Rough idle after replacing alternator (??)

[AbbadonTD]

I would say no voltage should be the same (but I could be 100% wrong on that one). Did you replace both tensioners and or is the belt loose? You connections could need cleaning too. The used part may have dirty connections.

 

[Mammoth]

Ok so went and had codes read and nothing, no codes. Also Alternator & battery were both good. I'm puzzled

 

[Mammoth]

Anbaddon, the alternator had plugs attached to it when I bought it, they were just cut off the other vehicle so none of the connectors were exposed. I also cleaned the MAF sensors this morning as well as checked the belt and its tight.

 

[AbbadonTD]

If this were an F150 I would tell you TPS or IAC...Both can fail and not throw codes, and both can fail from voltage changes, so your old alternator could have fried one. I am pretty sure these 5.4s are the same engine in these years. [I am new to my Expy, but I HAD an F150 before]

Throttle is worth an inspection. You could be stuck or not performing adeptly.

 

[BAD RONALD]

If this were an F150 I would tell you TPS or IAC...Both can fail and not throw codes, and both can fail from voltage changes, so your old alternator could have fried one...

It's a fact these engines are voltage sensitive. How old is the battery?

 

[Mammoth]

BadRonald- it's alittle over a year old. I had the battery and the alternator checked earlier this week, both were good.

 

[stamp11127]

The TPS works off of V-Ref (5 volts) the only issue that the ecu/pcm will not throw a code on is a flat spot in the sweep. Any failure in the connection will show 0 volts or 5 volts. The TPS is designed to work between .2 - 4.8 volts.

So in English - a "true" failure will throw a code.

To check if your problem is alternator related, while using a meter check the charging voltage at idle and at engine rpm's around 1500 at the battery posts.
You will need a load on the electrical system so I usually have the headlights high beams on and the blower motors for the a/c on high. The more of a load the better.

Voltage range should be between 13.5-14.5 volts. If it is within spec, the problem lies somewhere else.

 

[Mammoth]

Stamp11127- I had the Alternator checked....

No load - Loaded
14.38V. 14.56V.

I read the owners manual and it says to "re teach" the ECU after resetting you need about 10 mins city driving (stop and going) and about 30mins interstate (non stop) which I haven't done yet. I just don't understand, if it is an incomplete drive cycle why didn't it throw a code (????). Everything was fine until I replaced the alternator, that's why I'm hoping it's just the ECU needing to adjust. I will say it seem to have gotten a little bit better but still isn't right.

 

[stamp11127]

Depending on where you have the alternator or battery tested these days the results can be suspect. I've had one of the large chains test batteries in the past that passed the test but are really bad. I test myself now with a load tester and by age of the battery.

As far as the driveability - "drive it like you stole it"

 

[Mammoth]

Stamp11127-
I did, I tested it here at the house right after install and again at Advanced Auto when the issues started.