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TBI idleing funny help!

Chrisblazzer89

Chrisblazzer89

1/2 ton status
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Oct 12, 2006
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Massachusetts 02301
OK so when I go out and start my truck it starts up fine but then it starts to act funny it idles then it bogs down then back up to idle then bogs down and then back up to idle and so on. It does this about 4-6 times before it idles normally what do u guys think? Trucks facts in my sig.
 
thers a couple of us having this issue right now and im one of them So far ive got nothing. Let me know if you find anytihng out.
 
Chrisblazzer89 said:
OK so when I go out and start my truck it starts up fine but then it starts to act funny it idles then it bogs down then back up to idle then bogs down and then back up to idle and so on. It does this about 4-6 times before it idles normally what do u guys think? Trucks facts in my sig.
Click to expand...
vac. leak? tb gasket in good shape?
 
I have the same problem on my tbi. I'm going to switch out my IAC and see if it helps any. If not, then I'll change the 02 sensor. I have a few spare good parts just for times like these.
 
To be honest, I've got the same issue (well, many issues, this is one of them lol) so I'm not going to be much help. I know my setup is all wrong because the engine is so far from stock, and I've got marginal injectors, so this will be one of the last problems I tackle, IF solving the other issues doesn't fix it.

First things first, have you done a good visual inspection of the engine bay? Making sure no wires are out of place, disconnected, frayed, so on?

Do you have a scantool? I'm wondering if this is more or less prevalent based on outside temperature? If the engine thinks it's warmer than it is, it may be trying to go closed loop or simply bumping the idle down before the engine is really warmed up. This would likely be evident moreso in cold weather than warm. But I'd confirm it with a scantool instead of replacing.
 
You guys all need a scanner. Seriously.

Sounds like it could be a number of sensors or a vacuum leak that 'seals up' when the engine warms up and expands gaskets. EGR passage could be plugged..........sounds like it's doing it in open loop before it goes into closed loop.............hmm. Not sure.

I had that problem with my TPI setup a few years back, it's issue was the IAT (intake air temp) sensor in the plenum. Scanner found the problem in minutes. Cheaper than replacing parts in the long run. Don't know if TBI has such a thing as the IAT.

By the way, any of you guys try a 3 wire O2 sensor yet?
 
It won't be an o2 sensor unless like Mr. Yeager says, it thinks it's warmer than it is in which case it's the coolant temp sensor.

Stock TBI systems ddon't have IAT.

Sounds like you need to run winaldl and see what the IAC is up to. Sounds like the stall saver is cutting in. Winaldl will also let you know what the CT sensor is thinking.

I run heated o2. Good for keeping it in CL.

Dorian, that EBL system has adjustable proportional gains which adjust how much the ecu reacts to the swing in o2 readings and slows everything down a bit getting rid of the bouncing idle encountered with big cams etc.
We've talked of this before and after several weeks of tuning with EBL I have nothing but praise for it, you name it...it's adjustable! Hook up IAT and WBo2 and tuning is sooo easy and fine adjustable.....even with my limited grasp of the subject!
 
i had a problem with my truck shutting off going down the road. not to much fun. after the 3rd time of blowing fuses i found that the wires going through the firewall to the computer were getting frayed, and they were factory-never touched. oneday i'll replace them. so check all your wires out too. mine will be good for 4 months the act up again. yours could just be a different wire.
 
In my case it actually only does it when warm! just runns a little on the ruff side when cold. Once warm it will idle up and down about 5 times before it tells it self that enough is enough. Then it straightens itself out and runs perfect for about 1 minute then stqrts the cycle all over again.
 
Check the EGR valve...make sure it can hold vacuum. Easy way? Pull of the vacuum line and suck on it, if you hear air, replace it! Same thing happened to my burban.
 
It does it with the egr vac line hooked up and with the line caped off. BTW it is a new egr valve.
 
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