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View Full Version : Engine Low/poor idle intermittently at start



Jonathan
08-01-2025, 09:30 AM
Hoping to get a fresh set of eyes on a problem I'm having.

My car is basically stock... factory engine, transmission (automatic), fuel and exhaust systems.

I've noticed over the past couple of years that when I start the car up after sitting in my garage for a few days, that it will sometimes hesitate when trying to give it gas to drive off down the street. Like pressing the accelerator pedal doesn't translate to power and forward motion. It usually catches a moment later and off we go. I have often thought it is related to how my garage and driveway is on an incline and somehow the ATF isn't getting into all the places it needs to until you're back on level ground. ATF level and colour looks ok when I check it.

I have gotten into the habit of running through the gears while still in the garage with it running. PRND21 and back to up to P. I had been thinking this might get some of that ATF moving around as intended. Not sure if that was doing anything or not.

More recently though, it has been harder to start. I will turn the key and listen for the fuel pump to prime. I'll turn the key on and off a few times to let the fuel pump try and run to ensure the lines are at their full pressure. Then I start the car and it roars to life and we're good to go. I still will sometimes get that no power auto trans thing that may or may not be related.

In the past month though, the car has stalled a couple of times soon after heading out. The first time it did it, I started the car after driving it the day before and quite a bit that weekend, and it seemed fine until a couple minutes later when I was in the coffee shop drive thru. The RPMs were fluttering down to 500-600 or so and it stalled right when I was at the window. Ugh. It took probably ten tries to get it to start again. It seemed like it was not getting the fuel it needed. Electrical looked ok, voltage was about right and lights and radio were working. Just insufficient fuel (or air?) at the time. When it finally started, I quickly left and got out on the highway and it was fine after that. I didn't really need to slow down to a full stop for a while, so not sure when it got better.

I thought at the time it was because I had to leave the car outdoors the night before and we got quite a storm and figured some rain got in to the engine bay and maybe got a spark plug wire wet. Or maybe that first turn to the right to enter the coffee shop slopped some water over. Not sure, but was trying to think of a logical reason at the time.

I parked the car once home in the garage and looked and nothing was wrong that I could see. I checked the ballast resistor connections and the other quick connectors for the idle speed motor, CSV and frequency valve and all seemed fine and snug. Air filter is clean and the air filter housing seems on straight and not impeding anything from moving smoothly. I have thought maybe that the air flap and that lever arm underneath was sticking, but it doesn't seem obvious that it is.

I got two drives in in the past two weeks and both were fine. No stalling or low/weird idling. Then yesterday it happened again. It didn't stall outright because I was able to pull to the side of my street and put it in neutral and give it some gas. I babied it for a bit down my street and then it seemed better and off we went. For some reason though it has this low/weak idle where it feels like it isn't getting enough of something, fuel likely or maybe air, and then for whatever reason it is better soon after and not a problem again for the rest of the drive. I will sometimes stop and then start the car again and it doesn't do it again so thinking it gets better when the engine is hot.

I'm really just confused as to what might be going on. Too much thinking on my part and figuring one thing is good or another is bad and not really sure anymore. So thought I'd ask the group here for what comes to mind with that description. Thanks!

Bitsyncmaster
08-01-2025, 12:29 PM
Well the first major problem is stalling hot and hard to get it started. That could be a fuel pump problem or it's electrical circuit. Have you checked the mixture with a dwell meter? Normally I would say check fuel pressures first but most owners don't have that equipment. I suspect your mixture is off since that would also cause cold starting and running problems.

Jonathan
08-01-2025, 05:40 PM
Thanks Dave. This is the issue I had in mind when I asked about buying one of your solid state RPM relays.

Agreed it sounds like a fuel pump issue in some way. I'll definitely check the wiring and connectors up front. I take it a possibly problematic RPM relay wouldn't likely be the only thing going on here?

I can check the dwell too. I have a dwell meter, but no fuel pressure gauges as you guessed.

Just for clarity, it has struggled to start while cold not hot, if that makes a difference in your assessment.

Bitsyncmaster
08-01-2025, 07:17 PM
Thanks Dave. This is the issue I had in mind when I asked about buying one of your solid state RPM relays.

Agreed it sounds like a fuel pump issue in some way. I'll definitely check the wiring and connectors up front. I take it a possibly problematic RPM relay wouldn't likely be the only thing going on here?

I can check the dwell too. I have a dwell meter, but no fuel pressure gauges as you guessed.

Just for clarity, it has struggled to start while cold not hot, if that makes a difference in your assessment.

Pop your RPM relay open and wiggle the relay to see if it has broken solder joints on the circuit board. Very common problem that can be intermittent.

David T
08-01-2025, 10:32 PM
Sounds like you could have several problems. I suspect the Control Pressure Regulator, Cold Start Valve system, accumulator, and idle speed motor circuit. Maybe some plugged or dirty fuel injectors. The only way to properly diagnose the fuel system is with a pressure gauge. Not uncommon to also have intermittent electrical problems too. Leaving the car out in the rain can cause water to get into the spark plug wells. It could also be that your car is due for a tune-up. As for the transmission, make sure the fluid level is in between cold and hot and doesn't smell burnt.

Jonathan
08-02-2025, 07:51 AM
Thanks for the suggestions. I'll look at my notes and see how long it has been for certain maintenance things and maybe just start knocking them out. I won't go all the way into the valley, but can do spark plugs and all my fluids pretty easily.