(T) Garage lying about Cinq idle speed?

Last week the slightly dodgy head-gasket on my Cinq Sporting finally gave up the ghost big time. The local garage that was recommended was booked up to Christmas and I couldn’t wait so I used another garage near work.

After two days, a new gasket, a new water pump (the old one was well shagged) and a load of dosh, I take the old girl home, but she’s not happy.

When I start, the revs climb to about 3000 and then drop to 1500 with a regular 1 second pulse @ 2000. Once it warms up, things calm down a bit and the engine sits at a steady 1600 (ish). I’ve spoken to the garage and the bloke told me that it was an electrical snag that was probably already there but has only become obvious now that the engine has stopped sucking air through the shagged gasket. Unfortunately, he didn’t have the right diagnostics adaptor for the Cinq. He assured me it wasn’t their fault though.

Haynes was fcuk all use so I took the car into a garage for a diagnostic check. The MAP, lambda sensor and temp probe all check out and he suspected and air leak somewhere in the throttle body or thereabouts.

The car is going back to the original garage because they have agreed to look over what they did at no cost.

My question is basically this: Did the original garage cause this when changing the gasket or could it be an old problem that has appeared since the repair?

Extra info that may be of use to the technically minded:

1) The red engine warning light now stays on all the time.
2) Pulling the vacuum pipe off at the MAP and blocking it sets the idle at normal (950/1000) but the emissions go to pieces (HC through the roof).

Apologies for the huge post, Thanks in advance for any help.

something isn't right. the warning light should not be on.

It sounds like the map sensor is damaged, and when it is connected it's letting air through.

If it wasn't doing this before, and it is now - then the garage should be sorting it for you.

Basically a high idle means an air leak. The throttle body might not be sat correctly - also there are a few vacuum lines on the back of the throttle body that if they are connected up wrong (easy mistake) it can cause this. Get them to double check that they are right.

on my 899cc,theres a pipe from the tb to the ecu,thin black one,if this is bent or moved the engine idle rasies and car runs rough,make sure its not bent or attatched round something

If the Engine warning light wasnt on before or during your head gasket problem - but is on now, after the garage fixed the head gasket - Then I would suggest that they have disturbed something, or perhaps not re-connected some sensor..... Either way, it's their fault if you didnt have the problem before they worked on your car.

As for idle speed, and MAP tube - There must be an air leak somewhere or there is a sensor that has failed / been broken or not re-connected.

The idle speed (and fuel air mixture) is controlled by an Idle Control Valve and MAP sensor which send the information to the ECU. The ECU gets it's information from various other sensors, and if one of these has failed or not been re-connected - Then it doesnt have all the correct information needed to make the engine run properly.

Either way - Get the garage to double check everything - Make sure you tell them that these faults were not there before the head gasket problem - Dig you heels in - Tell them you know your rights... You have paid for work - but there is still outstanding problems. May be an idea to speak with the Citzens Advice people.

Well, I had a call from the ranch yesterday evening and picked up the Red Shed on my way home.

He swears that it was a bad connection at the back of the temperature probe (still sticking to his "electrical fault, nowt to do with us" story). He didn't try and charge me though so I'm not too fussed.

The idle is still a bit higher than when the car went in (about 1300 now), but at least it's steady so people at the lights don't think I'm trying to race them (I'm much too old to be taking on Spaxos at the lights)!

The idle was high when I got the car and came down gradually over time. Would that have been caused by the slow breakdown of the head-gasket, the ECU re-mapping itself or just coincidence?

Cheers for your advice.