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Old 01-29-2005, 06:10 PM
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Weekly Fuel injection puzzler #2

lol, bosses car is acting up again. She swears that I "fixed it" last night, but I don't think I did.

So the problem with it is that it had like zero power. Again, I just drove it to see how it felt. It basically accelerated like you had your foot a 1/4 inch on the throttle no matter how hard you pushed the peddal? I rapped it up a couple of times, didn't smell rich or anything. It accelerated very smoothly, just didn't recognize the amount of throttle you had. If you floored it, it would slowly accelerate, hold its shift like its supposed to, but give no throttle. Keep in mind, it started very easily, ran smoothly and well. If I had to guess, I would say the AF ratio was right on the money, computer driven of course.

SO I figure it must be a sensor of some sort. I got under the hood and felt around the throttle linkage to see if maybe a trigger was being held up by the throttle body. I rapped it a couple of times and we went inside to our company function. She said when she drove home the car was all better?

So what's the deal? Throttle position sensor gone bad or something? If that's the case, the trans uses a separate unit (like a kickdown cable) right?

Am I right on the money on this one, or off?

1994 volvo turbo inline 5 cyl.

K

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Old 01-29-2005, 06:22 PM
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A buddy of mine had a Mitsubishi eclipse that didthe same thing he put a new throttle position sensor on there and it fixed it. About the trans cable im not sure on that.
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Old 01-29-2005, 08:37 PM
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If you surf on this site you will find the part where it tell's you how to check it with a OHM meter. Has all cars and diesel motors.
If something was bad the OBD should have the idiot light on or a code to check. Maybe a good wash with some carb cleaner would help with some MMO in the gas. Gas filter can be pluged.
http://www.troublecodes.net/
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Old 01-29-2005, 08:43 PM
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yeah, I don't have the car or an ohm meter nearby. It seems to be intermitantly bad, so probably, like you're sying, just needs to be cleaned or something-

K
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Old 01-29-2005, 09:30 PM
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Killer,I do not know on that car,but a TPS should store some sort of fault code.What type of ignition is her car?If it has individual coil packs for each cylinder,one or more may be dropping after they are warmed up. She drove it home after it cooled down and it seemed to be ok. A coil pack will not throw a code. Find out what the resistence is and when it gets to acting funny check the coils.Hope that helps you some man.
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Old 01-29-2005, 09:50 PM
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The coil pack may not set off a code but an intermittent misfire will. Tell her to go to a parts store and get them to plug in the code reader and write the codes down. That'll give you an idead where to look if the TPS is fine.

Larry
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Old 01-29-2005, 10:55 PM
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Typically TPS is used for acceleration enrichment only. An alphaN type setup trys to run the engine off of TPS alone, but I dont think any oems used anything like this. It just does not work well. My bet would be in the fuel filter. Seems like if that was the case, however, when you punched it the car would stumble and backfire.

Chris
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Old 01-29-2005, 11:42 PM
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It could also be the VSS. it won't show up with the car setting still, but will under load going down the road. It should set a code though.
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Old 01-30-2005, 02:09 AM
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My boss had a Volvo with the same problem. It ran perfectly but acceleration crawled. It turned out to be the ecm. Just like a rev limiter can prohibit your car from going over a certain speed while runing perfectly fine, so can the ecm fail and produce the same effects at lower than normal speeds. Got one at a junk yard for 150 dollars and it ran fine ever since. Rick BTW Loved your troll kill. lol
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Old 01-30-2005, 03:53 AM
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lol, thanks!

Yeah its not the fuel filter or ignition. I said it ran really smoothly, its obviously the computer thinking its at a lower throttle. If it were a mechanical problem or a fuel problem we'd have misfires, however we have none of that. Thanks for the help, I'm pretty sure its a TPS.

K
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Old 01-30-2005, 06:16 AM
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You are not understanding the TPS sensor role in the system. The ECU changes fuel pulse based on the MAP,IAT, and engine speed. The MAP sensor reflects what is happening with the throttle position. ECU in turn changes timing based on similiar parameters and the engine revs up. TPS has few other functions, but the main one is for the ECU to produce a "accelerator pump" shot when the throttle position changes rapidly. Typically this is a time/distance ratio.

Before you go changing anything, I would get the codes read. If it is the TPS, it should show up. If there are no codes, I would not be surprised if it was the ECU. It almost sounds to me like it is running in "limp home" mode. Sounds silly, but this is usually a backup set of parameters so if something goes really wrong you can "limp home".

Chris
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Old 01-30-2005, 06:31 AM
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It's the engine gremlin. These little critters live in engines during the cold weather to stay out of the elements. They get bored and do random things to the motor for entertainment. When you rapped on the engine it understood the warning that you considering taking apart his winter environment and cut it out for awhile.





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Old 01-30-2005, 02:33 PM
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Before you go changing anything, I would get the codes read. If it is the TPS, it should show up. If there are no codes, I would not be surprised if it was the ECU. It almost sounds to me like it is running in "limp home" mode. Sounds silly, but this is usually a backup set of parameters so if something goes really wrong you can "limp home".

Chris [/B][/QUOTE] Isn't that what i just said, just not so techically?
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Old 01-30-2005, 03:23 PM
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Oh, I'm not going to be doing the work more than likely. I'm just trying to think of things to help out a little bit. There's got to be an electronic cause to this, maybe MAF if its not the TPS. Its also odd that its such a smooth running problem, lol. I immagine that the motor knows how much air its getting, because it doesn't backfire or anything. Its also odd that when I messed with the thottle body it went away. THis car, as I mentioned, is turbo equipped, I wonder if it has much to do with that? The boost gauge wasn't building much, but at 1/4 throttle as the motor "thought" it was at, I wouldn't immage it would-

K
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Old 01-30-2005, 03:52 PM
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Is there any possibility that the turbine was iced over or the water doesn't have enough anti-freeze(if it's a water cooler turbo)?
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