[megazoid]

Been driving a 2003 petrol mondeo for the last couple of weeks. Car's done 80k or so. Been serviced a week back at Metro Ford Hesserghatta and air, oil and fuel filter have been replaced. Car is going great except for one thing.

When I have AC turned on and driving normally, the engine RPM does not go beyond 2000 and it feels sluggish. Feels like engine is starved of fuel and air. Pedal to the floor will not make the engine RPM go above 2000-2500 rpm. This happens a little while after the AC is turned on and not immediately. For example, yesterday I started from home without the AC switched on and drove for about 20 mts, then received a phone call and sat in the car with the AC switched on for about 20 mts parked by the side on the road. The call finishes and I start driving and the car feels starved and sluggish. I reach MG road, park the car have dinner and start again without the AC and its all back to perfect shape. I drive around for quite a while to see if the problem resurfaces without AC. It hasn't.

Some observations.

1) I am ruling out fuel as without AC, there seems to be no issues.

2) I drove about 70km one side flat out without AC..no issues but on the way back put the AC and drove. 20 kms into the drive I am having trouble with the car. Choking feeling at full throttle. No response from the engine.

3) I reach home and after a few hours take the car out and start without AC and no problems at all.

4) After running into the problem with AC on, if I quickly switch off the AC and drive, the problem still persists. I park the car and come back to it after a while, i dont see the problem again.

5) One thing I havent done is to stop and start the car without AC the moment it starts showing the problem. (i only switched off the AC and drove and the problem remained). What Iam getting at here is that once the problem shows up does restarting of the car make a difference?

The car otherwise is doing good. Good pickup and nice top speeds.

Your thoughts?

[jatinpatel]

Has any malfunction light or engine checklight come up?
Do you feel any difference in cooling effect of the AC?

also please get the ac system pressure checked if its very high it might result in high pressure reading to ECM which would then regulate amount of rpm so as to not cause damage to compressor.
And the issue of the issue gettin solved after switching the car off for few moments and then starting and issue stopping could be cause high gas pressure getting reduced thus ECM getting proper reading.

[megazoid]

Originally Posted by jatinpatel

Has any malfunction light or engine checklight come up?
Do you feel any difference in cooling effect of the AC?

also please get the ac system pressure checked if its very high it might result in high pressure reading to ECM which would then regulate amount of rpm so as to not cause damage to compressor.
And the issue of the issue gettin solved after switching the car off for few moments and then starting and issue stopping could be cause high gas pressure getting reduced thus ECM getting proper reading.

Thanks for the quick reply.

AC is working wonderfully well. No malfunction light at all.

Interesting reason you have there.

Would that also explain why the problem persists if I simply switch off the AC as I encounter the problem (with AC on)? I guess it does from the way you put it. Note that the problem continues once it surfaces irrespective of whether the AC is ON/OFF. Maybe driving it with AC off for sufficiently long might solve it too(just guessing).

The problem goes away only after a restart. I restart after a break. Did not do an instantaneous restart after I encountered the problem. Logically, I presume an instantaneous restart should also solve it rather than having to take dinner breaks etc before a restart.

[dhanushs]

Originally Posted by megazoid

Would that also explain why the problem persists if I simply switch off the AC as I encounter the problem (with AC on)?

I would suggest you to check

1. Ignition Coil
2. HT Cables
3. Fuel Pump

[VCheng]

This car should be diagnosed with a proper scan tool attached to the diagnostic port while driving to reproduce the problem and troubleshoot from there.

[GTO]

I would have thought it's the ignition coil, or even a clogged filter / exhaust, but you say the problem only occurs with the air-conditioner?

Why not reset the ECU first? Remove the battery connectors for an hour / overnight, fit them back and see if that solves the problem. If not, as VCheng posted, you need to get the car hooked up to a diagnostic tool.

[Sprucegoose]

Happened to my OHC as well...
The AC used to cool, but when it was switched on, after a while the car became supremely sluggish.

The car in 1st gear would not cross 25 odd kmph.

a couple of months later the compressor seized.

Got a new one... no issues after that.

[dashoin]

Could it be a case of the ECM going in the "limp" mode?

IIRC, the limp mode would also not allow the rpm / speed to exceed beyond a limit. I am assuming the Mondeo also uses the EEC V ECM.

I think a scan should be the top priority.

[narayanang76]

exactly my thoughts @dashoin.

looks like the car is getting into limp/safe mode when AC is turned on, restricting the rpm and thus performance. something should be wrong hence take it to mechanic asap.

[mayankk]

get it to ford and a diagnosis scan pronto.
it'll give you a spot-on error, rather than an external hit-and-try diagnosis.
Read around, and your problem seems indicative of an impending coil failure.

[dashoin]

Just a wild thought - could you pop the hood and see if there are any open connectors? Make sure the engine has cooled down sufficiently before this.

[megazoid]

Thanks for the suggestions. Quick update.

Had been to Ford for service today. Had to replace the rear left arm(slightly bent) and the drive belt(life over). Took a look at the spark plugs and they seem to have oil around it. The gasket is faulty and is leaking oil into the plugs. So did a cleanup of the area and used sealant while putting back the piece. Have placed an order for a new gasket (no mondeo parts are ever in stock )

Reason for bringing this up is to discuss whether this might have anything to do with the problem. The technician seemed to think so.

btw, I have to drive 60kms to get to service. Thought I could use this chance to recreate the problem by driving with AC switched on and felt that by the time I got to the service center, I would have the problem reproduced for them to debug. In spite of driving the pants of the car with the Aircon switched ON, I land at the service center without a problem and could only explain the experience to them.

What I havent done are to use the diagnostic equipment as suggested. Will do so in my next outing which is not more than a few days away(for the gasket fitment)