Im trying to figure out why my truck stumbles when revving it below 2k rpms when its cold. If you mash the gas slowly from idle, the rpms will stumble up and down, and you can hear it too. Once it runs for a couple minutes, the problem disappears for the most part. Im taking auto courses in a technical college now, and we've tested the TP sensor, engine temp sensor, and a bunch of others with a lab scope, but everything checks out ok. This isn't a big problem or anything, but right now, we are working with scan tools and stuff, so this falls right into place. Any ideas on what it is?

 

Check the pressure at the fuel rail.
Also check the alternator output.

 

Have you been experiencing any disappearing coolant in the past few months?

 

no, its all still there.

Im starting to wonder if maybe it is the TP sensor, b/c I unpluged it and then ran the engine, and it acted practically the same as it did when its pluged in when you first crank the engine. When its first unpluged, it will be pretty irratic when you slowly rev it, but after revving it up several times to about 3k rpms, it smooths out pretty good when you slowly rev it, it barely stumbles.....all this makes me think the computer compensates for this, and adjusts the voltage from the TP sensor or whatever to make up for it, or ignores it and uses what it knows from the past. This would probably be why it only stumbles for a minute or so when its first cranked up with it pluged in. Does this make since/ sound reasonable?

 

anyone?

 

I know you have a different engine but this post may give you a clue :

https://www.ranger-forums.com/forum2...sensor+voltage

 

How did you test the TP sensor?

 

https://www.ranger-forums.com/forum2...sensor+voltage

Read the post by rwenzing.

 

I think we just stuck the probe things into the connector on the right wires. I dont think we tested it disconnected.

 

We backprobed it using a snap-on "vantage". We did a Voltage test, Resistance test, and used the lab scope to check the waveform, which was smooth with no glitches and voltage and resistance was all with in factory spec. Telling me that the TPS if fine but that just me, we can always try a new TPS. We also checked the MAF, IAT, TPS, ECT, and a few others and all were with in factory spec. I think that all EGR related sensors needs to be checked. Thats what the problem was with mine. We also did a KOEO and KOER test, which didn't throw any codes...

 

I still think its the TPS!!!

 

Your Truck, you make the call.....

 

If it can be tested unpluged, I think it would be a good idea to do. Also, we tested it after it had been running, and wasn't stumbling at the time.

 

Than bring it in the shop and leave it on one of the lifts till after Lunch.... And the only thing that you can do to the TPS while its unplugged is ohm it.

 

What did I Say ? I Said it would be the EGR, didnt I. So now we know what part of the engine to look at.

 

yea yea sure....I dont even really know how the egr could effect it.....

no

 

Sorry I had to do it.... anyways, the EGR is what was messing up my trucks idle at low RPM's.

 

So hows the truck running ??

 

the same as it has been. I looked up the price of a new EGR valve, and its like 80 bucks! hmmmm

 

What about the EGR flow sensor, you know the one that i changed on my truck twice already. That little black box, I think yours is still factory becouse its metal. Now you know how i feel when it happened to my truck.

 

for my 3.0 it was 50 bucks.

my truck would run like **** when i first started it up it was the egr valve but i knew it was that because of the check engine light.

if your going to replace the egr might as well replace the dpfe at the same time because they go bad basically at once.