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95 etc stalling at steady speed


rmac-etc

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150k, car has stalled twice this week while driving at a steady speed (~50 mph). Pull over and it starts right up. The fuel rail recall was performed 2 weeks ago (dealer). I replaced the FPR a couple years ago and it looks ok (no fuel drips). Also, I am pretty sure the cat is bad.

The codes haven't been cleared for a long time, but here they are:

P039 - Torque converter clutch, had this one for years

P056 - Transaxle speed sensor, had this one for years

P095 - Stall detected, yep

I027 - PRND321 sensor - haven't seen this one before

S061 - Suspension (still on original shocks)

So, is the PRND321 relevant? Should I be looking at fuel delivery problems, fuel filter, fuel pump (hope not) .... the codes don't seem to give much to go on.

Haven't seen any posts about stalling at speed, has this happened to anyone?? :)

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car has stalled twice this week while driving at a steady speed (~50 mph). Pull over and it starts right up.

That is a classic symptom a faulty CKP (Crankshaft Position) sensor. Is should set a DTC but I have heard other say that it does not always.

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The cat can cause stalling while running if it is really clogged. If it happens at speeds above 40 mph or so, and you can feel it coming on as the engine weakens, then finally stalls, then it could be the cat or clogged mufflers. Another symptom of exhaust obstruction is poor fuel economy.

If the car abruptly stalls at any speed with no warning or weaking of torque, I would venture that the fuel pump needs looking at. The PRND321 sensor can cause the car to fail to turn over by locking out the starter when the sensor says the car isn't in Park or Neutral, but it shouldn't cause it to stall while running.

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Thanks for the replies. I like the phrase "classic symptom" so I went the crankshaft pos sensor route, although I am going to get the cat replaced also. Thankfully the dealer parts dept is open on Saturdays so I was able to get the sensors. Checked out other posts on the replacement and went at it. Its pretty tight in there but I got them out. Turns out the dealer gave me the wrong ones, apparently for somewhat newer N*'s. Dont know when it changed but mine are both black (identical) with a 2 lead side connection. The ones the dealer gave are different, ones black the other grey with 3 lead connectors coming straight off the top. arrrrrrrrrrgh. Can 't put it back together till monday (unless pep boys has them - unlikely) ....

While at the dealer I noticed a gleaming silver 2000 eldo with only 35k for $13900. hmmmmmm

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Crankshaft sensor problems are usually confined to the 2000-2003 models. Not to say yours aren't bad but replacement may not be the cure.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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  • 4 weeks later...

Still stalling occasionally. Did a 100 mile trip last w/e, no stall. Yesterday after ~25 mi, it shut down. When this happens the electronics are still alive, it doesn't start imediately, it needs ~10-15 secs before restarting. I was going ~80 and put it in neutral, coasted on the generous shoulder and it started back up on the 2nd or third try and I was back on the hiway before it even coasted down to 65.

There is a new code since my original post - T077, PCM Serial Data Link fault. As this was not present orignally (or I missed it :)) it would seem that its not relevant, but perhaps it is. Not sure.

So far, I have replace the cat (it had been bad and rattling for a long time) and the crank position sensors. There is a lot written about the map sensor that connects it with bad running or stalling, so that and the fuel pump/filter are my current suspects.

I find it odd that no one has reported this specific problem. There are some stalling posts, but they usually are not at hiway speeds and usually report bad idling or missing etc. Mine runs perfectly until it shuts down with no warning.

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Check your fuel pressure, tape a gage to your windshield if possible and watch it when you stall. The fuel pump relay would not be at fault here, as the backup power system through the oil pump would 'take over'. It would be a fuel pump stopping for some reason, ie ground, armature, etc.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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I'm going to order a fuel pressure gauge so taping it to the windshield might be a possibility.

I forgot to mention that this started happening right after the dealer did the fuel rail replacement (recall). Coincidence?

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I'm crossing the map sensor off the list of suspects. The more I read about it the less I think that it could cause an engine to shut down at 80 mph. If anyone disagrees, I'm all ears.

As Sherlock said, "Eliminate all other factors, and the one which remains must be the truth."

I think that leaves the fuel pump/filter as the remaining most likely culprit. I will be checking the fuel pressure for corroboration, but as its an intermittent problem, I may not have the opportunity to actually see it when it fails. Since my wife and daughter use the car, I am not going to wait. Looks like I may be dropping the fuel tank in the near future ....

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I would expect to see a higher fuel pressure. If there is a way to block or disable the FPR on your engine model, I would try that to see if the pump is capable of 50 PSI. Try key on, engine off and cycle the key on - off several times.

You mentioned a fuel rail replacement and that plus the FPR is where I would concentrate the investigation.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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The fpr was replaced about 3 yrs ago and is not leaking at the vacumn hose. Don't know of a way to disable it. The only thing you can do is pull of the hose. Not sure if that would disable it or not.

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not only will it leak but it will fail to hold a vacuum, if you have a hand held vacuum pump with gage (sears), you can test to see if it holds a vacuum. I agree with JIM your pressure sounds low, especially at 4000 RPM

By the way, since this coincides with your fuel rail replacement, there are two o-rings inside the FPR, its possible that the small lower oring is not seated.. KHE has posted details on this if I recall, do a search and see what you can find by him on this

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Just popped the fpr off, and the o rings seem ok ... I did another fuel pressure check with the vacumn line connected and disconnected. As I said before connected the pressure is 36 and drops to 32 when revved up. With out the vacumn line connected it is a constant 44.

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But is it possible that the pump intermittently loses pressure, or is that unlikely .... if its not the pump then there aren't many possibilities left ... PCM?

It's not likely the pump is intermittent; possible, but not likely.

That leaves an ignition issue causing your stall at speed and it could be related to road / engine vibration and that points to a possible loose or corroded connector.

What I would do next is remove and install (several times) the low voltage connectors on both ends of your coil pack / ignition control module. My '98 has four connectors but I have no idea how many might be on your model. Exercising the connectors that way will wipe any corrosion off the contacts.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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I have to disagree Jim. I had a Chevy Blazer years ago that would just drop dead at speed. It would always restart and run fine for a day or two. The pump had an intermittent failure. My '92 Deville would run fine until I went WOT. Then it would fall flat on its face, like a carburated engine with a bad accelerator pump. I would get that guage taped to the windshield and see what the pressure is and how it acts when it fails. I think normal fuel pressure is about 45 psi. 33 - 39 sounds low. My money is on a failing pump in its death throws.

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I found this information for a 96 Eldorado, it was not included for the 95, but it should be helpful:

The Fuel Pressure Check determines if the fuel system is providing fuel pressure. The components involved include the fuel tank, sending unit, pump, pipes and hoses, pressure regulator, fuel rail, and injectors. Also checked is the electrical operation of the fuel pump relay. This chart requires J 34730-1A , Fuel Pressure Gauge J 37287 , Inlet and Return Fuel Line Shut-off Adapters.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

With the ignition switch ON and the fuel pump running, the fuel pressure indicated by the fuel pressure gauge should be 333-376 kPa (48-55 psi). This pressure is controlled by the amount of pressure the spring inside the fuel pressure regulator can provide.

A fuel system that drops more than 5 psi in 10 minutes has a leak in one or more of the following areas:

The Fuel Pump Check Valve.

The Fuel Pump Flex Pipe.

The Fuel Pressure Regulator.

The Fuel Injector(s).

Fuel pressure that drops-off during acceleration, cruise, or hard cornering can cause a lean condition. A lean condition can cause loss of power, surging, or misfire. A lean condition can be diagnosed using a scan tool.

Important

Make sure the fuel system is not operating in the Fuel Cut-Off Mode. This can cause false indications by the scan tool.

When the engine is at idle, the manifold pressure is low (high vacuum). This low pressure (high vacuum) is applied to the fuel pressure regulator diaphragm. The low pressure (high vacuum) will offset the pressure being applied to the fuel pressure regulator diaphragm by the spring inside fuel pressure regulator. When this happens, the result is lower fuel pressure. The fuel pressure at idle will vary slightly as the barometric pressure changes, but the fuel pressure at idle should always be less than the fuel pressure noted in Step 2 with the Engine not running.

A rich condition may result from the fuel pressure being above 376 kPa (55 psi). A rich condition may cause a DTC P0132 or a DTC P0172 to set. Driveability conditions associated with rich conditions can include hard starting (followed by black smoke) and a strong sulfur smell in the exhaust.

This test determines if the high fuel pressure is due to a restricted fuel return pipe or if the high fuel pressure is due to a faulty fuel pressure regulator.

A lean condition may result from the fuel pressure being below 333 kPa (48 psi). A lean condition may cause a DTC P0131 or a DTC P0171 to set. Driveability conditions associated with lean conditions can include hard starting (when the engine is cold), hesitation, poor driveability, lack of power, surging, and misfiring.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Really appreciate all the input.

I have disconnected/reconnected the coil pack connectors (4) as well as the ground cable which I cleaned thoroughly with a brass wire brush. There was some corrosion there.

I plan to replace the fuel pump/filter next w/e (I am out-of-town mon-thurs) so hopefully the issue will be resolved. Unfortunately you can't know when/if the shut down will happen so there will be no certainty as to whether its fixed until some time passes, however if the new fuel pump increases the pressure notably then that gives one reason to hope.

Thanks again, and I will update this thread if the fuel pump does not solve the problem.

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Do not replace the fuel pump until you confirm that your pressures are bad, look for another source of "normal" pressures beside what I posted just above. The pressures I posted above are a test that was in the service manual..that involves shuting off the return. I will look for more information for you on normal fuel pressure and others can post their knowledge on it. I don't want you to pre-maturely replace the fuel pump based on my post above even though your fuel pressure does appear low..

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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I am happy to get any additional info re fuel pressure or anything else that would be relevant to an engine shutting down at hiway speed .... nothing entirely makes sense, I know that there is no smoking gun here ...

... but upon further reflection, i think .... i think the solution is in bbf's fine print. C Walken is right .... more Cow Bell!! Does he drive a Caddy? :)

... uhh I think he doesn't drive at all, actually.

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  • 1 month later...

Just replaced the fuel pump. Working under the assumption that the pump shuts down intermittently. I think that even if the fpr had a vacumn leak, that would not cause a stall. It runs with the vacumn line disconnected, after all.

Had another stall this week, this time at a stop sign 2 blocks from my house (it was idling and running smoothly). I then hooked up fuel pressure gauge and let it idle for a long time and rev'd it ever now and then but it did not stall while being watched. When I turned it off, the hose to the gauge was very hot near where it was attached to the rail, so not knowing what it's rating was I was disinclined to tape it to the windshield and leave it until it failed again. My wife and daughter (w/baby) sometimes use the car, and was worried that that fuel gauge hose could fail in some way and be dangerous. Good idea, but not prudent in this case.

So, there is a new pump and filter in there. It is a calculated risk. For the record, I was able to empty the tank which make the removal much easier. One of the 4 bolts holding the straps is under some exhaust shielding. I was able to leave that one alone and drop the tank by removing the 3 exposed bolts.

Total time (working sloooow (remember uncle joe on petticoat junction?)):

45 mins to remove empty tank (the bolts were tight and stiff - now I am, and not in a good way :) )

30 min to clean off the tank and replace the pump (gentle use of a rubber mallet was needed to loosen the collar)

30 mins to put it back up

So about 2 slow hrs with clean up.

Nothing obviously wrong with the old pump. The screen mesh filters (there is one inside the pump housing as well as the external one) are dark but that is the only notable observation. The pump motor is in a metal can, and I might try to cut it out to see what the internal bits look like.

For the record the fuel pressure with a new pump and filter is unchanged from what I posted earlier, ~36 with small drop when revved up. With the fpr vacuum line disconnected it is a constant 44.

So, fingers crossed we go forth!

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Nothing obviously wrong with the old pump. The screen mesh filters (there is one inside the pump housing as well as the external one) are dark but that is the only notable observation. The pump motor is in a metal can, and I might try to cut it out to see what the internal bits look like.

I did that on a Chevy Blazer pump once. Look at the electrical contacts inside. I found them burned.

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Thanks for the update... good job

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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