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1991 Chevy Suburban My Suburban coudn`t climb from a comple

Tiny
ERNESTO TOLEDO
  • MEMBER
  • 1991 CHEVROLET SUBURBAN
  • V8
  • 2WD
  • AUTOMATIC
  • 100,000 MILES
Three days ago, I went to a parking place that is underground, and the suburban coudn ´t climb, so I had to go to a horizontal place and then go up without stopping all the way up. It looks that it is an engine problem because I coudn ´t rev the engine.

In the other hand I was travelling 300 miles with hills and I had no problem to get back home.
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Thursday, January 21st, 2010 AT 5:20 PM

15 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,703 POSTS
Was the check engine light on? Have you checked the catylatic converter to make sure it isn't pluggug? Have you checked fuel pump pressure?

Let me know or if you need directions, let me know.

Joe
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Friday, January 22nd, 2010 AT 11:22 AM
Tiny
ERNESTO TOLEDO
  • MEMBER
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This is a mexican carburetted model. I doesn ´t have check engine light, It doesn ´t have a cathalitic converter installed and it has a new electric fuel pump that I adapted to this vehicule. The original was mechanic. This particular vehicule also has a IMPCO LPG System that allows the car to run with LPG gas and with gasoline.
In this case I tried to climb first with gasoline, that has more power and then changed to LPG gas, but in both cases the truck couldnt cliimb the ramp to leave the parking place. I had to go back to an horizontal surface and then shifted to dirve and climb without stopping to leave the underground parking place. Thanks in advance for your help.
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Friday, January 22nd, 2010 AT 2:00 PM
Tiny
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I still think you need to check fuel pump pressure. What kind of pump did you put on it? What type of carb? GM started throttle body injection in the mid to late 80's.
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Monday, January 25th, 2010 AT 5:57 PM
Tiny
ERNESTO TOLEDO
  • MEMBER
  • 8 POSTS
It is a filter type gasoline electric pump (looks like a fuel filter), it is installled in the fuel line near the right rear door of the suburban. The carburator is a quadrajet. Here in Mexico 1991 was the last carburetted suburban.

It doesn ´t need the fuel pump when the truck is used with LPG gas, and it couldn ´t climb the ramp too.

What about the distributor? I has a centrifugal and a vacuum time advance device.
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Tuesday, January 26th, 2010 AT 9:31 AM
Tiny
JACOBANDNICKOLAS
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I'm sorry, I didn't realize they still used carbs in 91. However, I've been in the business for nearly 30 years, so I remember them well.

As far as the timing advance, it doesn't change the timing that much to cause that much of a difference at low RPM's. The only thing I can think of to cause that much of a power loss is a major vacuum leak or a really weak spark from the ignition causing the fuel not to fully burn. At 100K miles, the engine shouldn't be worn out and the timing chain should still be fine, and you tried both gas and LPG so it isn't a fuel pump problem or carb problem. Has the vehicle ever just died on you and then restarted? Has this problem ever happened in the past where you lost that much power?
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Tuesday, January 26th, 2010 AT 1:31 PM
Tiny
ERNESTO TOLEDO
  • MEMBER
  • 8 POSTS
Has the vehicle ever just died on you and then restarted? No, this has never happened to my truck.

Has this problem ever happened in the past where you lost that much power?[/Quote]
Yes, In my garage there is a small ramp, and I have to enter the garage with some speed, When I try to stop in the middle, there is a point when I can ´t go up, and I have to go back and enter again with some speed.

The spark plug cables are two years old, I changed the spark plugs about six months ago. But I dont ´use much this truck, only weekends and on hollydays. That ´s why it has a low mileage after almost 20 years of use.

What I have noticed lately is thay the rpm ´s are very high when the engine is idiling with gasoline. Maybe 900 or 1000 rpm idle. I don ´t have a tachomenter.
Installed.

Hiow can I check a vacuum loose?

Thanks for your time.
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Tuesday, January 26th, 2010 AT 3:13 PM
Tiny
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Check for damaged, dryrotted, or disconnected vacuum hoses on the engine. Also, some people will spray carb cleaner around them. If there is a leak, the RPM's will increase. Please keep in mind that carb cleaner is very flamable. If you hit a spot that is really hot, it could catch fire. Have a fire extinguisher near by.
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Wednesday, January 27th, 2010 AT 8:03 AM
Tiny
ERNESTO TOLEDO
  • MEMBER
  • 8 POSTS
I found a disconnected vacuum hose, that goes from the carburator to one of the head covers. I thnk that it is the PCV valve. The performance of the engine improved, and it could climb the entrance to my garage. I was prepared to check spark plug wires and change spark plugs but it looks unnnecesary.
My last question is that sometimes iddling goes upper, abd I get desperate.

Can it be the PCV valve, where I connected the discconented?

Thanks for your comments.
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Tuesday, February 2nd, 2010 AT 3:13 PM
Tiny
JACOBANDNICKOLAS
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THe PCV will cause a large vacuum leak, so I'm glad you found it. As far as the high idle, does it do it all of the time or only once in a while?

Joe

PS: You said "One more question". You can ask as many questions as you like. That is why I am here, and I'm glad to help.
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Tuesday, February 2nd, 2010 AT 10:23 PM
Tiny
ERNESTO TOLEDO
  • MEMBER
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The high idle is once in a while. I think is relationed with the PCV valve. I noticed that RPM went down when I connected the vacuum hose to the PCV valve, but now that it id already connected, sometimes the revolutions go high. I am sure that the carburetor throtle valve is closed. If this valve is damaged is it easy to find. How can I test the PCV valve.
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Wednesday, February 3rd, 2010 AT 9:30 AM
Tiny
JACOBANDNICKOLAS
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The PCV valve is easy to check. It has a check ball in it that needs to be loose. Remove it and shake it. If you hear a rattle, it's good. If there is no rattle, replace it.

As far as the carb, are you refering to the throttle plate at the bottom of the carb? Also, how often do the RPM's go up?
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Wednesday, February 3rd, 2010 AT 1:48 PM
Tiny
ERNESTO TOLEDO
  • MEMBER
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Yes, I ´m refering to the throttle plate. It ´s closed when the engine is iddling.

Let me check, because I think that the engine was working with High RPM`s for a long time since the problem of the loosen vacuum lines.

I will check the PCV valve thank you.
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Wednesday, February 3rd, 2010 AT 2:52 PM
Tiny
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Let me know about the PCV. Also, the throttle plate should be basically all the way closed at an idle. THere is a what is called a "Curb Idle" screw that the throttle sets against. It stops the throttle from returning too far and the engine dieing. If the idle is too high, loosten that screw a little at a time until you get the RPM's around 900 at an idle.

Let me know if you have other questions.

Take care,
Joe
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Friday, February 5th, 2010 AT 6:24 PM
Tiny
ERNESTO TOLEDO
  • MEMBER
  • 8 POSTS
I removed the PCV valve and it rattled, but it was so dirty and I decided to clean it with WD-40. I installed it again, started the engine and the idle speed seems to be find. I will dirive the truck on weekend to test how it works. I will look for the "curb idle" screw. I have seen a solenoid with a nut that touches the acelerator lever. Is there something else?

I use this suburban on weekends and to travel with my family, because of the fuel consumption. I get 7 MPG (city) and 12.9 MPG (freeway). It is the same gasoline or LPG, but here in Mexico gasoline is $2.40 USD/GAL and LPG is $1.78 USD/GAL. That ´s why I use LPG. However I have always been looking for a way to improve MPG in miy truck:
It has a KYN cotton filter, 2 mufflers, one for 4 cilinders and another for the other 4, the two lines conected with a line behind the transmission. I also installed two magnet savers in the LPG line.

I have read that I would get a 30 % better fuel MPG, changing the 3 speed transmission for a 4 speed transmission.

What do you think?

I say hello from the beautiful beaches of Mazatlan, Sinaloa, Mexico.

Ernesto Toledo
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Saturday, February 6th, 2010 AT 11:28 AM
Tiny
JACOBANDNICKOLAS
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Beautiful beaches? Do you want to trade? We just got 3 feet of snow. It gets old. The irony of it is that I have 2 snowmobiles but there is too much snow to ride them. Thats my luck.

As far as the truck, let me know how it works for you. Your MPG is really bad. Chances are it has a lot to do with the carb on it. Most around here average 13+ in the city and around 18+ on the highway. Regardless, let me know what you find.

Joe
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Saturday, February 6th, 2010 AT 11:31 PM

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