code 33- MAP too high after motor rebuild.

[y5mgisi]

So i just rebuilt the motor in my truck(90 burban with 350) Its totally stock exept its bored .020 over, and has a diffrent(still very computer freindly). Now i have a code 33. According to this sighthttp://chevythunder.com/fuel%20injection%20troubleshooting%20pg%20a.htm#32 It means that the map is bad. I replaced it, and still no diffrence. Does anyone know if a valve staying open(as in being too tight) can cause this? I put a vacume gauge on it and it reads about 20in of vacume which tells me it dosnt have a vacume leak. The needle on the guage dosnt stay exactly in one spot but its pretty close.

The symptoms: Basicly only at idle, it will kinda run like it has a really big cam in it. smells like its running rich, then while driving it just dosnt quite feel like it has the off the line pep that it ought to. Though i have only got on it about 35% throttle sence the motor is so new. I dont know anyone have any ideas?

 

[dyeager535]

You followed this: http://www.chevythunder.com/map_code_33.htm to arrive at the conclusion the MAP is bad?

 

[y5mgisi]

no i took this from the chevy thunder sight to come to the conclusion the map was bad.

Code 33- This indicates a faulty maf or map sensor, depending on your tpi system. MAF: This code is set when the ecm sees a indicated airflow of greater than 45 grams per sec (gps) and the tps is less than idle, and engine rpm's is around 2000. This can be set by intermittent problems, usually a bad connection. These can be extremely difficult to find. Check the harness and connections very thoroughly. Also check for routing of wiring near the spark plug wires, this can induce a voltage high enough to cause problems. If this code is being set along with other maf related codes (34 and 36) suspect strongly a bad maf connector. If all else checks out, the maf is bad. But since this sensor is very expensive, exhaust all your efforts to find and correct a wiring problem first. MAP: If you have speed density, this code will be set when the ecm sees the engine running, tps less than 2%, and a indicated air flow of 11psi or about 8" of vacuum. A faulty map sensor is the problem.

that link is confusing because it says to fix your rough idle problem before you go to the next step. I mean the rest of it makes total sence and i will deffintly do that stuff to see if that leads me to anyithng.

 

[dyeager535]

I interpret that to read that "yes" it is running incorrectly, (in your case, otherwise it idles fine and still has a code stored, therefore intermittent and "no") and you proceed under the "yes" section. But this should all be preceeded by a good visual inspection of course. Wires, hoses, etc.

You can't assume components are bad based on a code. One wire in an ECM connector can be loose and not making contact, and would show a code 33, it just means the ECM isn't seeing what it expects from that component, whether caused by that component or a result of another problem making that components readings incorrect for the engine conditions at the time.

 

[beater_k20]

Code 33- This indicates a faulty maf or map sensor, depending on your tpi system. MAF: This code is set when the ecm sees a indicated airflow of greater than 45 grams per sec (gps) and the tps is less than idle, and engine rpm's is around 2000. This can be set by intermittent problems, usually a bad connection. These can be extremely difficult to find. Check the harness and connections very thoroughly. Also check for routing of wiring near the spark plug wires, this can induce a voltage high enough to cause problems. If this code is being set along with other maf related codes (34 and 36) suspect strongly a bad maf connector. If all else checks out, the maf is bad. But since this sensor is very expensive, exhaust all your efforts to find and correct a wiring problem first. MAP: If you have speed density, this code will be set when the ecm sees the engine running, tps less than 2%, and a indicated air flow of 11psi or about 8" of vacuum. A faulty map sensor is the problem. .

that could very well be your problem right there, 90 Suburbans werent offered with TPI.

 

[y5mgisi]

Yes i am aware that they never had tpi, Mine has TBI of coarse. like i said its all stock. thats why i was only prett much using this portion of the quote,

MAP: If you have speed density, this code will be set when the ecm sees the engine running, tps less than 2%, and a indicated air flow of 11psi or about 8" of vacuum. A faulty map sensor is the problem. .

I bleive that TBI is a speed density setup, so i belive this statement applies to me. Im still not entirely sure whats up but i did test the MAP ground and its good. I think that even though i have almost 20" of vacume(or perhaps my vac. gauge is wrong) it might actually still have a vac. leak. But i'll test that theory more when i head up to the parts store and use there scan tool. Thanks for the help though so far dyeager535