Here's the story... I had my truck (01 Screw, 5.4) at the dealer last week for routine stuff, basically an oil change. Since then, the engine seems to occasionally idle rough at red lights and lug under moderate acceleration. I originally wrote it off to a bad tank of gas, but a week (and two tankfuls) later, it's still occurring.

Anybody have any ideas? I'm beside myself on this one. I don't know if the dealer could possibly have done something to cause this or what.

Thanks.

 

Check the #4 cyl. (the last one on the passenger side) for a green residue on it. If that is the case, then you have a very small leak from the heater lines directly above that coil pack, and it's causing it to short. That's what happened to mine. Replace the coil and put a screw-type hose clamp on the offending heater lines.

How many miles are on it? If it's been more than 10-15k miles since the last time you changed your fuel filter, you may want to go ahead and do that to see if that doesn't help your problem.

Try some fuel injector cleaner. Sometimes the strangest of problems have the simplest solutions...

Also... if none of the above work, take it back to the dealer and complain that they screwed it up.

-Flea

 

do you know for sure what oil they put in it?

i have seen this happen on new engines that call for a 5w-X and the shop uses 10w-X.

it's just a hunch and i am not trying to start an oil debate.

just my .02

 

bw,

Just a wild guess. The tech who worked on you're truck managed to loosen a vacuum hose. Listen for the "giant sucking sound" or maybe an intermittant and not so "giant" sucking sound.

Good Luck

 

Well, I had it into the dealer for something else and mentioned the problem. They couldn't recreate it, but downloaded the latest shift patterns and what not into the computer. We'll see if it helps.

 

hcmq,

You aren't serious are you? Do you really think that a 10w-30 would affect how a vehicle idles? He's be laughed right out of the shop if he complained about that.

This happens quit often. When my dad had his shop, we would have customers come in for one thing and then bring it back a day later and claim that we did something to their vehicle. When the problem was diagnosed, it was totally unrelated to the original repair. Most people understood, but a few idiots would get irate and expect us to eat the bill. My dad would sometimes make an adjustment just to appease the customer, but I felt they should have paid the full rate for fixing the new problem for them.


bwestcott,

My advice is to approach the shop and mention the new problem. They may do a diagnosis on it and determine what the problem is. Unless it is something that was created by them, expect to pay for their time and service though. Good luck.

 

I am absolutely serious! I have seen it before! I know it sounds crazy but I have really experienced this before. I worked at a very reputable shop that had been around a long time and they had a heck of a time accepting the modern world and inssited on using 10w-30 in vehicles that required 5w-30, and we experienced all kinds of idle concerns, although only the pickiest would notice! (just like all of us in here lol!!)

I mean no dissrespect/flame this is just what I have seen in my years of working on cars. I am just trying to offer an alternative theory.


as always just my .02-

 

hcmq,

The only problem I have with that reasoning, is that at operating temperature, which is where the car would be idling very quickly after startup, both oils would be of virtually the same viscosity. The only real difference between the two would be at startup, where a 5w would be a slightly thinner oil.

 

navi man,

I absolutely agree with you hands down! However it is my understanding that there are many more modifiers in 10w-30 than 5w-30 which may be the reason they affect the engine differently at operating temp.

it's strange isn't it!

have a great day-

 

Actually the opposite is true, but it is really insignificant between these two viscosities. A 5w-30 uses a small amount more of polymers to allow it to have a larger spread between startup and operating temperature viscosity. One of the reasons that 10w-40 is no longer recommended is because the amount of polymers needed to get that large of spread in viscosity have been known to break down much quicker. As for additive packages, they would essentially be the same between 5w-30 and 10w-30 for the same brand of oil.

Maybe it could happen, as I have seen stranger things, but I would bet my life savings that his problems aren't anywhere related to using 10w-30 over 5w-30.

My first guess would be to change the fuel filter and add some fuel injector cleaner in the system and see if that took care of the problem. It was also a good suggestion to check for vacuum leaks, although this would usually set off the check engine light and throw a code.

Any how, good luck.

 

Well I did have it in to the dealer. They couldn't find anything, but they downloaded the latest programs for the engine/transmission.

The ride home from the dealership was OK. Went to take her out yesterday (after it sat outside for a day) and it was absosutely horrible. Ended up turning around and parking it and taking by wife's car.... grrrrr. At idle, the tach kept jumping between 600 and 750 rpm, under acceleration it was very definitely missing on a couple of cylinders..... It'll go back to the dealer on Monday....

 

navi-man is the man!

another thing you might want to check out is the throttle plate. If it gets a little dirty say from a bad seal around your airfilter and you take a trip down a dirt road etc.etc. The computer constantly monitors the amount of air that gets around the throttle plate when at idle, if there is dirt there the computer will constantly re-adjust itself, hence the rpms going up and down.

Maybe the dealer dislodged a bunch of dust while doing some routine maint on your truck.

Remember DO NOT USE CARB cleaner on these trucks!

Just another thought! Good luck-