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starbai

Truck keeps dying at idle after a bunch of work completed... need help... at wits end...

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Okay guys, I had a bad ticking going on. Had to replace a bunch of valve lifter buckets, did chains, tensioners, guides, water pump, and oil pump, bunch of seals/gaskets.

 

I cleaned out the throttle body really well as well as the upper and lower intake manifolds.

 

Ticking is gone, actually runs really nice when at speed.

 

Problem is when i start it, it idles very rough like its ready to die. Something kicks in (dunno if its the thermostat turning on or what) but then it runs fine... no problems... ticks down/off... rough idle, and then it ticks back up idles great... and so on and so forth... maybe 20 seconds or so in between each 'cycle'.

 

My first thought is that I really need to bleed this thing better. I have been bleeding the coolant now for hours and I'm not seeing any more bubbles...but I'm still getting this rough idle like its ready to die... till it catches itself.

 

I'm starting to be concerned that its not just coolant but another issue. But if thats the case, why would it tick up in cycles and run great? (only to click at me, then run rough) it really sounds like coolant but I dont know what more to try.

 

Heres a few videos of the behavior. Please help!

 

This video begins with the rough idle. At about :07 it runs fine, at :32 the rough idle returns, and then by the end of the video its fine again. On and on.

 

 

 

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My second thoughts were vacuum leaks or leaks in the intake manifold...

One method people use is the smoke test which wasn't working for me well beacuse the fan was blowing the smoke.

The other method of spraying carb cleaner to see if there is a change in idle seemed to reveal something but I dont know if it makes sense.

I sprayed carb cleaner on the hoses to see if it changed any reactions... also around where the upper and lower intake manifold meet... and at the very front of the two manifolds made a huge difference... it ticked way up right away...

This tells me that theres a leak there between the upper and lower inake manifold... am I right?

I didn't replace those gaskets when I put them back together, so i'm thinking thats what I need to try... what do you guys think?

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What did you clean the throttle body with? They have a special coating and anything but the right stuff will mess it up.

Edited by adamzan

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And yes if you sprayed something and it made a difference you have a leak. You should always use new gaskets. Not worth the headache for the cost!

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First I'd heard of a coated TB. Did a little digging and found a thread on BITOG talking about the drive-by-wire systems throwing a tantrum if you clean the TB. A little change in air flow is apparently enough to freak it out.

 

Hopefully new gaskets are all yours needs!

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I've cleaned tons of drive by wire throttle bodies and haven't had an issue other than the occasional re-learn on Toyotas.

 

If you can consistently change the idle with spray then you definitely have a leak that needs to be addressed.

 

The VQs also have an issue with the IACV going bad causing idle issues and sometimes shorting out the computer not long after. But first things first...

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