y5mgisi

I just rebuilt the motor. Now i have a problem with surging at idle. It only does it in gear, like if you stop at a stop light it will run /idle just fine for about 30 seconds then start to do this wiered up-down surge where it tries to die then picks back up over and over but never actually dies. The truck is throughing a code 33 that i cant seam to figure out. I took the truck up to a parts store here in portland that has one of those hand held scan tools(autoxray 6000) It has a function where you can watch what all the sensors are reading but it didnt show map. So here is the stuff that i got from it; this is running at idle in park
promID: 4551
IAC:39steps
temp:165.2
open loop
TPS: .62 volts
Intergrater: 128
O2:448mVolts
Knock: 0
Block learn: 126
o2 cross count:174 and rising quickly.

Does any of that strike anyone as odd? I really would like to get this surge problem out of my hair.

Fast355

iTrader: (2)

Well open loop idle is fairly common on alot of the HD 4.3/305/350/454 TBI engines. I would take a guess that your timing is off.

thepoz89

double check plugs and wires, fuel filter.

Darkshot

iTrader: (4)

Not familiar with a Suburban, but I'll give it my best shot. Sounds like something is causing it to want to stall, and the surging is the stall saver function just doing what it is supposed to be doing. Code 33 is a MAP sensor, I would start by checking that out. If you can, disconnect it and see what happens.

y5mgisi

Allright mnow were getting somewhere. I belive my timing is about 6* advance(base timing tes? wire disconected) But ive got a little bit of a cam in it(still computer freindly by a long way) and ive heard that they like a few degrees extra base timing with a cam in them. Does anyone know how much is too much? And i suppose it is about time for a fuel filter change but the truck runs good at more than idle. Maybe i'll double DOUBLE check everything including the timing, and maybey take it to like 3* advance and see what happens. Thanks for the advise thus far, and i'll let you know what i come up with.
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BTW Fast355 How do you have a MAF TBI?

Fast355

iTrader: (2)

http://www.youtube.com/watch?v=7nVQePIYzhI

https://www.thirdgen.org/forums/tbi/...i-zz4-cam.html

y5mgisi

i'll be damed... Good work my freind!