So my check engine light came on and it to get the intake manifold gasket replaced and then things went crazy from there at the moment the truck smells like a gas tank. It’s it’s so rich that it smells like raw gas sometimes it’s it runs smooth as can be and other times it runs like like it has no business running at all. It sounds horrible. Usually when I take off, it’s rough and then all cylinders kick in. I got power running smooth but as soon as I start to slow down to come up to a light, it starts up again and every time I take off it feels as though I can’t barely get up a hill. It takes a little bit to get going again, but then it’ll smooth out for maybe a minute and then it’ll start misfiring again So far I have replaced plugs, wires, ignition coils, injectors, engine, control, module, both catalytic, converters and muffler, both knock sensors and the intake manifold gasket.

I have sprayed brake cleaner into the engine by the intake to see if the engine revved and it did not so I assume no vacuums leak.

I checked the fuel pressure it maintains 55 psi

what else should I try? My next guess is idle air control valve. This has been very frustrating. I’ve tried everything I can think of as anybody else had this problem. I feel like it’s a vacuum issue, but I’m no mechanic.

 

Did you do a crank relearn? Did you use AC Delco parts that were not purchased on Amazon or Ebay?

 

No I bought most off Amazon and eBay. But I keep replacing and nothing is changing. I have not done a relearn. I am going to reinstall the original ecm and replace the IAC valve and see what happens. It seems that when slowing down and / or coming to a stop is when it misfires. I thought it was fuel related. Fuel pump pressure good. Replaced injectors. Been that it is intermittent and not permanent means a sensor or something electrical? Looking into that there must be 50 different sensors on this motor. Do I have to do a relearn if putting the original in changed ecm back in?
thanks for the reply.

 

the coils ground to the back of each head make sure your grounds are clean and have continuity.
the coil plug harnesse to engine harness pigtail where known to need replacement when replacing coils, dorman sells them. same for the knock sensor harness.

 

Vapor purge valve on front driver side of intake manifold....sticking open maybe

 

you've changed a lot of parts and still the same issue, do you have access to a scanner to see live data from the sensors?
You can get a cheap dongle with Torque lite and see the general sensor feedback which would be helpful for troubleshooting.
What codes are you seeing when it starts acting up?
Is your truck stock or has someone performed engine upgrades?
I may have missed it but don't see where you stated the year of your truck.

Neal

 

It’s a 2005. I don’t know what a vapor purge is but I will look into that. Also the coils clean out may be worth a shot. I’m really sure it’s something so simple. I am going to try the IAC valve next. Thanks for the ideas. One of these will get it.

 

 

It's mounted on the driver side of your intake manifold. Controlled by the ECM, it opens up and lets you burn off the fuel vapors from the fuel tank. If it sticks open, it floods the intake with fuel vapor resulting in a rich mixture. Can make starting difficult. Misfires. Not expensive at all. If yours is original it's long past due to be changed. Literally takes 5 minutes.

 

2005 you have the 6 liter, should be at the front of the intake on top. 6.2 has it on the driver side