94 Yukon 350 Idle issues and Loss of power.

[AllStrobedUp]

Someone please help, I am at my wits end with this. Truck has been running amazing, all the sudden on the way home it lost almost all power. Now it is idling terrible. I can hear what I think is an exhaust leak but now think it's vacuum. I did get mad and floor it and it cleared up for a few minutes and the exhaust/vacuum leak sound went away. I have taken a video.

So far I have replaced the EGR and MAP sensor, it also has a new TPS sensor as of a month ago.

Also I noticed a single wire and terminal on the coil harness that is not connected to anything and that cought my attention.

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[1997]

any codes? why did you change the TPS a month ago?

OBD1 can set codes without check engine light coming on.

seems like it's surging, was it warmed up when you took the video?

 

[NorthState]

Not sure it solves the problem, but did y’all notice the injectors firing irregularly? Just an observation.

Great video @AllStrobedUp! It’s always good to have supporting video to go along with a post!

 

[AllStrobedUp]

TPS had been bad for years didn't know it. Only after changing it did I get torque converter lockup and amazing change in fuel economy.

No check engine light, I do have an ABS light. Need a new hub assembly on the PASS side.

This was taken after it was running for about 5 minutes and approximately 160°

This issue was night and day. It was fine one minute then way down on power and felt like I was pulling a house and now it doesn't even want to run.

I did however get frustrated, floored it a few times and it seemed to come back, idle normal and had power back, until I went to drive it around the black and the it seemed in and out, hold the throttle in one position and it would throw you back in the seat or try to throw you out of the windshield that's where I have gotten with it. The EGR was replaced because I thought it was the source of the exhaust leak sound and original, and the map was also original. Both replaced with Delco parts. Hissing sound seems to be coming from the IAC port on the throttle body. I preventatively replaced it a about 5 years ago and am going to swap the old one back Sunday when I get it from my other house.

 

[AllStrobedUp]

This was the day it happened when i limped home from work.

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[AllStrobedUp]

Not sure it solves the problem, but did y’all notice the injectors firing irregularly? Just an observation.

Great video @AllStrobedUp! It’s always good to have supporting video to go along with a post!

I think it's from the frame rate of the camera and, the surging. it is spraying a nice uniform cone of fuel when it's running smoothly.

 

[1997]

OBD1 can set codes without check engine light coming on.

 

[AllStrobedUp]

OBD1 can set codes without check engine light coming on.

I will have to try and read them tomorrow morning and I will post my findings. It would occasionally throw an EGR code when cruising, that's why I started with that. I appreciate your help!

 

[1997]

you can download manuals here ...

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

 

[AllStrobedUp]

you can download manuals here ...

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

The manuals seem to be what I am doing with limited diagnostics tools correct. I still can't figure out what the unused single wire connector on the coil harness is for. I googled pictures and in all the pictures it's taped to the harness and not used so I'm. Not as concerned anymore. I still haven't checked codes yet but I'll post back when I get a minute to continue troubleshooting.