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I am going to second 1project on this. Is actually sounds like a bad pickup coil in the distributor. I had that happen on my s10. It would die, then after sitting it would usually restart. On all tbi engines my mechanic always replaces the distributor on nostarts.
Thanks for the comments. This approach seems reasonable and since the stalling/dying is the overriding factor at this point I'll be looking into this. A couple of questions (which will demonstrate my lack of knowledge and understanding of the components involved):
1) How does one check the resistance of the pick up coil. Yes, I have a multi-meter. But what exactly is the pickup coil? I presume it's part of the ICM. Which pins do I check? I presume the resistance should be low but what value?
2) If the pickup coil is part of the ICM then the old unit had the same problem but did it much less frequently. The replacement ICM is stalling/dying every few minutes and doesn't specifically have to be "hot" as it has done it within 5 minutes of starting the engine. Do I need yet another ICM? If so, a particular brand?
I'll report more later today.
Thanks again.
The pickup coil is located at the center of the distributor. The distributor shaft passes thru the center of the coil assembly. The two leads from the coil attach (ie. plug into) the ICM. Unplug the coil to ICM and with your multi-meter you can check the coil for shorts to ground and measure the resistance of the coil which should be 500-1500 ohms. To replace the coil, you need to pull the distributor and remove the distributor shaft from the housing to access the coil. Replacing the pickup coil does not require you to purchase another ICM.
Thank you, very helpful.Quote:
Originally Posted by Eds
Prior to starting the engine today I checked the resistance of the pickup coil - 1,100 ohms. Just for grins I checked each pin to ground and moved the wires, pulled and pushed gently to see if there may be some sort of intermittent but everything checked okay.
I started and stopped the engine several times and let it idle for 20 minutes or so in the garage. It did not die during that time and I did not get a check engine light signal either. There are some other odd things about the idle and I'll explain those in another post. I may have also found some other unusual aspects of my installation that will be revealing but I'm holding off on describing those until I take it for a test drive. With a little luck I'll make it around the block a few times and run a few errands.
More to come...
Speculating on why the engine was dying...
I installed the ECM under the A/C & heater duct in the passenger footwell area. It's visible and easy to access. I painted the ECM box black so it would blend in with the A/C & heater duct.
The other day when I was checking wiring and looking for reasons that the engine was dying I looked at the A/C & heater duct and noticed some moisture. When I removed the ECM to check its connections I found a small amount of moisture on the sheet metal ECM enclosure. I subsequently removed the access panel for the PROM but did not see any moisture inside the ECM enclosure. But any moisture, a drop or two of water from the A/C condensation might cause problems with the ECM.
Upon further inspection I'm not certain if the moisture is condensation from the A/C or maybe a leaking heater core.
The ECM is temporarily sitting on the floorboard in an effort to keep it away from any moisture that may be coming from the A/C & heater duct.
What are your thoughts? The engine didn't die in my recent series of test. Neither did I get a check engine light. It's too early to say it's "fixed" but maybe this moisture thing was causing some problems.
Is it reasonable to disassemble the ECM box to look for moisture/damage? Looks like a few screws hold it together. Do I run any risk of damaging components inside? If it's working now maybe I should hold off opening it. I obviously need to fix the moisture in my A/C & heater duct before I put the ECM back into position.
This is similar to what I went through with my truck. In the barn it started fine and ran for quite a while. Days later I replaced the battery only to find that it cranked but would not start. I tried pouring some fuel into the engine but it still would not start that was at 11:00 pm so I called it quits. Four days later, with my laptop connected and time set aside to diagnose the no-start, it started fine. I let it idle for over 1/2 hour then drove it out of the barn and parked it. I shut the truck off for about 20 minutes, restarted it, and drove it to the end of the driveway to wash it. I spent over an hour cleaning the exterior then started the truck again. I washed the engine and ran the truck for another 20-25 minutes for the engine to dry. I shut the truck off while I cleaned up my supplies then it wouldn't start.Quote:
Just for grins I checked each pin to ground and moved the wires, pulled and pushed gently to see if there may be some sort of intermittent but everything checked okay.
This intermittent issue was caused by a broken wire inside the pickup coil. The wire made contact temporarily. Once the wire stopped making contact I was able to confirm my suspicion. Luckily the wire stayed broken long enough to find the problem.
It's definitely a good idea to solve the moisture problem in your a/c ducts. You could visually check the ecm for problems as well. Water damage can show up as white corrosion at the solder joints or as green corrosion on various circuits. I would probably wait for a string of successes with the ecm residing in its temporary home before I decided to pull the case apart. In fact, I would probably purchase a spare ecm from a junkyard before tearing into the one currently in the car.
I drove the vehicle for the first time in several weeks. The ECM remains temporarily moved away from any moisture that might drip from the air conditioning ducts. In total I drove about 50 miles today. I did not use the A/C today because the outside temperature & humidity were quite pleasant.
About 20 miles into the stop & go traffic and errands I was running I was idling at a traffic light. The car surged and I could hear the IAC counts must have increased dramatically because the sucking sound under the hood. Fortunately my foot was firmly on the brake pedal so the car didn't move much before I stepped even harder on the brake to keep it from lunging forward and hitting the car in front of me. As I said, this thing has a mind of it's own.
As I was getting close to the end of my 50 mile round trip the check engine light came on. Arggh. The engine became sluggish because it was back to base timing without any advance. I knew from past experience that if I turned off the ignition and restarted the engine the CEL would turn off and the timing would be back to normal. So when I was coasting down a hill I did just that - turned off the key for a moment and then turned it back on - and the timing went back to normal.
So here's my latest question/issue:
The idle speed on the engine is not consistent. When I go through the entire process of setting the throttle plates, the engine idle, TPS voltage, the IAC closed, and get it tuned in with the engine idling and in gear (I have a powerglide) it seems to be fine for a few minutes. If I rev the engine and let it come back to idle it doesn't return to the idle speed that I set previously. Sometimes it's higher and sometimes it's lower RPM. I'm thinking this variation in idle speed and corresponding variation in TPS voltage might be causing a problem. In particular if the idle goes a little low it seems like the ECM may try to compensate and open the IAC to bring the idle up to the set point. But this may not be the right TPS voltage because the throttle plates aren't where their supposed to be. Okay, I'm going around in circles again but this dang thing has me baffled. Why does it run fine for a period of time then go a bit crazy?
Some helpful information on the position of the throttle plates - It appears the throttle plate screw will not control the actual position of the butterflies on a consistent basis. One time I set the parameters and the next time I drive the car those parameters are off kilter. It's as if the throttle plates are not returning to the same position each time. There doesn't seem to be any slop/wiggle in the throttle shaft. What should I look at to investigate this further?
1project2many indicated I should try to follow the stalling/hard start issue and I'd like to do that but it seems to have gone away for now. I plan to drive the vehicle several times in the upcoming week so I'll keep an eye on that issue too.
Something to try is to disconnect the throttle cable and manually flick the throttle to verify it is returning to the same place every time. If it doesn't, your throttle body is binding. If it looks good, start thinking about your throttle cable. It should be parallel to the manifold and at about the same height as the throttle connector on the throttle body. With it disconnected, tug on it to see if it feels sticky.Quote:
Originally Posted by nvestysly
Yes, I've done that and that's what caused me to realize there is something strange in the throttle body. My vehicle is a 1966 El Camino so it doesn't have a cable but uses old-fashioned linkages (rods). Those linkages are moving freely as far as I know. I believe the problem is in the throttle body. I'll double check when I have time.Quote:
Originally Posted by jim_in_dorris
If the throttle body has been machined, it could be binding. Another thought I had was this, is your icm on a heatsink with heat sink paste? Overheating the icm could be part of your stalling problem
Are your motor mounts in good shape?Quote:
Originally Posted by nvestysly
I'm guessing Fast355 asked about motor mounts because the engine could be shifting/rotating as the RPM increases/decreases. Yes, as far as I know they're fine. I had the transmission rebuilt recently and the shop looked at the engine and transmission mounts at that point. I'll double-check that to be sure.
I drove the vehicle again today. The engine did not stall/die like it did in the past. As I mentioned above, I've moved the ECM to keep it away from any moisture coming from the A/C duct work.
I did get a check engine light and it seems it always comes on at idle or when the engine is dropping down to idle. I don't recall that it every came on at highway speeds.
At one stop light the IAC clicked up several ticks and I could hear the sucking sound and noticed the increased RPM. Once again, I think the ECM is trying to compensate for a below set-point idle speed so the IAC overcompensates. The A/C was on at the time and that old A6 style compressor really puts a drag on the engine. Combine that with the variation I see in the idle speed screw setting and it's easy to imagine the ECM is doing some wacky stuff.
Any new ideas to consider?
I've attached three Excel spreadsheet files recorded while I drove the vehicle. I use a simple OBD-I scan tool made by 1320 Electronics to record the data. I drove the car for 20+ minutes and it had a CEL event near the end of the drive. I was driving at relatively low, constant speed - maybe 10miles per hour. Low speed seems to be a common denominator in the CEL event I'm experiencing. I don't think it's ever come on at highway speed.
If you have experience in looking at this type of data please help me understand if there is something useful that can be identified so I can begin to fix this problem. I think the CEL came on at line 1380 in the associated data files.
Thanks.
P.S. I have not experienced the unexplained stalling and hard starts recently. I seem to be back to just getting a code 42 on the CEL.
I asked about the possibility of motor mounts because of the mechanical linkage to the throttle and the possibility of the engine moving around.Quote:
Originally Posted by nvestysly
Seems like a tuning issue at this point.
I had an A6 on my 1983 G20 van and my TBI system did not have a problem keeping the idle stable on my 305 with a mild 204/214@ .050 Federal Mogul RV cam. It also did not have an issue running my 350 TBI with 305 heads and the same size cam. The TBI engines mostly ran R4 compressors and those have near the same engine load as the A6 if not more. One bit of advice I have is to start with the closest calibration in terms of engine size when it comes to a TBI system. For your 283 you would want to use the 305 base program to start with. It will be closer to what the 283 will want when it comes to idle airflow, fueling, transitional fueling, etc. I will say however with the old style cylinder heads and the RV cam my timing map and fueling was way off compared to a TBI 305. When I started tuning the system to get it to run correctly I also discovered that the small 55 lb/hr 305 injectors were too small and I had to switch to 61 lb/hr 350 injectors at 14 psi to get the 305 enough to drink at higher rpm and WOT. Where the stock TBI 305s started choking and wheezing at 4,000 rpm the RV cammed 601 headed 305 would keep on pulling to 5,500 rpm. The 305 injectors were setup to deliver about 170-180 hp worth of fuel when my 305 was making 240-250 made for ALOT of tuning changes.