snacks

2000 3.4 Limited 4x4 auto

For a few months, I've been having a low idle issue at start when it has set for a half day or more. Truck will idle up then drop to around 500 rpms and will choke itself til it dies. I can keep it running with very light pressure on throttle, put in reverse, put in drive, and by time I'm at first stop sign, its all good. If I rev it, it seems to make no difference, just wants some time to warm up "electrically" it seems (guessing sensor).

Yesterday, between 45-60 mph, I had a constant, significant loss of power and what seemed like a knock or miss. It was more pronounced the more I got into the throttle and would be less pronounced if I eased up to speed.

Coincidentally, I do not believe the truck had an idle issue this morning upon start.

On my 35 mile drive in this morn, the loss of power/miss was MUCH more evident, but still mostly in the 45-60 range still. Some loss of power at lower speeds, but really only noticeable if you really got into the throttle. When using 75% of throttle, seemed like was only getting 25% power. There were occasions when I floored it, RPMs rev'd but got no additional power. It did not feel like a slip or gear catch at anytime either and no trans whine.

Checked over fluids - oil, coolant, trans, all looked good. Even drained the trans pan and replaced that since I had a strawberry milkshake a year and half ago, but fluid looked brand new and no chunks or slivers found. No chk eng lights, recent engine work, tuneups, or anything else of note.

Any ideas on which direction to start? Could the problems be related? Thanks in advance for any help!!!

Junkyard Dog

Yeah... wth???
No codes too. Baffling.
My first guess would be a coolant temp sensor going south.
Do you have access to a scan tool to read sensor inputs?
Second guess would be a dirty MAF, but I'm not versed enough to know if it is used during 'open loop' mode when it is cold.
Maybe one of the gurus could chime in...

Tony

Beto

RPM's rev up with no increase in power? That is the most puzzling of all.

When you say like a "missing or knocking" do you actually have a pulsating or audible engine noise like it's really missing?

Not sure if you have the ECT on that 2000 limited. (Electronically controlled transmission). If you do it should have the ECT PWR switch on the dash. Might have some relevance here.

If your RPM's are going up and no increase in power, is it because the transmission is kicking down (like it should) to a lower gear, but the engine isn't developing any power? Or is it more like the transmission isn't kicking down and the engine is kind of lugging up to speed with a lack of power?

If you don't have the ECT, maybe you have a BIG vacuum leak that is causing the engine to idle poorly and affecting the transmission shifting. Should be pretty easy to track down if you are looking for it in the engine bay (a big hose disconnected, or a hole in something, probably even an audible sucking noise with the engine running). Could also be related to the kickdown cable adjustment on the TB.

If you do have ECT, then no kickdown cable and no reliance on Vacuum for transmission shifting. If your RPM's are going up with no increase in power it is probably your transmission kicking down, and your engine not developing power.

If any of these possible cases seem to make more sense than the others, post it here and we can start narrowing down the possibilities....

snacks

Thanks for the reply guys.

I do have ECT PWR and I have tried it on and off, same response.

I just went and started the truck and it idled fine. Dropped to 500 rpm then went to about 650 and was idling like it should. First time in months?????

There is an audible knock or possibly just shake-noise when giving over 25% throttle above 40 mph.

When it has rev'd and given no engine response, it is only when I have it floored. Seems most like it should be dropping gears and then its not engaging but there isn't really a whine and never really "catches." I back off it some, ease back into it, it accelerates (roughly) again.

Do not have a scan tool at the moment.

Planning to clean the MAF sensor and throttle intake later today. Good start?!?

snacks

Update - cleaned the MAF sensor and things did improve considerably. Only got about a 1 mile test drive, but the "shake" was lessened, acceleration was much smoother and it now feels more like a restriction/gunked up than a knock or miss. Waiting on some sea foam to add to the system and hoping its just a buildup issue inside.

snacks

Update 2 - got a longer drive in on way to get the Seafoam. Def better but still an issue with power and slight knock-type noise at higher speeds. Really seems like fuel or air restriction now. Got 2 cans Seafoam, put one can in a lil over half tank of gas. Used a hair under a half can in the PCV hose and the other half in the brake booster line. Letting the brake booster side sit now then gonna run it about 15-30 miles then fill up the tank.

I will report back later or in morn, should know a lot more soon!

Beto

I think it's running lean. The ECT transmission explains the kickdown and increase in RPM's - I wasn't thinking that pushing the switch would actually make a difference, just an easy way to tell what kind of transmission is in the truck.

I have the ECT as well and have noticed power surging and sometimes a knocking sound periodically at mid to high throttle. Usually at full throttle the knocking goes away but the power surging still happens. I had narrowed my problem down to lean running due to the lack of fuel delivery upgrades (7th injector) with a supercharger and 9psi pulley. (still waiting for an "extra" $1K for the fuel upgrades.)

In your case, the MAF is suspect, as well as fuel filter, injectors, and possible vacuum leaks. Maybe even the O2 sensor or "air fuel ratio meter" depending on which system your truck has.

snacks

Thanks again Beto, here's the latest info...

A friend decided to piss on my (improving) parade...it appears my 'check engine' light is not working. There is no sign of it on key turn or ignition. When I bought it, 35k ago, it had a chk eng light related to O2 sensor. Had it checked and turned off and haven't seen it since. Is there a fuse or any way the mech disabled the light? Simply a bulb? I'm guessing I have some error codes I don't know about.

Another piece of info, it has Cal Emissions to complicate things.

The next 20 mile drive was better but still rough. It seemed to smooth out more and quicker though. After sitting 1.5 hrs though, it ran like crap! Even at low speeds it was knocking and powerless. After 2-3 miles it cleared up at lower speeds, stayed as usual at higher. Drove it home, let it sit 2 hrs. It drove like crap again from the start. Drove it a mile and filled it up as I had forgotten to after adding 1x Seafoam to half a tank. By the time I was back home it seemed to have smoothed out again.

It still seems to feel more like running lean by sucking air, fuel supply or restricted flow from buildup. I was getting worried again about trans but once it clears up it stays fine, no coming and going.

Just trying to give as much info as possible...its off to the mech soon anyway, I would just like to have the simple possibilities already covered. Prob have plugs and wires done too following these issues. Hoping its good for a 200 mile run to Daytona tomorrow - we'll see how she feels in the morn!

Beto

Pull the code, when my Air Fuel Ratio meter went bad it used to stall out and lack power on an intermittent basis, but it did trip a code every time it happened. My code was "heater circuit fault" or something similar. Sounds nearly exactly like what you are describing - we ruled it out b/c of the lack it tripping a code and turning on your check engine light. Mystery solved, I think - pull the code to find our for sure.

You can change it yourself pretty easy but the part is a little expensive (close to $200 if I remember right).

snacks

Still trying to get the codes downloaded (if any). Hope to try AutoZone at lunch to at least get some info back. Will be this wknd before I can get a mech to hook up to it.

Any idea on why the chk eng light is not operating?

Another interesting note, got 19.7 mpg on a half tank with all of these issues. Usually between 18.5-20.5 mpg so it was normal. This morning, it did its usual idle start problem, had to stay on throttle to keep running for first 30 secs after start.

Doing 70-80 on 95 yesterday was the smoothest it had been, almost no issues once I got over 70. Still having power issues at low end now too! It has to be related to a sensor - but which one!?!?!

Hope to report codes soon...

buglao

you need new pcv valve, new fuel filter & re-gap your spark plug. After your done these, disconnect batt. terminal for at least 90 sec. you should be back to normal

snacks

Thanks Buglao, any more info on why you suggest this will solve all?!? Similar prob before?

snacks

Update on codes from AutoZone cheap reader:

- Multiple Random Misfires
- Running too lean
- Misfires on 1, 3, 4, and 5

TheDurk

First guess: Fuel starvation. Fuel pump, fuel filter, fuel pressure regulator. Buy any funky gas lately? Or run the tank dry?

snacks

Could of had some bad fuel. Have added a can of Seafoam to the fuel tank. Over half through my next tank of gas that should be clean.

snacks

Had the codes read again to confirm:

P0300
P0301
P0303
P0304 Multiple
P0305
P0171 Multiple

MIL On
Monitors
2 Incl catalyst
02 Sensor
5 Ready Misfire


Have a new fuel filter I will put on in morn. Looks like plugs and wires as the next step? Coil packs? Could it be the MAF sensor still?

snacks

R/R fuel filter, is running a little better but problem still there.

Might be getting beyond my abilities now...