Surging when cold - 00' 4.3L

[Tink]

My 00 BlaZeR2 has 98K on it and has started surging when cold (not at idle, only when driven)... you can actually see the tach jumping when going down the road. I get no engine light and it goes away after the truck warms up. It only does this on a cold (under 50 degrees) morning, does not do it in the afternoon. The last thing I did was clean the super carboned up throttle body. Previously, I did a tune-up and descreened the MAF. Replacement w/ a screen MAF makes no difference. Any thoughts?

[droopy89]

Mine does that occassionally, but its happening more often hopefully cause it almost winter, but i dont have a tach so i cant be exact but i can feel it surging a little bit

[20Blazer00]

When you cleaned the TB did you remove the TPS or IAC?? It might be that when you cleaned the carbon off some of it may have disturbed the settings on the TPS or IAC. Or you could also have more carbon in the EGR valve or passage in the manifold.

[Tink]

This morning I noticed when I was sitting in the drive with the defrost on, it was 'surging' at idle, I turned off the defrost and it went away. I didn't turn it back on and it seemed fine going down the road. I usually always turn on and run the defrost as I'm leaving the driveway. Now, since I bought this truck a month ago, the voltage always read at 14 or a hair below, which seemed low to me. I suspect the alternator or battery is on it's way out, so could it be that running the defrost is causing a voltage drop which is causing problems or am I way off here??

I did remove the TPS and IAC when I cleaned the throttle body...

[Sparky2263]

Is the A/C comp. cycling causing this? If it's above 30 degs and below 60 it'll cycle pretty quickly.

[turboz400]

my truck does the same thing when i drive u can really see the tach move and it like chugs the truck , i was thinkin tps am i right

[Tink]

Mine is definitely the compressor cycling causing the problem... if I don't use the defrost and leave it on OFF, I don't have any problems... I think the compressor cycling was causing intermittant voltage drop to the sensors.