moto_ty Posted December 6, 2007 Report Share Posted December 6, 2007 ok well here's a rundown of whats going on when it's cold it start pretty easily. but as soon as you shut it off then it don't want to start at all. but if you push the petal to the floor while trying to start it, it goes. when it is running and you tap the gas, it has a pretty good hesitation to it, almost wants to die. so i took it to get it diagnosed, and the mechanic said it was the computer. so i bought a new one, and it don't even start with the new one. so i put the old one back on and started screwing around. i figured out when its running, and i unplugged the TPS it runs perfect. but shut it off it dont start. i am quickly running out of ideas here.. i need help!!! any words of wisdom? Quote Link to comment Share on other sites More sharing options...
joey b Posted December 6, 2007 Report Share Posted December 6, 2007 Does it reek of gas? Possibly the temp sensor has failed. I'm not sure of the resistance values, but using those you can determine the value that is being sent to the computer. If the temp sensor fails the computer thinks that the engine is -40* and dumps gasoline into the engine. At the colder temperatures it may be able to run, but when it gets warmer the A/F mixture becomes too rich to run. Does the car remain running once it is started? Quote Link to comment Share on other sites More sharing options...
moto_ty Posted December 6, 2007 Author Report Share Posted December 6, 2007 yeah it stays running. and the temp goes way high, but fans don't kick on. Quote Link to comment Share on other sites More sharing options...
BXX Posted December 6, 2007 Report Share Posted December 6, 2007 sounds like a bad temp sensor to me as well... Quote Link to comment Share on other sites More sharing options...
joey b Posted December 6, 2007 Report Share Posted December 6, 2007 Next step I would suggest is to see what kind of resistance you get from the TPS. Back probe it both cold and warm and see what values you get. Or you could back probe and get an output voltage. Just probe the back of the wire harness with a voltmeter. Touch the other end to ground. One wire will give you no value, one will give you a 5 volt value, and the other will be a variable value. Once again, I do not know the expected values, but I think I may be able to find them. Quote Link to comment Share on other sites More sharing options...
BXX Posted December 6, 2007 Report Share Posted December 6, 2007 thats not the resistance of the tps... You gotta test for proper voltage by backprobing it as you described. You will have your ground, 5V+ reference in, and then the signal out to the ECM... Check the signal out voltages against the spec that they should be.. Quote Link to comment Share on other sites More sharing options...
CNBZ34 Posted December 6, 2007 Report Share Posted December 6, 2007 You need a lab scope for that, a DVM cannot read it that quickly. A lab scope will do a sweep reading and if there is a dead spot anywhere in the TPS, it will show a downward spike. The TPS is nothing more than a variable resistor, similar to a reostat. Quote Link to comment Share on other sites More sharing options...
moto_ty Posted December 6, 2007 Author Report Share Posted December 6, 2007 FIXED! it was the temp sensor.... Thanks for all the help. Quote Link to comment Share on other sites More sharing options...
BXX Posted December 7, 2007 Report Share Posted December 7, 2007 You need a lab scope for that, a DVM cannot read it that quickly. A lab scope will do a sweep reading and if there is a dead spot anywhere in the TPS, it will show a downward spike. The TPS is nothing more than a variable resistor, similar to a reostat. A good DMM, a steady hand, and a person who knows what they are doing can easily catch a dead spot. A good analog MM is actually the best way to do it because the dead spot makes itself more pronounced Quote Link to comment Share on other sites More sharing options...
joey b Posted December 7, 2007 Report Share Posted December 7, 2007 and a shitty DMM and myself will be able to tell if the thing is completely shit. Quote Link to comment Share on other sites More sharing options...
CNBZ34 Posted December 8, 2007 Report Share Posted December 8, 2007 Hate to break it to you but even the best Fluke meter and a steady hand won't find the smallest of dead spots in a bad TPS that would cause a runability problem, they do not read fast enough. If a whole section of the surface were dead then it might. You need to be able to see the whole pattern sweep signal from the switch. Just my .02 and years in she shop. Don't matter, he solved it. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.