Posted a while back and I thought the problem was bad balancer wasn't keeping time. So I changed the timing chain and the balancer but it seems to have changed nothing. Car runs and sounds fine under constant throttle, just refuses to idol.
No vaccumm leaks detected, ioc is new.
Does the ecm need reset? I know they need to learn how to idol and I've done a lot of work and have only took it for one drive but not far from the house since the idol issue could leave me stranded.
[This message has been edited by Notamechanic (edited 11-05-2022).]
Originally posted by Notamechanic: Does the ecm need reset?
ECM will Reset IAC when you drive > 35 MPH If you haven't driven then ECM has not Reset the IAC and have to guess the IAC Steps to set Idle.
Some engines in some years also reset the IAC when Park and sees RPM > 2200-2500 when you push the gas pedal. 87-88 Fiero L4 can so this.
If a sensor etc change happens w/o battery disconnected then ECM often have bad data and may think IAC is Reset but isn't and have same problem until drive > 35 MPH.
Even when scan tool said IAC Reset Yes/True... I think ECM will reset this at some point to make sure IAC didn't miss a Step or more and mess up Steps Count thus screw up idle.
Went to check the TPS for voltage and got nothing. I found a broken wire leading into the TPS. Ordered a new TPS and pigtail. Will replace those and go from there.
Need this turd running by the 19th. Just need it to make a 10 mile round trip without dying. I want to it to drive the Fiance and I away from our ceremony. Wish me luck.
Patrick! Don't be soo cruel! Canadians can't spell either. If you want proper grammar/spelling, it is best to check in with a recent immigrant. I am sure you cringed at the recent Cadillac "Break" conversion title as much as I did...
Idle is for cars. Idol is for White Wedding,., baby! one of the best songs in decades!
Got the wires and TPS fixed and still no luck. Started to suspect fuel pump or maybe regulator? Previous owner put a new pump in shortly before I bought the car.
When key turns to on, the pressure shoots up to 45 psi then drops immediately. Down to zero within a minute while key is still on.
When the car starts it maintains the 45 psi then settles down to around 40. Dropping to 35 if revved. Then the second my foot comes off the gas the car dies while psi maintains around 40. Then drops a second or so after the engine shuts off.
When key turns to on, the pressure shoots up to 45 psi then drops immediately. Down to zero within a minute while key is still on.
That information is critical. There's obviously a fuel pressure leak somewhere. Could be in the tank (where the pump connects to the hard fuel line), could be the fuel pressure regulator diaphragm, could be one or more fuel injectors.
That is a big fuel pressure leak... you should be able to turn the key off and hold pressure for a couple minutes at least. I would suspect the fuel pump hose first.
I agree with Patrick. The fuel pressure shouldn't drop that fast. There's a simple test you can perform, to see where the pressure is going. It involves pinching the rubber fuel lines. So if they're cracked or dry-rotted, you may not want to try it (might cause a leak).
Anyway, here's how it goes. If you pinch the supply line (from the fuel pump) and pressure holds steady, then something is wrong with the fuel pump. If you pinch the return line and pressure holds steady, something is wrong with the pressure regulator. If pinching either line (or both) has no effect, then you have one or more leaky injectors.
There's a simple test you can perform, to see where the pressure is going. It involves pinching the rubber fuel lines. So if they're cracked or dry-rotted, you may not want to try it (might cause a leak).
I've always shied away from doing that test... for the very reason you've given!
Alright, I did the pinch test as suggested (thank you btw). Seems like it's an injector(s) stuck open. While running the test I also noticed a hissing/gurgling noise from around the fuel rail. Was unable to locate where exactly it was.
Is their a quick test to find which injector is open? Maybe which spark plug is wet? Is it possible to smoke test the whole fuel rail to find any other leak?s
I did replace the fuel injectors when I got the car. I did a quick ohms test to check if any were faulty but they all were in adequate range of each other.
While running the test I also noticed a hissing/gurgling noise from around the fuel rail. Was unable to locate where exactly it was.
If the diaphragm is leaking, gas gets sucked into the vacuum line. Would it "gurgle"? I dunno... possibly.
quote
Originally posted by Patrick:
That information is critical. There's obviously a fuel pressure leak somewhere. Could be in the tank (where the pump connects to the hard fuel line), could be the fuel pressure regulator diaphragm, could be one or more fuel injectors.
[This message has been edited by Patrick (edited 11-14-2022).]
My 1987 GT suddenly (after getting gas at a station) started to run very rough and would not idle without gooseing the throttle. It turns out a mouse ate through my IAT wires near the air cleaner. I fixed that and it idled and bit better. I found that my EGR Solenoid coil was reading in the mega Ohms (should be around 80 to 100 Ohms). I rebuilt the Solenoid but little improvement. Then I found that CTS was reading open (fooling the ECM) that the engine was very hot even at start. I replaced it and now the idle is more stable, still a bit rough and idling at 1100 RPM, but it is drivable. The next step is to check the IAC Valve to make sure the port is clean, the steeper motor works, and it is getting proper signals. I think it would be a good idea to check the EGR Valve to make sure it works and the port is clean.
If it still won't idle, my next step is a plug, wire, rotor tuneup and ignition system/timing check. Then replace the fuel filter and check the fuel injectors (a big job).
But there could be dozens of things that may be wrong. Mine was a $10 Coolant Temperature Sensor (CTS) which was easy to replace and gave the biggest improvement. Start with low cost items. I try to keep at least one of every sensor, actuator, belt, bulb, plugs, rotor, cap, filters, etc in my personal stock room. They don't go bad on the shelf and the prices never drop in the future - get them over time and have them on hand - a good investment.
