I have an 89 240 that will not stay running or even idle. I took it to a mechanic and he tried the air flow meter with a known good one and it did not fix the problem. When the air flow meter is disconnected the car will start and idle but does not have enough power to drive. As soon as you reconnect the air flow meter the car dies. Before he starts replacing all sorts of parts I would like to know if anyone has experienced this problem and knows exactly what the problem could be? The mechanic thinks it could be the computer but before I spend $300 - $400 I would like to see if it is anything simple.

Thanks for your help in advance.

Wow, sounds exactly like my '84 DL problems...sure, I've tested the Air Mass Meter, which turns out to be fine, but i still have the cold start problems. My mechanic 'friend' (who want to charge me $70 an hour, but is still a cool dude) says I don't even have a cold start injector, so it really leaves me with little options to persue. I'd love to see some more posts about this particular car's problems, and the solutions. I really want mine to start right before I invest in really anything more. Good luck!

Your 84 could have cold start problems because the air mass meter is out of spec. This is nothing you can measure going by the checks in Bentley or Haynes, but just a degraded AMM that sends the computer a bit less voltage than it used to for the air drawn in by cranking.

But it could be hard to start cold for many other reasons too; to name a few, vacuum leak, engine coolant temp sensor faulty, clogged injectors or low compression. Your cool dude mechanic is right -- there's no separate cold start injector.
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Art Benstein near Baltimore

I agree with Greg, his AMM could be NFG, oops I mean NG. The common computer ('89 is a bad year for ECUs) fault is usually a loss of fuel pump ground, but I have seen cases where a 561 ECU would just not support an idle and the car would die after each start. In any case, a simple swap test from a running car should be done to convince you before sticking you with a replacement.

Thanks for the quick response and your knowledge.

Wow it actually does sound like the AMM... how confident are you that the mechanics AMM is a good one?
BTW, DO NOT CONNECT OR DISCONNECT THE AMM WHILE THE CAR IS RUNNING!!! KNOWN FACT YOU CAN FRY THE COMPUTER AND EVEN A GOOD AMM, if your mechanic did that run away from him fast.

Another common fault point for such failure could the the IACV (idle air control valve).

Greg Mustang
Montreal - Ottawa
Canada

Greg,
I was searching earlier after when I left this message and I saw where somebody else had the same symptoms. Their problem ended up being as O2 Sensor. My mechanic tried this and the problkem has seemed to work. He said that it's a little rough when cold but idles annd runs great when warmed up. I think I might want to still lok at the IACV, where is this and is it expensive? Could that be the issue with the cold start roughness? It was never like that in the past. If my mechanic did pull the AMM while the car was started, is there a way to see if it effected the computer?

Thanks for all your help in advance,

Don