Engine starts then stalls immediately

[Jmattioli]

I have a 2001 GMC Sierra 1500 SLT 5.3l that I bought used with only 80k miles on it. This truck starts then immediately stalls. Here is a list of things that I have replaced to no avail. Any help would be greatly appreciated.

 

2001 gmc sierra 1500 SLT 5.3l

Replaced TPS

Replaced TBI

Replaced ignition

Replaced passlock housing

Replaced Ignition cylinder

Replaced PCM/ECM/ECU

Replaced fuel pressure regulator

 

Truck had codes of P0102, P0105 and P0507

 

No codes available at this point because of changing PCM/ECM/ECU

 

Thanks

Jeff

[Jmattioli]

I know there will be question why I replaced a couple of things so I will let you all know that I first replaced the TPS because an extremely high idle and found no vacuum leaks. Then replaced the TBI because the Airflow code I had on the truck. The AIC was also new on the TBI. The stalling issue happened intermittently while I was working on the truck and now does it constantly. So I replaced some of the other items listed in this post. I do not have access to a tech2 so some of the proper testing is not an option for me, and I live in the middle of no where.

Edited April 17, 2017 by Jmattioli

[Podor]

Does the security light flash?

 

If you unplug the MAF sensor, does it run?

[HeathT-87]

Had the same issue when I had mine, I changed fuel filter and pump, and all the coils. The coils were my problem. Check fuel pressure its supposed to be 50-55 I believe.

[Jmattioli]

fuel pressure is normal it is 55lbs when ignition is turned to on and jumps to 62lbs when engine cranks, No the security light is off. i did the passlock reset after installing new PCM. Engine ran without MAF when it would start.

[Jmattioli]

Had the same issue when I had mine, I changed fuel filter and pump, and all the coils. The coils were my problem. Check fuel pressure its supposed to be 50-55 I believe.

 

was it one coil or did you change all 8? was not sure about coils since it does start then stall immediately.

[muddkatt]

Not any water in the fuel is it?

[Podor]

fuel pressure is normal it is 55lbs when ignition is turned to on and jumps to 62lbs when engine cranks, No the security light is off. i did the passlock reset after installing new PCM. Engine ran without MAF when it would start.

 

We have 2 potential issues that may or may not be related. The first issue is the high idle. The question is was that caused by a mechanical issue or an electronic issue. The 3 codes come from a higher idle condition that isn't controlled. If the TPS sensor sees closed throttle, but a high idle with matching MAF/Map signals, it flags the codes. That could have been caused by an open Pcv system or stuck open IAC valve. It could also be an electrical issue, but highly unlikely. Now we have the no start condition, which may or may not be caused by the repairs for the first issue. I suggest putting everything back, including the PCM and starting from scratch on the high idle issue first.

[Jmattioli]

We have 2 potential issues that may or may not be related. The first issue is the high idle. The question is was that caused by a mechanical issue or an electronic issue. The 3 codes come from a higher idle condition that isn't controlled. If the TPS sensor sees closed throttle, but a high idle with matching MAF/Map signals, it flags the codes. That could have been caused by an open Pcv system or stuck open IAC valve. It could also be an electrical issue, but highly unlikely. Now we have the no start condition, which may or may not be caused by the repairs for the first issue. I suggest putting everything back, including the PCM and starting from scratch on the high idle issue first.

Can't just put everything back (the arm for the adjuster screw on the TBI was bent, causing the high idle, couldn't be adjusted properly). the no start is what cause the changing of the PCM (not the high idle condition), everything that relates to the high idle Air flow issue is brand new. TBI, AIC,TPS, and MAF as far the PVC valve itself it is unlikely, but i have one just in case. It is the no start/stalling issue that is the problem at this point. Which I have already replaced any part that had been tampered with (many resistors soldered into the ignition wireset, and the passlock housing which had been drilled into by the previous owner). The no start stalling issue was intermittent before the repairs. would start and run, then wouldnt start for a whole day afterwards. now just never stays running.

 

I opted to replace the PCM because I felt it was more probable than the BCM to cause the stalling issue. I may be wrong about this and that is why I am here. Any chance the BCM would interfere with the truck staying running?

 

I don't have much invested into this truck, bought it for less than $1000 (80k miles and excellent body and frame) plus have only parts and my time into as far as repairing it.

[Jmattioli]

Not any water in the fuel is it?

not to my knowledge, but i cannot be 100% positive(bought the truck used with 3/4 tank of gas in it). A small oversight like this would be great news. I'll add drygas and see if that helps.

[Mike GMC]

Unfortunately, new does not necessarily mean functional. If you have a multi meter, search for the correct readings for each sensor and check them. Have you tried starting with the throttle open part way? I had a bad IAC and it acted like your, but would start and run if I held the throttle pedal down a bit. Also, check your MAP sensor on the back of the manifold.

[Jmattioli]

Unfortunately, new does not necessarily mean functional. If you have a multi meter, search for the correct readings for each sensor and check them. Have you tried starting with the throttle open part way? I had a bad IAC and it acted like your, but would start and run if I held the throttle pedal down a bit. Also, check your MAP sensor on the back of the manifold.

 

thanks,

 

I have no knowledge of how to check the MAP sensor without the truck actually running. any suggestion?

 

[Mike GMC]

It's difficult but can be done. You'll have to remove it and find a piece of hose that fits over the sensor tightly. Fit a vacuum nipple into the other end. Use a hand vacuum pump to change the "pressure" and read the ohms across the pins. That's the best method I can think of.

[Podor]

Map sensors are used for monitoring only, they will not cause a no start condition unless it is shorted causing another sensor to lose 5v reference.

 

Just for clarification;

At what point did the no start condition start, what did you replace before and what did you replace afterwards?

 

Mike Gmc has a good idea. Will it run above closed throttle? It is very possible that has to relearn idle if everything was so off. IAC motors will cause this also and not set a code. If it runs with a little throttle, we may be in pretty good shape. Keep it running until it gets a little warm, then let off and see what happens. It may take a little bit to relearn. If it runs but still won't idle, It's probably the IAC motor itself. The IAC motor allows a metered vacuum leak to control idle. If the motor itself is bad or the port is clogged, it won't be able to raise the idle on startup. So it will fire with the initial rich mixture controlled by the PCM, but if it can't raise the idle it will stall.

[Jmattioli]

Map sensors are used for monitoring only, they will not cause a no start condition unless it is shorted causing another sensor to lose 5v reference.

 

Just for clarification;

At what point did the no start condition start, what did you replace before and what did you replace afterwards?

 

Mike Gmc has a good idea. Will it run above closed throttle? It is very possible that has to relearn idle if everything was so off. IAC motors will cause this also and not set a code. If it runs with a little throttle, we may be in pretty good shape. Keep it running until it gets a little warm, then let off and see what happens. It may take a little bit to relearn. If it runs but still won't idle, It's probably the IAC motor itself. The IAC motor allows a metered vacuum leak to control idle. If the motor itself is bad or the port is clogged, it won't be able to raise the idle on startup. So it will fire with the initial rich mixture controlled by the PCM, but if it can't raise the idle it will stall.

 

Its not a No Start its a Start then immediately stalls.

the starting then immediately stalling has happened since the day i bought the truck. It happened intermittently at the time, but i would wait until the next day and the truck would start. then i would continue on with the repairs from the codes. after about a week of waiting for a day for it to start and stay running, it finally decided to never stay running again.

 

there were several problems that were being worked on at once.

1) High Idle

2) Intermittent Start and immediate stall

3) passlock housing needed to be changed because previous owner drill several holes into the housing next to the sensor.

 

After TBI, TPS, AIC were change the truck started and i drove it several miles to my house. Started it up the next morning to make sure it was going to start in the Sub Zero temperatures we were having at the time. It started and stayed running. tried again after temps warmed up outside again so i could work on the ignition and passlock housing issues. The truck at that point only started and stalled every since that time.

 

now cannot get the truck to stay running.

Edited April 18, 2017 by Jmattioli