Idle problems - Page 2

The knock sensor wouldn't affect my idle, would it. I rebooted the ecm last night and that didn't do anything for me. I think I'll pick up an ECM today to at least use as a trouble shooting tool. Thanks for the help. 

Knock sensor won't affect idle. It is used by spark timing control to retard timing when detonation is picked up by sensor. Code 44 is a lean code and maybe the result, not the cause of poor idle problems. What kind of O2 readings do you have at idle and cruising speed?
 

quote:

ORIGINAL: cwb


As far as the 43 code, I would NOT spring for a new ECM, until testing for a signal for timing retard. The 43 code says retard has been on too long (which would mean there IS a signal) OR ignition retard system failure (no signal). TEST FOR SIGNAL FIRST!!!

 
Here's your ESC signal test:
 
Take the idle speed up a couple of hundred rev's over idle - 900 - 1000. Hit the block quickly on the passenger side a couple of times with a screwdriver. If the idle drops, your ESC system works (or at least has a signal complete circuit.
 
If there's no drop, there's no signal gettin' to the computer to retard the timimg.

sounds to me like your running lean, I also wouldnt give up on  the vacuum leak possibilty until I was 100% sure it was not the problem

Tearing the intake apart again insearch of a possible leak. Thanks.

I missed the second page....... change your burnoff relays right behind the battery on the fire wall 15mins-$15 easy cheap o2 sensor if not new replace it cheap easy, the maf should be pulling 4-8 grams per second past it if too high the ecm will try to compenstate by starving the car and lowering the RPM's if its at 9grams or higher change it, also if you know somone who has and extra one you can swap it and see if that changes it. keep in mind mid america has a the ecm for $329.00 but super expensive.
also check the connections to the relays and the connection to the MAF , also with the engine idling, try tapping the MAF sensor with the handle of a 6" screwdriver. I don't mean belt it with a 3 pound hammer, just tap it lightly, if the engine stumbles with ever tap=bad
ECM is the last resort it may be bad and hunting for the idle all on its own but UNLIKELY
                                                      hope this helps you bro!!!

 ment MAF for $329.00 sorry

quote:

ORIGINAL: 84corvetteC4

...   , I also wouldnt give up on  the vacuum leak possibilty until I was 100% sure it was not the problem

 
That's what I was thinkin' too there, '84. Ya' don't wanna' hear it after you re-do the entire intake, but I got no clues what else could cause lopin' idle with no codes...
 
ibelew, did you get a good grease film on the gaskets at re-assembly? Grease film helps seal, AND helps hold the gaskets to the intake runners, when you're puttin' the plenum back in between the [still-loose] left and right intake runners... And the TB passages gotta' match up with the right gasket openings. What a pain that was.
 
At the same time, you don't wanna' over-torque any bolts in the aluminum either.

OK, just finished putting my second set of gaskets in. Still have the erratic idle. If I disconnect the ESC the idle smooths out. I've got a new MAF sensor, new IAC plugs, wires, cap and rotor and two sets of intake gaskets. I'll check out a burn-off relay tomorrow. Where is the MAF power relay located. By the way I plugged a new ECM in with no luck so I returned it. I think I'll go tune my 79 up since it's alot easier to work on. Give me some good advice guys. Thanks.   

Chevrolet Corvette Check Engine Light
Q. I sure hope you can help me. I have an 1988 Chevrolet Corvette with an L98 engine with 113,000 miles and automatic transmission with little, if any problems mechanically. The check engine light is intermittent. Some days its on and others its off. I have taken it a few mechanics and all say its a wiring problem, probably a short somewhere.

But they are unable to locate. I have noticed when the check engine light is on it is giving me a code with some thing to do with the MAF sensor or the burnout circuit relay. All of that has been changed so its got to be a wire problem.
I noticed a green wire on the drivers side near the engine block and transmission. I have attempted to ground it but is a hot wire. I know a green wire comes from the MAF sensor but unsure where this green wire goes.
I don't know if this is the problem or this needs to be connected somewhere. Do you have any reference material showing wiring locations and if there is any remedies for this? Any help?
Thanks,
Michael
A. Have you tried a dealer? There are a few service bulletins out pertaining to this code and replacement of power and burn off relays with a new design relay.Number: 88-251-8a
Section: 8a
Date: June, 1988
Subject: Intermittent Connection To The ECM
Model And Year: 1988 Chevrolet Passenger Cars And Light Duty Trucks T: All Chevrolet Dealers
A condition may exist in which the female terminals in the connector to the ECM do not make a solid connection to the male pins in the ECM (see illustration). This can result in an intermittent condition, in any circuit operated by the ECM. The Service Manuals direct a check of connections any time an intermittent condition is found, and this may be the cause of some of these conditions.
Visually inspect the terminal using a flashlight, or use a .95 mm pin gauge. The gauge should not pass freely through the female terminal. Do not probe the terminal with anything other than the pin gauge, as probing could damage the terminal. If the female terminal does not grip properly, replace the terminal with P/N 12020757. General directions on wiring repair are shown in Section 8A of the service Manual.
Number: 89-327-6D
Section: 6D
Date: May 1991
Corporate Bulletin No.: 138111
Subject: Intermittent No Start, Long Crank, Stall, Or Engine Surge
Model and Year: 1988-1989 Corvette
Condition:
On the 1988-89 Y Car, the engine may have intermittent no start, long crank times, may start and stall after start, or may have engine surge or rough running. No codes will be set, and no trouble can be found using normal diagnostic procedures.
Cause:
The relay used for production, P/N 14103304, may not conduct enough current to allow the Mass Air Flow (MAF) circuits to operate properly. The relays will test OK.
Correction:
Both the MAF relays (Burn-off and Burn-off control) should be replaced with relay P/N 14089936. This relay is serviced with a bracket, which is used only for 1988, and can be discarded for the 1989 model year. The location of the relays is shown on page 8A-20-9 of the 1988 and 1989 Y Car Service Manual.
Pad is currently available from GMSPO.
The O2 sensor may also be carbon-coated because of this condition. To clear the carbon, apply the parking brake, and allow the engine to warm up to normal operating temperature. Then hold the RPM at 1,800 RPM for three minutes.
I KNOW ITS A LOT TO READ BUT IT WILL HELP YOU UNDER STAND THE PROBLEM A LITTLE BIT BETTER TO COME TO THE SOULUTION
COURTESY OF ALLDATA

Hello, wires are good. Installed new burnoff relay with no luck. No vacuum leaks. Idle is still erratic until I pull off the connector to the ESC. Plan on installing a new a new knock sensor tomorrow since it failed the ping test, I think I'll have a spare ESC standing by as a trouble shooting aid. What else do you guys think I should check.Thanks.

quote:

ORIGINAL: lbelew

Hello, wires are good. Installed new burnoff relay with no luck. No vacuum leaks. Idle is still erratic until I pull off the connector to the ESC. Plan on installing a new a new knock sensor tomorrow since it failed the ping test, I think I'll have a spare ESC standing by as a trouble shooting aid. What else do you guys think I should check.Thanks.

 
This knock-sensor test failure will have an effect on your timing.
 
Normally it would retard the timing when a vibration (knock) is detected. You'd have less power. But didn't you before have a code for 'too long retarded timing', or something like that [no signal]???

Hello. I had a code 43 that led me to check the knock sensor and it failed the test you recommended. I need to start back probing some pins on the computer. I can't afford to keep throwing parts at it. I still have the erratic idle but not as bad. The car runs great when accelerating but crappy at cruise and idle. Thanks.

Does it feel like it's surging at cruising speed? If so, heres something to try...temporarily disconnect the vacuum line going to the EGR valve and plug it with something. You'll need to disconnect it at the EGR solenoid because you won't be able to get your hand under the plenum to reach the egr valve. Take it for a drive and see if it runs any better at cruising speed.

Do you have a K&N filter?

I'll try bypassing the EGR tonight. I had a K&N filter on but replaced it with a stock one in the beginning to see if it was causing the idle problem. Thanks.

quote:

ORIGINAL: lbelew

Hello, wires are good. Installed new burnoff relay with no luck. No vacuum leaks. Idle is still erratic until I pull off the connector to the ESC. Plan on installing a new a new knock sensor tomorrow since it failed the ping test, I think I'll have a spare ESC standing by as a trouble shooting aid. What else do you guys think I should check.Thanks.

 
Alright dere buddy - you ain't makin' this enny ezier.
 
If your induction ain't suckin' air somewhere, THEN the spark timing control has a loose wire - NOT a short!
 
Check to see what the voltage should be from the computer, to the actual device that changes the spark time. Say for instance, at idle, it's 5 volts when warmed up. Get your multi-meter on that circuit and verify that you got a constant 5V signal. Cross yer fingers (and yer little piggies), that you don't have steady signal.
 
Since you have surging, at idle, AND at speed, you might indeed not be leakin' intake, but the spark time is gettin' fluctuated erroneously. THAT would manifest at speed, but suckin' air would NOT manifest at speed.
 
I'm guessin that now the signal to the timing controller is shorting out 1) either between the computer and the timer controller, or 2) between one or more sensors that the computer gets it's information from, when it makes the timing decision to send to the timer controller.
 
Say for instance the coolant temperature, exhaust temp, and maybe some other 'reads' influence the computer's timing decision. If one of 'em has loose wire (NOT A TOTAL SHORT-OUT), and your computer is getting a yo-yo reading from one of 'em, you got your surge, due to timing variation.
 
Check the pc-to-timer voltage, then check by the wiring diagram for the voltage FROM the sensors, TO the pc, for timing control.
 

Hello, maybe a dumb question but what is and where is the timing controller. Thanks.

I take it he's talking about the Electronic Spark Control Module, if so, it's located under the hood on the passengers side, mounted on the left hand side of the AC blower housing. Also,there's a Distributor Ignition Module located inside of the distributor, but I doubt thats the one in question.

quote:

ORIGINAL: lbelew

Hello, maybe a dumb question but what is and where is the timing controller. Thanks.

I don't know exactly; I think rshive called it.

There has to be some device that the computer controls, which in turn fires the plugs. I think rshive named it there - the ESC module, or the other module that he referred to, the Distributor Ignition module. ONE of those two, which is controlled by the computer, has got to be the issue here... 

How 'bout it there, rshive - which one actually varies the spark time??? That has to be the problem...

From what I understand, they both play an important roll in the spark timing.

Did a little searching and found this info on the subject...


Electronic Spark Control (ESC) senses knocking and adjusts timing to fit fuel octane.

Solid valvetrain components, open exhaust systems and many other high-performance engine components inherently create noise that a knock sensor can perceive to be spark knock, even if the engine is running properly. The end result is that power output can be unnecessarily reduced.

To control spark knock, and to use maximum spark advance to improve driveability, an Electronic Spark Control (ESC) system is used. This system consists of a knock sensor, Electronic Spark Control module, and the ECM. The ECM monitors the ESC signal to determine when engine knock occurs. The (ECM) Electronic Control Module receives the signal from (ESC) Electronic Spark Control module (mounted beside the AC blower housing), and retards the (EST) Electronic Spark Timing to reduce detonation.

HEI Ignition Control 

(Module inside the distributor)

The ECM uses the (EST) Electronic Spark Timing circuit to control spark advance and ignition dwell, when the ignition system is operating in the EST mode.

There are 2 modes of ignition system operation. These modes are as follows:

Module mode - the ignition system operates independently of the ECM/PCM, with module mode spark advance is always at 10 degrees BTDC. The ECM has no control of the ignition system when in this mode. I take it, that is open loop mode, correct me if I'm wrong

EST mode - the ignition spark timing and ignition dwell time ( the length of time the ignition coil is saturated) is fully controlled by the ECM. EST spark advance and ignition dwell is calculated by the ECM. Closed loop mode?

quote:

ORIGINAL: rshiver

From what I understand, they both play an important roll in the spark timing.

Did a little searching and found this info on the subject...


Electronic Spark Control (ESC) senses knocking and adjusts timing to fit fuel octane.

Solid valvetrain components, open exhaust systems and many other high-performance engine components inherently create noise that a knock sensor can perceive to be spark knock, even if the engine is running properly. The end result is that power output can be unnecessarily reduced.

To control spark knock, and to use maximum spark advance to improve driveability, an Electronic Spark Control (ESC) system is used. This system consists of a knock sensor, Electronic Spark Control module, and the ECM. The ECM monitors the ESC signal to determine when engine knock occurs. The (ECM) Electronic Control Module receives the signal from (ESC) Electronic Spark Control module (mounted beside the AC blower housing), and retards the (EST) Electronic Spark Timing to reduce detonation.

HEI Ignition Control 

(Module inside the distributor)

The ECM uses the (EST) Electronic Spark Timing circuit to control spark advance and ignition dwell, when the ignition system is operating in the EST mode.

There are 2 modes of ignition system operation. These modes are as follows:

Module mode - the ignition system operates independently of the ECM/PCM, with module mode spark advance is always at 10 degrees BTDC. The ECM has no control of the ignition system when in this mode. I take it, that is open loop mode, correct me if I'm wrong

EST mode - the ignition spark timing and ignition dwell time ( the length of time the ignition coil is saturated) is fully controlled by the ECM. EST spark advance and ignition dwell is calculated by the ECM. Closed loop mode?

 
Good stuff.
 
So now where do we go with his 43 code, I think it was... IF, that code is still logged??? I think it was "Timing was being retarded for too long, OR, signal to retard timing was being sent for too long"...
 
I doubt that it is being retarded too long for an actual knock problem. I'm inclined to think there's a weak (not missing) electrical connection either from the computer to the timing controller (whichever device that is), OR, the computer is gettin' a just-as-bad signal FROM one of the sensors that the computer uses to 'decide' advance/retard.
 
Attached - a not totally technical schematic. I'm guessin' he's got an erratic signal in one of the variable-to-pc leads, or in the ECM-to-timer lead.


Thumbnail Image

OK, I went back and looked, he had code 43 & 44




43 - Electronic spark control unit
The ESC retard signal has been on for too long or the system has failed a functional check





44 - Lean exhaust
Check the ECM wiring connections, particularly terminals 15 and B. Check for vacuum leakage at the TBI base gasket, vacuum hoses or the intake manifold gasket. Replace the oxygen sensor

The timing may be retarding to the point that the engine runs poorly. Like cwb said, you could have a bad connection causing an erratic signal to the ECM.

An EGR malfunction can also cause the timing to retard also. I'll explain it the way it was told to me. The EGR helps keep the cylinders cool by recirculating exhaust gas back onto the cylinders, exhaust gasses won't burn, in effect, cooling the cylinders. If the EGR valve isn't working, the cylinders heat up to the point of detonation (engine ping or knock), the knock sensor detects the knock and retards the timing. So the EGR also plays an important roll in maintaining the proper timing.

Also, fault codes can be misleading sometimes. I worked on a GM pickup once where the guy rinsed the engine off with water and the engine wouldn't start, no fuel from the throttle body injectors, the code that we were getting was a faulty HEI spark module, we replaced it and still had the same no start problem. It ended up that the  throttle position sensor (TPS) had a small crack and water made it's way inside causing the ECM to think the engine was flooded, thus no fuel from the injectors. We replaced it and it ran like a top. Thing is, we never got a code about the TPS. Fault codes are more or less a reference point, somewhere to start.

quote:

ORIGINAL: rshiver
43 -
The ESC retard signal has been on for too long or the system has failed a functional check

This is what we got here. The code is tripped cause of a loose connection. Check voltage for the input variables to the ECM, and the output to the timer controller.

Now... where's Rip Van ibeleWinkle here? Hey! Wake up 'ere.

Thanks again guys. Wondering if a slight rattle in my catalytic converter can cause my idle problem. Also hooked up a pressure gauge to my schraeder valve and am reading 28psi, a little low. When I plug the return line I get 70psi. If I run the car with the return line returning the fuel to a gas can I get 28psi. What do you think.  No codes present but still erratic idle a low power off the line and crappy cruise performance. No surges at power but not alot of power.