Green_Machine

Hey all. I posted about an intermittent fuel cut (Idle/2krpm/idle/2krpm over about 2 seconds).

I thought I got it with a loose connector on the iat sensor.

Well, today, it would loose power then regain over and over at about a 1 hz rate, from 2.5 down to 2K for 3 or 4 cycles before I could get off the throttle.

Then, a minute later, it would pull great again.

I'm going to change the map and iat; any other ideas out there?


Thanks,

Chay

TonyB

Just a shot in the dark...lift pump starting to go?

Any codes?

Tony

Green_Machine

I suppose it could be the leading edge of the lift pump.

I should probably replace it anyway. I'm not in the best spot to do it though.

I should probably do the filter too.

I haven't pulled the codes 'cause i know there are some extras in there due to trying to read the codes with the iat disconnected. I need to clear the codes (pull batteries for ? seconds) then run it again and get the issue to occur somehow, then read the codes again.

I'm got a couple of leads as well:

Clean both the iat and map sensor

Check for debris in the exhaust elbow

Check for a stuck wastegate rod

Check lift pump

Replace filter (fuel)

Trace/inspect 5V routing all over the place

Also, some were reporting that the fan wanting to turn on was causing a power loss and so they disconnected it. I may try that and see.

It's hard to troubleshoot an intermittent which only occurs one per running hour or so. You think you got it...oh no not again!

That kind of thing.

Chay

Green_Machine

Thanks to everyone who helped or tried to help me out.

Basically, I'm a bonehead.

When I turned the key, I heard a noise which i thought was the lift pump, but it was some other pump instead (Vacuum pump)?

Anyway, I had some assistance today, and found there was no noise or vibration from the lift pump. I removed it...it's completely dead.

I think the cp3 was pulling fuel ok for a while, and when the fuel filter started to cause some resistance it started to be unhappy.


Hopefully the lift pump is my only problem! I suspect the codes are stale. I had no luck resetting them by pulling the batt leads.

I guess I'll have to break down and get a smarty!!!

Thanks again everybody.

Chay

SpeedyWS6

It takes longer than seven seconds. The computers have batteries in them now to save certain info when you perform battery swaps. How long it takes just depends. They will clear themselves if you fixed the problem.

gcssr

have you checked the wire over the a/c compressor tube, there was a article on this some time back. you need to crawl under the truck. on the right side you will see a wire crossing behind the a/c tube , look at it, try repositioning it, i had this happen to me, after lift pump change, all kind of codes, moved wire all cleared, installed shield over wire 35k and no problem again.

Green_Machine

I had the batteries disconnected overnight...still not cleared.

Someone suggested turning on the key and holding the brake light while the batts were disconnected, but it's time for a proper code reader anyway: I like to have the right tools around 'cause I do all my own work (For better or for worse!)

I found that there was a wear spot on the power lead going to the switch. I pulled the pass side fender well to access it easily. It was worn to the copper, but was not the problem. I armored the wires before reinstalling the fender well.

Also, I checked the wastegate for easy operation while I was there (In case of overboost fuel cut)...no problem, nice and loose.

I never had a cel on, just called up the codes...I should have known they were stale.

Chay