slow starting

[innerware]

Hey all, what would cause my stock 280z to not like to start up when it is cool? I think it is a fuel or air issue. It cranks just fine and when it finally takes it will loose rpms if I apply the gas. When I let it warm up for a couple of minutes it is fine. But if I don't let it warm up enough it will loose rpms and want to backfire. So I feel it can be a fuel or air issue. I have new plugs, airfilter, and just passed smog fine. My vacuum checked ok and this will only happen when it is below 65 degrees or so. I am in the Bay area of Northern Cali so it isn't too cold. Could my Air Flow meter be sticking when cool or my throttle body? I have all new ( year and a half old ) sensors. When I ran too rich it wasn't that bad but I just had the car adjusted to pass smog and now it is bad again. My injectors are all less than 2 years old too. It doesn't sound cold start valve issue since it chokes up on me right after start, plus it hasn't been that cold. Could it be a pressure regulator, or air regulator? I don't know where to look and how to test it if it is the problem.

 

Any help is appreciated as always.

 

Thanks

[Guest Nic-Rebel450CA]

It backfires when it is still cold? That is odd. The exhaust system shouldnt be nearly hot enough. I would say that your FI is making the system a bit too rich, except for the backfiring part. Perhaps your ECU is advancing the timing too much or not nearly enough? (I am not familiar with those FI systems so I dont know if the ECU controls the distributor advance, if it does then that could be a possibility)

[innerware]

Thanks, yeah when it is still cold ( still within 2-3 minutes after start) if I hit the gas it will sputter and drop rpm's. Sometimes it will sputter and choke up and backfire or front fire in the intake. Not sure where the firing is coming from. I was running way too rich not too long ago and couldn't pass smog (gross poluter) Since I had that fixed and have passed smog things seem to be worse than before. It takes me 2-3 times of cranking the car to get it to start. It is almost like it is flooded, I can turn it over and over with nothing at first until like something warms up or something. Than after the 3rd time it will start and right away idle real low like it will die and than not die and idle at cold idle. This is when it will choke up if I try and drive too soon. So thoughts about what it could be. Computer, sensors, fuel pump etc?

 

Thanks all,

[Tim240z]

Sounds like it's not getting enough fuel at cold start up. Do these things have a cold start valve, or some kind of cold enrichment?

Tim

[Nismo280zEd]

Disconnect your cold start valve.. sounds like it's stuck open flooding the intake. See if that helps.

If not... make sure you AFM is propery connected... and check your timing... the ECU does not control timing on a 280z, Also check the TP switch that could be part of your "chugging" problem as well.

-Ed

[innerware]

Thanks for all the help guys. I will try and disconnect the cold start valve tomorrow and see if that helps at all. What is the temp that the cold start valve runs at? I thought it was for COLD weather, not what I am used to as cold in Oakland which really isn't cold at all. I know that my timing is OK and I just had it all adjusted to pass smog so my afm is properly adjusted. I will also look at my TPS and see if there is something there wrong.

 

Thanks again and any other suggestions are always welcome.

 

Kyle

[innerware]

Hey all, I am revisiting this problem mainly cause I haven't fixed it yet and it is getting harder to start in the morning. I haven't ruled anything out yet but this is what I think. I am thinking that my fuel is fine. I haven't checked pressure yet but it just seems ok. I am thinking that my Air Flow Meter is ieter sticking shut when cold or reading bad measurements. This is because after I can get it started it chokes up and wants to die if I give it gas. Almost as if it isn;t getting enough air. Since fuel is at a constant pressure this could be the only cause right? IF I were to replace the AFM would I need to get it tuned up or is it plug and play? And should I buy new or buy from someone selling old stuf cause of a v8 swap?

 

What do y'all think? Thanks as always,

Kyle

 

Just added:

Well, for the last few days I needed to jump the car cause I would try and start it intill the battery slowed beyond cranking. It worked though. After jumping the car it would generally start on the 2nd try or 3rd. I just came back in from trying that and no go. I can't get it started at all today. Now it is mighty fridged for Oakland. There was a good thick layer of frost on the car. I will try again later. Could my starter be going? I couldn't get a good high reving start out of the battery even when I switched my wifes with mine. Everyonce in a while it will grind like it has teeth missing. I don't know much about starters. Maybe it isn't spinning fast enough. I know this is probably not my only problem but what do you think?

[jeffp]

since you have tried the rich problems, try this. clamp off the return line of the fuel injection and try to start the car. Let someone else try to start it, or get one of those starter switches gizmoes and hook it to the starter to engauge the starter. Turn the car to on, clamp off the return line and hit the starter. See if it starts that way, and if it does, then you just may be way to lean for some reason. use pliers with tape around the teeth so you dont mess up the rubber FI hose in the process.

hope that helps.

[innerware]

FIXED!!!!!!!!!! Yeah!!!! Though all should know that I had my thermotime switch and water temp sender wires crossed and that was causing bad readings to the computer. All is fixed now and it starts up in the cold.