Has anyone here ever experience an intermittent hesitation,stumbling,no throttle response,ignition shut-down only when their motor is cold(about 125 degrees) during driving.When it warms up(150-160 degrees) it's fine and runs excellent. My car is a 1988 Iroc-z with a 305 tpi.Thanks.

 

When the ignition switch is turned to the crank position power is sent to the purple and white wire of the cold start timer switch and the ninth injector. The timer switch controls the ground side of the injector.

 

Are you thinking the cold start injector is sticking and continuing to spray fuel even after start-up and into warm-up? I can't probe my wires its the original harness and I don't want to put holes in it.
Let me ad that sometimes when I crank the engine from a cold start and it turns over it idles fine for just a second or two but then immediatly after the engine starts to spit and stumble and sometimes even stall.

 

If it were carbed I'd say your choke was sticking or not opening at all. I'm wondering if your cold start injector is working at all since everything works fine once the car warms up.

 

How long is this cold start injector normally operate for? It sprays all the way through open loop and shuts off in closed loop?

 

I'm not a TPI expert, but according to the picture posted by Tuned Performance, no. However, everything you described is what happens when a carb choke doesn't work causing the car to "run cold" until the engine heats up.

 

Interesting.I do prime the motor for oil pressure first before I fire it up.Which kinda makes sense because the whole time I'm priming it its dumping fuel into the combustion chamber.

 

Are you throwing any codes?

 

I wish it was that simple.No none at all.

 

I've read that the coolant temp sensor might also be the problem,which can cause a rich or a lean condition?

 

Here is a chart for resistance vs coolant temp on the cts. The cts is also reading sets your cold start high idle. If you have high idle and it slowly drops when the engine warms up it sounds like the cold start injector isnt working at all. Im not a fan of the csi going to 89 programing is a great way to toss the csi to the curb.

 

The engine does idle at 1500 rpms initially when i start it from cold then gradually drop down to a 1000 rpms within a minute or so.It has always done that but it wasn't till recently that the erratic cold driving issues arose.

 

To physically see if the ninth injector is spraying , loosen up the csi feed line tube nut and the torx hold down bolt and rotate the csi. Turn the key on for prime and see if the csi sprays fuel.

 

Ok I did what you said and pulled the cold start injector out of the runner and I can physically see that it is NOT spraying.What do I do next?

 

Also the weird part about it is that normally I hear some kinda relay click when i turn the key to the start position and it does some kinda fuel pump like prime sound for a couple of seconds and now its not doing it?

 

You have a few options, Live with it, Buy a used 9th injector or If you want to go to 89 programing send me a pm I offer that service.

 

I'm going to get another 9th injector.I can't live with that its unbearable.Thank you for you help I really appreciate it.

 

Its working again disregard this quote.

 

You might want to ask Don
https://www.thirdgen.org/forums/member.php?u=37644
or John
https://www.thirdgen.org/forums/member.php?u=884

 

Ok thanks again.I'm guessing they would have a new or used one for sale?Preferably oem bosch factory stock original.

 

They might have a used one , new is nla iirc.

 

Awesome! yea I read that they were discontinued by GM.I was just thinking that maybe one of those guys might have scooped a bunch of them up when they were available and happened to have a few left.

 

When you tested the 9th injector, was the engine cool and coolant temp below 95*F? If not, the cold start switch will not turn on the 9th injector when cranking. I've been chasing a cold start problem of my own this summer and it's been so hot here that my engine temp rarely gets below 90*F even after sitting over night. so it's been hard for me to test the switch in the engine.It was finally cool enough early one morning last week to do it, it tested ok.

When the engine is cold (or cool if you live in the south), check that the cold start switch is closed. Pull the connector off and check for continuity between the two contacts on the switch and contacts to ground. If you read high resistance when cold, the switch is probably bad. Also, check that the switch opens when the engine coolant get above 95*.

 

just I case you need the part number for the cold start timer switch. It is bosch 0280130229 . To verify the csi is not operational check the ohms resistance and you can even bypass the timer switch when the rail is primed.
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Sorry My mind is working on a few hours of sleep. the csi is powered during crank.

 

Where is the cold start timer switch.I was looking into that but I have no idea where it is.Thanks

 

Out of curiosity i did crank the motor and still no fuel came out of the csi.I checked my fuse also and it was good.

 

It under the throttle body on the front of the intake manifold. The one with the red circle is the coolent temp sensor, the brown one to the left is the cold start switch.

 

Again, if the coolant is even luke warm, the csi should not be energized if the system is working right.

 

Look at the diagram Tunedpreformance posted, looks like you can test the CSI bypassing the switch (timer) by disconnecting it and grounding the tan wire.

 

I'm sorry bro got alot going on today.To answer your question I live in north east pennsylvania.It was like 70 degrees here today outside. I tested the csi while it was dead cold.

 

That would be sweet if that was the case.I really don't want to ground any circuits unless I'm 100% sure its not going to fry/hurt anything.

 

Ok, at 70* the CSI should be releasing some gas. You can go through and check all the items on the chart for testing the cold start system. I guess you can skip the first step with the fuel pressure gauge sense you already know it's not releasing pressure when cranking. If you have an ohm meter, you can check to see it the csi coil is shorted or open. You measure about 4 ohms on the injector if windings are good. A much higher or lower reading would indicate a bad injector, but a 4 ohm reading doesn't completly rule out something else could be wrong with the injector. It's probably worth going through the test chart to find out which parts are bad. New replacement parts are hard to find and expensive. Even used parts are pricy, and you got to be careful not to get a part as bad as the one you're replacing.

 

I'm going to run through a couple of things tomorrow.Suns going down and its like the dessert here in the fall.Hot during the day freezing at night.Even when I do get to bottom of what's wrong,like you said parts are hard to find and pricey.I'm not looking forward to that part of the recovery.But hey it will be worth it in the end.Thanks for your help I really appreciate it.

 

Alright,I pulled the pigtail off of the cold start switch and grounded the tan wire fired the engine up and still ran like garbage.Meanwhile I was pulling the jumper wire off of the ground that I used while the engine was running and no change occurred. I also put my finger on the csi and could not feel a pulse.
I would say that I have a definitive answer that the csi is faulty.

 

Well I'm no expert, but I've read a lot recently about the cold start system. Here's the way I understand it currently.

The cold start system only injects fuel while the starter is cranking, continuous stream, no pulsing.

The injector will operate for a maximum of about 8 secs. in very cold conditions even if you crank longer.

Current running through the cold start switch (timer) heats the bi-metal contact inside to open the switch. The amount of time the switch is closed is determined by the coolant temp, above 95* the switch is open.

If some of you real experts see a mistake there, let me know, I'm really trying to understand this system.
There's another thing I'm wondering about. After the car starts, extra fuel supplied by the csi should be used up pretty quickly. I'm thinking if the car still runs crappy after 30sec to 1 min., the csi may not be the only problem. I didn't see it in your original post, but have you gone through a basic tune up, check/replace plugs and wires, dizzy cap/rotor, adjust timing, TPS, etc? I know from bad experience some of these things can cause starting/idling issues.

 

Plugs and wires, dizzy cap/rotor,timing,TPS,was all checked and changed.I physically seen with my eyes the csi was not shooting fuel when I pulled it out of the runner.I put it all back together fired the engine up from dead cold while the timer switch was jumped and it still ran rough,pulled the jumper wire off and no change.The issue is that the engine carries on from dead cold all the way up to 150-160 degrees.After that it is fine.

 

bad coolant temp sensor maybe?One or more bad injectors?idk....

 

bump.Would like a third opinion please

 

bump,bump