K Series rough idle, possible reasons?

[Nic Jones]

The ZR (1.8) seems to have decided to have developed a lumpy idle these past couple of days and I'm not sure why!

On tickover it seems to oscillate between 500 and 1500 rpm, almost dropping to the point of stall.
According to her indoors it sometimes also coughs when you're driving but I've not noticed this.

I took it out earlier this evening and gave it a couple of full throttle accelerations up to 60 and it felt fine then behaved itself once back at the idle.

Can anyone give me any pointers? I'm wondering if it's the fuel filter or injectors that are clogged up.

[Justin S]

IACV on the inlet manifold is possibly the cause. Get some carb cleaner, remove from the manifold ( 4 bolts on later cars), flush out the crap and put back on.

[anonymous-user]

The TPS sensors on K series also can fail and get a bit "scratchy" at zero pedal, which means the ems doesn't stop the fully shut throttle, and the dashpot and idle control goes to pieces.

(mind you, usually it's the higher reving / ally manifold VVC's that knacker the pot the easiest, but it might be worth a check with a multimeter to look for a smooth and linear output voltage with angle??)

[porka911t]

Inlet manifold gasket/rubber is very common failure.

[Cyder]

Thanks for the advice guys, the car went in and came out with a cleaned IACV, replaced TPS and they traced a broken wire through the system apparently.

The missus drove it home last night and it ran sweet as a nut...

However, she drove it to work this morning and just after putting some fuel in whilst she was driving it cut out on her 3 times.
No warning lights came on prior to the cut out, but weirdly she says the blower stopped working just before it cut out the first time and then started again when she restarted the engine!

Any ideas? I'm thinking it could be the fuel filter/pickup that has collected some crap, but it wouldn't explain the blower cutting out.

To the best of my knowledge they plugged it in to the diagnostics when it was in the garage, so surely that would have discovered any ECU/electrical problems?

[Incorrigible]

Cyder said:

To the best of my knowledge they plugged it in to the diagnostics when it was in the garage, so surely that would have discovered any ECU/electrical problems?

But it ran fine when it left...

It still sounds to me like the IACV, although the wiring to the TPS does have a habit of becoming intermittent. If you hold it on about 1/10 throttle (2,000 rpm) and wiggle the wires what happens ?

[Cyder]

Thanks for the reply, I've driven it all weekend from bimbling around town, to thrashing around the B roads and commuted to work in this week (50 miles per day) and it's not cut out/coughed once!

I wonder if it was just crap in the fuel when it played up on Friday, if it plays up again I'll go with the wiggle of wires on the TPS.