Lack Of Power 94 350

[dji]

I have a 94 350 with about 150,000 miles on it. I replaced the intake gaskets because it has been leaking oil and water. Before I did the intake gasket the truck was running great but I fail the emissions test high HC (high speed 145 intead of 143). The last 15 years it has always been between 45-60ppm. Now I have a lack of power when I accelerate and it uses more gas. It passed the emission test HC of 96. Idle speed is okay. Not sure what to check? Timing? The emission hoses look okay. No codes errors.

 

I did switch the spark plugs to champion platium 3018 a month before I failed the emissions test. The truck ran fine and I pulled a couple of plugs this morning and they looked good. I have been using champion truck plug 4018 and never had a problem with them. I also added a fuel additive before re-doing the emission test.

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Could be many things on a tbi. Weak f-pump, dirty TB, vacuum leak. I'd start checking for a vacuum leak since you said it ran just fine before changing the intake gasket. You could've left something unplugged or whatnot.

[thebandnerd03]

you said you added a fuel additive to it. you might want to think about changing your fuel filter. sometimes that stuff will break up unwanted dirt and sediment from the tank and plug up the filter

[minibike132]

Before I did the intake gasket the truck was running great but I fail the emissions test high HC (high speed 145 intead of 143). The last 15 years it has always been between 45-60ppm.

 

What was the CO#

 

 

 

I did switch the spark plugs to champion platium 3018 a month before I failed the emissions test. The truck ran fine and I pulled a couple of plugs this morning and they looked good. I have been using champion truck plug 4018 and never had a problem with them. I also added a fuel additive before re-doing the emission test.

 

I like to run delco in anything GM, just my opinion but pretty much every mechanic I have ever talked to about the issue feels the same. Some odd problems have been cured by changing from Champion to Delco.

[dji]

you said you added a fuel additive to it. you might want to think about changing your fuel filter. sometimes that stuff will break up unwanted dirt and sediment from the tank and plug up the filter

 

Good point. A few summers ago I had a problem with the fuel filter getting plugged and having to replace it every 2000 miles for a while. I also checked for vacuum leaks and everythings seems to be hooked up.

[dji]

Before I did the intake gasket the truck was running great but I fail the emissions test high HC (high speed 145 intead of 143). The last 15 years it has always been between 45-60ppm.

 

What was the CO#

 

 

 

I did switch the spark plugs to champion platium 3018 a month before I failed the emissions test. The truck ran fine and I pulled a couple of plugs this morning and they looked good. I have been using champion truck plug 4018 and never had a problem with them. I also added a fuel additive before re-doing the emission test.

 

I like to run delco in anything GM, just my opinion but pretty much every mechanic I have ever talked to about the issue feels the same. Some odd problems have been cured by changing from Champion to Delco.

 

 

 

The CO when it failed was high speed .54 low speed .38.standard is 1.60 and 1.24.

When it passed the CO was .56 .54

[minibike132]

Before I did the intake gasket the truck was running great but I fail the emissions test high HC (high speed 145 intead of 143). The last 15 years it has always been between 45-60ppm.

 

What was the CO#

 

 

 

I did switch the spark plugs to champion platium 3018 a month before I failed the emissions test. The truck ran fine and I pulled a couple of plugs this morning and they looked good. I have been using champion truck plug 4018 and never had a problem with them. I also added a fuel additive before re-doing the emission test.

 

I like to run delco in anything GM, just my opinion but pretty much every mechanic I have ever talked to about the issue feels the same. Some odd problems have been cured by changing from Champion to Delco.

 

 

 

The CO when it failed was high speed .54 low speed .38.standard is 1.60 and 1.24.

When it passed the CO was .56 .54

 

 

So CO stayed the about the same but HC went up. Looks like you are lean, +1 on change the fuel filter then look again for vacuum leaks.

[minibike132]

Before I did the intake gasket the truck was running great but I fail the emissions test high HC (high speed 145 intead of 143). The last 15 years it has always been between 45-60ppm.

 

What was the CO#

 

 

 

I did switch the spark plugs to champion platium 3018 a month before I failed the emissions test. The truck ran fine and I pulled a couple of plugs this morning and they looked good. I have been using champion truck plug 4018 and never had a problem with them. I also added a fuel additive before re-doing the emission test.

 

I like to run delco in anything GM, just my opinion but pretty much every mechanic I have ever talked to about the issue feels the same. Some odd problems have been cured by changing from Champion to Delco.

 

 

 

The CO when it failed was high speed .54 low speed .38.standard is 1.60 and 1.24.

When it passed the CO was .56 .54

 

 

So CO stayed the about the same but HC went up. Looks like you are lean, +1 on change the fuel filter then look again for vacuum leaks.

 

 

DOH, I'm not fully awake yet. What was the low speed HC?

[dji]

you said you added a fuel additive to it. you might want to think about changing your fuel filter. sometimes that stuff will break up unwanted dirt and sediment from the tank and plug up the filter

 

I replaced the fuel filter yesterday and drove around a little and it has made a difference. I will be driving the truck more this week then I will know for sure. I think this has corrected the problem. I am starting to wonder about fuel additives and fuel filters. Normally I don't use them much.

 

Thanks everyone..