Took my Series 3 in to have the upper timing chain tensioners adjusted (due to some nasty timing chain rattle) and, as a result, the timing was re-done. And also the belts because they were due. And the fan blade/fan clutch because they were also due.

Anyway, now I have a new and recurring stumble where the idle drops from 1000 RPM to an uncertain 600 to 700 RPM that feels like the car is about to stall (adding some throttle doesn't smooth things out). Some say it sounds like a misfire, others say it sounds like dirt in the injectors.

This event happens roughly 2 minutes, 49 seconds after every single cold ignition and lasts about :49 seconds. It also happens when the car is started warm but not as predictably, sometimes taking as long as 4 minutes to happen and lasting as long as 2 minutes before recovering its composure.

The "event" only happens once and only a few minutes after startup, hot or cold. Switching tanks doesn't affect or resolve the problem.

The vacuum hoses have all been checked (one was found loose but reconnected), the idle is very smooth the rest of the time and, with the exception of these events, the car is its usual fine running self.

Note: This is not the cold-to-warm power loss that is resolved by the capacitor mod.

Any ideas?

Thanks in advance,
Rhett

 

I wonder if the coolant temp sensor is skewed or has a dead spot? The CTS is key player in fueling until the coolant hits about 160ºF.

Easy to replace and only about $25 so it isn't too painful as guesses go. Or you can check it with an ohm meter and a pan of water on the stove. I can give you the specs.

Cheers
DD

 

Hi Rhett,

1000rpm seems a bit high for idle??

I get that if the climate control compressor hasn't kicked in.

These engines should (if a little lumpily) idle fairly happily at 700-750rpm.

I have had a similar problem with my cat, although my ignition would just cut out but happily restart like nothing had happened.

It didn't help that there was a fault in the injector harness wiring as well.

As Doug suggests, Coolant Temp Sensor was swapped out, but didn't correct the problem in my case.

I also checked and did the following:-

Pecktron (Red) Relay swapped out on firewall as it played up when the engine bay got hot.

Throttle Micro Switch replaced as old unit had a crack in the casing where the spade connected to the wire. At idle, the vibration would wreak havoc with the connection and the engine would drop revs and all but stall...

This after I replaced pretty much anything electrical in the ignition system over the last 7-8 months including Ignition Module and wiring, Ignition Resistor Pack and Ignition Injector harness.

Not trying to scare you, but I had several small problems that lead to major ignition trouble just like yours.

Looking back I probably didn't need the Resistor Pack, but it's done now..

Good luck problem solving :-)

Cheers,

Nigel

 

Idle is a bit advanced so I can run the climate controls without stalling the car. 1000 RPM with a/c or heat off. With a/c on, idle is closer to 750 to 800. Anyway, it's not a problem I'm trying to solve.

 

Okay, problem solved. It was the 02 sensor. The warning timer/light tripped a few months ago and it was on my list but my list has 3 cars on it and it's long and I hadn't got to it yet. Anyway, new 02 sensor and not only is the stumble gone but the car starts much considerably more confidence and certainty.