hi all,
initial problem was my '90 firebird v6 had bad oil leak and would surge real bad till it stalled.

I just got car back from big tune up. Distributor seal was replaced, fuel injectors cleaned and all sort of other little tune up stuff. It also is runnning on a new(used, hoping new comp was problem) computer.

Car was running fine for a couple trips around town, then it happened again. shortly after leaving the store, just about when car comes up to temp, it starts to surge, erratic idle, rpm's drop and the engine wants to stall. Pressing on gas does nothing, no power or gas at all. About 2 min after the surging starts it will stall, and not run again till it cools down.

I bought the car from my girlfriends dad, and he said he had weird trouble years ago. He eventually found a guy who replaced the MAP sensor. So, i grabbed a small piece of wire, did like a post here said and connected to the aldl thingy, and got an error code. Sure enough it was 33...MAP sensor. I repleced the sensor today, and not wanting to stray to far, let the car idle till warm. About 3 min later, when it warmed up, all of a sudden, boom, not gradual, just the sudden surging again.

Im lost at this point guys. I check for vaccuum leak to the MAP sensor, it looks fine. I dont really know much more beyond this point. Im not really proficient with cars, just going by what I found here so far.

Any ideas????????

thnx,

jrjkd

 

does the SES light come on right away, or is it only during the surging? There is a good chance that there is another underlying problem that is causing the surging/stall to occure and the ecm sets the code when it sees the map signal is high at idle, indicating that the vacuum in the manifold is very low. Get a vacuum gauge and see what the vacuum is and check for leaks. One possibility that would explain what is going on is that the egr may be clogged by deposits that cause it to remain open, but since giving it gas doesnt help this probably isnt the cause of your problems. I had very similar symptoms when the egr got jammed open on my 4.3 after i relplaced the dud cpi injector. It would run fine, and as soon as i went to drive it, now that the engine was running properly, the crud would burn off the chambers and lodge in the egr valve, cause the pintle to jam open.

 

as for the replacement ecm, i had the same thing happen. The brain doners at the shop that my parents took it to didnt know what was going on and they wanted to charge me $1300 to replace every sensor that the pcm coded, and the pcm as well. Of coarse i said no, since i knew what the problem was.

 

Just so we're all on the same page, a '33' on a S/D schem is for a higher than expected absolute pressure (insufficient vacuum) under operating conditions.

There can be many reasons other than a failing MAP sensor. Make sure you have the required 5VDC reference voltage across the sensor 'A' and 'C' terminals - 'A' is usually grounded, 'C' is 5VDC.

Check the hose to the MAP for kinks and splits.

Make sure the PCV valve is the correct one for the engine. Improper valves can allow more idle air flow, lowering the MAP.

Make sure the EGR valve is sealed and not leaking internally.

Check the brake power booster for internal vacuum leakage.

And of course, check for any other hose or gasket leaks.