rags Posted June 10, 2007 Share Posted June 10, 2007 Guy's, I've been having trouble tuning for a while now and yesterday I found my TPS wasn't working correctly with dead spots throughout the sweep. Well today I picked up a 240SX TPS (wrong one, 2 connectors) and after playing with it to figure out which connector was the pot connector, I get it hooked up again. Now my problem is WOT voltage which I think is way too low. I have 4.91 volts at the 5 volt pin but can only muster 2.3 volts at WOT. And yes I am making sure the TPS is turned al the way. Shouldn't I be seeing 4.91 volts? Is this TPS bad or am I missing something? As always, any help is greatly appreciated. Joe Quote Link to comment Share on other sites More sharing options...
Thumper Posted June 10, 2007 Share Posted June 10, 2007 Sounds like a bad tps. You should see atleast low 4's to high 4's to get a good accurate throttle position. Also as you know no deadspots. Quote Link to comment Share on other sites More sharing options...
TimZ Posted June 12, 2007 Share Posted June 12, 2007 Guy's, I've been having trouble tuning for a while now and yesterday I found my TPS wasn't working correctly with dead spots throughout the sweep. Well today I picked up a 240SX TPS (wrong one, 2 connectors) and after playing with it to figure out which connector was the pot connector, I get it hooked up again. Now my problem is WOT voltage which I think is way too low. I have 4.91 volts at the 5 volt pin but can only muster 2.3 volts at WOT. And yes I am making sure the TPS is turned al the way. Shouldn't I be seeing 4.91 volts? Is this TPS bad or am I missing something? As always, any help is greatly appreciated. Joe How many pins are on the connector that you are using and how did you determine which one was which? Also, does the voltage change linearly with throttle opening now? Aside from the voltage being lower than you expected, does the voltage look like what you would expect? If your throttle body wasn't originally from a 240sx, it's possible that it just doesn't move the tps through the same amount of travel. For instance, on my TWMs, the GM tps only reads from ~.75V closed to ~3.5V WOT. Quote Link to comment Share on other sites More sharing options...
rags Posted June 12, 2007 Author Share Posted June 12, 2007 Thanks for the reply Tim. The throttle body is from (I think) a 240SX. I have 3 pins in each connector and I used an Ohm meter to determine which connector to use. Of course, the one I needed to use was not the same connector type as I was using on the original. The potentiometer was on the pigtail and the connector on the body of the TPS worked like an old 280Z TPS with 3 positions. This is the original. The voltage change is linear but still doesn't look right. At closed throttle I have no voltage so the software will always show the failed sensor low value, what ever I set it at. Also, it seems the TPS doesn't "turn on until about 1/4 throttle which is way past the adjustability of the TPS. Once it reaches the point of turning on the voltage change is linear up to 3.2 volts. My patients has worn thin and I've thrown in the towel. This Thursday the car goes to Bob Ida for a new TPS and a dyno tune. If I can afford to keep by broadband after that bill I'll let everyone know how I made out. Joe Quote Link to comment Share on other sites More sharing options...
z-ya Posted June 12, 2007 Share Posted June 12, 2007 I never tuned a Tech II, but there must be a way to calibrate the TPS to the system. Check your manual. The middle pin of the connector should go to the ECU. One of the other pins should have 5V on it. The other should be ground. You need to determine the proper polarity. Use an Ohm meter to check this. At idle, the resistance between ground and the middle pin should be close to zero. At WOT, the resistance should be maximum (like 5KOhm or so). Quote Link to comment Share on other sites More sharing options...
RB26powered74zcar Posted June 12, 2007 Share Posted June 12, 2007 I had that prob once with that TPS What I did was use a larger drill bit than the holes in the TPS for attachment, and make them oval/oblong shaped so I could adjust the TPS... it worked for me.... Quote Link to comment Share on other sites More sharing options...
TimZ Posted June 12, 2007 Share Posted June 12, 2007 I had that prob once with that TPS What I did was use a larger drill bit than the holes in the TPS for attachment, and make them oval/oblong shaped so I could adjust the TPS... it worked for me.... If you take the TPS off the throttle body and rotate its shaft input, you should see voltage changing linearly from 0 to 5V. It sounds like the d-shape on the TB shaft isn't lining up properly with the one in the TPS. If this is the case, you could probably do like Joel suggested and modify the tps. Quote Link to comment Share on other sites More sharing options...
rags Posted June 12, 2007 Author Share Posted June 12, 2007 Hi Joel, I actually have a backing plate from an old 280Z TPS bolted to the back of this TPS so I can use the slots on it for adjustment. Also, I might not have explained myself correctly. The original TPS did work correctly at one time. I just noticed the dead spots in it after I was having trouble tuning. I bought the 240sx TPS and have had nothing but trouble with it. That's the reason for ordering a new TPS from E-motive and sending the car to Ida's for the tuning. Pete, Yes, I have checked the polarity. I get an infinite reading at idle until 1/4 throttle between ground and tps signal connections, but I will check again tonight when I get home. Tim, That is how the original worked with the exception of a few places where it would drop down to 0. The new one is 0 volts for 1/4 of the rotation before going linear to 3.2v and then WOT back to 0v again. Joe Quote Link to comment Share on other sites More sharing options...
RB26powered74zcar Posted June 12, 2007 Share Posted June 12, 2007 I understand now Joe. I've also had that same dead spot problem with that sensor...lol. I've ended up using three of them in a 10 yr period. I now use one like the other pic you posted, that came on my q45 90mm TB. Good luck to you with the new TPS and tune! Quote Link to comment Share on other sites More sharing options...
rags Posted June 12, 2007 Author Share Posted June 12, 2007 Joel, When you used the Q TPS did you also have to use the pigtail connection? It looks like it from your pictures but I want to make sure. Joe Uh oh, now I see one that looks like your using the connector that is on the TPS itself. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted June 12, 2007 Share Posted June 12, 2007 I'm using that first sensor from a 240SX on my MS-II setup and it is linear with no dead spots. I am using the pigtail wires. I don't know the voltage numbers off hand but I calibrate it by stepping on the pedal in calibration mode. Quote Link to comment Share on other sites More sharing options...
rags Posted June 12, 2007 Author Share Posted June 12, 2007 Well I just got home and had to check the "new" 240sx TPS. It has been confirmed it's screwed. I opened it up to see what's going on. It seems as soon as the 3 position portion of the TPS goes to WOT, the pigtail portion drops to 0 volts. The sweep before WOT seems to work correctly. I am just going to use the one with the dead spots to get the car down to Ida's. I told them the TPS is NG and we will change it with the same type proir to tuning. I really like how the 240sx TPS looks and will still look into changing it. Thanks for all the suggestions guys. I really appreciate it. Joe Quote Link to comment Share on other sites More sharing options...
rags Posted June 16, 2007 Author Share Posted June 16, 2007 Well I took the car the 55 miles to Bob Ida's place to have it tuned. What an experience the drive down was. Rush hour traffic, bumper to bumper for almost 2 hours on a poorly tuned car is NO fun. And after $450 the car is still NOT tuned! But I did find out why I was having so much trouble tuning and it wasn't only because of the bad TPS. We did change the TPS and get the car strapped to the dyno only to see the car go full lean (>17-1?) by 4k at 10 lbs of boost! A look at the the data shows fuel pressure steadily dropped off. We initially thought it was a FPR issue because I'm using an Aeromotive A1000 pump with 3/8" feed line. Plenty big enough. After I got it home and spent some time on the phone with Aeromotive it was determined the pump wasn't putting out what it was supposed to be putting out. I opened the pump and found a broken o-ring between the pump and pump housing. Aeormotive wanted $210 to rebuild it so I ordered a new 225lph Walbro. I hope that one is big enough. So how did it do on my crappy tune before it got shut down? 210rwhp and 302rwtq. I actually think that's promissing considering there was no fuel, only 10 lbs of boost, and the run was stopped at 4K. What do you think guys? I should have done this 2 years ago! Joe Quote Link to comment Share on other sites More sharing options...
z-ya Posted June 17, 2007 Share Posted June 17, 2007 Get your fuel pressure issue fixed, and get it back on the dyno. $450, for how many hours? Seems kind of steep considering that you could do many runs because of the fuel pressure issue. The Walbro pump should work fine. Quote Link to comment Share on other sites More sharing options...
rags Posted June 26, 2007 Author Share Posted June 26, 2007 Woohoo! After much trouble with sellers on the web who take payment but don't ship product, I finally received a new fuel pump in the mail yesterday. I just couldn't bring myself to spend $350 on another Aeromotive pump so I went with a Walbro. All I can say is I should have listened to all of you a long time ago. This pump just plain works! Without making any other changes except for the pump replacement the car is running 100% better. What I was attributing to a poor tune was not the tune at all but a bad pump. Embarrassed? To say the least! I spent all of 20 minutes last night fine tuning IOT and TOG setting and I'm amazed at the way the car responded. Now I can't wait to get back to the dyno! Joe Quote Link to comment Share on other sites More sharing options...
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