Hey guys,

I've been battling a low idle on cold start ever since I've owned my car. Right now I'm concentrating on the fuel system to make sure it's right.

Have any of you with the cold start injector ever tried unplugging it? I know you can leave it unplugged if you switch to the 89 ECM, but it seems like I've seen people unplugging it without modifying their ECM and having no problems except maybe an extra crank or two.

I tried unplugging mine just to see how much (if any) it changed, and the car doesn't start. It'll crank for about 10 seconds, finally start, then die. Is this normal, or may I have something going on with my fuel system? Of course when I plug it back in I get the same start as normal.

I'm to the point where I don't have any little parts (IAC, relays) left to throw at it as far as I know, so it looks like it's time to start throwing some higher dollar parts at it.

 

How does it start if the car is warm?

 

If the car is warm then it starts great. Starts around 1200'ish (don't have the exact number) and smoothly comes down to about 800 rpm.

When it's cold it starts around 800 and drops to around 500-600 and fluctuates. If I don't feather the gas I'll get a check engine light (code 34). I replaced my MAF and the relays just to be sure, but my service manual says this can be thrown if I have an abnormally low idle (which I do during this condition). if I feather the gas a few times the idle evens right up.

The first thing I thought was IAC or TPS, so I've already replaced them and set them according to my service manual's (and this forum's) instructions.

 

I forgot to mention.. I'm not sure if this is relevant or not, but it does seem a bit odd to me.

When I start the car in the morning, I turn the ignition on but not the motor. That way I can ensure that my fuel pump is cycling, which it is.

While the car is off the speedometer reads 36, then 4, then 0.. all over the timespan of about 2 seconds. The RPM's coincide accordingly.

Being a computer controlled car and all, I'm not sure if this is an abnormality that the car is trying to compensate for or if this is normal. So once again I'd appreciate if someone would let me know if they've noticed something similar, and if not what would be a good place to start in order to get it fixed.

 

The cold start injector (CSV) is controlled by the cold start switch and not connected to the ECM at all. The cold start switch is in the front of the engine just below the throttle body and is a bi-metal thermo switch that activates the CSV based upon temperature. The GM manual has the details on how to test the switch for resistance when the engine is cold and when it is hot. If the switch is bad it will not open the CSV properly. The switch is about $20 to replace.

If the problem is the CSV then you need to pull it out and have it reconditioned. No one makes or stocks CSVs for our cars anymore. I'd suggest contacting Rich at cruiznperformance.com to have it rebuilt. That is about $15 plus shipping.

Removing the CSV is a bit of a pain and requires the use of flare wrenches for the CSV fuel line fittings. A decent set of SAE flare wrenches is available from NAPA or PepBoys for around $15. You will also want a couple of new o-rings for the fuel line connections, about $2 each.

You could also disconnect the CSV and install a fuel pressure regulator. Crank the pressure up a few pounds over stock and see if that helps the cold start. Once the engine reaches temp and goes into closed loop the ECM will adjust for the extra fuel pressure. The downside is that WOT will probably be too rich. Some tweaking may be required to get you a reasonable idle and WOT.

 

Thanks for the information, but I'm basically familiar with how the cold start valve works. I was also reading through the cold start system troubleshooting this morning but I'm going to have to wait for better weather to give it a try.

I'm primarily interested in whether or not the whole car should refuse to run (and hardly start at all) if the cold start injector is unplugged. I'm seeing that it should run with a couple of cranks on the forum, but my real world experience is that after 10 seconds of cranking it finally runs then dies.

So given that factor I can probably assume that my cold start injector is doing at least something, but I'm not sure what's causing the long cranking with the injector unplugged. Or for that matter, it may be normal. That's what I'm here to find out. :cheers: