305 TPI cold start switch - Team Camaro Tech
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post #1 of 11 (permalink) Old Apr 29th, 09, 12:30 AM Thread Starter
eyal
 
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305 TPI cold start switch

i have 88 iroc z with the 305 tpi
i noticed latley that when i start it after it sat for long hours
it does start at the first time
but it seems like when i started it, it doesnt get enough fuel when its cold
so i figured maybe it is the cold start switch...
can someone tell me where exactly its located...and whats the easiest way to check if it is working proaparly or not??
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post #2 of 11 (permalink) Old Apr 29th, 09, 06:23 AM
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Re: 305 TPI cold start switch

E87,

The cold start injection system which consists of the "cold start switch" and "cold start injector" only operates with the engine temperature below 100 deg. F and while the engine is cranking (Key in the START position). If the car "starts the first time" when cold then there is nothing wrong with the cold start system. The problem is somewhere else. I would look at the MAF and ECT sensors and check for vacuum leaks and correct fuel pressure next.

Don't chase your tail on the cold start system 'cuz it sounds like it's working properly.

Paul D.

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post #3 of 11 (permalink) Old Apr 29th, 09, 12:26 PM Thread Starter
eyal
 
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Re: 305 TPI cold start switch

thanx for ur replay

the MAF sensor is actually new
so i know its not that
it might be a cluged fuel filter maybe??
the spark plugs are pritty shot too...i dont know if its related or not...but im gonna change them anyway
by the way...what is the ECT sensor?
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post #4 of 11 (permalink) Old Apr 29th, 09, 07:07 PM
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Re: 305 TPI cold start switch

I have personally dealt with a bad MAF signal problem that was a bad connection issue. I used a small straigt pin and shoved it in the back side of the MAF connector on the signal line. I started the motor and expected to see the voltage signal to start low at idle and increase smoothly with engine speed. Instead what I saw was a stead 5 volts meaning the ECU had supplied the bias signal but the MAF wasn't loading it down to generate the signal. The issue was that the MAF socket pins in the connector were slightly sprung and had a thin layer of oxidation on them. I tiny rolled up piece of sand paper buffed the terminals up. A tiny pick probe was used to squeeze the socket pins closed slightly. A light doping of dielectric grease kept the moisture out and it's been running fine for 5 or so years now.

You really need to get codes out of the ECM. On that model year it's as easy as shorting two pins together on the diag connector, turning the key on and counting flashes of the noid light. I'd tell you which pins, but I'm afraid I'd be wrong so I'll leave that to someone else who remembers.

http://www.thirdgen.org is a great site for technical info. You might find some stuff there that will help you with your 3rd gen.

By the way, thirdgen is where I found a new ECM program based on a popular 'ARAP' bin file that came on later in year which eliminates the need for a cold start injector all together.

Dave
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post #5 of 11 (permalink) Old Apr 29th, 09, 09:00 PM Thread Starter
eyal
 
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Re: 305 TPI cold start switch

i actually havnt got any check engine light
so i know its proabably not something related to the ecm system
and i actually well traind about checking the codes with a pin...u need to ground the A and B terminals...(this is my 4th 3rd gen camaro)....thanx for the advice
when i start the car its actually starts above th 1000 rpm and start to drop slowly after and shuts down if i will not press the gass pedal few times
sometimes its happen even after driving when i park the rpm would drop and the engine will shut off....but usually it stays on the 900 rpm mark
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post #6 of 11 (permalink) Old Apr 29th, 09, 09:30 PM
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Re: 305 TPI cold start switch

If the idle is not working, you might need a new IAC, Idle Air Control motor, or its power is not getting to it either the driver may be faulty in the ECm or faulty wiring from the ECM to the IAC.

Idle should remain the same regardless of the load placed upon the engine. maybe remove it and clean out the air passage the pintle seats against. kill the power to the ECM and let it reset/relearn itself.

There may be a code set even without the CEL coming on. Check all vacuum hoses for good condition and replace those you have doubts about. Even the EGR valve may have a leaky seat or broken itself.

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post #7 of 11 (permalink) Old Apr 30th, 09, 07:39 PM
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Re: 305 TPI cold start switch

There is a way to check the IAC motor. It's actually part of the procedure for setting the base idle. It goes something like this.

Remove the IAC motor from the throttle body. You'll need to disconnect the harness to spin it free, but hook it back up once your done. Then put your diagnostic jumper in place (A and B terminals of the diag connector you say?). Have a helper turn the key on, but don't start the engine. The IAC motor should full extend and then back up a predetermined number of pulses. This will confirm the operation of the IAC motor.

If that checks out, give the IAC air passage a good looking over. Use a flashlight and peek in the hole. Open the trottle plates and observe the IAC passage from inside the throttle body. If you see any carbon, use a pick probe and carb cleaner to chizzle it away. Try to suck up all the crusty piece you can when you're done. Then reinstall the IAC and see if that helps.

While you're in there checking the IAC, do the same anti-coking process to the EGR passage if you can get to it.

Dave
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post #8 of 11 (permalink) Old May 1st, 09, 12:27 AM Thread Starter
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Re: 305 TPI cold start switch

so u think even if the car idles fine most of the time..u think it still can be a bad IAC motor??...also ..i actually checked the throttle plate yesterday and everything there looked pritty fine....
u think maybe i should readjust the IAC??...cause the procidure u just explain to check the motor is almost the same like adjusting it
by the way...i need to change the spark plugs and wires anyway..so can u recomend me of something good for this engine or it doesnt really matters?
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post #9 of 11 (permalink) Old May 1st, 09, 08:04 AM
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Re: 305 TPI cold start switch

There is no adjustment to the IAC. The ECM controls the rotation of the IAC motor to move its pintle in/out of the seat to control the engine idle rpm. The whole concept is a controlled vacuum leak to adjust idle rpm.

Sometimes, the hole/seat gets carboned up and needs cleaning. What Dave is suggesting is to clean the passage, with the IAC out, gently push the pintle back into the casing, install the IAC, disconnect the battery for about 20-30 seconds, reconnect, then turn on to IGN only for 15 seconds, then off. This power up sets the IAC via ECM for initial run. Then start the engine and drive the car up to say 55 MPH for the ECM to relearn.

Changing plugs & wires will definately help. A new air filter will also.

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post #10 of 11 (permalink) Old May 1st, 09, 04:51 PM
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Re: 305 TPI cold start switch

Its worth adding that your engine controller will have to re-learn it's base idle setting if the battery is ever disconnected. The re-learn just requires some driving until the vehicle gets warmed up. During the drive cycle exercise all things that alter the IAC setting like touching the brake, shifting the gear selector, turning the steering wheel (perhaps not a factor on your 87), turning on electrical loads like lights and A/C. Once the ECM has experienced those things it should control your idle pretty well. But while it's learning it can really act weird and may even come close to stalling at idle. But once the re-learn cycle is over (one hot drive with all the fiddling) it should be very stable.

Dave
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post #11 of 11 (permalink) Old May 3rd, 09, 08:43 PM Thread Starter
eyal
 
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Re: 305 TPI cold start switch

thanks guys for the advices
i think i started to understand about this a little bit more about
what i should do
just waiting to get a bit of nice weather...pritty rainy outside in the nw these few days
by the way...u got some recomendation about what king of spark plugs should i use??
some recomended me about the ngk
any ideas?
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