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  #1  
Old 05-07-2004, 02:31 AM
Phil Hill Phil Hill is offline
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Elastic throttle ??

First senaro : You're at a junction, foot brake applied, in Drive ready to go, waiting for your opportunity to pull out. A gap appears so you release the brake and gently press the throttle, and the car crawls forwards. You press the throttle some more, still nothing. You apply more throttle, and then all hell breaks loose, you shoot forwards in a flurry of revs.

Second senaro : You're proceeding at a steady speed, on light throttle. Either you are about to overtake or anticipate a change in load, like an incline. Again you gently apply some throttle, and not much happens, you press a bit further but still little or no response from the engine room. Eventually the engine obliges your request in a "boot in the pants" kind of way.

There is no apparent transmission "slippage", no "flare" in revs, in fact the engine revs don't increase initially then do so all in a rush. There are no problems with the engine, it starts easily, is not down on power, does not burn oil, runs correct temperature etc, and behaves normally except for this fault.

My thinking is this is likely to be a sensor problem, most likely a worn TPS, so I've tried another one. Accepting that I didn't exactly go to town with setting it up, and this alternate TPS isn't new so may be similarly worn, it displays similar symptoms, although it is better at initial pull away from idle. We normally run "preimum" fuel (Shell Otimax or Super Unleaded @ 97-98 Ron), I didn't leave the battery disconnected to "clear" the "learned" settings in the ECU.

Am I barking up the wrong tree ?? Before I shell out on a new TPS should I be looking at something else, like O2 sensors, MAF sensor, EGR valves ?? On initial start up we get 16 "flashes" of the Power light but I've not read the actual codes. Any thoughts guys ?? Thanks !!
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  #2  
Old 05-07-2004, 02:57 AM
deruvian
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The 16 flashes indicate that the TCU has stored a transmission error code in the ECU's memory. You definitely need to check that ASAP. Do a search for the TCU error codes. There is a lot of info available. Try checking svx-iw.com as well.

Do you have any kind of shift kit installed? Maybe the one from smallcar.com?

I'm not sure that the UK SVXen had this problem, but in the earlier models (up to a manufacture date of 10/93), there was a "noise suppresser" ferrite bead inside the ECU. It is a small blackish/brownish bead that encases a small wire. This bead was designed to limit throttle in off-the-line acceleration and very quick jumps to WOT when already cruising down the road. Eventually, simply due to the bead's nature (the fact that it essentially absorbs current), it can... uhm... go bad, I suppose you could say.

The fix to this you need to remove the ECU, open it up, and carefully crush the bead without breaking the wire. It's a very easy mod, and lots of us here have done it. You might want to search for the ECU bead crush mod, as it is commonly called around here. There's also a lot of info for that.
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  #3  
Old 05-07-2004, 03:16 AM
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Sonar Sonar is offline
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Question Phil, if you cruise steady at say 20mph with cold engine, does the engine sort of vary it's power a bit , just detectable (sorry but my english is bad), sort of slight up and down and up and down in power at roughly 1 sec. intervals ?

(Hope that was understandable )

The reason I ask is that it could be a lean condition on the engine, and if running lean, it could do all above.

/Sonny
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Last edited by Sonar; 05-07-2004 at 03:19 AM.
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  #4  
Old 05-07-2004, 03:51 AM
Phil Hill Phil Hill is offline
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Sonar

Yes, know what you mean, and yes it does that sometimes. Perhaps the O2 (lambda) sensor have become "poisoned" by 86k miles worth of exhaust gases.........

deruvian

Vehicle is a '96 so as I understand it it shouldn't have the ferrite bead in the TCU. Vehicle is completely stock, no shift kits or free-flow filters or anything like. I'll try to read out the error codes and see what that says. I'm sure I did read them out once before, but can't remember now.
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  #5  
Old 05-07-2004, 05:44 AM
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n00b on demand n00b on demand is offline
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the same happens to my car when the engine is cold....ill give it some gas and it wont go and then it just bursts out like someone kicked it....if i let it warm up to its full operating temp then it never happens.....sometimes when im crusing the rpms drop to like 1.5 like it went into a 5th gear or something and then u have to press the throttle a little bit and it downshifts to get more power and the rpms jump.....i have been told this car has a problem with cold weather hesitation....but who knows...the SVX has alot of strange problems and weirdness ive never seen before haha......especially in cold weather!
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  #6  
Old 05-07-2004, 01:53 PM
deruvian
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Quote:
Originally posted by soobiesvx93
the same happens to my car when the engine is cold....ill give it some gas and it wont go and then it just bursts out like someone kicked it....if i let it warm up to its full operating temp then it never happens.....sometimes when im crusing the rpms drop to like 1.5 like it went into a 5th gear or something and then u have to press the throttle a little bit and it downshifts to get more power and the rpms jump.....i have been told this car has a problem with cold weather hesitation....but who knows...the SVX has alot of strange problems and weirdness ive never seen before haha......especially in cold weather!
That would be your torque converter locking up There is a lowering in the RPM equal to approximately 300 - 500 revs. Notice that this usually happens at about 50mph, and that when you apply light throttle you still accelerate without seeing a change in RPMs. Apply liberal throttle, and the TC either unlocks or the tranny downshifts to third.
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  #7  
Old 05-07-2004, 08:09 PM
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n00b on demand n00b on demand is offline
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YESSSS!!! finally.....thats exactly what happens to my car...i speed up and no change in the RPM's....is this a problem or is it fine the way it is?
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  #8  
Old 05-07-2004, 11:07 PM
deruvian
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Originally posted by soobiesvx93
YESSSS!!! finally.....thats exactly what happens to my car...i speed up and no change in the RPM's....is this a problem or is it fine the way it is?
The whole speeding up with no change in RPM thing should only happen in 4th gear. When I say "4th", I mean when the tranny is in 4th... Not just when the gear selector is in "D". Typically, top gear and torque converter lockup mean that you're going over 50mph.

It's fine the way it is, so long as it only does it with very light throttle. Moderatel to liberal throttle application should cause the TC to unlock, or the tranny to downshift. It's supposed to do that.
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  #9  
Old 05-08-2004, 07:49 AM
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Have you cleaned the throttle body recently? It might help.
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  #10  
Old 05-11-2004, 01:32 AM
Phil Hill Phil Hill is offline
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I've not cleaned the throttle body yet, I have got some de-greaser kinking about though. I'm not sure how this would help unless the throttle spindle is sticking, which I guess possible given the dual control mechanisim for the cruse control.

Is it better to remove the throttle body from the intake and clean on the bench, or does anyone have a pet method of keeping the butterfly's open while cleaning ??
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  #11  
Old 05-11-2004, 11:37 AM
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Some people take it off. I used a screw driver to hold it open and wiped it out with solvent on paper towels. It may also be the TPS.
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