My 88 is having problems again. This time it intermittently runs very poorly. It will run fine and the all of the sudden, like someone flipped a switch, it will falter and barely run or completely die. Sometimes I can start and stop it a few times and then it will all of the sudden run right again.I recently replaced the fuel pump (about 1,000 miles ago). Yesterday I pulled it back out and checked to see if the screen was clean and it was. I replaced the fuel filter and today I checked the fuel pressure and it is right at 42-44 lbs. even when it isn't running right. It smokes heavy black smoke when it is acting up which seems to indicate that it is getting fuel but not igniting it. It feels like it is firing on about half the cylinders. I'm not getting any codes in the computer. Again, when it happens it is like a switch is flipped and it acts up. Then sometimes it will just clear up like someone flipped a switch. Where do I go from here?

 

Some things to check, spark (good quality), injector pulse rate (need scan tool for that), ESC (Electronic spark control enabled, again scan tool), MAF (unplug when car is acting up, puts it in backup mode), and coolant temp (not what is showing on dash, but what CTS is reporting to ECM, again scan tool) Good Luck[8D]

 

Thanks Mech259. I guess I will have to break down and take it to the shop where they can put a scanner on it. I have tried everything I know including the MAF test and nearly every ignition part on the car. I have replaced the plugs, wires, cap, rotor, ignition module, pick-up. No difference. I runs fantastic when it is not acting up and then all of the sudden it barely runs. It is clearly flooding. I don't know if it is because there is an ignition issue or if it is dumping fuel in that it doesn't need. Because of the suddenness of the on and off I still think it is ignition. Just like a light switch on and off. Urgh....

 

Have you checked for vacuum leaks?

 

Ok. I hooked it to a computer and what we found is that when the car acts up the computer is only showing 6 volts to the fuel pump. It shows 14 when it is running right. This confused me because the car was flooding. Next I checked voltage at the relay and had 14 volts going in and coming out of the relay when it was acting up. Now I just checked the voltage at the ECM and it is good but the ECM is reading 6 volts. I guess that even though the fuel pump is working as it should (fuel pressure is 44lbs at all times) the computer is trying to compensate for seeing low voltage to the pump and flooding the engine. Does this sound like the ECM is bad? That is my conclusion. Any ideas?

 

Joe; That was kinda my thought in the first place,but I;m pretty new around here. It seems like if something's wrong and the computer won't tell you about it,it's probably the computer. Won't tell on itself! Had a very similar problem with my 84. I watch fleabay for good deals on ecm's and try to keep a spare on hand.
Ron

 

In this case everything was working as it should until the ECM thought it saw a problem and tried to fix it. I found an aftermarket ECM at Autozone for $66 dollars (I hope that wasn't a mistake)and stuck it in. It's running great for now. I will have to see what happens over the next few days. I hate to get my hopes up. I have thought I had it fixed too many times before.I'll keep you posted.

 

Great! I really prefer learning thru others problems! Usually it's thru my mistakes!
Ron

 

Well if you are only getting 6 v to fuel pump, ECM has nothing to do with that. I would check your chassis ground system.

 

Check the ground for the computer too, had a '90 Caddy that was like that once.....