This is getting old quick!!!

[markNtennessee]

My 01 Expy EB 4x4 5.4l and the lack of power at low end is really getting to me. When im driving about 15-20 mph and floor it, you dont feel the engines power until around 3500 rpm's, and also when at idle and a gas it a little the rpms hang up at 1000 then slowly drop to 750, and start it up it idles up to around 1200 and then drops to 750 and sits there for a few seconds and idles back up to almost 1000 then idles down again. Also i have noticed a little more engine shake at idle, its not smooth at all, but not missing.

the mods done to this truck it rear 2 cats removed, flowmaster 40 seriers SI/SO in place of the factory muffler and a K&N filter with the gotts mod. Also i took the throttle body off and cleaned it and cleaned the EGR passage.

 

[97EB5.4]

Have you run codes yet whether the light is on or not? I had a similar problem and it wound up being a bad coil pack. Whens the last time a tune up has been done, fuel filter? Just trying to rattle off things to look into.

 

[markNtennessee]

I replaced plugs and fuel filter about 8 months ago, and there are no codes present. I never changed the coils or boots, and i didnt use any type of electrical grease when i done the plugs. I have cleaned the IAC and the MAF. Im at a loss. the truck doesnt miss, it just dont have any power at all. how can you check the coils to see if one is bad without having a check engine light.

 

[Racenut]

I replaced plugs and fuel filter about 8 months ago, and there are no codes present. I never changed the coils or boots, and i didnt use any type of electrical grease when i done the plugs. I have cleaned the IAC and the MAF. Im at a loss. the truck doesnt miss, it just dont have any power at all. how can you check the coils to see if one is bad without having a check engine light.

Carefully with the truck running pull the electrical conector off one coil at a time, if the coil is good you will notice the rpms drop and it will start stumbling but if the coil is bad there will be no change at all because that cylendar is not firing anyway. Hook the plug back up and go to the next, it is a pain but it is a sure test to see if you have a bad COP.

 

[markNtennessee]

Racenut, I have already checked the coils that way and I also checked the injectors the same way.

Im running NGK plugs in the truck. I wonder if the boots are bad and arching to the head, causing a low grade mis fire? the truck has 160000 on it and from what i can tell its the original coils and boots. I have checked the PVC hose.

it drives me crazy when i know something is wrong with it, but i cant figure out what it may be.

 

[panda24619]

sounds like vacuum leak. just the pvc valve the elbow and that entire line. mine was the elbow but i replaced the valve too. and i broke the hard line but fixed it with some fuel line. works great.

 

[markNtennessee]

I thought it might be a leak also, and i have sprayed all over every hose and every joint with started fluid, brake cleaner and carb cleaner. I have even used a propane torch. now the weird part is, that i even removed a vacuum line to see if it was working and sprayed over the hose and even ran the propane over it and the truck done nothing. no increase or decrease in the idle.

 

[Racenut]

I thought it might be a leak also, and i have sprayed all over every hose and every joint with started fluid, brake cleaner and carb cleaner. I have even used a propane torch. now the weird part is, that i even removed a vacuum line to see if it was working and sprayed over the hose and even ran the propane over it and the truck done nothing. no increase or decrease in the idle.

That is weird I will have to try that out on mine tomorrow and see if it makes a difference. Which vacuum line did you try?

As for the COP's if you are questioning the boots, I have seen them for like $5 a piece. But for me I would just order a set off Ebay, I have heard alot of people talking about them and they are good factory replacements. The best part is under $100 shipped and you get all 8 coils plus the boots, if your going to go thru the work of replacing boots might as well replace the coils at the same time and kill two birds with one stone.

 

[markNtennessee]

the small white hard line that connects to the valve on the brake booster.

 

[markNtennessee]

I replaced all the coil boots and springs today and so far it seems to be running better.