Alright guys and gals go easy on me. I have a newly rebuilt 22re motor with 6000 mile on it .It runs better than i could have hoped and then some until recently. Everything is new or fairly new. I have a slight miss at idle and the truck stumbles on acceleration or load. I'll give you a quick run down or list of stuff that has been replaced or is fairly new. By fairly new i mean replaced in the last 6 months. Plugs, wires, rotor, cap, fuel pump, fuel sending unit, fuel filter, new motor from the block up with a rv head, 268 cam, full header back exhaust, kn intake, cold start injector, radiator and all lines, t-stat, and i'm sure i'm forgetting some stuff but thats what i can think of now. Like i said the truck ran like a top before but now, not so much. Here are the things that may or may not be related that i performed just prior to the current issue. lucas fuel system cleaner and a full tank of gas, oil change and filter, and replaced the plugs just in case they were the problem. This just recently developed as the weather changed and the area i live in got colder and wetter. It's been raining it's butt off here. When i changed the oil i switched to 10w30 as opposed to 10w40 i had been running previously since it's colder out now. A similiar scenario happened to me last feb. and it turned out to be the plugs but not this time. I'm lost could it be the coil? ECU?! Grounds are good no codes from the engine. It had the miss at idle before but ran fine when i drove the truck. Could it be the o2 sensor? There are no vaccum leaks to be found, trust me i've looked. The pvc valve is also new. Sorry just remembered. Also as i'm driving it will stumble some then cut out other times It runs fine with no pattern what so ever. Stumbles then just kicks in for whatever reason. It will also have the problem weather the engine is hot or cold, while i'm driving or in the garage revving it. Could it be a bad fuel pressure regulator or egr valve. I would rather not start replacing parts no matter how cheap they are without a general direction. Also my belts are all new as is the alternator, starter, and battery. Seriously i've replaced a lot of stuff when i rebuilt the motor. feel free to chime in I'm a little stumped. I'm leaning towards replacing the coil because i don't think it's a fuel issue or an intake issue. The afm has been cleaned recently as well as the throttle body both of wich function properly and there are no leaks to be found there. I also just replaced the radiator cap as the previous one leaked a little even though it was new. I know it shouldn't have an effect on the problem but i'm just covering as many bases as possible to get to the root of the problem.

 

bump....

 

Check the TSP as well as the AFM. But in all seriousness sounds like a vacuum leak somewhere.

Since it's been raining a lot check all your electrical connections as well and add some contact grease to them. I don't think the O2 sensor would do this.

 

I had a similar issue and replaced the pick-up coil. It solved the issue for the most part. The tps needed adjustment as well. After I tested it out.

I have an issue where in first and second gear when I try to keep it at 10 to 30 mph it will drop like a rock and then come back up if I reduce one smidge off the accelarator. That sounds similar.

 

Thanks lumpy I'll check for leaks again. I'm gonna replace the coil anyways since everything else is new and i've been meaning to do that anyways. TSP is the throttle position sensor right? If so that's new as well and the AFM checks out upon visual inspection and moving the little flap it doesn't stick at all. I have an extra TPS so i might swap that in if all else fails to see if it works. I do have a crack on the new pvc valve boot and I'm gonna replace that just in case. After i do this stuff I'll come back and update for those of you watching and wondering.

 

paragraphs are your friend.

 

No change!!! Oh well. I wanted to change the coil and needed to change the pvc valve grommet any way. Next I'm gonna swap the old tps in and see if that makes a difference. Doubt it though. I used my stethoscope to check again for leaks and sprayed the vaccum lines with carb cleaner but no dice!! Can't find any leaks. Me and paragraphs along with proper grammar split up a long time ago. I hang out with run on sentence and ditch spell check whenever we hang out. LOL

 

"I hang out with run on sentence and ditch spell check whenever we hang out. LOL"

veryfunnyman.

 

well guys I'm stumped, I'm leaning towards the egr or bad injector. What do you think?

 

could be an injector sticking I suppose. Run a can of SeaFoam through it and see if it does anything.

 

Kind of sounds like a pluged up EGR. Might want to check that and see...

 

What did the plugs look like - that tells you a lot. Were they all the same? What color/appearance?

http://www.tuner-junction.com/TJForu...ark-plugs.html
http://aboutkarting.com/plugs/
http://roadstarclinic.com/content/view/70/127/
http://www.theultralightplace.com/sparkplugs.htm

 

plugs are all the same and are fairly new! I tinkered with it today and found the plug going to the TPS was without a clip and hanging awfully loose. Ah ha i'm thinking, so i proceed to unplug it, halfway expecting the engine to stumble and die, but there was absolutley no change! Does that mean the TPS is bad? I would think so since there is no change when unplugged. The only question i have is does the TPS just randomly go out? Given the connector was probably loose in the first place but still on none the less.

 

'Course if the plugs are almost new they won't tell you much. Have you checked for codes? Should certainly have a tps code by now, but if you have any others they might help.

If you want to know if the tps is good, check it - just takes a few minutes with an ohmmeter & the fsm.

Have you made sure the O2 sensor wires aren't melted & shorting on the exhaust? Does the stumbling occur just when moving or when parked, also?

 

stumbling occurs throughout the rpm range but with no pattern. It happens then stops. The o2 wires is an interesting concept I'll check those tomorrow. I have yet to check for codes but the check engine light has never reared it's ugly head. I'll check for codes tomorrow as well. Electrical systems have always given me trouble. How do I check the TPS with an ohmmeter? I have the crappy haynes book not the FSM. Thank you sb5walker for your help.

 

TPS can cause a rough idle, either if it is bad or not adjusted properly (or the plug is not making good contact):
- http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

In you case, maybe the plug is making poor contact, if so unplugging the TPS would make no difference as you observed.

 

4Crawler you are the man!! Thanks for the input I'll dig in tomorrow and chime in after with results!

 

I asked if it happens when moving only or also when stopped, because if only when moving it could be the vehicle speed sensor, which can cause stumbling.

The computer can store codes without lighting the CEL, so it will be worth it to check.

Read the stickies and you'll find plenty of links to online factory manuals.

 

for those of you wondering, it was the tps and the idle smoothed out and the truck runs perfectly. thanks all for the input .

 

Thanks for posting fix