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Oil pressure jittery; spontaneous misfire; then engine cut off
I was at a stop light the other day, just started driving my Blazer that day, and I noticed the oil pressure gauge was acting jittery. At idle on a hot engine it would bounce around 20 PSI and jitter right there. I also felt the engine misfire a bit. So I gave the engine a good rev there at the stop light, brought it back down to idle, then the oil pressure would drop very close to 0 and the engine felt it was misfiring. I revved it again, brought it back down to idle, then it suddenly cut off. What could cause this sort of behavior?
My 2002 S10 Blazer has 170k miles on it, and this is the first time ever it had done this. I just replaced the spark plugs a few weeks ago.
A lot of things can cause this. Fuel delivery, ignition, bad sensor, air delivery, bad cat, etc. If you want to figure it out without the parts cannon then you will need to do a proper diagnosis. A lot of guys here go straight to swapping parts but that can get expensive.
How was your oil pressure before this?
What did the plugs look like?
Have you done a compression test recently?
Do you have a scanner with live data capability? If so, any codes? If you want to do your own diagnosis and repair, this is pretty essential and not that expensive. The key is live data and a few special things like misfire counter and cam retard. There are members here that can hook you up on the cheap.
Depending on the answers to the items above, you should do the fuel pressure tests in the sticky above.
It would always bounce just a little while idle/hot around 20. That's been normal never since I've owned the vehicle. This instance the other day was far more pronounced than ever.
Originally Posted by GeorgeLG
What did the plugs look like?
Originally Posted by GeorgeLG
Have you done a compression test recently?
I've never done one before. I suppose I should look into it.
Originally Posted by GeorgeLG
Do you have a scanner with live data capability? If so, any codes?
I have a BlueDriver I can use to pull live data. I'll collect some data over the next few days. There are no code though. At least nothing relating to this. I have ABS module errors, but that's a different thing I'm still trying to diagnose.
GeorgeLG, you mentioned bad sensor. Could it be MAF sensor or oxygen sensors? I don't think they're bad, but they are the original factory parts. I guess pulling live data would determine that.
It sounds like your oil pressure was normal for an engine of this age before hand so the oil pressure jitters are probably related to the engine stumbling.
Your plugs look fairly normal for an older engine.
Live data will help you get to the bottom of this. Start with the misfire counters by cylinder to see if its random or specific to a cylinder. Look at fuel trims to see if they are out of bounds. If nothing there then you can go through the sensor data. There are many possibilities there: O2 sensors, MAF, MAP, TPS, ECT, crank, cam, ....
Don't forget fuel pressure. How old is the fuel pump?
Here's some live data I pulled yesterday on a short drive.
The first set CSV is me driving around my neighborhood with speed bumps. Engine RPM may seem high compared to vehicle speed because I was driving around only in first gear trying to diagnose a vehicle shaking/balance problem for another thread. https://docs.google.com/spreadsheets...it?usp=sharing
08-14-2020, 09:14 AM
Oil pressure jittery; spontaneous misfire; then engine cut off
