2.9 idle jumps around.. help

[Bill in Arizona]

My idle keeps bouncing between 900 and 800 rpm. Dose it every 2 seconds. Now and then it will fall to 500 rpm and die. I have searched everywhere for a vacuum leak. No codes. checked everything. Put a hose clamp on the pvc to manifold vacuum line. It was working perfect staying right at 850 rpm. 2.9 auto trans 4x4.... Also seems to have a little of a shake when taking off the line. doing vacuum gauge at idle was 17. I changed out the valve on the intake. no difference.

 

[RustedRanger]

Did you change the IAC valve? Did you spray out the port? Also use cleaner and spray out the throttle body and soak a rag in cleaner and wipe off the backside of the blade as best as you can and make sure the little hole in the blade is clear. Also if you didn't already,unhook the battery for 15-20 minutes to reset the computer. If you spray the port out and it is really dirty and it runs worse.....it may have had enough crap built up to foul the spark plugs...mine did lol

 

[jhammel85]

Have you checked the computer for codes? I'd start with some of the things that rusted ranger said (less valve since you already changed that) but ultimately, I think you may find a dying sensor somewhere. easiest way other than throwing parts at it is to check for codes.

When was the last time a tune up was done? Plugs, wires, cap, rotor, filters, ect.....

 

[Bill in Arizona]

No codes. I will clean the port out. I hadn't done that. I did all the tune up items. I have the idle holding steady now, It is at 1000 rpm though. Maybe the valve is sticking. The intake was dirty . The guy I bought the truck from had the injector wires wrong. He had he had 6 and 3 switched with 1 and 4, so it was running very rich due to a miss fire. I will [ick up some spray cleaner

 

[Bill in Arizona]

running great now. Put a new TFI in after changing the 22k resistor that was not working at All. This solved my issues and the misfire. Went ahead and bought new air intake and temp sensor too. Installed them. Tested the old ones with a lighter and an OHM meter. They were fine. Going to keep a TFI around just incase for now on. I may go ahead and purchase the remote mount kit. I think the failure of the 22k resistor may have caused the TFI to fail?
Thanks for your IDeas.

 

[jhammel85]

The 22K resistor...

That's the big rubber "block" that seems to just dead end right? In the harness under the hood? How did you check that? Also, Where did you get another?

By the way, I'm glad to hear you got it running again. I'm chasing an issue myself but the resistor is the only thing I haven't messed with yet.

 

[Bill in Arizona]

It should not dead end. It has a wire going to it and coming out. I cut it out tested it with an OHM meter. No continuity at all. I went on eBay. Searched 22 k resistor. Was able to get five for about $6 delivered. They look like two inch long ceramic blocks. I think they are rated at ten watts. the resistor reduces the current used for the trip signal used by the ignition. Remember in the old days , if you didn't have one your points would always fry. Think something similar occurs on the TFI. If you can't find one let me know I can send ya one. I heard radio shack has them too. I will post a photo.

 

[Bill in Arizona]

Once you replace it. You'll probably need to change your TFI ignitor too. Like 30 bucks at a parts store. Cheaper online. Easy to change. Entire job was less than an hour.

 

[jhammel85]

The one that it's in it is new so It should be OK. If not , I have another in my glovebox.

As far as the resistor goes, I bet that's an issue for me. Mine is just hanging there. Do you recall the color of the wire coming from the "top" or "right" side of it. What I mean is, if you hold it horizonally, the wire that goes to mine comes from the harness, so it's entering the resistor from the left and it exits to who knows where. I don't have any open wires under the hood.

Ugh, gotta love prev owners right? If you can get pics, that would be fantastic. It would really help me out.

Thanks!