Hello all, I am new on Z28.com. My Z-28 stalls ever now and then. It will be driving fine for days then all of the sudden the engine will start hesitating and the tach starts jumping. Sometimes if I hold the throttle it will work thru without stalling sometimes not. It can take anywhere from 1 min to 3 hours to refire it, then it will run fine most of the time. I have replaced the fuel filter and started checking different sensors. Can anyone help me with this? I am stumped with this one.
Matt

 

Welcome!!

Have you scanned the PCM for codes? Sounds like you may have an erratic signal from the optical module in the distributor (Optispark). If that is the problem, its likely to set codes DTC 16 and or DTC 36.

Could also be a poor ground for the PCM or the engine. Or maybe heat soak on the IC Module. Start with the codes.

 

i am not getting any codes nor a check engine light

 

I am going through the same problem. Mine only happens if the temp outside is over 95 degrees. I have heard of these problems being the fuel pump, fuel filter, opti, icm, coil and the throttle position sensor. You could replace them all and it will still do it, so don't make my mistake and just throw money at it. Start out cheap and see if it fixed the problem. Most can be checked and eliminated without replacing.

 

Injuneer had the same thoughts I did but based on tach being involved, I point towards the opticrap.

I have replaced many and my best time ever to do it (you better have the right tools to draw on the dampener) was 4 hours. I timed myself.

 

How did you scan it for codes?

The Opti codes typically do not turn on the SES light.

 

Thanks for all the great information. I used a OBD2 scan tool to check for codes at my local Auto Zone. It only happens when it is hot out, but this is the first summer this has happened. I bought the car in Florida in 2005 and was there for a year off and on before I moved to Louisana. I need to play elimination game. mrmint69 at least I know that I am not the only one with this problem. It makes me feel a little more at ease.

 

That explains why you didn't get any codes. Your 95 is OBD-I. GM just made it confusing, by putting a 16-pin OBD-II style ALDL connector under the dash. Get an OBD-I scanner, and make sure it has an adapter plug for the 95 16-pin connector, or jump the wires as shown on Shoebox's website:

http://shbox.com/1/xraycable.jpg

Get the codes and come back and tell us SPECIFICALLY what they are.

 

FWIW .. I had similar problems on my '95 LT1 Corvette. My problem turned out to be the water temperature sensor connector. The wiring to the connector had aged poorly over time and made for intermittent readings. I assumed from this that the PCM would get a erratic reading and jump from table to table within the programming based on the water temp reading. I found this by letting the engine idle and shaking wires looking for issues while someone else inside the car watched the guages. When I shook the water temp wiring, the guages would show all sorts of odd things and the engine would eventually stall.

I sawpped out the water temp sensor but the problem continued. I spliced in a new connector and thigs cleared up. No issues in over 2K miles of driving since then.

Later ... Larry S.