Idle Problems
Thread Starter
Burning Brakes
Joined: Sep 2006
Posts: 1,142
Likes: 0
From: Spring Grove Illinois
Idle Problems
Well my 86 still has a hard start Problem when cold (Sometimes I have to open the TB a little with the pedal to start) and a surging idle..The engine has been rebuilt and chipped..mild cam,pistons,heads..All but 02 remains the rest chipped out..no cold start..Anyway,, No codes..Tps is .54..new IACV..Plugs good but black from rich running..New Injectors..Fuel Pressure 46 at Idle..I'm going to check Compression today ..maybe I adjusted my valves too tight,,You Can still do it the old fashion way by looseing them till they clack then tighten them till they just stop clacking Right
?? I want to be sure about this..I adjusted them on the stand for Zero Lash but I'm hearing a slight popping comming from the exhaust..More so on the right side...So Maybe It's only the valves causeing the rough Idle and the rich running: ...We'll see.. If this don't work it might be time to call the man
?? I want to be sure about this..I adjusted them on the stand for Zero Lash but I'm hearing a slight popping comming from the exhaust..More so on the right side...So Maybe It's only the valves causeing the rough Idle and the rich running: ...We'll see.. If this don't work it might be time to call the man
Burning Brakes
Joined: Oct 2004
Posts: 898
Likes: 1
From: Pearland Texas
Listen to your fuel injectors, make sure they are working. Just replaced all of mine and had a terrible miss, idled and accelerated rough. A long screwdriver placed against the injector with my ear to the handle revealed # 5 was not working, closed the connection inside the harness connector with a small screwdriver,contact restored, working injector,ran good after that, thought this might help, good luck. 
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
I would confirm that the cold start valve was indeed deleted from the chip. There is a 5 amp fuse behind the DIC in the dash. There is a CSV switch in the front of the intake manifold next to the CTS. If the fuse is good, check, with a test light, the fuse when cranking. If the tester lights up then the CSV is still active and might not be working downstream. Also disconnect the MAF and see if there is any change when trying to start the engine.
When the CSV is not getting signal you will have to crank the engine a number of times before it starts.
When the CSV is not getting signal you will have to crank the engine a number of times before it starts.
Pro
Joined: Jun 2001
Posts: 520
Likes: 6
From: Elverson PA
Did you use larger than stock injectors? If so, lower fuel pressure unless you have a custom tune for the larger injectors, regardless of what you have done to your engine at rebuild. Sounds like you are rich across the board.
If your chips are for stock injectors at stock fuel pressure, you will run rich when adding more fuel pressure or bigger injectors until you use a larger MAF. Your computer should compensate for this rich mix at cruise, but not WOT, idle, cold start, etc (open loop).
I would put the fuel pressure to about 37 psi and see if all clears up.
Dave
If your chips are for stock injectors at stock fuel pressure, you will run rich when adding more fuel pressure or bigger injectors until you use a larger MAF. Your computer should compensate for this rich mix at cruise, but not WOT, idle, cold start, etc (open loop).
I would put the fuel pressure to about 37 psi and see if all clears up.
Dave
Last edited by black85; Jan 7, 2007 at 10:49 AM.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
I believe Ken has 24 lb Accels and a AFPR with a modified engine. Ran into a problem with my 86 with the 24 lb Accels. Rich across the board. If even dropped the fuel pressure to 39 psi vac off or 34 vac on and still my BLM's were 108. Even had the chip tuned by a fellow member to 26 lbs and it helped, but still rich. Taking the Accels out and going with stockers.
Pro
Joined: Jun 2001
Posts: 520
Likes: 6
From: Elverson PA
+1 Try the stockers if lower fuel pressure doesn't work. Has anyone ever used a larger MAF housing to compensate for larger injectors? If you increase the size in ratio w/ injector size you will meter enough air to go with your larger injectors. I have put stock MAF guts in larger tubes to go with large injectors before, but not on a vette. These already have 3" MAF tube, so the larger tube would be very large. Could also do the same thing with some resistors on the current MAF to lower the output voltage.
I would only do all this if you can't get your chip tuned to work, and you really think you need that extra fuel before the stock injectors max out. BTW-were the stockers 22 lbs? you should be able to get 24's to flow the same amount w/ a lower than stock fuel pressure.
Dave
I would only do all this if you can't get your chip tuned to work, and you really think you need that extra fuel before the stock injectors max out. BTW-were the stockers 22 lbs? you should be able to get 24's to flow the same amount w/ a lower than stock fuel pressure.
Dave
Thread Starter
Burning Brakes
Joined: Sep 2006
Posts: 1,142
Likes: 0
From: Spring Grove Illinois
+1 Try the stockers if lower fuel pressure doesn't work. Has anyone ever used a larger MAF housing to compensate for larger injectors? If you increase the size in ratio w/ injector size you will meter enough air to go with your larger injectors. I have put stock MAF guts in larger tubes to go with large injectors before, but not on a vette. These already have 3" MAF tube, so the larger tube would be very large. Could also do the same thing with some resistors on the current MAF to lower the output voltage.
I would only do all this if you can't get your chip tuned to work, and you really think you need that extra fuel before the stock injectors max out. BTW-were the stockers 22 lbs? you should be able to get 24's to flow the same amount w/ a lower than stock fuel pressure.
Dave
I would only do all this if you can't get your chip tuned to work, and you really think you need that extra fuel before the stock injectors max out. BTW-were the stockers 22 lbs? you should be able to get 24's to flow the same amount w/ a lower than stock fuel pressure.
Dave
It's running so rich it makes your eyes water and like stated it takes a few cranks to start because the only thing left is the o2 sensor....Then it does'nt want to idle untill warm..I did Finaly drive it today 1.1 mile
and it did'nt run too bad ...But you could tell it was'nt quiet right...I have Windata and will try to see what the engine is doing..I had problems with the cable so I took out the resistor and resoldered it and will try again today..Keep Ya'll Posted
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Pro
Joined: Jun 2001
Posts: 520
Likes: 6
From: Elverson PA
.......I had Alvin Chip it for stock injectors...
That is the problem. It is easy to figure out how much fuel pressure you would need to make 22 lbs with 24 lb injectors. I'm sorry that I don't have the formula for you.