Rough idle when cold

This could be one of several things.

MAF sensor's, ECU's, Ground wires at intake (happened to mine), Spark plug wires, Fuel pressure regulators, 02 sensors... Need to start somewhere - try that short list.

 

Do you get a check-engine light even intermittently? We have had some similar issues but we also got a light. I wonder if it could be a bad heater in an o2 sensor?
Dave

PS> Does your car have the Motronic 2.7 where you can pull your error codes by pushing a button in the trunk and watching the dash lights?

 

As my Mondial is going under the knife very soon, while the engine is out i'm having Bradan install Dave Helms supremo GCK which is supposed to eliminate most of the erroneous CEL, ECU and various electrical gremlins with better performance all around.

You may want to consider this but while the engine is in, its a 12-14 hour job, engine out - 7-9 hours. There’s a big write up on it in the 348 room.

 

I just had this same issue on my Mondial t and it turned out that one of the air hoses had come off.
The idle was erratic and there was no power at low RPM during cold starts. It also shunted under acceleration.

The hose had come off under the plenum chamber. Check all your air hoses to see if any are loose or have come off. This hose was impossible to see by looking at the engine and unfortunately required removal of the plenum chamber top to refit it.
The car ran fine once warm (about a mile)

 

Easiest is the MAF.

When the car is running poorly unplug the quick connector on each MAF (one at a time) and see if it changes the characteristics. If it does then that MAF is probably responding. If it makes no change to the running once unplugged then that MAF would be suspect.

If they do respond then second on the list of easy is the 02 sensors. Unplug them from the harness (up near the oil filter stand) and un-thread them from the exhaust stream. Replace with new (they are just Bosch sensors) and then report back.

 

And check for loose hoses....my comment has been skipped over but I had all these issues, I had the MAF units off and checked them, plus other stuff, and in the end it was just a hose.
It's probably not that on yours but can be checked in a few minutes.

 

No, there are multiples of different Bosch 02 sensors. You will require the one that has the correct connector and values.

Chances are that it will fit something like a Camry as well though. I am sure the 348 forums will list the exact cheapest cross reference available for the 348 version of the Mondial 3.4 (yep, the Mondial t had this engine before the 348 did). That often times seems to be what they strive for over there.

Here is a great site that will get you close on a lot of the 3.4 stuff like this. Look up simular issues as yours (TPS, MAF, Phase, loose hose, Codes). http://my348.com/

 

The 348 parts sticky shows a walker replacement for the o2. We are runnung two of them with no issues at about $60 each.
Dave

 

Good for you for taking on the diagnosing. Keep notes, check all easy things 1st and don't worry too much about it - as anything can be fixed.

If you end up going to new converters please consider the high performance replacements like Hyperflow available through our forum sponsors.

 

Have you had any water on the engine recently, say from washing the car or going out in the rain?

 

Have you done a reset on the ecu. ...turn off battery for a few hours, turn everything electrical off ie fans aircon etc. let sit for a few hours, turn switch back on start car without doing anything other than turning the key, let it idle for about 10 mins til the fans come on. it will go through some check cycles and this may fix your problem or at least help

 

How can i read ECU codes.

is it standard OBD?

thanks,

lino

 

That's good enuf for me! Happy driving.