85 coupe A4 L98, mostly stock, ragged out 148K.....

I've done alot of searching and seen several ideas for a 42 and several ideas for a 43, but does anyone have any experience with both? What's the common denominator? In a nutshell, tried to give it alittle extra gas (not flooring it) and it had some hesitation. SES came on. pulled up to pull codes, and got 42, 43. had a hard time starting back up and idling. Drove home and parked it... I've got all of agent86's code pages, which should be similar to my car. His is an 86 and mine's an 85. If there are any significant changes that I need to know, just let me know.

Any ideas as to what's causing both of these to pop up at once, please let me know!!!!

much love....

 

Code 42 is Electronic Spark Timing Sensor (EST)
Code 43 is Knock Sensor (KS)

 

Thanks, where are these located? Are they hard to change out? I new what the codes were for, but my other question was, can they be connected in any way? As in, if one's bad, could it possibly cause the other to go bad. Should I go on and get both parts or start out with the easiest first and see if it fixes the problem?
Thanks!

 

EST is located between the brake booster and distrubitor. It;'s a one wire hook up and is disconnected when setting timing. The Knock sensor is located on the right side engine block. There is also the knock sensor hookup located on the right side just behind the fender and next to the blower. It is about 5-6 pin hookup. These could possible be disconnected....check it out.

 

If you have the trouble shooting chart from a FSM than use it first to TEST the problems as opposed to throwing money at it. Something triggered your code 42, 43 and it very well could be something else other than the EST and knock sensor. I'm at work right now and unfortuenately don't have my 85 FSM to give you some ideas of where to start. The FSM can be had here at www.helminc.com or sometimes on Ebay or the for sale section of this board. Invaluable tool and will save you lots of green backs!

 

Hope you have the FSMs or Helms, cause I think you need to trouble shoot the ESC Module -that's Electronic Spark Control Module-may be a problem with it or somewhere in the circuit.

 

That's what I needed to here! Thanks alot. So these aren't related in that one could cause the other to go off.

 

I'm not saying that at all!! there are several things-or conditions in our C4s that can be caused by one thing, that point a finger at another! IN one of my instances an EGR code was triggered by the EGR switch, rather than the EGR itself, but you end up with the same code. A MAF code can be triggered by many things. I just happen to believe the best place for you to start trouble shooting is the ESC module-or ESC circuit.

 

Thanks. I'm gonna start working on it tomorrow. One thing I forgot to mention, was that I pulled off the road and ran the codes. cranked it up, and that's when it had a hard time starting. on the way home (which is about 10 minutes) the SES light never came on again. Does that mean anything? Is there a reason why the light could be intermittent?

 

The light comes on to let you know there is a problem, then goes out so as not to make you go crazy looking at it.

On your car, the knock sensor is located on the lower right side of the block, just in front of the starter motor. It probably has a heat shield around it

The Electronic Spark Control Module is attatched to the right side of the evaporator blower with two bolts. It's about 3 inches square. Easy to spot.

Electronic Spark Timing EST

General:
1. To provide improved engine performance, fuel economy, and control of exhaust emissions. The ECM controls distributor spark advance with the EST system.
2.. The ECM receives a reference pulse from the distributor, which indicates both engine rpm and crankshafft position. The ECM then determines the proper spark advance for the engine operating conditions and sends an EST pulse to the distributor.

Check:
1. The ECM will set EST at a specified value when the diagnostic test terminal in the ALCL connector is grounded. To check for EST operation, the timing should be checked at 2000 rpm with the terminal ungrounded. Then ground the test terminal. If the timing changes at 2000 rpm, the EST is operating. A fault in the EST system will usually set a Code 42.

1. To set base timing, disconnect the timing connector near the brake booster.
2. Set the timing as specified on the VECI label. This will cause a Code 42 to be stored in the memory. Don't forget to clear the memory after you set the timing.

 

http://members.shaw.ca/corvette86/Code%2042.pdf
http://members.shaw.ca/corvette86/Code%2043.pdf

 

Ah, Agent 86 came through again. Take a look at these troubleshooting charts. These will lead you in the right direction. These are from a 86 but probably just like yours.