Engine stumbles, unstable idle after WARM start-up

[edwinn]

That also.. makes me consider the fuel vapor cannister...on your car - no idea where it would be.

Yeah.. the vap canister is directly behind the LR wheelhouse (the wheelhouse closeout panel that is.) You can just about see the fuel filler pipe and vent tube on far LEFT of pic, going inboard thru the fender well opening.

That's it right above the LR muffler. You can look through from the LR airshock area and see everything. So it's an easy inspection.. remove the plastic closeout panel. The whole rear end is rust-free from the wheel wells (especially top of ww's) back.


-Ed

 

[edwinn]

Sounds like a leaky injector that dribbles after shutting it off. Does it blow black smoke when it clears it's throat?

Was able to do a warn start-up in the garage yesterday with hood open, driver door open with observer Ms Carol standing behind the car. I clearly heard (from under hood and exhaust pipes) the RPM stumbling, and roughness for 3 - 5 sec before it smoothed out. No smoke at all was seen by observer coming from the exhaust, which is good.

It threw me off a bit when you mentioned "smoke." The 97 Riv does not produce ANY smoke, and never has.

Also removed the VAC line from the FPR and did the ruptured diaphragm test in the video. There was no fuel discharge, no smell of fuel at all and no wetness in the vac elbow. I ran a cotton swab into the rubber elbow fitting and it had dry black flakes or crumbs on it.. like deteriorated rubber. No evidence of fuel... very dry and flaky inside.

Also bought a Fuel Pressure Test Gauge and will do some FP measurements today.

Any other suggestions?


-Ed

 

[edwinn]

I bought an Actron #CP7818 FPT Kit. Not a bad unit!

Here are some Fuel Pressure test results from yesterday Nov 11, 2013.

              Fuel Pressure (PSI)
 
Trial  Ignition  Engine  FPR Vac  Engine  After
Num    On        Start    pulled    OFF  5-min
------------------------------------------------
  1    30
  2    34
  3    40->38(1)
  4    37->35
  5    43->39
  6    37
  7    37        41-45(2)  47-51    48
  8    46->45    41-45     47-51    43    51
  9    45->44    39-48     47-50    44    51
 10    47->46                       45    51
 11    44->42    33-45(3)           40
------------------------------------------------
 
(1) Initial pressure, drops to ->P after ~1 min.
 
(2) Pressure jittery, range of gauge indicator.
 
(3) Starts up at 42, drops to 33 and chugs,
    smooths out to 43, then jitters 41-45.

Here's a chart plotting the pressure readings above.

I'll have some photos and a VIDEO to post later today. It should be clear to you experience guys what the issue is after seeing gauge readings in the video.

Not exactly sure, but the fuel pump could be old or obstructed.


-Ed

 

[edwinn]

Video of the Fuel Pressure start-up test is pasted below (12.2 MB)

http://home.comcast.net/~edwinn/97_Riv_FP_startup.mp4​

What do you think about that? Is it normal for the gauge to `jitter´ like it's doing? Notice the pressure goes LOW right after the engine starts, then is constant, then becomes erratic. Why does the FP rise after the engine is turned off?

I hear a strange sound after engine shutdown.. like a vacuum solenoid?

Thanks,

-Ed

 

[edwinn]

Still kind of think that is the classic symptom of the FPR leaking.
Although smelling fuel...hmmmm..not sure about where the vapors are escaping..but somewhere - right?..

Yeah.. I got into the left rear wheel well over the weekend to see if there were any 'crisp' hoses, etc. Everything is original and whole fuel system should probably be gone through. I'd really like to drop the fuel tank and change ANYTHING that is deteriorated.

What causes the FP gauge to flutter so much? It should be pretty steady, yes? Will have to do some snap-throttle tests next. We're running out of warm days though.

Thanks,

-Ed

 

[Heisenberg]

Yeah.. the vap canister is directly behind the LR wheelhouse (the wheelhouse closeout panel that is.) You can just about see the fuel filler pipe and vent tube on far LEFT of pic, going inboard thru the fender well opening.

That's it right above the LR muffler. You can look through from the LR airshock area and see everything. So it's an easy inspection.. remove the plastic closeout panel. The whole rear end is rust-free from the wheel wells (especially top of ww's) back.


-Ed

Nice of them to hide that up under there.

 

[edwinn]

Nice of them to hide that up under there.

The canister is easy to remove with one bolt threaded upward on the aft inboard side.

As you can see from the pressure readings, we've determined in the AF forum that the fuel pump is weak. Not only that.. the seal around the fuel pump is leaking. That would explain the smell of fuel from LR wheel well area. Here is a photo of the FP looking through the access cover in trunk.

And a photo of the access cover in trunk. The entire trunk pan and floor has been sponged out and waxed with auto polish!

Got a replacement Delco FP unit and new locking (cam) ring yesterday. Should be able to get the FP replaced this weekend.


-Ed