Supa Troopa Posted October 11, 2009 Share Posted October 11, 2009 Ok so here is the scenario. Just finished putting together a car for my mother and for the first few days it seemed to run fine. By fine I mean I would drive it around the block and there would not be a heavy presence of low end hesitation. Lately it seems to have progressed exponentially and now its almost impossible to drive unless your foot is mashed down on the pedal. Here are some quick facts.. Stock 1978z L28 California Model 6-2 header EGR removed So here is what I think is going wrong, I think the Throttle Positioning Sensor is going bad or it bad or needs recalibration. It seems like the car dumps fuel at low rpms but once the revs pass 3k, the car starts to move pretty smooth. Even at initial start up, if you try to give the car any gas it will just die. I tested the OHM reading of the TPS sensor from closed to WOT. I am not sure if I got the right pins or not but they were the only two that created a number on the multimeter. I had the OHM setting at 2k (not sure if thats right). In the video you can see the number go from .002 to 1 with just a hair move of the throttle linkage. I know I say I am giving it gas in the video but I only move the linkage very small. I guess you can say the butterfly on the throttle body doesn't even open up 1/16th of the entire range and that is what happens. If I go WOT, the reading still stays at 1. I am not sure if that is correct or not but also notice when i flick the box of the TPS sensor with my finger, the numbers start to jump around on the multimeter. I don't think it should do that should it? Anyways, here is the video. If I forgot to mention something let me know bu the car is all stock other than header and exhaust. http://www.youtube.com/watch?v=ltU2ZKCqqak Quote Link to comment Share on other sites More sharing options...
Supa Troopa Posted October 12, 2009 Author Share Posted October 12, 2009 I am not sure if I posted this in the right thread? Does it need to be under the Ignition forum?? Quote Link to comment Share on other sites More sharing options...
lowrider Posted October 12, 2009 Share Posted October 12, 2009 I would sugest searching for the "EFI bible". It has the procedures to check the ohms of the tps, along with the specs that it should be at. Quote Link to comment Share on other sites More sharing options...
loy Posted October 12, 2009 Share Posted October 12, 2009 Here you are http://atlanticz.ca/zclub/techtips/tps/index.html Quote Link to comment Share on other sites More sharing options...
Supa Troopa Posted October 12, 2009 Author Share Posted October 12, 2009 Thank you very much for that link. I will investigate. I am just hoping this is my problem. When you cold start the car its almost impossible to start. If you try to give it gas it'll die. But if you wait a while it revs across the range great but driving is a nightmare and it smells like constant gas. Quote Link to comment Share on other sites More sharing options...
Supa Troopa Posted October 13, 2009 Author Share Posted October 13, 2009 Ok so I looked at the tps and it appeared to be a little off at 1400rpms so I adjusted it some. I did also record some video to show how freaking hard it is to get the car started and the popping and struggling it has revving. The video is kind of long but it i starts to run after about 2 minutes of trying and trying. After that I get out and baby the linkage to try and help it warm up and at 6 minutes, the car starts to rev real smooth. Before that when i give it gas, it just bogs down heavily. http://www.youtube.com/watch?v=G1IGkcI-TIk Here is another video of the car driving by after I drove it around for a good 20 minutes or so. I will admit this time driving it around it was a hell of a lot smoother through the rpms. So the only think left for me to do is now change the plugs. I pulled them out and they were clean but they might be fouled from the old fuel. Other than that I have a new cap, rotor, and wires on the car. Is there another reason why it would be so hard to start???:hs: Quote Link to comment Share on other sites More sharing options...
Supa Troopa Posted October 13, 2009 Author Share Posted October 13, 2009 I did just think of something, I don't think the ground for the AFM is connected. Where does it connect to??? Just any bolt that the AFM bolts to the body? Quote Link to comment Share on other sites More sharing options...
lowrider Posted October 13, 2009 Share Posted October 13, 2009 The poping through the intake is an indication of it being lean. It seems like in the video when you stoped cranking and let the fuel pump run it tried to run. I would sugest putting a fuel guage in the line to see how much fuel pressure you are getting at startup. Ofcourse im just throwing things out there, someone who has more experience might like to chime in. You can ground the AFM to any bolt that connects to the body, as long as its grounded. Quote Link to comment Share on other sites More sharing options...
Supa Troopa Posted October 13, 2009 Author Share Posted October 13, 2009 Ok I grounded the AFM but I also did some troubleshooting as recommended by the "EFI Bible". Here is what I did in the following steps. 1. Ground the AFM, confirmed continuity after wards (there was none prior to the wire being attached) 2. Tried to start car, still hesitant to start but not as bad in the video. Stopped trying after 3 attempts. 3. Disconnected the thermotimer and then tried to start the car and the car started right away and was decently responsive but was running pig rich, there was a huge cloud of fuel filled exhaust filling up the garage. 4. As I said the car was responsive and would rev so I stayed there for about a minute or two revving it on and off to about 1.5k. With the thermotimer disconnected, it would not idle on the cold start. 5. Turned the car off, reconnected the thermotimer and started the car back up. It did start right up, wasn't as responsive as with the thermotimer disconnected but wasn't running pig rich this time so I backed it out and took it for a drive. Car still hesitant at first in bottom end rpms but would take off after about 2.5k. It's like there is a dead spot in the pedal. I kept driving it and driving it and of course as it warms up it ran fantastic. Every stop sign/light I came to it would idle right around 700rpm without skipping a beat. The bottom end also felt smoother and smoother. So now I have to wait for the entire car to get cold again and see if it wants to start. There are still two variables in the equation in which I still won't allow me to point my finger at a problem is: A) Gas might be bad, I did change the fuel filter and it smelled like paint thinner. Car was only sitting for about 6 months but I don't remember how much was in the tank. I have since put in half a tank and its almost down to a quarter of a tank. Possibly fouled plugs from sending all the bad fuel through the system. The plugs were brand new but if the gas is that bad, they are probably toast. I need to put in the new plugs to eliminate that variable and I will as soon as I get a hold of them. Also on a side note, does the voltage gauge always read voltage even with the car off? With my key in the hand, the voltage gauge still reads about 12v. Is that normal for the gauge to still operate when the car is off. I know the clock operates without the key because you can hear it clicking but I don't know about the voltage gauge. Thanks again, I'll post up results after the next cold start. Quote Link to comment Share on other sites More sharing options...
Guest stdgrabbag Posted October 13, 2009 Share Posted October 13, 2009 i think my car had a similar problem. if i drove it and got it warm then shut it and waited a few mins and then tried to start it, it would not start. if it did start it was i had to feather the pedal abit in order to get it to stay running. thought that i could be the coolant tempswitch causing it to run rich, since my exhaust also smelled rich. Quote Link to comment Share on other sites More sharing options...
m4xwellmurd3r Posted October 13, 2009 Share Posted October 13, 2009 doesn't make sense that it would run richer when the thermotime is unplugged. it's running perfect once it's warm? how cold is it out there. also, the TPS is just a 3 way switch. it's on idle circuit on pins 2 and 3 (looking at it from the drivers side) cruise circuit when open, and WOT circuit when pins 1 and 2 are closed. Quote Link to comment Share on other sites More sharing options...
Supa Troopa Posted October 13, 2009 Author Share Posted October 13, 2009 So tried starting it again and it started second try but it was still really fussy. Would not do anything and idled around 600. So the start times are getting quicker but its still fussy as hell until it warms up. doesn't make sense that it would run richer when the thermotime is unplugged. it's running perfect once it's warm? how cold is it out there. also, the TPS is just a 3 way switch. it's on idle circuit on pins 2 and 3 (looking at it from the drivers side) cruise circuit when open, and WOT circuit when pins 1 and 2 are closed. Yea I soon found out that I did not need to check the level of resistance to that extreme in the tps. Also I am in San Antonio, Texas and today it was mid 80s so it is not cold at all. As far as when the thermotimer was unplugged, yes it made one hell of a difference in the start but there sure was a lot of smoke that came through the exhaust. Is it possible to have the thermotimer and water temperature sensor plugs switched? I don't think they are. I guess what I need to do is another video of the car trying to start with the thermotimer in and one without the thermotimer unplugged. I don't have the air regulator on the car and I did unplug the Cold start Valve. I have been reading and does the Cold Start Valve "only" inject fuel when the car is "cranking" or is it also controlled by the thermotimer and after the car is idling and the car is on, does the Cold Start Valve continue to inject fuel until the motor has reached operating temperatures? So the Cold Start Valve is unplugged from the extra injector on the manifold, there is no air regulator on the manifold as well. That is where I stand. Quote Link to comment Share on other sites More sharing options...
Supa Troopa Posted October 14, 2009 Author Share Posted October 14, 2009 Did another cold start tonight and still the same thing happened, sputtered and snorted and didn't idle for ♥♥♥♥. I have basically eliminated everything out of the occasion... :evil::evil: Any suggestions? Quote Link to comment Share on other sites More sharing options...
m4xwellmurd3r Posted October 14, 2009 Share Posted October 14, 2009 nah you can't have the two switched. the car wouldn't run. have you checked for corrosion on the water temp sensor plug? and verify the resistance of the sensor? if it's corroded, or there's corrosion on any of the wiring for that sensor, it'll make your car run really rich. also, have you checked the fuel pressure? The cold start injector only works when the car is cold. it's controlled by the thermotime switch, which shuts off at a certian temperature. i don't know exactly when it does kick on and off though. I have mine unplugged and i never have a problem starting my car cold at temps in the low 70's Quote Link to comment Share on other sites More sharing options...
Supa Troopa Posted October 15, 2009 Author Share Posted October 15, 2009 Ok, where do I begin? Maybe I should start by saying I FIXED IT... or should I explain the extensive amount of work I did.,, So first off, yes the car is now fixed and here is what I did. Checked resistance in water temp sensor ( Everything was good) Checked for continuity between a wire from the sensor to chassis ground (Not good... only getting about .33 on the voltmeter) cut wires at the bullet point, connected both with a straight wire andddddddddddd nothing. Car still running awful. At this point I check the ecu pin to see if continuity exist.. Low and behold.... the thermotimer and water temp sensor were switched!!!!!! So now I just have the water temp sensor, nothing at all emission/cold start related exist. I did have to change plugs, there were heavily charred with carbon from the car running rich. Ran into a problem with the car misfiring, redid all the distributor cap. Start car and BAM PERFECT!!!! backed out the drive way, started to take off and within two seconds of me starting driving.. the entire exhaust fell off !!!!!!!!! So that was a whole another 2 hour ordeal and finaaaaaaaaaaaaaaaaaly got it back up and the car is perfect as it was the day it was made. No flat spot in the peddle, no rough cold start, no hesitation... perfection if I shall say! So lesson learned.... EFI BIBLE, but thank you everyone for pointing me in directions. I now know more than I wanted to ever know about the fuel injection process on this car and honestly I was over analyzing everything because I guess I am used to cars that are more technical if I dare say rather than basic open/close circuitry. BTW here are 2 videos of driving the car. They are at night so its kind of like watching warped speed on star trek to the sounds of the L28. http://www.youtube.com/watch?v=eYLx8KZvG_E (To the liquor store for some celebration drank) http://www.youtube.com/watch?v=CTWFsoMiooc (Back from the liquor store) Quote Link to comment Share on other sites More sharing options...
Careless Posted October 15, 2009 Share Posted October 15, 2009 Awesome! someone trip the Hannibal @ A-Team switch! Quote Link to comment Share on other sites More sharing options...
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