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Discussion Starter #1
Had my car tuned over the summer. Seemed like it was running pretty good when I first got it back. Now I am having big problems with lean spikes at part throttle. If I am just cruising and hardly step on the pedal it will go lean to the point of pegging my wideband lean. Car stumbles and feels really bad. If I get a little deeper in the peddle it will clean up and be fine. I have an ms2 computer and I data logged it and between 10% and 15% tps is where it happens. I tried fattening up the fuel table and it did not help. It’s just weird how this just started happening and it has been getting worse and worse. Could my tps be going bad and causing this? Anyone have any ideas?
 

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if the ecm is seeing TPS voltage going to closed throttle position

does it is go into fuel cut off?

have you measured tps voltage? what does the log show for voltage?
 

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Discussion Starter #3
I’ll have to check the log for voltage. I’m new to this whole thing still trying to learn it all. What would tell me if it’s going into fuel cut off? It happens at just hardly stepping on the pedal and if I get into the pedal more it will clear its self up.
 

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Discussion Starter #5
Ok I’ll give it a shot. Would that also cause the car to sputter when the lean conditions happen. I just wanted to make sure I explained everything correctly. I don’t think I’m getting just a false reading. Or if there was a false reading would it cause something like that to happen? Sorry if this is stupid questions I never did any tuning and I’m trying to learn as much as I can
 

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I’ll have to check the log for voltage. I’m new to this whole thing still trying to learn it all. What would tell me if it’s going into fuel cut off? It happens at just hardly stepping on the pedal and if I get into the pedal more it will clear its self up.
I have no idea with your strategy, but if you are closing the throttle on stock one, the fuel gets cut off during decel


report the voltage log, NOT this % stuff
 

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Discussion Starter #7
Ok I will check the log this weekend
 

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Discussion Starter #8
I pulled up my log this morning the only info I can find about tps is labeled tps and tpsdot

During this lean condition
Tps-13.4
Tpsdot-12.6

It also shows on the log that at one point my lowest tps was -5.0%. I had noticed that previously and tried to recalibrate the tps and that did not help. If there is any other info from the log that could help let me know. I got the -5 reading after getting on the throttle then letting off quick
 

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what are the units?

negative tps is odd, no?

lets forget this processed data, and stick a volt meter on the signal and sensor ground and measure directly what is happening
 

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Discussion Starter #10
When I test voltage on that can I do it with the car off key on just parked or do I need to measure the voltage while actually driving
 

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Discussion Starter #13
Yeah your right I can check the filter. Everything is brand new but who knows. My fuel pressure never drops though at all but definitely with a shot. As I said when the car was first tuned it was fine then it all of a sudden just started happening and seemed to be getting worse and worse
 

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when something fails

you will get a problem that seems to happen out of nowhere, that is to be expected
 

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Discussion Starter #15
Yeah I need to check the tps voltage this weekend and I’ll check the fuel filter. Pretty sure the pump is good. I thought just maybe it could have been something in the tune because I had it tuned when it was real hot now the temperature has been dropping and I thought maybe it was a correlation to the weather. Like I said I don’t know much about tuning but I would assume that should not be an issue
 

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Discussion Starter #16
Had a min today to check the voltage. It was .88, tomorrow I will have someone sweep the pedal for me and see how it looks
 

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you want to see it while driving, logging it preferably
 

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Discussion Starter #18
I just don’t know if that’s an option in the data log I didn’t see anything for it
 

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I am sure it has programmable inputs

you have to program it, that is what MS is all about
 

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Discussion Starter #20
Checked out all the voltages and tps seems to be fine. Fuel filter is good so I don’t know really where to go from here
 
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