Truck idling rough and wants to stall.

[Walking Eagle]

The past few days the truck has started idling rough. It even happens after the truck has warmed up and been driven. I will be sitting at a stop light and the truck will start to lightly vibrate and feel like it's going to stall. Last night I had to stop abruptly behind someone who made a last minute turn. I initially thought the truck stopped, but I gave it gas and it went ahead and accelerated normally. I guess I should go drive the truck around the neighborhood, and see if it will actually die if I just let it idle.

[mattadams]

First thing I would check for is loose vacuum lines. Theres some trick like you spray wd-40 on the vacuum line and if it causes the engine to hesitate, you've got a leak... Tough to say though, before my tranny went out I spent countless hours working on an idle problem that was quite annoying, it wasn't quite to stalling point though.

[Walking Eagle]

I just got back from testing it out. I drove over to the local grocery store and pulled into an empty area of the parking lot. At first I put the truck in drive and let it idle. At first it was fine, but it gradually started to hesitate after 20 seconds. The RPM's slowly dropped to 600, but it kept running. After a few minutes I shifted into drive to leave and the RPM's dropped and fluctuated between 400 and 500. I left it in drive, but just stayed there with the foot on the brake. It never did stall, but continuously vibrated.

[Tray]

Sounds a lot like a vacuum problem. Same thing happened to my Dad's work truck ('99 F-150). He never heard what got fixed/replaced, as he works for the city, and they just take it out to have things fixed, but they did mention that it was something to do with a vaccuum. That was all he could tell me.

[clavos]

I'm not positive, but I'm fairly sure that the idle air control valve on these trucks are controlled by vacuum. I can check on the computer at school tonight and find out exactly how it works, and if the printer is working, I can make some copies and fax them to you. Sorry, I don't have a scanner. Your truck has the 5.4, correct?

[mattadams]

Yeah it could be the IAC Valve. I replaced mine when troubleshooting the Idle problem, it was about $60 I think (maybe better with discount from Phil Long :)), and on the 5.4's it is a pain to get to, but if it fixes the problem then all is happy.

[Walking Eagle]

Yes, I have the 5.4L.

[clavos]

The computers were down at school last night, I'll try again tonight.

[Walking Eagle]

This afternoon the check engine light came on. I'll be heading over to Autozone or Checkers in the morning so they can tell me the codes.

[clavos]

Might be a good idea, pay good money for an education, and the equipment never works.

[Walking Eagle]

First off the Checkers near my house no longer reads codes. They rent the machine out and somebody else was already using it. I went to Autozone and I was told bank 1 and bank 2 are lean. I asked what that meant and the guy said well now you need to determine what's causing the problem and he walked off. I know I'm stupid when it comes to mechanics, I know both of my bank accounts are lean of funds, but I don't know what the heck a bank has to do with a truck.

I think I'm going to have to take some basic automotive classes, because I don't get this stuff.

[Walking Eagle]

What I can gather searching the internet, it means the O2 sensors on the passenger and driver side before the cats need to be replaced.

[mattadams]

my check engine light is coming on too... and I checked the codes and it says o2 sensors too, but mine were recently replaced, thats the weird thing... and mine is showing both are disconnected...so we'll see....

[clavos]

Lean refers to the air/fuel ratio, having too little fuel for the amount of air. This could be caused by the 02s on the exhaust manifold, but more likely by the 02s further down the exhaust stream since both cylinder banks are running lean. If I had lots of money, and therefor high tech tools it would be easier to pinpoint the cause of your problem. I can try to test your 02 sensors tomorrow and see if that is the problem.

[clavos]

Also Jeff, if you have the code that they read from your truck, that could be helpful.

[mattadams]

I can bring my laptop tomorrow, we can check your codes.

[Walking Eagle]

He showed me the screen and it said Bank 1 lean and then the next screen said Bank 2 lean. On the screen I did not see in code numbers.

[Burg460]

Usually bank 1 is your pre cat O2 sensor (the one before the cat) and bank 2 is the post cat (after/behind cat). My guess is if it is throwing both codes then your truck is running lean. Not sure on the post-97's but a post cat O2 sensor for my truck is like $80.

I do know that sometimes if your throttle position sensor is going bad it will throw a code for the oxygen sensors. The throttle posistion sensor can go bad and the computer won't see it and sometimes it will.

I would check/clean your throttle body assembly for starters.
Also, depending on how many miles you have your fuel pump or fuel pressure regulator can be on its way out also, this will cause it to run lean.

[Walking Eagle]

The truck has almost 137,000 miles. I did have the throttle sensor replaced back in January.

[Walking Eagle]

It turns out the problem was a vacuum leak. Firestone said my O2 sensors were acting sluggish and will need to be changed in the near future. I did not do the sensors today. They wanted $512 to do the four 02 sensors.

[mattadams]

The O2s are a giant pain, but not sure they're worth $300... LOL. So did you get the vacuum leak taken care of and everything?

[Walking Eagle]

Yes, I did get the vacuum leak fixed and it solved the idling issue.

[mattadams]

Thats good... when it comes time to do O2's, let us know... Im sure some of us can help out... they cost about $40-50 a piece.

[Walking Eagle]

Well my problem came back today and the Check Engine light also has come back on.

[mattadams]

That sucks, I'd take it back and say its not fixed afterall!
in a strange twist of fate, I ended up changing one of my front O2 sensors last night... not fun to do at 8:30, but oh well.

[Walking Eagle]

I already called to make sure they will not charge me for the diagnostic again when I get there tomorrow.

[Walking Eagle]

Went in this morning. They came up with the same error code when they read the codes. They did some further tests and reset the light, but the light, symptoms, and codes never reappeared and were unable to detect anything wrong. The technician that did the work is out until Wednesday and they asked if I could drive it for the next few days to see if it happens again. In the meantime they would ask the technician what work he did last week.

At least I did not have to spend anymore money.

[Walking Eagle]

Well the symptoms came back this afternoon for a third time and the check engine light is back on. This crap is starting to piss me off.

[Walking Eagle]

The idling problem has continued up to this point, but I've been living with it. Well today the truck now has started to stall when I'm idling.

[mattadams]

Jeff, another thing I thought of is your PCV Valve. Its a $5 part and takes about 5 minutes to replace. might be worth it. if not, it doesnt cost you anything :)

[Walking Eagle]

I did stop tonight and pick up the PCV valve. PCV valve and 12oz Coke was $4 something.

[Tray]

Have you happened to replace your fuel filter any time recently? I've never had one get to the point of running rough, but clogged ones have really hurt my performance.

Bastards in Missouri - mine began to rust after 15000 miles at a little over 9 months of me having it.

It may be worth a shot. I think the new filter is something around $12, and it's a 10 minute job, including the 12 oz coke.

[Walking Eagle]

The fuel filter was changed recently.

[Glass]

I dont know if any of the technicians mentioned anything about an EGR valve, i dont know too much about these "computerized" engines, but i think that if enough carbon deposit , or whatever that black crap in exhaust is, builds up in the valve it can cause piss poor idle and performance. If you remember the exact codes that were shot during the diagnostic though, i could talk to some of the county mechanics here and see what they think, we have a few 150's around here..

---JOHN

[Glass]

BTW, here is a list of things that could be wrong with your truck, if the idle is erratic, and rough after start, and eratic and rough when warmed up:

1 Inspect AIR FILTER Restricted or clogged air filter.

2 Inspect FUEL FILTER Clogged or dirty fuel filter

3 Inspect WIRESET Damaged, worn, or deteriorating spark plug or coil wire(s).

4 Inspect SPARK PLUG Fouled, damaged or broken spark plug(s).

5 Inspect PCV VALVE Plugged or damaged pcv valve.

6 Inspect DISTRIBUTOR CAP Loose or cracked distributor cap

7 Inspect CARBURETOR FLOAT Improperly adjusted/saturated or damaged carburetor float.

8 Inspect CHOKE PULLOFF Worn, defective, or faulty choke pulloff(s).

9 Inspect CHOKE THERMOSTAT Stuck or improperly functioning choke thermostat.

11 Inspect AIR CHARGE SENSOR Damaged or faulty air charge sensor or air charge sensor circuit.

12 Inspect AIR CLEANER TEMPERATURE SENSOR Damaged or faulty air cleaner temperature sensor or air cleaner temperature sensor circuit.

13 Inspect BAROMETRIC PRESSURE SENSOR Damaged or faulty barometric pressure sensor or barometric pressure sensor circuit.

14 Inspect FUEL INJECTOR COLD START VALVE Faulty cold start valve or circuit.

15 Inspect FUEL INJECTOR PRESSURE REGULATOR Faulty fuel injector pressure regulator or circuit.

16 Inspect CARBURETOR/FUEL INJECTION GSK Deteriorated, or faulty carburetor/throttle valve mounting gasket.

19 Inspect IDLE AIR CONTROL VALVE Damaged, loose, or faulty idle air control valve.

20 Inspect IDLE SPEED CONTROL ACTUATOR Damaged, loose, or faulty idle speed actuator.

21 Inspect M.A.P. SENSOR Improperly connected or faulty m.a.p. sensor.

22 Inspect MASS AIR FLOW SENSOR Improperly connected or faulty mass air flow sensor.

23 Inspect THROTTLE POSITION SENSOR Faulty throttle position sensor or throttle position sensor circuit.

24 Inspect TIMING SET Slipped timing chain or worn timing gear(s).

26 Inspect FUEL PUMP Improperly functioning fuel pump or circuits.

27 Inspect FUEL TANK Contaminated fuel from rusted or deteriorated fuel tank.

28 Inspect FUEL INJECTOR Plugged, dirty or poorly connected fuel injector.

29 Inspect EGR VALVE Clogged, dirty or improperly functioning or defective egr valve.

30 Inspect DISTRIBUTOR Worn, loose or incorrectly adjusted distributor.

31 Inspect CAMSHAFT Worn or scored camshaft lobes may affect proper fuel intake, compression, combustion and exhaust.

32 Inspect POINT SET Burned, worn or incorrectly set ignition points.

Doesnt really narrow it down, but this is a place to start, start small, and if it doesnt fix it, atleast you wont have to replace it as soon....

---JOHN

[clavos]

Jeff, a clean engine is a happy engine! Maybe its just being rebellious because of neglect. LOL...j/k. I'm stumped. :scratch:

[Tray]

If a clean engine is a happy engine, then he has one pissed off engine ready to go postal on someone.

[clavos]

Thats why it keeps stalling on him. Next it will leave him stranded in the left lane of I-25 at rush hour.

[mattadams]

Jeff, one more thing I thought of, and someone else mentioned dirty engine, but with allt he muddin you've been doing lately, have you checked your Mass Air Sensor? It's possible you got some goop on the little wire filaments of it and its not working properly? It's possible to clean those with some cleaner and a q-tip.

[clavos]

Good thought Matt!

[Walking Eagle]

I did get the cleaner a few weeks back, but I'm not sure what exactly is the MAF sensor.

[mattadams]

Jeff, if you bring the truck camping and bring the cleaner/q-tip with you, I'll show you... although you need the tools to, I can't remember exactly what tools it takes and not certain what I'll be taking.

[Walking Eagle]

Sounds good. I will have a lot tools that I always carry.

[mattadams]

Jeff, in addition to the mass air sensor, heres another thing I"d recommend. A lot of people in the pre-97 forum on FTW have been talking about a product called Seafoam. Basically you put it in your main vacuum tube while the vehicle is running, and it goes through your engine and cleans out a lot of hte carbon deposits and so forth that can cause rough idling and bad performance.
Another thought (in addition to the last two) is to run some Marvel Mystery Oil through it... you can buy it by the quart or gallon at most auto shops, its in a red package... you can and should use it two ways, one of which is adding it to a nearly full tank of gas. The other is when you are changing your oil, take a quart of MMO and run it instead of a quart of oil, for example use 5 quarts of oil, 1 quart of MMO instead of 6 quarts of oil. Running it through your gas will help clean your injectors and fuel lines, and running it with your oil will help clean the crankcase , pistons, yada yada...

[Walking Eagle]

I'm familiar with Marvel Mystery oil, but have not used it. Seafoam, is new to me. Is this something you can also pick up at the auto store?

[mattadams]

I couldn't find it at checker or autozone, but Im told carquest and napa carry it.

[Walking Eagle]

Alright, I guess I'll be checking NAPA out on the way home tonight. Thanks for the tips.

[clavos]

If you want to get in to cleaning things, most shops should be able to do a pressure cleaning of the injectors and induction system. I just did this on the Benz at school, and idle/throttle response were improved instantly.

[mattadams]

yeah that too... Jeff, I seem to recall a while ago talking to you about the Idle Air Control Valve... did that ever get replaced? I can't remember if it did or not. If not, that'd be something to consider too...

[Walking Eagle]

I'm kind of doing one or two things at a time. I did add the Mystery Oil last night. Did not help idling, but it did seem to help out on acceleration when I'm driving down the road.

My next step will be the EGR and Idle Air Control Valve.

[Walking Eagle]

This morning I got the EGR valve and all of the O2 sensors replaced. Thank you once again Cory for helping me save some money. The old EGR did not look too bad. The O2 sensors on the driver side had a black color on them while the ones on the passenger side had a white color on them. We did not know which were bad, but figured something had to be wrong with one of the sides.

I drove the truck for the last two hours and the idling problem has gone away, it did not stall or even sound like it might stall, the rpm's stayed at a constant level, and the check engine light stayed off. So far so good.

[clavos]

Sounds like you got the problem licked. They could have both been bad, one rich and one lean, causing the engine to fight against itself. You will probably notice better fuel mileage too.

[Glass]

Glad to hear it is working good for you..hopefully you got it taken care of for now, and can just enjoy the truck running like it should/

---JOHN

[mattadams]

Crossin fingers for ya! :)

[Mind_Boggler]

Aye! Computers! What a pain sometimes, huh? :oops:

[Walking Eagle]

Check engine light came back on this morning. Truck is running better.

[mattadams]

Damn I hate that check engine light! Might want to check the connections on the o2 sensors... when I got my truck back from the tranny shop, my check engine was on... they had disconnected the o2's and hadn't reconnected them properly. Did you hear them "click" when they were connected? Or as always, it could be something entirely different...