Alfa Romeo Forum banner

1 - 8 of 8 Posts

·
Registered
Joined
·
7 Posts
Discussion Starter · #1 ·
I have a well liked 156 JTS which has run very nicely for 72K but now the engine runs lumpily at tickover (sounds over rich) and has a flat spot at around 3500RPM yet cruises fine at 70-80mph, quiet and smooth as usual. Power is down a bit but fuel consumption is as good as ever with 420-440 miles on a tank
I've had the cam belt changed and a lamba sensor replaced which was causing a motor control system failure message. Now there are no messages and three computer checks reveal no faults. I have substituted another MAF sensor -no difference. Plugs were changed at 60K.Throttle body cleaned by local mechanic -unchanged.
Could this be a connector problem? Where should I look next? Should the plugs be changed? Are there sensors which malfunction without giving error messages? I need a systematic plan of things to try and need to pick the brains of those who know this rather nice engine well.
Oh, and this my opening post, so Hello
 

·
Registered
Joined
·
3,681 Posts
did the problem first occur before or after the belt change? if it was after then i would have the timing checked. if the timing was slightly out then it causes power loss and a lumpy tickover.
 

·
Registered
Joined
·
7 Posts
Discussion Starter · #3 ·
Thanks. The problem occurred after the timing belt was changed by Lyles who you may know as they're in Newcastle. The alternator drive belt pulley fragmented shortly after and was replaced. There was engine vibration for a while ? balancing incorrect and it had to be re-adjusted. I presume Lyles will have go the timing right. Then I had a Lambda sensor replaced.
At tickover when cold it, chugs like a car with the choke pulled out too far. There is a misfire at 1500-2000 and a flat spot at 3750. Its worse when cold and rather variable when hot. When you blip the throttle the revs rise but when they fall, again, it chugs. Several people have suggested changing the plugs; maybe I should before tinkering with anything else? But it sounds more like a fuel/air mixture problem to me. Any thoughts?
 

·
Banned
Joined
·
4,522 Posts
Power is down a bit but fuel consumption is as good as ever with 420-440 miles on a tank
thats a lot of miles for a tank! i just got 300 out of mine.
 

·
Registered
Joined
·
7 Posts
Discussion Starter · #5 ·
Its down to two things -almost all my miles are steady state a-road/dual carriageway driving; and I use high octane petrol which gives me at least 10% more mpg. In the summer, I see 420-440 miles per tank; in the winter 400-420. JTS seems very fuel efficient at cruise; nearly as good as a diesel. Less torque but more refined and with a nice appetite for revs.
Just wish it would idle smoothly like it used to.
 

·
Registered
Joined
·
3,681 Posts
your symptoms still sound a lot like a timing problem to me. i should know i've got timing wrong so many times in the past :D

i'd do a quick compression test to find out.
 

·
Registered
Joined
·
7 Posts
Discussion Starter · #7 ·
Thanks jug, like the red leather interior, by the way. In fact, having browsed the forum, I decided to do an an ECU reset.This has made a big difference -idles smoothly when warm, pulls smoothly from low revs, and performance vastly better. A little lumpy when cold but not really a problem. The compression test was OK and I also replaced the plugs. I may decide to do this anually as it made such a difference.
 
1 - 8 of 8 Posts
Top