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I'm trying to figure out the issue I described in a previous thread, as it continues to occur
Issue started after driving down a "bumpy" road
Idle Air Control Valves were changed 3-4 months ago. The car will not idle well occasionally and will just quietly die. Typically when coming from rolling to a stop. I've been able to reproduce it just driving out of the garage into the driveway, but its more scary when it happens on a public road at a stop light. There is nothing lit up on the dash when this happens.
Question:
1) Could it be that the bumpy road loosened some connection somewhere causing this?
2) Should I try adjusting the idle at the throttle body. When it idle's "normally", the idle is smooth and not bumpy.
3) Where else should I look? I haven't jumped the A&B pins to check for CEL's, but there is nothing on the dash when it happens so I'm a bit doubtful.
you really need a scan tool , could be a number of things but if I had a scan tool hooked up I would verify TPS (throttle position sensor) reads throttle closed idle position, when moving and letting off the throttle to return back to idle the ECM should kick up the IAC motor up 1000 to 1100 rpm and then slowly return the IAC motor down to factory speed 600-ish rpm and that kinda sounds like what you have going on but I'm mearly guessing , the early style ECT (engine coolant sensor)can cause dying and drive ability issues too after bumps and pot holes so if your car has one of those replace the sensor and connector with the newer style tp prevent future problems
you really need a scan tool , could be a number of things but if I had a scan tool hooked up I would verify TPS (throttle position sensor) reads throttle closed idle position, when moving and letting off the throttle to return back to idle the ECM should kick up the IAC motor up and then slowly return to idle down to factory spec and that kinda sounds like what you have going on but I'm mearly guessing , the early style ECT (engine coolant sensor)can cause dying and drive ability issues too after bumps and pot holes so if your car has one of those replace the sensor and connector with the newer style tp prevent future problems
Given that the car has OBD1, do you have a scanner you suggest? There are tons of OBD2 readers out there but it seems I need to use an adapter or some such?
Would you have the scan tool hooked up while the car is running?
If it is the 41 year old distributor in it.....the bumpy road probably separated the wires at the pickup coil ("cam sensor") or the ignition module......neither will code out......neither will fuel pressure, which you should check as well to rule it out.......get a test setup for your car......if you plan on keeping it, you will use it more than once.
You can rebuild the distributor or stab a new one in........depending on the condition and mileage of the distributor will determine if it needs to be replaced or refubished........
Rock Auto has several vendors that still sell the unit for about $100........that would be the way I would do it if it were here at my shop.......I can stab a distributor and set timing in about 45 minutes......
eBay is where you can find them , I have the GM Tech 1 and tech 2 , Snap On MT2500 aka the Brick and a Pro Link 9000 mpsi , the Snap On and Pro Link can be used in any of the early cars from Ford and Chrysler too , limited data available in service mode while driving but the TPS can be tested engine off key on and the same with the coolant sensor as you wiggle the wire it will read -40 degrees below zero momentarily if the connection is bad
1st...IMO, purchasing a GM service manual is ESSENTIAL for ANY CFI car. There is a ton of good information in that manual including all the diagrams you will need. 2nd, If you had an EBL ECM in a stock 82/84 corvette that is all you would need really. The EBL has the capability to troubleshoot, tell you what sensor is bad or going bad, and monitor ALL the sensor on the engine in real time just by using your laptop. Plus, you can data log at any time, idle, cruise or WOT and see what's going on. No need to buy all that fancy equipment. Data logging is rather important to finding an issue that is being elusive, the down side is that you need to know how to use the data to figure out what is going on. The real kicker is that the EBL is 100% plug-N-play with a stock motor. Pull the old ECM out, install the EBL, hit the key and your done. To monitor data, install the What's Up Display software (WUD) and you can do just about anything you want. To give you an idea about what the EBL can do, here is a pic of the main display, there are many different displays.
Last edited by XFire Performance; Apr 20, 2023 at 01:33 PM.
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