I have a 94 z28. It seems to be running fine until it gets hot. I just put a msd optispark on it and still has the same issue. I have a msd coil and msd plug wires and brand new plugs. It just don't understand how it can run fine when cold but when it gets hot is misses and runs super rich. The longer it runs the worse it runs. I'm assuming its something electrical but I'm not sure what to check and I don't have the money to just buy parts or take it to a garage. Some suggestions would be greatly appreciated Thanks

 

test the temp sensor on the water pump. they can go bad and show really cold, like -40. causes super rich condition, gets worse when the engine warms.

 

look at 20 here 4th Gen LT1 F-Body Tech Aids

 

If the maf is unhooked won't it bypass that sensor? I've had the maf unhooked with no change in how it acts?

 

all it takes is a ohm meter. simple test to remove that from the list. i think the temp sensor is used all the time. if its cold it changes the air fuel from the get go.

 

Do you know what the ohms should be on the temp sensor? I have a scan tool if can run diagnostics menu but I don't know what I should be looking for?

 

If you don't already have a copy, you should really download a copy of the 1994 F-Body Service Manual here. It contains all the troubleshooting information you're looking for, plus a lot more. If you use an Adobe Acrobat Reader program (Download here free) to open the file, you can use the Bookmark function to navigate the document just like you would use the table of contents in a paper version. Clicking on the bookmark of your chose, will take you to the first page of the subject you're wanting to learn more about. To open the bookmark window, click on the second icon on the top left side of the page. This should open a window to show a digital table of context. Any box with a + in it means the title is collapsed and clicking on the + will expand the bookmark to show all the topics contained in that section.

The resistance values for the temp sensor are shown on the attached pdf and the page also gives some insight on how to use the scanner to help troubleshoot. Hope this helps.

 

Just a FYI, this is not an uncommon complaint even before computers. Almost everything electrical has a higher resistance when hot then cold. So if a component is close to failing it can get worse when hot. Another issue is connectors, if the connection in a connector are loose then you heat will causes the plastic to expanded the connection can become intermittent.


Did you change the pig tail connector going to the opti. It is a common failure point.

 

MSD distributor has its own pigtail built in. It requires you remove the oem pigtail. I just new I changed that temp sensor like 2 years ago and only drove it a few thousand miles so didn't really think it would be the issue but I should just swap the old one back it since it wasnt defective

 

see link in post number 3. it has a graph that shows ohms per degree.