1. Home
  2. Car Maintenance
  3. misfiring/stalling Volvo 740 (1989 2.0)

misfiring/stalling Volvo 740 (1989 2.0)

I've just bought this 1989 740 Estate. Lovely drive along the motorway but every so often the engine would backfire and was totally unresponsive. I changed the spark plugs and the HT leads but it seems to be getting worse so much so that the moment I take my foot of the accelerator, the engine stalls. I thought it might be the petrol pump relay, swapped that with a known working spare that I had, but still the same. Has anyone got any ideas what else I should be looking at? I haven't changed the distributor cap or the rotor arm. Am I right in thinking that there is a sensor there which regulates the engine? Thanks very much in advance, JD

Reply to
jd
Loading thread data ...

My 1990 940 used to have similar symptoms. It was cured by removing and cleaning the MAF sensor and throtle body assembly. I assume the 740 is the same. They get gunged up over time.

Alan.

Reply to
Alan

There are two electrical devices right on top of the engine. One of them has a black rubber pipe about 3/4 of an inch wide on it with no clip to hold it in place. If it comes adrift the engine exhibits exactly the symptoms you describe but it can then reseat itself enough to keep the engine running, only to lift off again a bit further down the road.

If you find it is this pipe causing the problem get a jubilee clip on it and it will never happen again.

Si

Reply to
Mungo "Two Sheds" Toadfoot

Hi Si,

Yes, that was the first thing that I checked as it happened on a 240 that I had. All secure... Thanks anyway, JD

Reply to
jd

Bugger.

Oh well, don't know then, sorry.

Si

Reply to
Mungo "Two Sheds" Toadfoot

I assume this is the sort with the pain in the arse distributor on the back of the engine? if so:

They suffer from a bad connection onto the distributor, this is quite frequent, as is actual distrib failure, the caps do get gungy, but my first bet will be the connector, it is a sort of three blade affair inside. Clean it till both halves are sparkly clean, spray with wd40 and reassemble. it will probably work fine. Getting the distrib off the engine is awkward, but probably easiest in the long run for cleaning it all up.

mrcheerful

Reply to
mrcheerful

Well, bang goes a lazy Saturday doing nothing! Thanks Mr Cheerful - will give it a go and report back!

JD

Reply to
jd

"jd" wrote in news:1158758438.411002.325290 @m7g2000cwm.googlegroups.com:

The wiring to the Hall sensor tends to break up/come unsoldered. It's located in the distributer at the bottom when fitted. A small soldering iron will sort it.

Reply to
Tunku

Indeed - I took the distributor off today and saw that the connections to the Hall sensor were completely rotten. It is so gunged up that there is next to nothing to solder it to so here's a question - can I simply by-pass the connection box and crimp the wires using male/female electric connectors?

JD

Reply to
jd

Yes, but you would be even better to solder them and have a dedicated plug, but anything is probably better than nothing.

Bear in mind that the wires are tiny and won't take any mechanical strain.

mrcheerful

Reply to
mrcheerful

alt.autos.volvo is much more clueful than this ng.

The 740 (many variants) suffers from three common fault areas:fuel pump relay (it's dead) distributor (misfire at high speeds, short cutouts, or death) or inlet and air measuring (poor starting and idling).The older engine (240) has a bad air leak when a tiny hidden air hose spilts. 740s need their airflow sensor innards given a spit and polish. If you have the "bath plug" airflow sensor, then check it's centralised correctly.

It's all easy, and like all Volvos they all fail in just the same ways. You very rarely get anything "weird".

Reply to
dingbat

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.