Nismo280zEd Posted April 28, 2006 Share Posted April 28, 2006 So the car won't start and run unless i pull the air temp sensor wiring off... figuring it was a bad sensor i picked one up from O'Reillys earlier today. It wasn't the sensor, car smells rich, and as soon as i put the sensor connector back on, it starts to die. Any ideas? I don' thave a laptop avalaible to diagnose it right now. -Ed Quote Link to comment Share on other sites More sharing options...
z-ya Posted April 29, 2006 Share Posted April 29, 2006 Did you make any changes since it was running OK with the IAT connected? Is the CLT sensor connected? Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted April 29, 2006 Author Share Posted April 29, 2006 The CLT is connected, nothing was changed except the actual motor. The last motor blew a ring, so this is the spare motor i had in the garage. Hickl's 77 L28, and my head but with a felpro headgasket instead of my 1mm metal. Everything else is identical. I'll double check the ground on the CLT tomorrow. -Ed Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted April 29, 2006 Author Share Posted April 29, 2006 OK so i got to borrow the g/f's laptop today. Hooked it up... started the car... adjusted the timing so i got the lowets kpa number. Then pluged in the MAT sensor and it just about dies... after a couple tries i figured out what was going on, the map sensor reads back up to 98 which is about normal here. Still trying to figure out why at the moment and how to fix it. -Ed Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted April 29, 2006 Author Share Posted April 29, 2006 OK... trying playing with the ground, didn't do anything. I unplugged the coolant senosr.. and just ran the IAT and guess what.. it works. so it's not the sensors. I made a log of what happens when i plug in both sensors at the same time, i'll try to post that tonight. Is it ok to run on CLT only? -Ed Quote Link to comment Share on other sites More sharing options...
randy 77zt Posted April 30, 2006 Share Posted April 30, 2006 try another mat sensor?or check your sensor with dvom?sounds like a short to ground somewhere. Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted April 30, 2006 Author Share Posted April 30, 2006 this is a brand new IAT sensor, the old one does the same thing. I'm leaning on CLT sensor... I think water got inside it somehow and was causing grounding issues... anyway.. i loaded up some heavy fuel maps and got it to run with both sensors... made another log of that.. gonna have to get the G/F to send it to me so i can post it. The CLT would just 10 degrees up and down like a bad ground. finally steadied out at what it said was 207 i let it go up to 210 then cut the engine and left the fans on. Let it cool back down. I also took the DB37 i think it is.. connector from the back of the ecu.. used a straw and a razor blade, insulated every other wire with the thin plastic to keep things from grounding on another. That might have helped also. It's still jumpn' about 2-3 degrees. But it's much better. Still tracing it down little by little. I'll try to get the logs up tonight but no gaurentee... been up since 6am with 4hrs sleep. -Ed Quote Link to comment Share on other sites More sharing options...
olie05 Posted April 30, 2006 Share Posted April 30, 2006 did you make your own harness? Maybe there are just a few electrical gremlins from stuff grounding out... You said it helped when you isolated the wires... Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted April 30, 2006 Author Share Posted April 30, 2006 Yeah man you know me, I make all my own harnesses. I'm buying the actual DB25? DB32 whatever the number of pins are. I'm buying a pre made harness lead from DIY it has the DB37 with like 10" of wire leads, I used 14 ga wire for all my stuff so it's too big for the connector. I think that's causing solder to ground out and stuff. The harness if 50 bucks, either that or i buy another connector and some thin ga wire like 18 maybe and do it again myself. Anyway i'm at work now, see what happens when i get home with the car. -Ed Quote Link to comment Share on other sites More sharing options...
z-ya Posted May 1, 2006 Share Posted May 1, 2006 If the CLT or IAT is jumping around in Megatune, then there is a grounding problem. Make sure the MS has a good ground. Also check the CLT and IAT connectoirs for a good ground. Measure the resistance between the negative sensor terminal (at the sensor) and the point where the MS is grounded. Should be less than 1 Ohm. Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted May 1, 2006 Author Share Posted May 1, 2006 If the CLT or IAT is jumping around in Megatune, then there is a grounding problem. Make sure the MS has a good ground. Also check the CLT and IAT connectoirs for a good ground. Measure the resistance between the negative sensor terminal (at the sensor) and the point where the MS is grounded. Should be less than 1 Ohm. That's what i figured too when i saw it jumping, my CLT is grounded to the head pretty much with a bolt above the water pump that holds on the water bypass rail. The IAT is grounded back to the MS. I checked voltage the other day.. both 4.9V steaady no spikes. check ground, both read about .1ohm and read the same to body metal, engine metal, and bat neg. So it's not the direct ground from the sensors. So i figured MS ground like you mentioned. so i ran a jumper from where the ms is grounded to where the clt is grounded. Didn't change any ohm readings. I don't have the laptop now, should be able to use it tomorrow so i can't verify if it's jumping or not, however, the CLT did read 207 and up to 210 when i shut if off last night. I did the same thing i did last night, let it idle up real hot, turned on both cooling fans, same as last night. Then stuck a meat thermometer on the AL at the radiator inlet pipe. While runing it read right at 160 maybe 161. turn the car off went up to about 175 at the hotest. The outlet temp while running was about 130-140 I couldn't get a good reading as of the location. Either way... I don't see how the CLT would read 20-50 degrees higher than the radiator inlet metal. I did kinda ghetto rig the CLT sensor when i first put together the MS I had to grind the threades off the senor, then put JB weld around where the threads used to be and put it into the thermostat housing. I'm starting to think that might be throwing the temp off but i don't see how as it is remotely grounded. Either way i'm taking my spare housing to the machine shopt tomorrow to get some 3/8 NPT threads cut into one of the holes now that i have the money to pay for it. -Ed Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted May 1, 2006 Author Share Posted May 1, 2006 Didn't make to the machine shop in time this morning, first thing tomorrow though. I did some more investigating. I checked the grounds again cause something is still not feeling right... I did it with the car on this time and found something very odd. from battery to ms ground reads zero. from bat to sensor ground reads zero (ohms of course). tps ground to bat reads zero, but from tps ground to ms read betwee 7.5-11.9 ohm kept jumping, some sort of interference. Then from the MS ground to the sensor ground read 9.4 ohm. Same for tps to sensor ground 9.4ohm. when the car is turned off however, they all read 0-.1ohm. So i must be getting some sort of line feed back through a ground with something else. Tomorrow I'm going to make a bus bar and have it for dedicated ECU grounds, sensor, tps, ms with a direct 8ga from the battery neg. Hopefully that will solve the interference. Also the MS isn't powering on now, so i'm blaming the grounds as i checked all the power wires and they read about 12.1-12.3 volts. More joys. Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted May 3, 2006 Author Share Posted May 3, 2006 Well yesterday I spent the better part of it splicing out about 4' of wire from the MS harness so it's not just laying on my floor board in coils. While doing so i tested everywire to verify what it was and labeled it with a number system. Then i have a book with the numbers says what the wire is and what pin it is on the DB37 connector. Anyway I found 2 ground wires that i don't believe were previously hooked up. Also got the thermo. housing back from the machine shop today. 13.50 w/tax shoulda done that a long time ago. Pickn' up the new sensor tonight from O'Reillys. -Ed Quote Link to comment Share on other sites More sharing options...
z-ya Posted May 3, 2006 Share Posted May 3, 2006 Sounds like your on the right track. Get all those ground wires cleaned up and you'll be good to go! Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted May 5, 2006 Author Share Posted May 5, 2006 Well Great news!!! I just an oscilliscope in the mail today!!! This should help alot in examing the signals to the MS. Also assembled the thermo housing with new sensors. Should have it up and running tomorrow or Sunday. -Ed Quote Link to comment Share on other sites More sharing options...
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