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91 Eldorado loosing power


bschelle

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My 91 Eldo is acting up. It acts as if it is starving for fuel when it is under a load. It idles fine but when I am driving it feels like it is starving for gas and looses power when I put my foot in it. No codes, fuel pressure is 38-42 #'s even when it is acting up, new fuel filter, plugs, cap and rotor. What else am I missing?

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What is the fuel pressure at idle? You might want to check the connections at the cam sensor and ignition module in the distributor for green corrosion. Sometimes that will be a problem. Seems like the fuel pressure should be around 48 psi.

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

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My 91 Eldo is acting up. It acts as if it is starving for fuel when it is under a load. It idles fine but when I am driving it feels like it is starving for gas and looses power when I put my foot in it. No codes, fuel pressure is 38-42 #'s even when it is acting up, new fuel filter, plugs, cap and rotor. What else am I missing?

Does it miss? A 91 Eldo would not set miss code. How old are the plug wires? Any arcing when you spray water over the wires?

The saddest thing in life is wasted talent

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What is the fuel pressure at idle? You might want to check the connections at the cam sensor and ignition module in the distributor for green corrosion. Sometimes that will be a problem. Seems like the fuel pressure should be around 48 psi.

KHE, as far as I remember, the fuel pressure of a 4.9 engine should be around 40 psi.

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If everything else checks out, this is a classic clogged CAT problem or collapsed resonator or muffler restriction

There is a tool you can buy to check the back pressure it screws into the O2 sensor hole, if you can find it

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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You may find one cheaper than this but this is the idea

http://www.mytoolsto...id/diagn04.html

The CAT in my 91 4.9 self destructed but it didnt clog up, maybe yours is restricting

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 just replaced the wires and same thing. It is OK when cruising under light throttle but as soon as I give it some gas it looses power and stutters and hicups or backfires. I take my foot out of it and it runs fine. The cat was removed a long time ago and the muffler is new. No codes either. I replaced the distributor a couple of years ago with a NAPA reman. ??????

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I was once told that a bad TPS would act like a bad accelerator pump that was in carburators, but you are not getting a TPS code, I wonder if it could be out of adjustment

What are your volts, I had an issue with my 4.9 where I had a bad cell and it could not provide the current to accelerate

I would check (load test) battery and connections to eliminate that

Do you have a spare coil that you can swap in?

Water in the fuel? Try dry gas

Try taping a fuel pressure gage to the windshield and seeing what happens when you accelerate, maybe the fuel delivery can not keep up with demand.

Check all fuel related fuses and relays for corrosion on their contacts and clean. (fuel pump, injectors, ignition)

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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Also tap test the PCM, and reset its connector and nearby grounds

Check the ground near the starter

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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Fuel pressure is 38-42 even when it looses power. I did the load test and terminal cleaning and the battery is good. I do not have a coil but it looks like I am going to replace it with the module. I will put the water absorbent in but I do not think that is it. I went to DeKalb and I filled it up there and then drove 80 miles back home without any problem. The next morning the problem occurred.

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It sounds like its bogging, not getting enough fuel

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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You know, now that I think about it, this is exactly how my '92 acted when the fuel pump started to go. Follow Mike's advice and tape a fuel pressure gauge to the windshield and see what it does when you put your foot in it. I'll bet it falls off (pressure that is).

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Gents - does this sound like a vacuum leak?

Are there any other systems related to vacuum that act funny?

A stuck open EGR valve might be a source of massive vacuum leak, but it would affect idle too.

The saddest thing in life is wasted talent

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Gents - does this sound like a vacuum leak?

Are there any other systems related to vacuum that act funny?

A stuck open EGR valve might be a source of massive vacuum leak, but it would affect idle too.

It idles fine. ICM is the next part to be hung!

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The TPS is a varistor. You can check it with an Ohmmeter. The resistance should change gradually while you turn the throttle lever. There should be no jumps in readings.

Mine is a Fleetwood, but the data should be in the same ballpark. It chages from 1.88 kOhm to 7.30 kOhm.

The saddest thing in life is wasted talent

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The TPS is a varistor. You can check it with an Ohmmeter. The resistance should change gradually while you turn the throttle lever. There should be no jumps in readings.

Mine is a Fleetwood, but the data should be in the same ballpark. It chages from 1.88 kOhm to 7.30 kOhm.

The new ICM and coil didn't change a thing. When I brake torque it, it misses like on the highway. Injectors maybe?

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The TPS is a varistor. You can check it with an Ohmmeter. The resistance should change gradually while you turn the throttle lever. There should be no jumps in readings.

Mine is a Fleetwood, but the data should be in the same ballpark. It chages from 1.88 kOhm to 7.30 kOhm.

The new ICM and coil didn't change a thing. When I brake torque it, it misses like on the highway. Injectors maybe?

Have you checked the TPS with Ohmmeter?

The saddest thing in life is wasted talent

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WOW.....

Everything I can think of, you have replaced already

I'm thinking on this

So it misfires under a load

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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WOW.....

Everything I can think of, you have replaced already

I'm thinking on this

So it misfires under a load

It didn't seem to miss while cruising before, but it does now. Even with a light throttle I can feel the miss like it is not hitting on all 8. Fuel pressure is stil good. I have not touched the TPS yet.

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So its getting worse.... drop your PCM down from under the passenger side dash and tap on it, to see if you can cause a misfire, while driving and idling

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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Did you replace the plugs and wires at the same time? IF you replaced the plugs and not the wires, and the plugs where carbon tracked, the wires will also be carbon tracked and will transfer that back to the new plugs. Just a thought.

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