c4 shakes violently upon slight acceleration cruising.
05-11-2016, 09:28 PM
#41
Fixed! well sort of, so I checked the harness to the fuel injector on cyc. 4 and the contacts were bent in a little not getting good contact with the injector. so the misfire went away and its sounds better. but I take it down the road and the car shakes really bad. I set the timing 8 degrees after TDC-about "because it runs out of timing mark tab. I'll I have to say is im amazed. their is no shake and it feels I gained 100hp. I never knew my c4 was as quick as it is. but Im confused as to why it runs great 8 degrees after TDC?
edit-I want to thank all of you forum members for the help and guidence
edit-I want to thank all of you forum members for the help and guidence
05-11-2016, 09:56 PM
#42
Fixed! well sort of, so I checked the harness to the fuel injector on cyc. 4 and the contacts were bent in a little not getting good contact with the injector. so the misfire went away and its sounds better. but I take it down the road and the car shakes really bad. I set the timing 8 degrees after TDC-about "because it runs out of timing mark tab. I'll I have to say is im amazed. their is no shake and it feels I gained 100hp. I never knew my c4 was as quick as it is. but Im confused as to why it runs great 8 degrees after TDC?
edit-I want to thank all of you forum members for the help and guidence
edit-I want to thank all of you forum members for the help and guidence
05-11-2016, 09:59 PM
#43
Team Owner
05-13-2016, 01:48 PM
#46
Burning Brakes
While injectors are important, I have a hunch you have an ignition problem. You said "Crane" ignition wires. I've had engines run like total crap with some brands of "spiral core" ignition wires on GM HEI ignitions systems. I don't know the why, I just know the problem went away with different stock style wires rather than wiz-bang boutique wires.
http://www.magnecor.com/magnecor1/truth.htm
09-22-2016, 02:31 AM
#47
Race Director
How would [low rpm/high load] shaking be the symptom on an EFI car with a knock sensor AND the ability to pull lots of timing?
Also, would it be possible for this to happen w/o seeing [significant] knock counts?
09-22-2016, 12:00 PM
#49
Race Director
First, this thread is older (5 mos). I trolled it up because I wanted the answer to a simple question (2 posts above). Next...
The "e" in your question creates some confusion. At first, I thought you were asking about running e85 fuel (in this thread?) Then I figured out what you must be asking....since the OP swapped an 87 engine into an 85.
85 fuel pressure was lower with a higher lb/hr injector. If the intakes were kept together their respective injectors, I would assume there wouldn't be serious problem. The higher FP rail -- with lower lb/hr injector offset each other. However, if the 87 injectors were placed in the earlier 85 fuel rail (which, according to this forum) is a lower pressure, the car would run seriously lean.
If the OP is still looking for answers to this problem, this is something to consider.
Maybe I should start a new thread on my question (2 posts up)? Having questioned the balance method of my RA, I stumbled across this thread saying too much timing would cause shaking. Extrapolating this, I wondered if slightly too much timing would cause vibration at lower rpms?
If so, I wondered how the knock-sensor/feedback circuit would "let this happen? And, really, was also curious that causes the vibration/shaking? Is ignition happening early enough the pistons are STARTING to buck back the other way (and shaking the car)? On a smaller scale (less serious over-advance), I assume vibration could be the beginning symptom as timing becomes over-advanced?
Sorry to confuse things by trolling this thread.
The "e" in your question creates some confusion. At first, I thought you were asking about running e85 fuel (in this thread?) Then I figured out what you must be asking....since the OP swapped an 87 engine into an 85.
85 fuel pressure was lower with a higher lb/hr injector. If the intakes were kept together their respective injectors, I would assume there wouldn't be serious problem. The higher FP rail -- with lower lb/hr injector offset each other. However, if the 87 injectors were placed in the earlier 85 fuel rail (which, according to this forum) is a lower pressure, the car would run seriously lean.
If the OP is still looking for answers to this problem, this is something to consider.
Maybe I should start a new thread on my question (2 posts up)? Having questioned the balance method of my RA, I stumbled across this thread saying too much timing would cause shaking. Extrapolating this, I wondered if slightly too much timing would cause vibration at lower rpms?
If so, I wondered how the knock-sensor/feedback circuit would "let this happen? And, really, was also curious that causes the vibration/shaking? Is ignition happening early enough the pistons are STARTING to buck back the other way (and shaking the car)? On a smaller scale (less serious over-advance), I assume vibration could be the beginning symptom as timing becomes over-advanced?
Sorry to confuse things by trolling this thread.
09-22-2016, 01:09 PM
#50
Burning Brakes
First, this thread is older (5 mos). I trolled it up because I wanted the answer to a simple question (2 posts above). Next...
The "e" in your question creates some confusion. At first, I thought you were asking about running e85 fuel (in this thread?) Then I figured out what you must be asking....since the OP swapped an 87 engine into an 85.
85 fuel pressure was lower with a higher lb/hr injector. If the intakes were kept together their respective injectors, I would assume there wouldn't be serious problem. The higher FP rail -- with lower lb/hr injector offset each other. However, if the 87 injectors were placed in the earlier 85 fuel rail (which, according to this forum) is a lower pressure, the car would run seriously lean.
If the OP is still looking for answers to this problem, this is something to consider.
Maybe I should start a new thread on my question (2 posts up)? Having questioned the balance method of my RA, I stumbled across this thread saying too much timing would cause shaking. Extrapolating this, I wondered if slightly too much timing would cause vibration at lower rpms?
If so, I wondered how the knock-sensor/feedback circuit would "let this happen? And, really, was also curious that causes the vibration/shaking? Is ignition happening early enough the pistons are STARTING to buck back the other way (and shaking the car)? On a smaller scale (less serious over-advance), I assume vibration could be the beginning symptom as timing becomes over-advanced?
Sorry to confuse things by trolling this thread.
The "e" in your question creates some confusion. At first, I thought you were asking about running e85 fuel (in this thread?) Then I figured out what you must be asking....since the OP swapped an 87 engine into an 85.
85 fuel pressure was lower with a higher lb/hr injector. If the intakes were kept together their respective injectors, I would assume there wouldn't be serious problem. The higher FP rail -- with lower lb/hr injector offset each other. However, if the 87 injectors were placed in the earlier 85 fuel rail (which, according to this forum) is a lower pressure, the car would run seriously lean.
If the OP is still looking for answers to this problem, this is something to consider.
Maybe I should start a new thread on my question (2 posts up)? Having questioned the balance method of my RA, I stumbled across this thread saying too much timing would cause shaking. Extrapolating this, I wondered if slightly too much timing would cause vibration at lower rpms?
If so, I wondered how the knock-sensor/feedback circuit would "let this happen? And, really, was also curious that causes the vibration/shaking? Is ignition happening early enough the pistons are STARTING to buck back the other way (and shaking the car)? On a smaller scale (less serious over-advance), I assume vibration could be the beginning symptom as timing becomes over-advanced?
Sorry to confuse things by trolling this thread.
Since the thread has already been reanimated I would like to have it clarified, set the timing btdc not after as it was stated in some previous posts?
09-22-2016, 02:10 PM
#51
Safety Car
I do not know if the OP has solved the problem and I agree that the basics should be checked to rule them all out. With that being said I have seen a failing lock-up torque converter cause this problem. When the transmission is locked up at light load and the converter slips it will shake the whole car. When you apply heavier throttle the converter unlocks and car operates smoothly. To check this (when you are experiencing the shake) lightly apply the breaks which will unlock the converter and cause the shake to stop if this is the problem.
Last edited by bjankuski; 09-22-2016 at 02:11 PM.
09-22-2016, 09:22 PM
#52
Burning Brakes
Verify that timeing mark is correct,bring #1 to top dead center on compression stoke and use good timeing light.You said you were just turning distributor by hand back and forth ? Hope you have this figured out by the time you see the helpful previous posts.
Last edited by A Peter C4; 09-22-2016 at 09:26 PM.