Hi All,
This vehicle starts and idles well with no DTC's stored.
On the road though it is a flat as the proverbial pancake with very poor torque.The upstream lambda sensor keeps switching until WOT when it pegs rich.
At idle the lambda sensor switches well but the MAP is steady at about 60kPa where I would expect about 45kPa. The MAP sensor has been checked against my vacuum gauge.
Snap throttle naturally brings the MAP up to atmospheric and on the overrun it drops down to approximately 24kPa before returning up to 60kPa.
Dropping the exhaust manifold off (I could not get the lambda sensor out to open up the exhaust that way) improves the figure only very slightly to perhaps 58kPa so I think the catalyst is ok. On snap throttle there seems to be plenty of life in the exhaust, it doesn't seem restricted.
Sorry I have not done a 4-gas yet it's planned for the morning.
My first thoughts are that the valve timing is late, either skipped a tooth or opened up keyway on the crank or similar, or possibly late ignition timing but I'm not sure how that could happen on this engine.
Am I missing something obvious?
Shaun

Evening Shaun,

Whenever I get a similar problem and think its a blocked exhaust/cat I cannot be asked to drop the exhaust manifold or extract the HO2 sensor but rig up a vacuum guage and watch the readings from idle to near WOT. 4 gas readings would be good....yum

Regards

Pete M

Hi Pete, thanks for the reply.
Gas analysis results as follows:-
Fan off
O2 .39%
CO2 13.5%
HC 93ppm
CO 0.01%
Lambda 1.020
Fan running
O2 0.05%
CO2 13.8%
HC 269ppm
CO 0.00%
Lambda 0.993
The vacuum is poor at idle but raise the revs to a fast idle and they are very good.
Next job will be to check the timing belt, car is at 40475 miles so it's not done a great deal of work.
Shaun

Shaun

These can suffer with crank gear issues. Check for damage to the gear / crankshaft.

Steve

Hi Steve,
Thanks for that piece of info. I have already told the customer to go back to the referring garage and get his timing belt done as it's overdue on age if not mileage, I will make sure they pull the bottom pulley of the crank and check the keyway.
Regards Shaun

You can often see if crank keyway is damaged on these by using your old timing light, last one I saw was very retarded, but the garage ended up putting another engine in the car due to the damage caused.

Jim, Steve,
Thanks you were spot on, worn pulley and crankshaft. The garage put on a new pulley and warned the customer that a new crank was unlikely to be financially viable if the pulley should move again.
Horrible design with two flats instead of a key way, yuck! Usual rules apply though, it's only for location and not to do the driving so if the bolt stays tight enough it should be ok. The flange face on the crank seemed to be very small so that may be the root cause of the problem.
Didn't realise until I saw the pulley that it sends the ignition timing late as well.
Jim, what did you use as a reference for the timing light, are there marks on the flywheel?
Shaun.

Hi Shaun, it was a couple of years ago and I can't remember now but I may have just put my own marks on, the second hand car dealer I did the job for have had 2 like this, Jim.

There was a recall for this, but only involved replacement of the crank pulley bolt + washer.
But if finding the pulley worn then it was on warranty for replacement pulley, crankshaft and con rods.
I did quite a few of these while i was at the main dealer.

Hi Scott,
Thanks for that info.
Hopefully the customer will have no further problems.
I wonder how much effort the manufacturers put into these recalls? Seems like not very much to me.
It never ceases to amaze me how manufacturers beta test their product in the marketplace. What product testing do they do before releasing their next wonder vehicle? then as soon as they've got the bugs ironed out they come out with a new bag of worms and it all starts again.
Shaun