Tune up

[Holsenback]

Okay so here is the issue. I notice that my throttle response extremely lags. I have gone through all the basic tune up items

-Gapped spark plugs (they are fairly new and do not require replacement)
-Checked plug wires (new also)
-Replaced fuel filter
-Changed oil / oil filter
-Changed air filter
-Cleaned the MAF

I am running out of resonable things to check/replace. Truck runs top notch until it warms up, so I'm stumped.

[4.0 SOHC]

 

[Big Jim M]

Ok!

Okay so here is the issue. I notice that my throttle response extremely lags. I have gone through all the basic tune up items

-Gapped spark plugs (they are fairly new and do not require replacement)
-Checked plug wires (new also)
-Replaced fuel filter
-Changed oil / oil filter
-Changed air filter
-Cleaned the MAF

I am running out of resonable things to check/replace. Truck runs top notch until it warms up, so I'm stumped.

[4.0 SOHC]

Now give a better description of what is happening that leads you to make a post. Give us the facts man, just the facts.
Big JIm

 

[Holsenback]

Well basically my throttle response is terrible, when I touch the gas it has a dramatic delay. I used to all the time, but after the tune up it now lags as said above when it warms up.

I even ran some fuel injector cleaner and a couple tanks of premium gas to clean the injectors. I have no DTCs. It's strange when I start up it is top notch.

 

[Big Jim M]

Ok so you are saying it was running fine and you decided to TUNE it up... Then after you messed with it it is lugging and doesn't run as good as it did before?
From your description I'd make a wild gues and say you have messed up your maf..
Big JIm

 

[Larry's shee]

The way I'm reading it , the problem went away as to cold engine but remains when hot . Correct me if I'm wrong Holsenback. What about O2 sensors? What did you use on the MAF? How many miles on truck?

 

[Holsenback]

You are right Larry. I was preset all the time, but after the tune up the issue is still there when the engine is warmed up. [I have 85K]

I used MAF cleaner, I used a security torx bit to remove the MAF sensor from the housing. Never touched the wires or the elements just sprayed a few times and let it air dry.

I have done a fair bit of research before I posted anything about the issue. I'm not completely ignorant, just wondering if I have overlooked anything thats all...

 

[88_Eddie]

seafoam that bitch, and yeah, clean or replace an 02 sensor

 

[Holsenback]

Yeah Seafom was next on the list, I was looking for a reason to piss my neighbor off today.

 

[modelageek]

You are right Larry. I was preset all the time, but after the tune up the issue is still there when the engine is warmed up. [I have 85K]

I used MAF cleaner, I used a security torx bit to remove the MAF sensor from the housing. Never touched the wires or the elements just sprayed a few times and let it air dry.

I have done a fair bit of research before I posted anything about the issue. I'm not completely ignorant, just wondering if I have overlooked anything thats all...

I am not clear if the issue started after the tuneup? did you put the FF in the right direction? did you spray the MAF when it was hot? did you reset the PCM?

I am sure you know but i will remind you that if you seafoam it be prepared to maybe blow out a plug and make sure you seafoam it and then change the O2 sensors(if you change them)

 

[Holsenback]

- The issue has been around the whole time (On start up and while at normal operating temperature)

- After the tune up it runs great at startup UNTIL it gets to normal operating temperature)

- I did not spray the MAF when it was hot. I let the truck sit overnight before working on it.

- Yes every thing was installed to proper specs.


Thanks for the O2 sensor tip, I have not done the seafoam treatment yet.

 

[modelageek]

Couldbe a bad MAF. Disconect it when it is warmed up. Ect sensor?

 

[nitrofan1]

Hmmmm. I'm not sold on the MAF still being the issue. As long as you cleaned it with MAF cleaner and nothing else, didn't touch the fine wire it should be OK. Get a code reader to double check for any codes that may be stored even if the check engine light is off. Next get Seafoam in 2 steps. The liquid and the new spray. The spray was developed for crazies like us that like to pour it right into the intake via suction and piss of neighbors, insects, etc..... The spray directions tell of a port most cars have that you can spray it into and lessen the risk of too much cleaner at once.

If no codes are found and you've done all the things you stated I know this sounds silly but have a fuel pressure check. Mine was doing a similar thing and next thing I knew I was putting a new fuel pump in. I'm old school and a fuel pump either works or it doesn't. But my pump was going down a little at a time until it puked. Now it has normal power and runs fine.

 

[modelageek]

Hmmmm. I'm not sold on the MAF still being the issue. As long as you cleaned it with MAF cleaner and nothing else, didn't touch the fine wire it should be OK. Get a code reader to double check for any codes that may be stored even if the check engine light is off. Next get Seafoam in 2 steps. The liquid and the new spray. The spray was developed for crazies like us that like to pour it right into the intake via suction and piss of neighbors, insects, etc..... The spray directions tell of a port most cars have that you can spray it into and lessen the risk of too much cleaner at once.

If no codes are found and you've done all the things you stated I know this sounds silly but have a fuel pressure check. Mine was doing a similar thing and next thing I knew I was putting a new fuel pump in. I'm old school and a fuel pump either works or it doesn't. But my pump was going down a little at a time until it puked. Now it has normal power and runs fine.

a fuel pressure test is always a good thing to do. if you have the tester it only takes 15 minutes or less. that being said I ont think it is the pump because it is fine on start up and then goes bad when it warms up. that is a very consistent issue.....to consistent for the fuel pump, imho. I think big jims first guess is a good one(the maf) and i also would test ohms on the ect sensor. see if you can catch a pending code...maybe even a stuck egr valve?

 

[Holsenback]

I followed the advice to dissconnect the MAF and run it at default. I did notice that the drop in response was gone, of coarse I got a DTC. Strange that I never got a DTC on the MAF I was running to start with. I replaced the MAF and it now runs fine.

 

[Big Jim M]

Today is the 25th.. I suggested the maf on the 18th...
Big JIm