Heres my dilemma. Ive got an 89 LO3 nearly stock. It has just recently started hesitating on launch from idle. I thought it was due to warmer weather and a lack of an Incoming Air Temp sensor. I bought the sensor and cleared the code 23. After running for a day, the car started idleing really rough and low. While trying to trouble shoot the low idle, it started hunting for an idle speed between 350-900. I unplugged the IAT sensor, but no luck then. I shut off the car till morning. Drove to work, ran great (sensor unplugged still) Came home from work, idle dropped and ran rough again (still no sensor plugged in) Adjusted idle stop screw on TB today and it ran ok until warm then drpped some more, so I adjusted again. Took it for a quick drive, ran ok for a while then it cut out for 1 second after running hard and letting off (ran it wot from idle to 5000 then let off quick). Parked in the driveway and idle jumped and became way too high.

I think something is on the way out, I just dont know what yet. The coil seems to check out with my multimeter (according to my Chiltons wayof testing) but it is original. I can change the coil myself, but the fuel pump would have to go to a garage. Also, when it warms up a bit, the injectors chatter really loud, which makes me think its fuel related not ignition.

The car runs cold due to the high flow radiator and 160 thermostat the previous owner put in, if that matters at all.

 

It's not the fuel pump - when they go they go, and that's it - no fooling around - they just die.

How old are the plug wires? Make sure wires are all on the plugs - I had one that would come slightly off - looked good, but wasn't making sufficient contact. Also make sure no breaks in them (check with ohm meter). Bad wires usually cause a backfire though.

Try a fuel filter (my best guess).

Check the vacuum lines - vacuum problems are common, and the smallest one can make for a bad day (my 2nd best guess).

 

Well the reaon I mentioned the fuel pump was in searching the forums for hunting idle and surging, alot of folks were saying that a dying fuel pump will sometimes get weak when warm. Same goes for the coil with heat soak issues. The car runs fine for the first five minutes then starts acting up when it stats to get warm. It also has been throwing code 32 (egr) since I got the car, but ran great up until two weeks ago when all this started.

 

Ignition module

 

Some fuel pumps don't just die! I ran my car (Lo3 TBI) for a couple of mo. before I found out what the problem was. It was running on 7 1/2 lbs of pressure. Not verey good at all, but still running. Code 54 and a fuel pressure check is the only way to tell for sure unless you just like changing fuel pumps!
I could give you a whole bag full of problems that would cause his computerized, fuel injected motor to run like it is starting with the 160* thermoustat and a stock prom.

 

Same problem I'm having with my car at the moment.

Except - it can do this right from a cold engine - and can even idle fine during drives. But sometimes when you come off the gas it drops to a really low idle and stalls.

 

Yeah - i got an 87 TPI 350 that the fuel pump started going out gradually (fortunately for me!) it would kind of sputter on takeoff and then catch. Wasn't making more noise or anything, just dying. Ran long enough to get to the shop, lol!

 

Thanks, looks like the fuel pump will get checked. Not that I can check, but I was told the car has a custom prom in it. I have had the car now since January and had it up to operating temp numerous times without this problem before. Ive been getting so frustrated trying to get my code 23 and 32 to go away, now this starts. I am tempted to pull the whole deal out and go carb instead.