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Stock chip

The voltage at the temp. sensor is correct at 5v. If it was partially grounded would the voltage be different. Another thing I was thinking about, was the plug put on the wire harness correctly assembled in terms of polarity or does this not make a difference.
As I stated, the dealer said the car was in open loop and would not go into closed loop when hot. Not sure if I have that reversed. Any thaughts on this.
 
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Should check whether it is fuel or spark or both that is not working when hot. Check injector pulse width or use a noid light across an injector to see if there is a signal. Spark , you should use a cheap spark checker or at least a grounded spark plug .
 
I don't have a Scanmaster, that is one of the reasons I took it to the dealer. The car is unmodified with 9'000 miles on it.
I checked the spark and injector pulse while the car was hot and cranking.
Spark was ok, fuel was questionable. The noid light showed a burst of light and then nothing. Fuel pressure was 42 lbs with ignition on. This was checked by me and the dealer.
I have been told that if the car starts when cold the cam and crank sensors are fine. Some have stated on this site that these parts could become heet soaked so I took CO2 and cooled them off and still no start.
 
vetttta said:
I don't have a Scanmaster, that is one of the reasons I took it to the dealer. The car is unmodified with 9'000 miles on it.
I checked the spark and injector pulse while the car was hot and cranking.
Spark was ok, fuel was questionable. The noid light showed a burst of light and then nothing. Fuel pressure was 42 lbs with ignition on. This was checked by me and the dealer.
I have been told that if the car starts when cold the cam and crank sensors are fine. Some have stated on this site that these parts could become heet soaked so I took CO2 and cooled them off and still no start.
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Even though this won't help your current problem a Powerlogger, SM, boost and fuel pressure gauge will be the best money you ever spent, just because FP is good at idle don't mean it is at WOT, having a elec. Fuel pressure gauge just recently saved me a $10 thousand dollar engine and trust me this won't be your last problem.
 
I had a bad air flow sensor on my Grand National and it was a completely different problem. The car goes into limp mode with a bad MAFS and barely
runs. My TTA runs just fine after its started when cold.
 
vetttta said:
My TTA runs just fine after its started when cold.
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I think you and Hoser are on the right track, and maybe there is something wierd going on with the chip when all the flags are set and the car should go into closed loop.

BUT! Most TT 5.x and 6.x chips are open loop idle chips.Be sure your GM guy knows this. If it can be started hot then revving it up to 2500 and holding it should send it into closed loop.

For shits and giggles on the next "no start" incident try jumpering the A&B pins on the ADL plug. You'll have to slightly depress the accelerator because the IAC wont allow any bypass air. But this starts and runs the car in "field service" mode. And if I recall this is closed loop only regardless of chip and lock timing advance of 15*....


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The dealer did jump the two pins in the ADL and started the car as you stated. Does this indicate a bad prom? If the car goes into closed loop at 2,500 rpm how would it effect the car from starting. If it dosen't go into closed loop over the 2500 rpm what does that indicate.
 
vetttta said:
The dealer did jump the two pins in the ADL and started the car as you stated. Does this indicate a bad prom? If the car goes into closed loop at 2,500 rpm how would it effect the car from starting. If it dosen't go into closed loop over the 2500 rpm what does that indicate.
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Jumping the pins was only an exercise as to whether it is an ECM/chip/sensor problem....see, if it started hot it's because it ignores certain things so as to get the car running and start diagnosing stuff.
So I would think we could rule out, starter/primary wiring and grounding issues and focus on what you are already looking at.

Now, if it goes into closed loop at higher RPM, then I would probably believe that the chip is okay and it is indeed an open loop idle chip and I would start going after coolant temp switches/wiring/connectors,opens or ground issues in the ECM's harness.

There are 3 coolant switches you know, and the ECM has a dedicated one,now I don't know if it (ECM) looks at the others or not(I doubt it,but hey?).

I would also look back into the cam sensor or at least see if it throws a code for that as if it is failing after heat soak and is producing a bad signal. That would indicate why it starts with pins jumpered as it ignores that and goes into "batch fire" mode as opposed to sequential.

This is a very interesting problem indeed.
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You stated that there is spark when it is no start (good consistant spark ?) but the injectors only give a quick flash on the node light , then nothing. Service manual says this about the Cam sensor ...The camshaft sensor is activated as the interrupter rotates with it's cam driven shaft and passes between the magnet and Hall-Effect switch. When the Hall-Effect switch is activated it grounds the signal to the ignition module, pulling the Crank Signal lines applied voltage low. This is interpreted by the ECM as a Cam Signal. This Cam Signal can also be seen as a square wave because the voltage is either high or low. The Cam Signal is created as piston #1 and piston #4 reach 25°after top dead center. It is then used by the ignition module to begin the ignition coil firing sequence starting with the #3/6 coil. The firing sequence begins with this coil because piston #6 is now in the correct position on it's compression stroke for the spark plugs to be fired. This cam signal is also used by the ECM to time the Sequential Fuel Injection (SFI) operation. If it can cause fuel to cut out and not spark it still doesnt explain how a cooled down temp sensor will let it start again.......just thinking out loud. This is an interesting problem..having a scanner on this would and should shed a lot of light.
 
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hoser said:
This cam signal is also used by the ECM to time the Sequential Fuel Injection (SFI) operation. If it can cause fuel to cut out and not spark it still doesnt explain how a cooled down temp sensor will let it start again.......just thinking out loud. This is an interesting problem..having a scanner on this would and should shed a lot of light.
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Agreed...but as a caveat...and I don't have proof, but of the mind that the cam sensor starts the sequential injection as stated, and then the ECM still takes a look at the cam sensor as reference every so often to make sure the order is still correct.My only proof is that I have had the car running and disconnected the cam sensor and the car throws a cam sensor code and starts to run in batch fire and has a noticebly different idle and runs "fatter" up top.
Now batch fire, for those who don't know is when all the injectors fire in a batch or group,like the TPI cars. wherein the fuel will sit on the back of the intake valve till its drawn into the combustion chamber.

I dont know how helpful a scanmaster would be other than to look at the ECM's temp sensor, but a full blown snap-on 2500 could show more parameters at one time....but so would a powerlogger though.


I'm starting to think it's a temp sender/circuit issue and that it is leaning the car out because it thinks it's really hot or that the air temp sensor is saying the air is really hot too....and one more thing....see if you can swap out another MAP sensor...maybe it's thinking the barometric pressure is way different...... just an idea.



EDIT...now that I think about it....take a look at the air temp sensor...it may be at the end of scale either way.



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Factory service manual has great troubleshooting flow charts, the turbo tweak forum has great articles on KR,start up loop operation all under the "download" tab. and of course turbo buick. Also allot of trial and error in experience with such problems.

The cam sensor operation has always bugged me because it didn't make sense that it is only used to locate a cylinder and the rest is a "given", right?
So I started digging around TB and found some discussions on whether it(ECM) references more that what the service manual says it does and it's my belief that it does look at for more than just start up.


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FWIW, my 'hoopy ole' 97 GMC truck acted just like vettta's car. It would start fine cold and run just fine forever....till I shut it off and I could only restart it if I held the pedal to the floor and put the PCM into "clear flood" mode that it would fire up.....it ended up being the ECMs coolant temp reference switch had failed and was telling the PCM that it was always -40*....so...



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Your ECM have the calpak chip in it? I have read that some cars stall like that too, mine didn't. maybe the calpak chip is missing.

Did you try the inlet air temp switch swap?

Have you run any of this by eric marshall at turbo tweak? or TurboBob at full throttle's website forum?
 
The cal pack chip was in the the ECM when I tried it.
Sent email to Eric a couple of weeks ago with no response. you have an email address for the other gentleman.
 
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vetttta said:
The cal pack chip was in the the ECM when I tried it.
Sent email to Eric a couple of weeks ago with no response. you have an email address for the other gentleman.
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He is on the turbobuick website as TurboBob. I believe the engine should continue to run after unplugging the cam sensor as it's only required at startup, at other times it is used only for reference by the ECM but not required. Not sure what would cause it to die.
 
Try registering at Eric's site.
http://www.turbotweak.com/forum/forum.php
post your problem and he should respond.

Turbo Bob can be found here too, register there and post under the "Buick Tech" or "ask Bob" sub forums.
http://www.fullthrottletech.com/

I know this is becoming a pain in the ass but it has got be something we"ve overlooked or above our collective skill level(s).

Eric can sometimes be hard to get a hold of but he monitors the website postings pretty well and should respond to you there.

.
 
The stock chip made no difference. The car still would not start when hot.
The head of the shop at the dealer is the one working on the car. He works on it when he has time. He is also having a hard time talking to any engineers that have knowledge of the engine. The one that does takes a long time to get back to him.
Thanks to all that have replied and I will post any new info when I get it.

Bruce Busse
 
Bruce have you tried posting this issue over on turbobuick.com ? There are a ton more users on that site and the workings of these motors and the ecm are the same between the TA and the Buicks, there are a hand full of folks over there that probably know more than anyone that can be found at GM anymore about how these motors work and all of the electronics.
 
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