244 1985 backfire when cold

85 240 dl · Post by **85 240 dl** » 17 Feb 2009, 12:45

I have a 85 244 dl that my daughter drives, it has 120000 miles on it just recently it started backfiring badly when driven from cold, once it warms up it runs like a dream. I have checked it out and found the air inlet hose split replaced it and all vacuum hoses all to no avail, I have looked for vacuum leaks using wd-40 but cannot find any, the reason I was thinking vacuum was that at idle when warm it almost stalls but usually catches itself and keeps running, any ideas would be very helpful. it has jetronic 2.2 fuel injection and all components check out good.
thanks B.

Post by **billofdurham** » 17 Feb 2009, 15:46

Welcome to Matthew's Volvo Site.

One of the causes of poor idle on this system is the throttle valve either loose or incorrectly adjusted. Also check all of the earth (ground) leads around the manifold area.

Bill.

85 240 dl · Post by **85 240 dl** » 18 Feb 2009, 07:35

I have checked all the grounds even cleaned and reconnected, my main concern is with the backfire and missing when cold it is dangerous for my daughter to drive, what can make it run so badly when cold and run so well when it warms a little the temp needle is not even in the operating range on the gauge and it is running like new, any help with this problem would be appreciated, I am not a trained mechanic but have done my own repairs and rebuilds all my life and this is a mystery to me.
thanks Bryan.

Post by **billofdurham** » 18 Feb 2009, 15:43

How long is it since the plugs, plug leads, air filter and fuel filter were replaced? When this backfire/miss occurs what is the outside temperature and is the air moist or dry?

Bill.

85 240 dl · Post by **85 240 dl** » 18 Feb 2009, 17:59

I replaced plug leads, air filter, fuel filter less than six months ago, this car sat for two years before I obtained it so I went through everything, as for the weather and temp it varies a lot here in Texas does not seem to matter whether it is warm or cold if the car has not run it backfires and misses untill it gets warm (just a few minutes) once it is warm it runs like a dream.
I know this is not the place but I was from england moved here to Texas in 1980, family still lives in the Liverpool area, so cheers Bill thanks for the advice, (still miss a good pint lol)

Post by **billofdurham** » 19 Feb 2009, 12:51

Have you checked for an intake manifold leak which could close up as the manifold warms?

Bill.

85 240 dl · Post by **85 240 dl** » 27 Feb 2009, 14:40

ok now I have a new problem, engine starts and idles fine as soon as you touch the accelerator it falls on its face and dies, I can get it to run to about 50 mph if I baby it and feather the throttle, I don't know what fuel pressure is when it is running but the pump will put out 85 psi, fuel pressure regulator is new as are plugs leads, air filter, fuel filter, plugs distributer cap and rotor all components of the fuel injection system check out fine i.e. coolant temp sensor mass air flow sensor oxygen sensor they all check out as good I am out of ideas I need some help please I am at a loss here thanks ....Bryan

85 240 dl · Post by **85 240 dl** » 28 Feb 2009, 11:41

went back and checked out all components again and found that the heated wire has a resistence of 2.9 ohms all the literature that I have tells me it should be 3.5 to 4.0 ohms would this be enough to have an effect, I will probably get a new amm

Post by **billofdurham** » 01 Mar 2009, 12:22

Before buying a new AMM there are some more checks you can do.

AMM 240 1985.pdf: (492.18 KiB) Downloaded 282 times

Bill.

85 240 dl · Post by **85 240 dl** » 01 Mar 2009, 18:30

thanks for the info Bill I do appreciate it, I have done all the checks for the amm and everything I can find out about it tells me that if the heated wire resistance is not right that I need to change it, I ordered one yesterday and hope it will arrive tomorrow, I will let you know what happens. thanks again for your reply it is what makes this site work ....Bryan