I bought an IROC about a month ago and am getting to checking codes. Reset the computer and I get Check Engine Light within less than a second of starting it. Check codes and it gives me a 34. I've read posts about code 34 and will try to clean MAF, check connections, replace relays, etc. Previous owner had problems too, I can tell. The car has a manual cooling fan on the front of the radiator and the factory fan never comes on. Had the radiator out yesterday and direct connecting the fan to a battery runs fine. But the computer controls that fan, so does this mean my computer (ECM) is fried? It also has a replaced (Bosch) MAF on it. Get the usual stuff I read about with a code 34, crappy idle, hard start, etc. Runs fine when I get on it though. Someone said to replace temp. sensor, should I try that and is that the same one that sends to my dash gauge 'cause it will show it getting plenty hot if I don't flip on the manual fan.

How much is an ECM anyway? 'cause if it is expensive, that WILL be the problem...
'86 IROC 5.0 TPI

Every damn day I fix something.... every damn day something else breaks... I feel like I'm treading water...

 

On single fan set-ups the ecm doesn't control the fan. Instead, there is an a/c high pressure switch (turns on fan when a/c is on) and a thermostatic switch (turns fan on when coolant temp is about 230), both of which ground to the coolant fan relay when either condition exists. So either you have a bad relay or a bad switch. If you are getting a code 34, check both of the MAF relays and check the connections.