Volvo 740 erratic idle

Hi Everyone:

The Machine:
1990 Volvo 740 GLT 16v 2.3l
4 speed + overdrive (ie stick shift)
Estate
193k miles, well looked after, used more-or-less daily on a variety of
short (10 min) and long (1 hour+) runs.


The Symptoms:
- On a cold start it is quite erratic when idling - will go between
~500rpm and ~900rpm.
- Initial accelleration from cold start is not smooth, but after a
minute or so accelleration is normal and smooth, although idling is
still erratic as above.
- Having been driven for about five minutes idle is less erratic, though
still wobbles between ~800rpm and ~900rpm.

Someone pointed out that it could be an air leak somewhere. Do you think
that this is feasible, and would it manifest itself anywhere else (eg at
the air filter?)

Many thanks for any replies received,

Andrew

 

Yeah it sounds like classic symptoms of a vacuum leak, look for any cracked
or disconnected hoses, and carefully inspect the accordian hose between the
AMM and the throttle body.

 

Check your distributer cap. Oil can get inside from the shaft seal
and cause poor performance.

 

A typical cause of cold idle problems is a dirty throttle body. When
cleaning it, pay particular attention to the passage at the bottom that goes
to the idle adjust knurled screw. Be sure to start with a nearly full can of
carb cleaner, because it takes most of a can to clean all the goo out.

Mike

 

Without actually having done anything, the car now refuses to start when
hot, yet starts first time from cold...any further thoughts anyone?

Cheers,

A

 

Without actually having done anything, the car now refuses to start when
hot, yet starts first time from cold...any further thoughts anyone?

Cheers,

A

 

Without actually having done anything, the car now refuses to start when
hot, yet starts first time from cold...any further thoughts anyone?

Cheers,

A

 

First try just one press of the send key. Next look on the Brickboard Forum
FAQs.

All the best, Peter.

700/900/90 Register Keeper,
Volvo Owners Club (UK).

 

Check the coolant temperature sensor, not the one for the guage but for the
injection, as well as the wiring to it.

 

Sorry, I reconfigured my SMTP server and it threw a bit of a wobbly...
Thanks for the tip about the Forum.

A

 

Hi A

JS, JT and MP have certainly hit the obvious suspects for your problem. We
have a 1989 740 gl auto 2 ltr with 130,000 miles and believe it or not have
been through the same as you more than once but with different solutions.

May I add to the list firstly, hardening of the fuel injector seals. These
do harden over time and need replacing. To check get a can of WD40 and
liberally spray around the base of the injectors where the injectors go into
the manifold. If you tickover picks up and suddenly becomes more consistant
then there you go. A couple of quids for replacement seals and it takes 5
mns per injector for an amateur to replace.

Secondly, over the years I also had a prob with the inlet manifold gasket
leaking which caused the same symptoms. In my case the gasket was ok cos
all I did was tighten the manifold nuts a smidgeon and all was well again.

Whilst posting, given the mileage of your 740 if you have not had the
distributor cap, HT leads (incl the king lead which is known to short out)
and rotor arm replaced - I am assuming here that your 1990 model is similar
to my Sept 89 which has the distributor at the bulkhead end of the engine -
then you might do well to invest in replacements. At 120,000 miles our tick
over had slowly become annoyingly erratic even though the car still went and
none of the other remedys seemed to work. When I rempved the Distributor
cap the contact posts and the rotor arm were so warn I was amazed the car
went at all. Replaced and all was well again. For some reason replacing
these parts does not feature on Volvo's service schedules anywhere but
clearly at some stage mechanical parts do wear out.

Hope you get it sorted. Our 740 still sounds and runs like it did on day
one.

Regards

Andy