Fuel Pump? Engine randomly cuts out.

[SHO Continental]

This is on my '90, bone stock except for Ypipe. First time was as I was pulling into my destination a few weeks ago. As soon as I pulled into the parking lot the engine power started cutting out. As if the fuel pump or coil pack was turning off every other second. In combination it appears the IAB is gone also as when idling the RPMs jump slightly. Tonight it creeped up on me in the middle of a drive, cutting out on acceleration only and stalling if i put it in neutral. I haven't run the codes yet, I'll do that tomorrow in the light. Any ideas what it could be? Cam sensor? Fuel pump? Time to buy the new SHO?

 

[SHO Continental]

On my drive back home this morning I was watching the tach jump, which the variation turns out to be only 200 RPM if that (does not drop to zero). It cut in and out at the beginning of the drive for the first ~2 minutes until the car warmed up. The first time it did it was at the very end of the drive so I don't think it's a matter of something warming up or not. On the drive over tonight it did it intermittently throughout the drive. After the car warmed up I went through the gears and with the liberal amount of throttle I gave it the car felt normal. I'm leaning away from the fuel pump and Crank sensor. Any ideas?

 

[Storm-Chaser]

Cam sensor.


As previously posted:

Generally, you can differentiate the crank sensor [intermittent] failure from camshaft identification sensor [intermittent] failure by whether it dies or not. For the most part . . .

• both will set codes and throw a check engine light
  
  
• intermittent Crankshaft Sensor Failure - tachometer always rapidly drops to "zero" rpms, and the engines dies as if the key has been moved to the "Off" position. May or may not restart immediately, and will run normally once it starts until it fails again.
  
  
• intermittent Camshaft Identification Sensor Failure - tachometer may or may not show rpm loss (ie. rapidly drop to "zero" rpms), and the engine may die, or run rough (minor to noticeable miss), or run as if there is nothing wrong. May or may not restart immediately, and may or may not run rough with a discernable miss once restarted.

Again, these are generalizations and assume that there are no other "compounding" problems at the time. The important thing to remember is, to look at how the tach is responding when the engine begins to bog, cutout, or die - as long as you don't have to sacrifice safety in monitoring the tach.

 

[SHO Continental]

I've been pretty busy lately. Got around to replacing the Cam sensor. It worked fine for a few miles. It was like driving on a cloud! Then it cropped up as it did intermittently before. So I still have the issue. Doesn't seem like the fuel pump would be the cause, I'd think that would just give me trouble at higher RPM, and a steady thing. After the cam sensor change I ran all the way to 7K and it pulled perfectly.

Ran the codes too... got a cam sensor code and seemingly unrelated EGR code.

19 - CID circuit failed.
33 - EGR valve opening not detected

In addition to the surging/bucking I'm also getting some bouncing RPMs at idle, or when I let off the gas from >3K coming to a stop, sometimes it leads to the car stalling. As I was not sure if it was the cam sensor or IAB causing that I changed the Cam sensor first. As it's still happening I was wondering if the IAB could cause the surging or bucking while at a constant throttle level while accelerating. I was under the impression the IAB would only mess with the engine while at idle.

Any ideas?

 

[SHO Continental]

Replaced the IAB and that fixed it!!

Problem solved.

 

[shoon]

wouldn't hurt to get some throttle body cleaner and give your MAF sensor a clean too.

 

[Shogun71]

Any ideas what it could be? Cam sensor? Fuel pump? Time to buy the new SHO?

i didn't notice it the first time around but that was pretty damned funny:laugh_ti:

as much of a pain in the ass as this doubtlessly was for you, i'm about 75% sure that i'm in the same boat and i'm going to change out both the cam sensor and IAB. i'll let you know how it turns out. thanks yet again.

 

[Shogun71]

intermittent Camshaft Identification Sensor Failure - tachometer may or may not show rpm loss (ie. rapidly drop to "zero" rpms), and the engine may die, or run rough (minor to noticeable miss), or run as if there is nothing wrong. May or may not restart immediately, and may or may not run rough with a discernable miss once restarted.

thank you very much as well. this sensor is clearly the father of my gremlins.