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Discussion Starter #1
When I'm crusin through town sometimes when I let off the gas and start coasting(downhill usually) My car will drop from like 2400 RPMS down to almost idle or 700 to 800 RPMS and then jump back up to about 1500 or 1600 RPMS. It does this everyonce in a while and not when I have been boosting or anything. The only mods I have are K&N FIPK and a Bosch Bypass valve. BTW I have my A/C hardwired to a toggle switch b/c it doesn't work but I have it turned off at nights b/c it is still cool at nights here. Don't know if that has any relevance but I thought I'd mention it. If anyone has any ideas or suggestions I'd like to hear em. Thanks Bill.
 

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Discussion Starter #2
Been off the forums for a few days anyone have any ideas?? Thanks Bill.
 

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Now with 0JZ
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are you auto or 5 speed?

Does it drop really really rapidly, then shoot up really fast? Or does it take its time going down and back up?
 

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Discussion Starter #4
are you auto or 5 speed?

Does it drop really really rapidly, then shoot up really fast? Or does it take its time going down and back up?
It's an Automatic. And yes it falls really fast then shoots back up quickly. It's done it to me a few times and its real hard to catch b/c it'll just drop down and when you look at the RPM gauge it shoots right back up. Feels like I let completely off the throttle.
 

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rockin the 60 trim
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yes!!! im not alone, i have the same problem!!! #1 do you have any type of boost controller/ shimmed wastegate, becuase i asked the same question and a man said that my ecu is reading boost cut due to a dirty sensor, but when im running 8psi it doesent do it but when im running 16 and up the rpms fall and then jump back.

so i dont no ive tryed cleaning everything and it still does it.
 

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Now with 0JZ
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It may either be your tranny shifting (which I doubt) or more likely, the ignitor.

If the ignitor doesn't fire, the tach doesn't get an RPM signal, and the needle jumps around.
 

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rockin the 60 trim
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the engine speed is actually falling, its really annoying to listen to with open down pipe too
 

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Discussion Starter #9
To answer all questions... I have no other mods than what I listed above in my first post. The engine speed is actually falling to this RPM and then jumping back. It feels like boost cut. Like someone just let off the throttle completely. It may be happening when I have my A/C button pushed. I haven't really paid that much attention. But my A/C does not work when the button is pushed that is why I have the compressor hard wired to the battery. It could be kicking in when I'm crusing through town and making my RPMs fall. It happens when I ease off the throttle a little; not all the way just a little. In town i'm usually in overdrive but sometimes it'll drop to third and i'll be running around 2400 RPMs. If you've ever drove a car with real dirty injectors and felt how draggy and lumpy it is that is the feeling I get when the RPMs drop. Any suggestions? PS sorry for the long ass post.
 

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Discussion Starter #10
Sorry haven't been on in a while again. Does anyone have any idea what could be causing this?? My cold Start injector is messed up and the car doesn't want to start cold. Could this have something to do with it? Thanks in advance Bill.
 

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NO SOUP 4 U
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Does this feel liek it happens at the same place in the throttle? Ive seen in some cases where the TPS gets a dead spot in it. I would pull the pig tail off and put a meter on your TPS and operate the throttle by hand or if you have long enough leads... bring the meter in the car or prop it up on the wind shield and move your throttle slowly. See if you notice a spot where you meter shows an open circuit.
Ive also seen grounds on the ECM (Cars Computer) having a bad ground or dirty plug.

Good Luck,

Wedge
 

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Shop Tech All Around Auto
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TPS maybe? I know that on Fords and Chevys, we can do a voltage test on the tps to find a dead spot. Key On Engine Off, at closed throttle the tps should read .5 to .75 volts (dc), and at WOT, should read around 5 volts. Going from closed throttle to WOT, the voltage should raise steadily from lowest to highest. If its got a dead spot, you'll see it drop to 0.00 in a certain spot, then continue where it left off at. Not sure where to do a voltage test on this tps, or whether it'll work the same or not. Gonna have to try it out...
 

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Discussion Starter #13
Hmm... I'll have to try that out and see what the results are. First I must find time. Between working at home and working at work i'm booked. Thanks Bill.
 

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Actually, I tested mine today to find what was what. I found that the brown wire and the white w/red stripe are where to perform the test I mentioned above.

Here's how the tsrm says to test the tps:
http://cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=FI&Page=101


My actual voltage readings were .47 in idle position, and 3.75 at wot, which has me wondering about my own tps now... Maybe someone else could check their's and see what readings they get?
 

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Discussion Starter #15
If I get the chance I'll check mine and let you know. Thanks Bill.
 

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Whoops, sorry Wedge, I didn't see your post ahead of mine until I scrolled through today. Guess I should learn to type faster(or watch t.v. less)....
 

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Discussion Starter #17
Also I was wondering what you guys thought about switching to synthetic oil? I was thinking of going to Royal purple. There used to be a thread on here somewhere where a guy was testing the different oils. But I can't seem to find it. Thanks Bill.
 
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