without spinning the wheels some. I have a choice of either that or stalling the engine, basically. Otherwise I like the car, though I can't understand why on earth anyone would put power steering in such a small car; if I keep it I am going to look into putting in an older model's manual rack and get back that feel of the road I like.
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