What's up with this engine??
Thread Starter
Drifting
Joined: Oct 2001
Posts: 1,444
Likes: 4
From: Hawthorne NJ
What's up with this engine??
Hi,
I put an '89 Corvette 350 TPI/700R4 into a hotrod, using all the stock sensors, wiring etc.
It has a peculiar "miss" coming out of the left exhaust(only after it warms up). The wiring is new, plugs, cap, coil new. Timing 6 degrees, TPS and IAC set properly. Compression tests good. I'm going to check if the exhaust valve or valves may be too tight, but other than that ...I'm at a loss.
Any suggestions?
I put an '89 Corvette 350 TPI/700R4 into a hotrod, using all the stock sensors, wiring etc.
It has a peculiar "miss" coming out of the left exhaust(only after it warms up). The wiring is new, plugs, cap, coil new. Timing 6 degrees, TPS and IAC set properly. Compression tests good. I'm going to check if the exhaust valve or valves may be too tight, but other than that ...I'm at a loss.
Any suggestions?
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Does that mean that the hot rod has no check engine light? Or that the CE light wasn't lit? How do you read codes? For my car, the code 43 is set when the ECM receives low voltage on circuit 485, from the ESC module for longer than 4 seconds. The voltage from ESC drops when the the ESC receives a signal from the knock sensor. The knock sensor can be triggered by "sounds" other than knock, known as "false knock". I would expect a custom engine installation might be even more prone to false knock than the factory installation. When the voltage from the ESC drops below 6 volts, the ECM retards the timing to stop the detonation. When 4 seconds of retarded timing doesn't stop the knock, the the ECM sets the code, and keeps the timing retarded as a fail safe. Obviously, retarding the timing won't stop false knock (like something banging against an exhaust pipe) and the ESC will continue to receive the knock sensor signals. A miss should not cause a code 43 to set, however, knock counts shouldn't cause a miss, either. Knock counts will, of course, cause the timing to be retarded which will reduce the power and make it sluggish. One way or the other the cause of the code 43 needs to be taken care of.
RACE ON!!!
RACE ON!!!
Thread Starter
Drifting
Joined: Oct 2001
Posts: 1,444
Likes: 4
From: Hawthorne NJ
CFI-EFI, you sound on track. The car does not have a CE light and I guess I don't understand the Code 43 as well as you do. The engine miss (actually sounds like it's puffing air out the left exhaust pipe) happens only after the engine has warmed up to the point where the idle drops. It is not there for the first 3 minutes or so when the engine is cold. Does that help explain my problem clearer? Help!
Thanks
Thanks
Safety Car
Joined: Nov 2004
Posts: 4,991
Likes: 5
From: The Pines South Jersey
CFI-EFI, you sound on track. The car does not have a CE light and I guess I don't understand the Code 43 as well as you do. The engine miss (actually sounds like it's puffing air out the left exhaust pipe) happens only after the engine has warmed up to the point where the idle drops. It is not there for the first 3 minutes or so when the engine is cold. Does that help explain my problem clearer? Help!
Thanks
Thanks
Your going to have to do some data logging
Thread Starter
Drifting
Joined: Oct 2001
Posts: 1,444
Likes: 4
From: Hawthorne NJ
According to the wiring harness manufacturer, I changed the engine from MAF to speed sensor and changed to a later ECU...could the fact that I didn't change the knock sensor cause this?
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Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by joseph p
CFI-EFI, you sound on track. The car does not have a CE light and I guess I don't understand the Code 43 as well as you do.
Originally Posted by joseph p
It has no check engine light and no codes except for a 43 (knock sensor) which I assume is the result of the engine's miss rather than the cause of it.
Originally Posted by joseph p
According to the wiring harness manufacturer, I changed the engine from MAF to speed sensor and changed to a later ECU...could the fact that I didn't change the knock sensor cause this?
I am 99.40% sure the ESC/knock sensor isn't causing the miss, but the code 43, wherever it came from, indicates a problem that should be fixed. It is easier to trouble shoot and isolate a problem, where there aren't OTHER problems complicating the issue and diagnostic test results.
RACE ON!!!
Thread Starter
Drifting
Joined: Oct 2001
Posts: 1,444
Likes: 4
From: Hawthorne NJ
It does not have a check engine light but it does have a simple red light on the Telervek unit where all the wires connect. Grounding A and B on the ADL produced the code 43.
This is a common practice when putting '89 and older TPI's into rods..to change to speed density so you have a clean air intake without the MAP sensor between it and the filter.
This is a common practice when putting '89 and older TPI's into rods..to change to speed density so you have a clean air intake without the MAP sensor between it and the filter.
Burning Brakes
Joined: Apr 2004
Posts: 762
Likes: 2
From: Huntington ma
That sort of "single cylinder", presumably, miss or oddness would have me looking for an exhaust leak (header flange maybe), a leak on the Intake side (vacuum), a bad or iffy injector and Last an ignition problem (plug, wire, cap, etc.).
Have you checked header temperatures? Is there a "cold" cylinder? Checked (with a timing light) for an electrical miss at a particular cylinder? How about using a 'noid light to watch the injectors on that bank for an intermittent no-fire...
Since you say the compression is fine I would stop worrying about a Valve problem - although a too tight adjustment could still be the cause. Did you do the compression check Cold, or warmed up?
BTW - which side (or both) is the O2 sensor in? Same side as the miss?
Is there an ALDL connector wired in to this harness - can you hook a scan tool or datalogger up? If not, it's easy enough to add - only a ground and serial data line that are really neecessary for a scan tool to show what's happening.
Have you checked header temperatures? Is there a "cold" cylinder? Checked (with a timing light) for an electrical miss at a particular cylinder? How about using a 'noid light to watch the injectors on that bank for an intermittent no-fire...
Since you say the compression is fine I would stop worrying about a Valve problem - although a too tight adjustment could still be the cause. Did you do the compression check Cold, or warmed up?
BTW - which side (or both) is the O2 sensor in? Same side as the miss?
Is there an ALDL connector wired in to this harness - can you hook a scan tool or datalogger up? If not, it's easy enough to add - only a ground and serial data line that are really neecessary for a scan tool to show what's happening.
Thread Starter
Drifting
Joined: Oct 2001
Posts: 1,444
Likes: 4
From: Hawthorne NJ
No exhaust or intake leak...header temps were checked and are all pretty much the same...(brand new)o2 sensor is on the same side...there is no ALDL sensor.
I cleared the codes yesterday and unhooked the knock sensor. The symptom was still ther whoever much less noticeable.
I cleared the codes yesterday and unhooked the knock sensor. The symptom was still ther whoever much less noticeable.
Thread Starter
Drifting
Joined: Oct 2001
Posts: 1,444
Likes: 4
From: Hawthorne NJ
Thread Starter
Drifting
Joined: Oct 2001
Posts: 1,444
Likes: 4
From: Hawthorne NJ
Incidently, I no longer have the code 43 readout since the wiring harness people told me to change the knock sensor to a '90-'92 KS. No codes, noise is quieter, but still there, only after going into "closed loop." It runs and sounds fine when cold.
