Coolant Temp. Sensor/Cold Start Woes

[tree fingers]

So, like many of you I suspect, my CA has a hard time starting cold. I have researched the issue for a while now, and I think that my coolant temp. sensor may be the culprit. When cold, the motor spins and sputters a number of times until it finally fires. This generally requires some messing with the throttle. After it starts, it idles fine and runs fine. This leads me to believe that it's the coolant temperature sensor's doing. However, getting it out is proving to be a huge PITA. It's just impossible to get a wrench on. Does anyone have any advice for a more pain free method to removing this little guy?

Thanks!

[TheMAN]

I think you can get it off with a deep socket?
do you have the butterfly system working? Not only does it add low end torque to the engine, but it helps startup a bit

make sure your ignition timing is set to specs too

[float_6969]

Yea, I've always removed it with a deep socket. He's also right about the butterfly system helping with cold starts.

[boost_boy]

A 19mm or 3/4 deep sockets is what you need. Using a wrench on that is close to being reckless and will prove to be inefficient.

[sjbsuperman1425]

i used a 3/4" wrench...

[tree fingers]

I ended up having to buy a 3/4 deep well, but, unfortunately, the new CTS didn't solve my problem. I noticed that my FPR was set too high, and I adjusted it back down to ~36PSI. I pulled my plugs, which were soaked in gas. I plan to clean them tomorrow and set my ignition timing, and I'll go from there. Does anyone have any other ideas? I'm aching to finally drive this car. ;_;

[float_6969]

If you're still having problems, try replacing the cold start valve under the TB.

[TheMAN]

this might sound like a stupid question but, what MAF are you using?

[tree fingers]

The problems only get worse as the outside temperature decreases. Yesterday, ~10F, the car wouldn't start at all. I am using a CA MAF, but maybe I ought to try another one. I believe it may be over-fueling at start-up, and either the spark isn't strong enough or I have some erroneous sensor. I have already replaced the CTS once, but I am starting to suspect that it may be wired incorrectly. I have replaced the spark plugs, coil-packs, set the ignition timing, although without a light, and it still doesn't want to start cold. This is curious, because my friend's CA, which just so happens to be parked next to my car, has no trouble with starting cold. I'll try pulling the cold start valve and see what it looks like. It's the rectangular box under the TB, right? If it is faulty, where I can find a replacement? This is a completely fresh engine, which was put together by a reputable machine shop: so I suspect that the problem is not the engine itself. HOWEVER, the wiseco pistons required the delete of the oil squirters. I'm not sure if that is relevant to my problem, but I thought it was maybe worth mentioning. In any case, my birthday is tomorrow, so I'll likely spend it trying to get this little corolla moving.

[TheMAN]

yes, it's the the little squarish/rectangular thingy... half of it is black... a replacement is easily available from your local nissan dealer as it's the same part as the pulsar IIRC

which ECT sensor are your using? OEM nissan? aftermarket? used? What are the resistance values you are getting and what temps are you measuring that at? Has the TPS in the throttle body been set to the proper place?

[tree fingers]

How do I determine if it is functional? I have read that, at cold temperature, the opening should be a pencil's width?

The sensor is aftermarket; it is possible that it's faulty. I haven't checked the resistance at the sensor, yet. I should do that tomorrow. I might have a grounding issue, come to think of it. Whenever I tap the brakes, the 'walbro fuel pump noise seems to change and other electrical components dim. As for the TPS, I haven't fiddled with it since I got the motor: I bought it when it was blown. That's a good idea.

I appreciate your suggestions, man. I'll have to fiddle with the car tomorrow, weather permitting, and see how it goes.

[TheMAN]

the fuel pump noise changes and the lights dim because of voltage drop... the brake lights take a lot of current... so if it's doing that, then yeah... grounding is a possible problem, but it's also possible that a weak or bad alternator can do that... bad batteries can do this too

since you're going to check the sensor's resistance, you can at the same time check the TPS... you will most definitely need the shop manual to get the specs and correct test procedures

[tree fingers]

I think my cold start issue may be resolved. I replaced the cold start valve, which didn't seem to do anything. However, I pulled and cleaned the IACV and where it mounts to the manifold, and the car seems to be starting 100% better. It doesn't burble and pop to life anymore, not it just spins and fires right up. However, after some fiddling with the idle screw on the IACV, I still think my idle is a little too high. It isn't as high as a cold start idle, but it's somewhere in the middle. Hopefully this issue is resolved. Only time will tell, though.

[TheMAN]

I forgot what the procedure was in the FSM to adjust idle, but there is a way you must follow to do it or it will never be right

[float_6969]

TheMAN is right. There is an idle adjustment procedure in the FSM.

[sjbsuperman1425]

make sure the ignitor has a good ground.
make sure your coils have a good ground.
remove CAS and check splines on CAS and the camshaft itself.
check ignition timing with a WORKING timing light by removing the first coil, using a jumper spark plug wire, and putting the timing light clamp onto that.
replace the air regulator underneath the throttle body.
disassemble IACV assembly and clean.

I think I've done all of this and my car starts terrific towards the end of last summer, but my timing would never stay the same because the teeth on the exhaust cam the CAS rides on are chewed up.

[boost_boy]

Did you check the codes on the ecu? Let us know what you find. Plugs soaked in fuel sounds like the water temperature sensor or its circuitry or a damaged ecu. Dimming lights is not good either. You will need to check the voltage of your alternator while the car is running to see what type of voltage it is putting out.

[tree fingers]

First of all, thanks for taking the time to help me figure this out. I really, really appreciate it.

Let me update you with everything I've tried/fixed/thought I've fixed but actually didn't fix:

The dimming lights was just a ground that I had forgotten. Once re-connected, the dimming issue seems to have stopped.

Here is what I have tried to fix the cold start problem:

I have tried my friend's cold start valve/ air regulator, and although the opening of his valve was noticeably larger than that of mine, it did not help. I have also replaced the ECT once already with a new aftermarket unit along with a fresh set of plugs, and it still didn't seem to help either. I doubt the exhaust cam is damaged, as it is brand new, and ever since the rebuild the engine has had cold start issues. Although it is worth checking out.

As soon as it gets less cold, I'll check codes on the ECU, maybe try a known functional ECU, clean IACV/ACC, check ignitor and coil pack ground, and if none of this works I'll buy a new air regulator.

Hopefully this will be resolved soon. Either way I'll update you guys.

Thanks!

[tree fingers]

Sorry that this update took so long. I've been sort of busy on my end. Suffice to say, the problem has not gone away.

The ECU shows no codes, which is strange because at that time the o2 sensor was unplugged. Isn't there an error code for an unplugged/faulty o2 sensor? In any event, the motor is still fouling plugs and having a hard time starting when the engine is cold. Although, I have learned a few things.

When someone partially covers the MAF sensor at start up, it significantly increases the quality of the start.
When the engine is warm, I disconnected the cold start valve and connected the vacuum lines. Afterwards, the engine started much better than it ever had, even under warm conditions. However, after it cooled, nothing seemed to change. I have since ordered a new cold start valve, but it won't be here until next Tuesday. Here is a list of what is happening:

No ECU Codes
MAF Manipulation Helps
Still Fouling Plugs
Seems stuck at fast idle
Doesn't like any throttle input when cold; however, when warm it seems to run fine, but it seems like when you rev it it doesn't want to "come down" very quickly. It's sort of difficult to explain. It's almost like it spins up due to throttle input, and then it takes longer than normal to come back down.

I've replaced the CTS, plugs, checked for codes, played with IGN timing, cleaned the AAC/IACV. I'm hoping that the new cold start valve will help, but, deep down, I suspect that it won't.

What else should I try?

[sjbsuperman1425]

I've had the same problem since day one, I've also replaced and check all the same things as you. I noticed after replacing the air regulator (under TB), cold start up was still a little finicky, but once I got it idling it would stay around 1500rpm. You may find similar results. I've just learned to deal with it but get back after replacing the air regulator and lets go from there.

[tree fingers]

Sorry for taking so long to update. The air regulator did nothing for me. I now suspect that my IACV is stuck open for some reason; either it's not getting power or it's defective. In any case, I think it is IACV related, because it helps to have someone 'choke the motor' by completely cover the MAF when starting the car. Any ideas will be appreciated.

[sjbsuperman1425]

Have you downloaded the FSM? There is a lot of help for diagnosing misc. problems. I went through them and slowly my car started to run better, idle better, and start better. Just a thought because it worked for me.

[tree fingers]

UPDATE: I had a full exhaust made for the car last week, so I've actually had the chance to drive it around a bit. The engine starts better cold now, but still sometimes takes a few tries. Anything good is worth waiting for, so I guess I'll keep trying new things until I figure the problem out.

Thanks for all of your help, and I'll update you in the future.

Also, might be getting a DMAX hood for the 86 tomorrow. So, at least I have that going for me. Haha..