Help with surging at idle on 90 burb TBI...

[y5mgisi]

I just rebuilt the motor as many of you know. 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 funvtion where you can whatch 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.

 

[CB77GMC]

code 33 Mass Air Flow sensor check here http://www.chevythunder.com/Flow%20chart%20index.htm

 

[y5mgisi]

In my particuler case its going to be a map problem not a MAF Someone else allready posted that link before and ive done it all with no real conclusion. The only thing i havnt been able to do is see if the map is reading .1volt or less.

 

[scooter122983]

take a multimeter to the map and check it there if you cant get it on the scantool

 

[y5mgisi]

Really? Do you hapen to know right off hand which wires i should probe?

 

[scooter122983]

Really? Do you hapen to know right off hand which wires i should probe?

Not off hand as im currently at work and do not have acess to my haynes book but im positive they cover it in the emissons section.

 

[y5mgisi]

Maybe this would help?

 

[HarryH3]

With the scanner, check to see that the Park/Neutral switch is operating properly. It can cause strange idling problems if it isn't telling the ECM the correct mode.

 

[mr.smartass]

Are you running anything aftermarket like headers or anything?

 

[dyeager535]

I'd say signal at "B" is where you'd look for the right voltage.

Autozone's scanner should show the MAP AND P/N switch, my Autoxray XP240 does, and it's only probably 10 years old lol.