trouble starting on a cold start

[akirmanidis08]

ok heres the deal. ive got a 90 laser turbo fwd

on a cold start, it takes a few tries to get the car started. Once the car starts, it sputters and acts like its going to die. It does this for about 5 to 10 minutes until it warms up. when i first start it my air/fuel guage is out, which tells me something is wrong with the o2 sensor. However, when the car is fully warm the air/fuel guage works fine and the car runs good.

A few days ago i had been checkin stuff under the hood, when i had noticed that one of the black wires on the o2 sensor was completely off. and the other wires were all rotten looking so i cut the plug off went to a junkyard and got one and just tied the wires together for the time being such as:

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but for some reason im getting a cel light still when the car is warm and nothing is different.

sorry to make this a book but i wanted to be through. let me know if you need more pictures

 

[big_d]

The ideal thing to do is to get a logger to verify that your ecu is getting signal from your o2 sensor. You could also read your cel with the logger and verify that your other sensors are functioning properly. I found on my winter car that the problem with my rough cold starts came from my coolant temp sensor. It was not working correctly and the ecu was not adding fuel for the cold start. After some elimination, I found that the ecu was the problem and ended up replacing it. As for your situation, I would rewire(or buy a new o2 sensor), and use the search function on here to correctly pull the cel code from your ecu.
Dustin

 

[NoCreep]

It's your coolant temp sensor

 

[tsi1991awd]

It's your coolant temp sensor

Not necessarily. Everyone told me my cold start was due to the CTS. True, my CTS was shot but that didn't fix the problem. Changed the fuel filter, that helped for a few days. Then back to the same old same old. I went out this morning to start and it wouldn't start for 5 minutes. Its never done that before. It sounds just like it would if you disconnected the fuel pump. Ill be checking into fuel leaks soon.

 

[akirmanidis08]

the thing is that the car would start and shut off fine before.

i just got the car about a month ago and the coolant sensor was not even plugged up. there was no plug even there. All i see is just wires that have been cut off.

here are the pictures:

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[tsi1991awd]

You see the part that you circled in red that has the white plug? That's the CTS...there was another thing you circled that has two prongs sticking out...that looks like the new style CTS.

They don't make the ones with the white plug anymore. And why you have two in there, I don't know...looks like someone eff'd up and put it where it doesn't belong.

The new style, you have to cut off the plug on the wiring harness and put female spades there...then you plug them into those two prongs that are sticking out of the CTS. But I'm not sure its actually a CTS that you circled.

 

[big_d]

^^Negative. There are three sensors on the thermostat housing. I attached a picture for you of how they are oriented. Your sensors are in the correct location. The sensor associated with cold start troubles is the lower left hand sensor (2 wires). It tells the ecu the water temperature. The bottom right is for the gauge unit on the dash (1 wire). The top sensor is for switch for the A/C fan. On the bottom of the radiator you have a 4th sensor which controls the fans also.

 

[tsi1991awd]

Wait, so the one to the left of the radiator hose controls the AC fan? Because that sensor read open when I tested the ohm, that's why I cought a new CTS and put it there. But its actualy the one below the radiator hose that's the CTS??

Do both of these sensors have the same ohm ratings? Because if not, I screwed up big time. Because I cut the plug off for that AC fan sensor already and whatnot

 

[big_d]

Yes, the one below the radiator hose is the CTS.

 

[akirmanidis08]

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QUOTE]

so that white plug there with the 2 prongs is what i need to fix so that the ecu can read the right temperature?

the a/c has been removed in the car

 

[big_d]

The bottom one with the 2 prongs is the one that needs wired up (not the top white one). I believe the wiring on that is a green wire with black stripe and a yellow wire. It seems to me that the two wires are the ones on the right(one has a blue butt connector on it) that you circled in the picture you took.

 

[tsi1991awd]

Yes, the one below the radiator hose is the CTS.

Do you know if the CTS and AC sensor read the same ohms? And if not. Is what I did really that bad? I don't have any cooling issues whatsoever.

 

[big_d]

I wouldn't really affect your cooling system...Your ecu wouldn't be receiving the right temperature readings. If just the CTS and A/C sensor aren't wired correctly, I don't believe you will have overheating issues or anything. The ecu needs to see that the motor is cool upon cold start-up, so it knows to richen it up.
...oh I'm not sure about the resistance of the sensors, maybe a wiseman can chime in on that.

 

[talon187]

if you hook up your coolant temp sensor it will fix your problem i just fixed my issue acutally. if i started my car when it was cold was fine. if i shut it off after it ran big problem. the wideband would reado 10.0 for fuel. becuase the ecu thinks the car is cold it dumps extra fuel that the car cant burn. if i were you i would go buy the ends for speakers the smaller ones. thats what i have and they stay on the two prongs for the coolant temp sensor just fine

 

[tsi1991awd]

I wouldn't really affect your cooling system...Your ecu wouldn't be receiving the right temperature readings. If just the CTS and A/C sensor aren't wired correctly, I don't believe you will have overheating issues or anything. The ecu needs to see that the motor is cool upon cold start-up, so it knows to richen it up.
...oh I'm not sure about the resistance of the sensors, maybe a wiseman can chime in on that.

Well if I got another CTS and put it where it goes, I'm sure it'll be no problem at all. It's just the AC sensor that's messed up now. I was told before that when you redo the CTS, you need to put female spades on the wires and it didn't matter which wire went to which prong. I'm wondering if it's the same with the AC sensor or what. If it only controls the fan, then I'm sure it's not that big of a deal....?

 

[big_d]

If you can wait until the weekend I can check my wiring, unless someone else chimes in.

 

[akirmanidis08]

so if the sensor has been unplugged this whole time why is my cel coming on now?

 

[jrohner]

Not necessarily. Everyone told me my cold start was due to the CTS. True, my CTS was shot but that didn't fix the problem. Changed the fuel filter, that helped for a few days. Then back to the same old same old. I went out this morning to start and it wouldn't start for 5 minutes. Its never done that before. It sounds just like it would if you disconnected the fuel pump. Ill be checking into fuel leaks soon.

Did you replace the right one? There are two; 1 for the gauge and 1 for the ecu. The ecu one is the important one. If you replaced the one that has 1 wire, it was just the one for the gauge.

 

[tsi1991awd]

Actually I put the new CTS I bought in the AC sensor location. The AC sensor was reading open circuit no matter what the temp was...it was shot, so I replaced it.

Last night when I got home from work I unplugged the real CTS and it was reading .28k ohms WHICH is in spec, about 180*. Today I'm going to do some more testing and see what the hell is up with everything. Its been sitting all night and its cold as hell outside, so it should be reading 5k ohms or so (32* or less)

I'm going to also use the fuel pump check near the battery and see if that helps. If it does, I'm almost 100% positive it is either my fuel pump or the fuel pump relay.

 

[akirmanidis08]

ok heres the update

I went outside today hooked up the temperature sensor wires that go to the ecu. I ran new wires and put female connectors on the end of them

and the car started right up as if nothing was ever wrong.

and now i have no CEL.

thank you guys so much im glad i got good help to fix this problem

 

[big_d]

Anytime. Always do all maintenance and such before doing any sort of modifications. You look to be on the right track.