Ok my first post here, been watching for some years and usually find great help. Bare with me since its long. And I will appreciate any suggestions.


Ok main issue, car drives great 0 issues, all of a sudden iddle stumbles and dies, hard to start sometimes, this is not a repetitive issue or based upon temp or time or fuel level etc. Its simply random. And has started to happen more frequently.


Started with the obvious, no check engine light or codes, so thought fuel related, changed the fuel pump. Same, monitored FP, right on even when failing, so regulator discarted.

Tb clean, maf clean, tps voltage ok and sweeping without cuts. Then noticed I had a code p0325 for knock sensor or circuit, checked the wiring ok, checked the knock sensor resistance and was ok within parameters, was able to clear the code after reinstalling it, then it appeared again so changed the knock sensor. Hasnt come up since.


Moved to live monitoring and notice the car does not goes into closed loop, unless you give it some throttle and moves to closed loop, if you release the throttle to idle it stays in CL for a while then goes back to open loop. (Regardless the temperature).

Ect cycles between 220f and drops to 213f when fans turn off.

02 sensors while in closed loop cycle voltage and fuel trims stay close to 0 usually.

Battery voltage 13.4ish at idle and goes to 13.9v with all accessories on.

Iat's 115 ish stationary.


Then noticed whenever the engine starts to die it states closed loop failure. So I start again and same story about the open loop closed loop issue.


Whenever its not acting up the idle is spot on 700 715 rpms. Either on Park or neutral and on 1st gear reverse or drive.


So decided to check the egr, it holds vaccum, so went and checked the upper tube, its clean (well not shiny but no carbon build up.) After all only 40k miles on it.


No air intake leaks, map sensor seems to be reading ok. Vacuums hoses dont seem cracked or any of them disconnected.

Pcv seems ok.


Im stunned and and cant seem to catch this issue.

Im starting to think about taking the pcm out and check if any corrosion or something on the wiring.

The inverted open/closed loop throws me out...

The hare part is that I can drive the car for a few days no issues and then it happens.. kinda frustrating...


Any ideas anyone?

 

Sounds to me like your MAF sensor is bad.

 

Could it be such a random problem? I do see the maf reading on my live scanner. Its clean as new, never dropped or had a dirty air filter.
Guess im gonna have to start throwing parts to see what hits the issue :/
Thabk you for your input

 

The telltale signs for a bad MAF include erratic idle, stalling and no CEL. Had this issue with my ‘98 a little while back.

 

Well I tried disconnecting the maf to see if it died, but car still runs, also tried the same for o2 sensors, wont die.
they do trigger CELs though...

 

Ignition switch failing intermittently?

 

Thought about that and wiggled key all around, messed with wiring plug to check a false, and even being stationary without touching the car watching the scanner it dies.
Thats where I went to check the alternator and battery voltage. Also I dont lose comunication with the live scanner when it dies.

 

Here are some images of live scan..
If i let the car idle

Open loop status

If I tap the throttle goes into closed loop

Closed loop working

Let the car idle for 30 seconds or so and goes back to open loop

Back to open loop

Heres a graph of o2 sensors while being at closed loop and going to open loop..

o2 sensors cycling and when it goes to open loop dead

 

double check the EGR valve it can cause that it happened on my 98 I had a hair line gap from the gasket after I fixed that it was fine. also check your intake plenum gaskets/valve cover gaskets could be losing compression which is stalling it at idle.

 

Took the egr system out to check, valve its holding pressure, solenoids are working, tubes are clear of carbon. No leaks that i can find there.
Also did a brake clean and carb clean on the intake gaskets and was not able to find a leak.

Im gonna check the correlation between 02 sensors with the cat sensor and see if theres something off.

 

Well after long diagnosis and data logging seems like a few users got it! , Apparently the MAF sensor goes crazy sporadically and reads high so its flooding the engine while on idle. This is not all the time, is all of sudden, then it goes back to normal.
Im gonna try out luck buying a new one, and check back if it persists or goes away

 

Well after long diagnosis and data logging seems like a few users got it! , Apparently the MAF sensor goes crazy sporadically and reads high so its flooding the engine while on idle. This is not all the time, is all of sudden, then it goes back to normal.
Im gonna try out luck buying a new one, and check back if it persists or goes away