Engine Breaking Down/misfiring under Acceleration.

[Dizza1]

Hi Guys My first post, I am trying to assist a friends neighbor with his VY Calais, it's a V6 ECOTEC engine and it breaks down or misfires under acceleration. I found that the vacuum hose from the throttle body to the Vacuum Switching Valve is disconnected from the VSV. I had to do some looking on my car to identify where the hose from the throttle body connects to and I have to wait till he finishes work to go back this arvo. The thing is that he had about 5 Fault codes logged but he has been disconnecting sensors all over the engine while it was running so I don't really know what is a valid fault and what isn't. The fuel trims are all in the negative, LTFT's are at -13% and the STFT's go up to -48% as I've seen so far. Which to my thinking so far would indicate a rich condition that the PCM is trying to correct, but the un-metered air must be a lot so it is a bit confusing. Unfortunately I didn't note down the fault codes before clearing them. It had an unspecified error as well as others that seemed to be likely caused by his disconnecting things and thus forcing the fault codes.

So I am wondering if anyone can tell me what the effect of a totally disconnected vacuum hose from the throttle body to the Vacuum Switching Valve would be. If I block that vacuum hose the engine stalls, which is probably normal. There is a strong smell of fuel as well. Apparently he has replaced the fuel pressure regulator the MAF sensor. I'm not sure how why or when the vacuum hose was disconnected.

I guess I will begin this arvo by reconnecting the Vacuum hose and see what happens. If it will run I'll have him take it for a good drive then see what else is happening after that. Has anyone encountered this problem and if so what was the effect ? Any help would be greatly appreciated. He got the car cheap and it has a funky paint job on the engine ect. so who knows what has been done. When I buy a car I look for everything to be as stock as possible as a good starting point.

It's my first go at troubleshooting a car with a computer, I've been under a rock for 20 years unfortunately. haha

EDIT: Well I reconnected the vacuum hose but the engine stalls now at idle with the MAF sensor connected, it will start with a second cranking, however it's spitting fuel out of the exhaust and has only a slight hesitation rather than breaking down repeatedly and chugging, although with any application of the throttle it stalls on rev down. Without the MAF sensor connected it starts and idles better, revs better but is still running high fuel consumption, smells fuely ect.

Something seems quite odd to me so I think he needs to take it to the shop. It will be interesting to find out just what is wrong with it.

 

[DOASKID]

I recently had to do lower intake manifold gaskets on my vy11 and when I put everything back together I could not work out where the hose from bottom of the throttle body is went to. So I drove it around for 1 day disconnected and the car would not idle properly and had trouble starting on cold start. but that was about it. Still couldn't find where it went so I just plugged it up with a bolt and it ran perfect. I've since found where it goes....

 

[Dizza1]

Well I figured by reconnecting the hose it might idle at the correct rpm, but it didn't. I worked out where it went by looking at the emissions diagram then at my own car engine to find the actual location of the VSV. I am thinking that maybe the engine could have been damaged if it was run like it was for too long with the check engine light on. It seemed to me that the hose was disconnected for some time going by the state of the connector where the vacuum hose attaches. Regardless I cannot help him as I lack the required equipment. I think it needs a compression test. Anyhow I think I learned something at no expense to myself.

My own car, a VX has a minor issue where it sometimes does not start on first crank, so I intend to clean the throttle body and check all the vacuum hoses. I'll wait till the weather cools off it is oppressive here lately. Thanks for the reply, it was helpful, from that I can deduce the VY has some other issue as well of course, indicated by the negative fuel corrections.

 

[DOASKID]

You can buy cheap obd11 scanners off eBay to find and clear trouble codes. I haven't bought one myself, but people say they get the job done.....you even have Access to real time data from the engine sensors......

Auto CAR V1 5 ELM327 OBD2 Odbii Bluetooth CAN BUS Scanner Tool Torque Android | eBay

For example.

 

[Woodsman444]

You can buy cheap obd11 scanners off eBay to find and clear trouble codes. I haven't bought one myself, but people say they get the job done.....you even have Access to real time data from the engine sensors......

Auto CAR V1 5 ELM327 OBD2 Odbii Bluetooth CAN BUS Scanner Tool Torque Android | eBay

For example.

Hello This question comes many months after your post I am just going through similar issues to correct a fault with my own VY2 I have an OB2 scanner I bought a ELM327 scanner and also had another one that connected straight to a laptop,anyway not one scanner will read my car. All I get is a message failure to connect message. My engine misses when hot I have changed the plugs the leads the coilpack the throttle body and the crank angle sensor and still cannot find the fault.

 

[Edmond Ugljesa]

You can buy cheap obd11 scanners off eBay to find and clear trouble codes. I haven't bought one myself, but people say they get the job done.....you even have Access to real time data from the engine sensors......

Auto CAR V1 5 ELM327 OBD2 Odbii Bluetooth CAN BUS Scanner Tool Torque Android | eBay

For example.

Hi will the scanner work on 2002 vx commodore ? Any reply appreciated

 

[Utel67]

Hi will the scanner work on 2002 vx commodore ? Any reply appreciated

If it's a V8 you will need the ELM327 if it's a V6 you will need a ALDL cable, checkout the link below.

https://forums.justcommodores.com.au/forums/envyous-customs.251/

 

[Ben420]

Hi Guys My first post, I am trying to assist a friends neighbor with his VY Calais, it's a V6 ECOTEC engine and it breaks down or misfires under acceleration. I found that the vacuum hose from the throttle body to the Vacuum Switching Valve is disconnected from the VSV. I had to do some looking on my car to identify where the hose from the throttle body connects to and I have to wait till he finishes work to go back this arvo. The thing is that he had about 5 Fault codes logged but he has been disconnecting sensors all over the engine while it was running so I don't really know what is a valid fault and what isn't. The fuel trims are all in the negative, LTFT's are at -13% and the STFT's go up to -48% as I've seen so far. Which to my thinking so far would indicate a rich condition that the PCM is trying to correct, but the un-metered air must be a lot so it is a bit confusing. Unfortunately I didn't note down the fault codes before clearing them. It had an unspecified error as well as others that seemed to be likely caused by his disconnecting things and thus forcing the fault codes.

So I am wondering if anyone can tell me what the effect of a totally disconnected vacuum hose from the throttle body to the Vacuum Switching Valve would be. If I block that vacuum hose the engine stalls, which is probably normal. There is a strong smell of fuel as well. Apparently he has replaced the fuel pressure regulator the MAF sensor. I'm not sure how why or when the vacuum hose was disconnected.

I guess I will begin this arvo by reconnecting the Vacuum hose and see what happens. If it will run I'll have him take it for a good drive then see what else is happening after that. Has anyone encountered this problem and if so what was the effect ? Any help would be greatly appreciated. He got the car cheap and it has a funky paint job on the engine ect. so who knows what has been done. When I buy a car I look for everything to be as stock as possible as a good starting point.

It's my first go at troubleshooting a car with a computer, I've been under a rock for 20 years unfortunately. haha

EDIT: Well I reconnected the vacuum hose but the engine stalls now at idle with the MAF sensor connected, it will start with a second cranking, however it's spitting fuel out of the exhaust and has only a slight hesitation rather than breaking down repeatedly and chugging, although with any application of the throttle it stalls on rev down. Without the MAF sensor connected it starts and idles better, revs better but is still running high fuel consumption, smells fuely ect.

Something seems quite odd to me so I think he needs to take it to the shop. It will be interesting to find out just what is wrong with it.

Hi I have had the exact same problem I changed everything then one day I started the car and it hydrolocked on me two injectors were stuck open flooding the engine changed the injectors and no more problems