Rough Idle, new guy here

[sboggs]

Hi guys, I have a 99 x with 5.0 When I start my engine, it runs as though it is flooded, rough idle, but after driving a few miles it clears up and runs fine. If i let it set a while, then start, same think again. A little history, the plugs, wires are new. The idle control valve is new, and the fuel pump is new but I still continue to have this "flooded like" stmpton. Any help would be great.Thanks,Sam.

I have now run sea foam and my results are the same. I did go and have the computer checked to see if there were any hidden codes, there were none. Does anyone think that maybe the mass air sensor could be bad or maybe the throttle sensor, and if so where on the 99 5.0 is the throttle sensor be located and can it be cleaned, thanks again, sam

 

[exploded99]

My 5.0 had a tough start / bad idle problem that would happen after being parked overnite. Starting and idle were great after short stops.

When I changed plugs, I found one of them covered in deposits - a leaky fuel injector. It may be a little hard to nail this down to a particular cylinder given you have new plugs.

If the truck is parked overnite, and the intake valve on the bad cylinder happens to be open, you will smell the raw gas on that plug when you pull it - the gas will trickle into that cylinder. Bit of a hit or miss thing though.

So if your hot starts are good, that is what I would suspect given your other new parts!

 

[sboggs]

thanks for the info. My starts are cold or hot, same rough idle, flooded like. I have searched further and I am going to try and clean the MAF tonight and see if that helps. It has not been cleaned since I got it. It had 52k when I bought it and now has 215k

 

[aldive]

Have you tried something simple like running Sea Foam through the intake and gas tank?

Good luck ........

 

[sboggs]

No I have not tried that yet. I had the injectors cleaned saturday, but I have been reading on here about the sea foam, never heard of that before but I am considering that as soon as I figure out which is the best way to do that, through the brake booster or the throttle body, any suggestions from your point of view?

 

[sboggs]

aldive, got the sea foam today. so is it ok to run this into the brake booster vacum hose, and i have also heard to put 1/3 in vacum, 1/3 in oil, 1/3 in gas tank, do you agree with that , I also cleaned the mass air sensor last night and it seemed to run a whole lot better today, but still going to so the sea foam, thanks, sam

 

[aldive]

The brake booster hose will work fine.

I would not put any in the oil; put in gas tank is OK.

Good luck ......

 

[sboggs]

ok, thanks alot for your help, sam

 

[sboggs]

Hi guys, I have a 99 x with 5.0 When I start my engine, it runs as though it is flooded, rough idle, but after driving a few miles it clears up and runs fine. If i let it set a while, then start, same think again. A little history, the plugs, wires are new. The idle control valve is new, and the fuel pump is new but I still continue to have this "flooded like" stmpton. Any help would be great.Thanks,Sam.

I have now run sea foam and my results are the same. I did go and have the computer checked to see if there were any hidden codes, there were none. Does anyone think that maybe the mass air sensor could be bad or maybe the throttle sensor, and if so where on the 99 5.0 is the throttle sensor be located and can it be cleaned, thanks again, sam

also did try and clean the mass air, but no change

 

[exploded99]

Disconnect the battery for 15 to 20 minutes so the engine has to relearn everything.

Unplug your maf. This puts the engine in limp mode. It will then use the throttle position sensor and rpm to determine how much air the engine gets. Timing advance will be cut back.

Start it and see if the idle is rough. Check cold and check after warm up. If the idle has smoothed out, shut the truck off and plug the maf back in and see if there is a change.

Post your results back!

 

[quasarsky]

try replacing the ect sensor

fixed my starting problems