84 with Idle Issues
Thread Starter
Instructor
Joined: Apr 2003
Posts: 104
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From: Fredericksburg Virginia
84 with Idle Issues
Hello,
I have an 84 that has 39k miles on it. It basically just sits, and I know that is probably why I am having this problem now. So here goes, when I try to start the car it will only run for a few seconds. If I keep the RPM's way up it will run a little bit longer but not for more than 10-15 seconds and as soon as I left off of the gas it dies. I pulled the plugs and they are covered in oil so I know that I have an additional problem with either the rings or the valve seals. My question is, could the plugs be causing the rough idle. I assume it isn't a fuel issue since it will rev up when I give it gas. I also learned that it could be the Air idle control valve. Where is that located so I can take it out and see if it is gummed up or defective? Thanks for any help.
I have an 84 that has 39k miles on it. It basically just sits, and I know that is probably why I am having this problem now. So here goes, when I try to start the car it will only run for a few seconds. If I keep the RPM's way up it will run a little bit longer but not for more than 10-15 seconds and as soon as I left off of the gas it dies. I pulled the plugs and they are covered in oil so I know that I have an additional problem with either the rings or the valve seals. My question is, could the plugs be causing the rough idle. I assume it isn't a fuel issue since it will rev up when I give it gas. I also learned that it could be the Air idle control valve. Where is that located so I can take it out and see if it is gummed up or defective? Thanks for any help.
Navigator
Joined: Apr 2010
Posts: 9
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From: Eureka Montana
Did you check engine light come on? If it did check your codes. You could take off the air box above the injectors and start the car and see if the injectors are functioning properly. Maybe you are not getting fuel, could be as simple as a new fuel filter or a fuel pump.
Thread Starter
Instructor
Joined: Apr 2003
Posts: 104
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From: Fredericksburg Virginia
So I now feel that it is a fuel issue. I put the new plugs in and confirmed that their is spark. The car turns over but doesn't try to start. It is basically just the starter spinning the engine over. I am thinking fuel filter or something with the pump/injectors. Where would be a good place to start that will minimize my costs as well? Like I said the car hasn't been driven in 2 years, it was parked with a full tank of good quality gas. Is it possible that something has clogged the pump? I pulled the air idle valve and it looked ok some carbon but nothing that would clog it. I am just confused as to before I changed the plugs it would start it just wouldn't stay idling, now it won't even turn over. Is it possible that maybe I pulled a vacuum hose or something that would cause these symptoms?
Racer
Joined: Jul 2009
Posts: 292
Likes: 1
From: Appleton, Wisconsin Boston originally - North End
84 Cherry, I also have an '84 Cherry with 50,000 miles. NO ISSUES AS BAD AS YOURS though.
But mine has had a rough idle for awhile - goes from 600 to 300 to 600 to 300.....
I did the IAC's, TPS, fuel filter, fuel pressure, gaskets, replaced all eight plugs with Bosch quad iridiums, new Magnecor wires, new MSD cap-rotor-coil, etc., etc.... None of those things fixed the rough idle on my '84 yet.
Researching more on this and other forums, most members will tell you there is an air leak in the throttle body / intake or the linkage is loose. Mine has none of these that I could find.
BUT, I have read numerous threads that say the fuel injectors could be the problem.
I just pulled mine and am having Jon at FIC rebuild them. He is quick, thorough and very reliable. Only $75 - that is a good deal in any case - them suckers are 26 years old
I'm willing to bet my idle surge will be gone soon.
Stay tuned and in touch with another low mileage '84 owner.
Got some pics of that cherry?????
Here's mine: http://s62.photobucket.com/albums/h1...TTE/?start=all
And here are some GREAT OEM pics - directly from GM: http://s62.photobucket.com/albums/h1...%20OEM%20pics/
Dave H. dchoran@athenet.net
But mine has had a rough idle for awhile - goes from 600 to 300 to 600 to 300.....
I did the IAC's, TPS, fuel filter, fuel pressure, gaskets, replaced all eight plugs with Bosch quad iridiums, new Magnecor wires, new MSD cap-rotor-coil, etc., etc.... None of those things fixed the rough idle on my '84 yet.
Researching more on this and other forums, most members will tell you there is an air leak in the throttle body / intake or the linkage is loose. Mine has none of these that I could find.
BUT, I have read numerous threads that say the fuel injectors could be the problem.
I just pulled mine and am having Jon at FIC rebuild them. He is quick, thorough and very reliable. Only $75 - that is a good deal in any case - them suckers are 26 years old
I'm willing to bet my idle surge will be gone soon.
Stay tuned and in touch with another low mileage '84 owner.
Got some pics of that cherry?????
Here's mine: http://s62.photobucket.com/albums/h1...TTE/?start=all
And here are some GREAT OEM pics - directly from GM: http://s62.photobucket.com/albums/h1...%20OEM%20pics/
Dave H. dchoran@athenet.net
Last edited by dchoran; Apr 19, 2010 at 08:28 PM.
Le Mans Master
Joined: May 2006
Posts: 9,226
Likes: 9
From: Irvine Ca
Check the fuel pump....actually replace the FP with an '85 Fuel pump....replace the fuel filter as well.
Of course you could verify the Fuel pressure prior to completing all those task I mentioned.
Of course you could verify the Fuel pressure prior to completing all those task I mentioned.
Le Mans Master
Joined: May 2006
Posts: 9,226
Likes: 9
From: Irvine Ca
Thread Starter
Instructor
Joined: Apr 2003
Posts: 104
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From: Fredericksburg Virginia
I was reading the manual and i am going to go thru the fuel system check as best I can. When I had the entire air cleaner assembly off, one of the bottom gaskets was cracked but it appears that it isn't getting fuel. The engine just turns over but doesn't attempt to fire. Should I see any fuel in the throttle bodies as I am trying to start it? Or would that all be running thru the injectors? Is pulling the injectors difficult?
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Thread Starter
Instructor
Joined: Apr 2003
Posts: 104
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From: Fredericksburg Virginia
i replaced the fuel filter and tested the fuel pump all ok. I had help so I was able to do a bit more tonight. The injectors are spraying fuel so I my next assumption is that the coil is bad? I do have a spark at the wires but could it be weak? The car would start for a second with starting fluid it just won't stay running. All fuses are all ok as well. Any ideas where to go from here? Can I pull the module on top of the distributor and take it somewhere to have it tested? Any help would be greatly appreciated. I am going nuts trying to find this demon.
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
To VERIFY that your spark is sufficient: You can check for spark jumping to ground while the engine is being cranked, but you've already done that and that doesn't necessarily prove that the spark is sufficient. If you make your "ground", the tip of one of a spark plug that is installed in the head, that will give you your proof; if you see a spark jump there, only wa for the spark to get to ground is to jump inside the cylinder too, under compression. If the spark jumps, you have sufficient spark.
Last edited by Tom400CFI; Apr 20, 2010 at 10:54 PM.
Thread Starter
Instructor
Joined: Apr 2003
Posts: 104
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From: Fredericksburg Virginia
So fuel pressure is the next guess. I was reading in the book about it and I don't have a fuel pressure gauge. Is there a way to make one? Or another way to test pressure?
Le Mans Master
Joined: May 2006
Posts: 9,226
Likes: 9
From: Irvine Ca
The fuel pressure thing and the running for a few seconds is why I suggested checking the pressure.
The fact that you can get the car to fire with starting fluid also leads back to a fuel delivery issue.
The fuel may build up to get the engine to fire...but once the initial sprays are gone there is not enough delivery as the pressure drops......
Your garden hose has a nice spray handle on it.........you open the spigot but only a little bit. The hose bulges with pressure but once you squeeze the handle and let some water spray out....that first few moments the water shoots very far...but as the hose contracts due to lack of pressure, the water stream gets lower and lower.....you can let go of the squeeze handle and let it build up pressure again to repeat the process....but unless you increase the amount the spigot is opened you only get a repeat of what happened before.
This is what is occuring with your injectors. You get 1-3 pulses and sprays from the ECU and then the pressure drops due to the delivery issue. Then the engine dies.
All just conjecture.......but this is where I would think the issue is
The fuel pressure gauge will verify/eliminate this question.
The fact that you can get the car to fire with starting fluid also leads back to a fuel delivery issue.
The fuel may build up to get the engine to fire...but once the initial sprays are gone there is not enough delivery as the pressure drops......
Your garden hose has a nice spray handle on it.........you open the spigot but only a little bit. The hose bulges with pressure but once you squeeze the handle and let some water spray out....that first few moments the water shoots very far...but as the hose contracts due to lack of pressure, the water stream gets lower and lower.....you can let go of the squeeze handle and let it build up pressure again to repeat the process....but unless you increase the amount the spigot is opened you only get a repeat of what happened before.
This is what is occuring with your injectors. You get 1-3 pulses and sprays from the ECU and then the pressure drops due to the delivery issue. Then the engine dies.
All just conjecture.......but this is where I would think the issue is
The fuel pressure gauge will verify/eliminate this question.
Thread Starter
Instructor
Joined: Apr 2003
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From: Fredericksburg Virginia
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
I don't know for sure what you need. My CFI car was a Trans Am, which from the factory uses a rubber line, hose clamped to the fuel filter. Easy. I know the Corvette, the filter uses threaded fittings on both sides of the filter, so that my not be a convenient place to test pressure. Most Corvette CFI folks permanently install a test fitting in the hard line that runs from one TB to the next, and test there.
For a temporary test location, I'd check at the back of the car where the fuel pump lines leave the tank/pump.
-Tom
For a temporary test location, I'd check at the back of the car where the fuel pump lines leave the tank/pump.
-Tom
Thread Starter
Instructor
Joined: Apr 2003
Posts: 104
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From: Fredericksburg Virginia
I thought it might be gas too but it smells fine so I don't think that is it. I can hear the fuel pump pressurizing the system when the key is turned on, however I don't know yet if it has the 9-13 psi that it calls for. I have rubber hoses @ the fuel filter so I will test pressure there.
