Bostons94Vert Posted August 18, 2012 Report Share Posted August 18, 2012 After taking the stereo out of my cutty the other day she has been running like crap. It takes a couple tries to start. I think im losing fuel pressure overnight but again im not sure. No C.E.L at all and voltage and oil pressure are perfect. I cant give her any real gas without the motor bogging down completely. The motor doesnt stall it just sounds like its only getting air and no fuel/spark. The plugs and wires are less than a year old and she runs fine until I get on it. It seems as if im losing fuel or spark at w.o.t and I need help before school starts in 2 weeks. Im going to try and record what is going on its just pouring out right now. As always any help is greatly appreciated Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted August 18, 2012 Report Share Posted August 18, 2012 know how to test the TPS? that would be one of the first places i would look. Quote Link to comment Share on other sites More sharing options...
Bostons94Vert Posted August 18, 2012 Author Report Share Posted August 18, 2012 Thanks for the fast response...the only reason i wasnt thinking the tps was because of the fact that i have to pump the gas a few times to get her started and I have no "service engine soon" light.I dont honestly know how to test the sensor but i do have a DMM and have done some reading. Do i have to backprobe the three wires comming of the tps? what exactly should i be looking for? Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted August 18, 2012 Report Share Posted August 18, 2012 that would be how it's done, preferably without causing damage that you can't repair(electrical tape should work fine). for a 94 CS 3100, you'll have dark blue, black and grey wires for the TPS. black is ground, grey is the 5V reference and dark blue is the actual signal. turn the key to the run position and then check the 5V reference to see if it's at least very close to 5 volts compared to ground. then measure on the signal wire and slowly open the throttle all the way and watch voltage. at idle, you should see roughly .5 volts, at WOT, you should see roughly 4.5 volts, and anywhere in between should be fairly linear. and what do you mean pump the gas? before you attempt to crank it or during cranking? Quote Link to comment Share on other sites More sharing options...
Bostons94Vert Posted August 18, 2012 Author Report Share Posted August 18, 2012 Cant test the sensor till the morning cuz I dont have my dmm my father borrowed it. It actually started without pumping the gas but it did take 3 times to fire up. I took a bunch of videos in order to give some better explanation so here is the link to the youtube channel http://www.youtube.com/channel/UCDS2ZVInJaSbCmGdRr8XxcQ Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted August 18, 2012 Report Share Posted August 18, 2012 also: your oil pressure guage is non-functional, it's actually an oil pressure switch and will only go to two spots on the guage, one for normal pressure, one for ~4 PSI or less. if you do think it's pressure leakdown after shutoff, there's only two places it can go where it's not supposed to, either through a leaking injector or through the vacuum line for the fuel pressure regulator. if you have a fuel pressure guage, that's easy to test, if not, you'll have to wait for a while with the engine off, then depress the schrader valve on the end of the fuel rail to see if you get any significant amount of fuel to come out due to residual pressure. you could also pull the vacuum line off of the fuel pressure regulator to see if fuel is pushing up through the diaphragm. Quote Link to comment Share on other sites More sharing options...
Bostons94Vert Posted August 19, 2012 Author Report Share Posted August 19, 2012 Alright so i checked the tps and i had 5.07v on the reference.... .700 at idle on the signal and 4.58v at w.o.t--From that im guessing the sensor is good right? I also took the cap off the fuel rail and push the valve in and I did get residual spray and the vacuum line from the regulator was dry Does that mean i have no leakage of fuel? I also took the gas cap off and turn the key and could definitely hear the pump running it was kinda loud idk if thats normal. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted August 19, 2012 Report Share Posted August 19, 2012 well, the minimum and maximum voltage seems normal, did you check to make sure the voltage climbed smoothly all the way from idle to WOT? getting pressurized fuel out of rail is a good sign(assuming the pump hadn't been run for a few hours before testing it), though without a pressure guage, you won't know exact pressure. no fuel coming up through the fuel pressure regulator diaphragm(with pressure in the line) is a good sign as well. the pump should be noticable when running, but i'm not sure if loud is how i would describe it. shouldn't need to remove the gas cap to hear it though, unless you have a lot of extra sound deadening between the driver's seat and fuel pump. Quote Link to comment Share on other sites More sharing options...
Bostons94Vert Posted August 19, 2012 Author Report Share Posted August 19, 2012 i will try the schrader valve again in a few hours because i cant remember if i turned the key and kicked the pump on before checking. Would a vacuum leak cause these problems? Just now when i started the car the idle shot up to 2 grand and stayed steady...it sounds like a loud hissing noise comming from the TB area...when i pulled the line of the fuel pr regulator it dropped down and kind of steadied. Thanks for the help Rob i really appreciate it...I hate to ask a million questions im just confused here Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted August 19, 2012 Report Share Posted August 19, 2012 high idle is either a vacuum leak or the IAC is acting badly(stuck open) or the PCM thinks the throttle is open. you can spray short(SHORT) bursts of certain chemicals around to find a vacuum leak, brake cleaner, starting fluid and a couple of others, along with a bit safer option of a propane torch(unlit), when you spray into a suspect area and the engine reacts to it, there is obviously a leak there. if it's the IAC, you can attempt to remove it and clean it out, sometimes it works, sometimes not. if it's the PCM thinking the throttle is open when it's not, temporarily remove the PCM BAT fuse for a couple of minutes to clear the learned TPS 0% point. Quote Link to comment Share on other sites More sharing options...
Bostons94Vert Posted August 19, 2012 Author Report Share Posted August 19, 2012 Does mapp gas work? I used a mapp torch and sprayed it everywhere with no change in rpms...what should i clean the IAC with? Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted August 19, 2012 Report Share Posted August 19, 2012 carb cleaner works decently on the IAC. no idea if MAPP would work or not. Quote Link to comment Share on other sites More sharing options...
Bostons94Vert Posted August 20, 2012 Author Report Share Posted August 20, 2012 i checked the schrader valve on the fuel rail first thing this morning and i got nothing. Does that mean i am losing all pressure overnight? that would cause extended starting but would it cause the high idle and the fact that it goes nowhere at w.o.t ? Anyway to tell if its the fuel regulator or if i need to pull the plenum? Would a scan tool help narrow down the problem areas? I gotta get the car running in two weeks for school and its becomming such a hassle sorry for the questions Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted August 20, 2012 Report Share Posted August 20, 2012 it does mean you're losing pressure somewhere, there's only a couple places it could be going. in order of where the fuel travels, fuel pump check valve, fuel filter, fuel injector, fuel pressure regulator. those are the only items on the pressurized side other than the fuel lines themselves. would it cause high idle? i wouldn't think so. that's probably another issue. scanner MIGHT be useful for both issues. i can't think of too many cheaper scanners that will work with the 94 3100 and by the time it would take me to get an ALDL cable out to you, it would be past the 2 week timeframe you have to deal with. you could order an ALDL cable from elsewhere and run tunerpro RT V5 with the definition i made for the 93-95 3100s and get sensor data/etc. other than pulling plugs and attempting to find fuel in the cylinders after a leakdown, i'm not 100% certain on how to determine which is causing it without part swapping. Quote Link to comment Share on other sites More sharing options...
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