I have a 1991 with a regular distributor. I had a problem and a forum member said to check the resistance in the fuel injectors hot and cold. Three of my injectors had very low readings when hot and low readings when cold. They did not leak but they wouldn't work very well when hot. I replaced them with stock injectors and the car runs great. My cars had 91,000 miles on the original injectors. Follow the advice of our members. They can save you a lot of money and time. Don't forget that odd things like a vacuum leak or a loose wire can cause your problem. Also, any kind of coil can develop a short when it gets hot. The heat expansion causes the broken wire to separate and lose contact.

Thanks, Mickey

 

Intermittent problems are the hardest to find and I recommend that you keep your timing light, fuel pressure gauge, noid light, and clip lead in your car and the next time it won't start, perform the diagnostics I recommended in my post!

 

I have some more insight into what my problem might be. My FSM will not arrive until Wednesday so I will be more educated once that arrives.

I have had the problem a couple more times since the last post, all of which were when the outside temperature was greater than 80.

I failed to mention an important detail in my previous posts because at the time I did not think it was relevant. My problem started two years ago and was very intermittent only happening once every couple of months. It would start always on the second try if I took the key out and retried. Also around that time I noticed that when I would be driving the security light would flash three times along with "sys" under the speedometer. Once it finished flashing the check ASR light would come on. Again I didn't think much of it since I always turn the ASR off anyways. I had the garage check it out at the time during a routine service and they could not find a problem. Prior to this I had the aftermarket alarm removed because the powerlock switches were not working and it was all buggered up. I can't remember the details about the situation but due to frustration I had them remove the aftermarket alarm and repair the lock switches.

Today I made somewhat of a breakthrough. I figured out that when the car does not want to start that security light and sys error are tripped as soon as i put in the key. as soon as they go off it will not start. If I take the key out and the warning lights trip again, same thing, cranks and cranks with no start. If the security light does not flash three times along with the sys error when I put the keys in it seems to fire right up and run fine. It did this to me this afternoon. I got home and tried to reproduce it again using both keys I have. One key would do it and the other one wouldn't. Although both keys at times have either worked or not worked.

I'm thinking that my problem is with the VATS. Now from what I have read, others say that 95% of the time when you think it is the VATS it is something else. I seem to be convinced that it is something with the VATS system and not something like the fuel pump, injections, distributor etc. I am going to check the resistance in my keys to start with.

Anybody have other thoughts?

 

It doesn't sound like a vats problem per se, but rather a CCM (Central Control Module) failure. You should be able to diagnose that with the FSM. To read the codes, put ground on the "G"" pin of the ADL (diagnostic connector, lower left hand one) Then turn on the ignition, DO NOT TRY TO START! Your speedometer should start flashing codes. When the SYS lamp flashes three times (every fifteen seconds) it means a stored error has occured. This will all be covered in the FSM, I'm using one now.

 

My keys are bang on with one of the possible 15 resistance options so it looks like they are not the culprit. I am going to try ZR1Fred's recommendations once my FSM arrives in a couple days.

 

I just got the codes off the car(1992).
Don't have my FSM so can't make anything of them yet.

1. C41

1. H41

1. H72

1. H74

1 ---

4 err

9 H72

9 ---

1.0

 

You have no CCM codes, one ride control and two abs codes that indicate voltage loss. This thread hasn't really followed a diagnostic pattern,. You need to short the two upper right pins on the ADL, and read your ECM (main computer) codes, this would tell you if you have an opti problem. No ccm codes and the fact that it cranks would seem to rule out vats. There are very good dianostic maps in the your new FSM. It would appear that your SYS lamp doesn't have anything to do with the starting problem, merely indicting stored codes in another area.

 

I have filled in what the above codes are as per my 1992 FSM

Appears I am interpreting the codes differently that ZR1Fred had. I am just following the instructions in the FSM so I'm not 100% sure I am doing it right. From what I gather my next step is to run the algorithm for CCM code 41. Once I get this working I'm assuming I will be able to see what ECM codes are causing me trouble and go from there.

 

 

You need to determine which module you are reading. Read the whole CCM section (8D) and this should help you. Do you have an aftermarket alarm system installed?

 

I read section 8D with regards to pulling codes etc. Didn't read about all the specific codes(8D-20 to 8D-79) seeing that this isn't relevant. It seems I am doing this correct. The module number is displayed on the trip monitor and the codes on the speedometer.

I did have an aftermarket alarm system installed but had it removed about two years ago. These problems started sometime after having it removed. Coincidence, who's to say?

 

sounds to me that guy just dont want the job,thats why he quoted you that high price.they do that sometimes.keep reading this thread.they will find your problem.then take your time and fix it yourself

 

The reason I wanted you to read the section was that we were talking about similar codes from different modules. Since your codes seem to point to a shorted or open wire/wires, I suspect the old alarm has something to do with your problem (I fight this alot). You should look for bare, touching or disconnected wires, especialy ground ones. Write down all you're codes, and then clear them by disconnecting the battery for 60 seconds. This will give you a new baseline.

 

Got all my stuff together and went down to the parking garage tonight to have a go at trying to solve that code 41 and see if I can read the ECM. Put the keys in to see if it would start and of course it did as I expected.( the temp in my parking garage is about 23 celsius/73F and I am convinced that I only get the problem when the temp is around 30) I turned it off and read the codes. This time it read the ECM and did not show any codes. I then manually checked it and same thing, no codes on the ECM. I took ZR1Freds advice and cleared all the codes. I started the engine and let is run for a while then turned it off and rechecked for codes. All I got was the C12 on module 1 (no stored codes) and nothing on modules 4 and 9.

So this is where I'm at. I have an intermittent problem starting the car when the outside temperature is close to 30C (86F). When I get the problem the engine cranks but does not start. It will start again later in the evening or the next morning when the temperature cools off. Once it does start it always runs great and does not miss or stall and my mileage is fantastic. When I did a previous diagnosis during the problem I got an "err" code on module 4(ECM).

My plan is to leave the car outside this weekend in hopes that it will heat up and I can reproduce my starting problem. Maybe I can find something at that point such as a stored code on the ECM to guide me.

I'm just throwing this out there, but could my ECM be on its way out and causing the problem? Other advice or suggestions? I feel the forum members have been very helpful and I have come a long way from almost throwing 2G away on a new distributor. ZR1Fred, I still plan on checking for bare, touching or disconnected wires from the alarm, although this seems to be temperature dependent and I would think bare wires etc would be a more random problem.

 

Just for grins, put a small bag of ice in the freezer. The next time you have this problem, put it on the ignition module to cool it down and see if it starts (you might try it on the ECM too). You may want to check your ground wires on the car/engine to see if any are loose. Unplug the computer and replug it in to make sure you don't have a loose connection there, Check the plug-in at the opti and at the Im for loosness, and it might also be a good idea to wiggle/re-plug all the connectors. (probably not the problem, but doesn't cost anything).

 

This evening I went down to the underground parking garage to check for loose wires. I put the keys in and the car was reading an outside temp of 27C. Not to my surprise the car would not start and again I was getting an "Err" on module 4 and a code 41 on module 1 (loss of communication with ECM). I ran upstairs and grabbed two cold gel packs from the freezer and put one underneath and one on top of the ECM. 10 minutes later it was running fine with no codes on the ECM. At one point while it was cooling off it also stored a code 54 on module 1.

Code 54 is Feds Fuel Enable Circuit. The FEDS fuel enable system uses the serial data communication link between the CCM and the ECM to perform a password exchange routine when the ignition is turned on. If the password exchange routine is successfully completed, the ECM can pulse the fuel injectors "on". If the FEDS fuel enable routine is not successfully completed within 2 seconds, code 54 will set and both the "security" and "sys" indicators will flash together. This seems to explain exactly what happens to me, except that my problem is intermittent.


I then checked the ECM connections. All good. I also checked for continuity on the two specific connections between the ECM and the CCM. All good. By this point I'm thinking it is the ECM crapping out. I put my two gel packs in the microwave and put them back on the ECM to see if heating it up again would cause the problem to come back. 10 minutes later, problem back.

My conclusion is that when the ECM heats up a little something inside goes wonky and it cannot communicate with the CCM properly. At startup the ECM cannot perform the password exchange routine with the CCM. The injectors are not pulsed "ON". The engine cranks with no start. I get the flashing of the security and sys indicators. The CCM shows me a code 41 on module 1 and an "Err" on module 4. As soon as the ECM cools down it functions normally. Seems to be a logical explanation to my problem. Anyone have a better explanation?

 

http://www.digitalcorvettes.com/foru...t=53168&page=1

http://forums.corvetteforum.com/show...light=ice+pack

 

Sounds like you got the problem pegged!

Great job-way to hang in there!

 

Has anyone ever taken one of these ECM's apart? I've been in the electronics and computer industry all my life and the number one most common failure is solder connections. particularly on high heat components and connection points. sounds like "Ring Cracks" around component leads. heat and cold expand and contract those connections and cause intermittants. Vibrations can also cause these cracks around modular connectors. Just wondering if anyone has ever looked at the printed side with a magnifying glass.

Could solve allot of problems for zero "$"

 

I know it sounds like you found it but if this were consistant across the model line my car would never start. In South Florida it's over 80F almost the entire year.

It has to be a loose connection somewhere that is expanding and contracting with cold and heat. Cold shrinks, heat expands.

Hopefully you did solve it. Good luck.