I recently purchased a 1991 740. It has an idle problem that the local Volvo mechanic cannot figure out. Anyone out there with some ideas? The idle fluctuates regularly. When in park it will start at about 700-800 rpm and then about every 5 to 10 seconds it will suddenly drop to about 200-300 rpm, then suddenly jump to about 1200 then settle back to 700-800 rpm. It does this only in park. When in gear at idle the tach wavers a little but does not make the big jumps. The engine often stalls when the rpm drops. On a couple occasions it would not re-start. Also, on a couple occasions the engine would not start initially at all. In these no-start situations the car would suddenly re-start ok when left sitting for a day or two. When the car is running in gear on the road it seems to perform normally.</P>


When the engine will not start, there is a smell of fuel after aperiod of cranking so the fuel delivery seems there. Also, on a couple of occasions when it won't start, in cranking it it would fire very breifly just as the key was being turned OFF. Could this be a problem with the ignition switch? As there are (apparently) no aftermarket repair books on this model I cannot figure out the starter and coil wiring. Maybe thefluctuating idle and the no-start problems are seperate? </P>


The local Volvo mechanic tried swapping out the computer boxes, the air temp sensor, the air control valve. The vacumn hoses all appear good. The throttle body gasket is new. The knock sensor is new. The sparkplugs, wires etc. are recent and appear good. There are no codes on the diagnostic box. The mechanic also checked the fuel pressure (apparently at the proper psi). The car seems to run fine on the road, however, I am hesitant to drive it anywhere for fear it may do the no-start thing again. </P>


Any thoughts or suggestions?</P>


Peter Hunt (alias Admrudder)</P>


PS - I have a 1982 240 that runs terrific - really reliable (CIS system), and is generally easy to work on. I thought the 740 would be a nice upgrade in style but I'm not sure on the reliability. Any thoughts on 740 (1991 Regina system) reliability? Are there any repair manuals available anywhere?</P>


</P>

 

Could be the idle air control valve that's full of gunk! I have a Haynes manual that diagnoses this as the cause of your idling problem.</P>


I have a 1991 940 SE 2.0 Turbo with EXACTLY the same problem. I am going to clean the idle air control valve on Saturday, and see if it solves the problem. I also have corroded fuel pipes which I will check aswell.</P>


I'll let you know how this goes, and e-mail me in the meantime if you have any other problems with ya motor!</P>


Cheers, Adam.</P>

 

Adam,</P>


Wow! that's interesting! 1st, you mention a Haynes manual. I have a Haynes for my 240 (1978 - 1993 but does not cover the 740 Regina system). I have heard two rumors - one that there is no (inexpensive) consumer manual for the 740 and two, that there is one but I cannot locate it.</P>


My 1st mechanic put another Idle air valve on (from another good running car apparently) and it did not do anything different. I have always suspectedthe idle air system is probably the problem but the valve appears to work fine (and was clean however I did not check the tube into the manifold). I disconnected the wires and re-wired it to a seperate 12v battery tomanually run it to see if the problem was in the wiring. However, I was surprised how much the valve apparently moves back and forth to control the idle. If I engaged it the engine would run right up to high rpm and if I stopped it the engine would die. If I rapidly clicked it on and off I could somewhat control the speed but not at all smoothly. So I know the valve works properly but there is still the suspicion that the wiring may be causing a loss (or intermitant loss) of signal (I don't trust Volvo wiring from having an old 240!). If I had a wiring diagram I could maybe trace it out but the wiring dissappears into the harness.</P>


Please let me know if cleaning solves your problem! (or what ever else you find with it!). Good Luck!</P>


Admrudder</P>


</P>

 

Hey mate!</P>


Well, funny that you mention the manual...I have a 740 Haynes Manual sitting in my front room!!! I think it covers various engine sizes, but not sure about the Regina. WHAT IS THE REGINA?? <IMG src=smileys/smiley16.gif border="0">It belongs to one of my flatmates, and i'll ask him if it's available for someone else to enjoy!</P>


Wow, seems like it can't be the idle control valve in that case! If you've replaced it and you know it works, then this may not work when I attempt it.</P>


Is the signal definately getting to the ECU from the idle control valve?</P>


Adam.</P>

 

I have a few ideas from the Haynes manual:</P>
<UL>
<LI>clogged air filter</LI>
<LI>vacuum leak at the inlet manifold (you've checked this)</LI>
<LI>spark plugs (could well be)</LI>
<LI>Incorrect valve clearance adjustment</LI>
<LI>uneven or low cylinder compressions</LI>
<LI>camshaft lobes worn</LI>
<LI>camshaft drivebelt incorrectly tensioned</LI>[/list]

Also, do you have an ECU warning light permanently on??</P>


Adam.</P>

 

Hi Adam,</P>


My Volvo mechanic said that the 1991 740 uses the "Regina" control system (as opposed to the LH-3.1 Jetronic system used on similar year 240's). He said that there is really no manual documentation on working on this system. I understand there was a Haynes manual that covered 740's up to 1988 but not later. Does your manual specifically cover 1991 740 cars?Does it mention anything about a "Regina" system? If it does, I would be very interested.</P>


I have checked some of the other things you mentioned here but not compression or valve clearance. I don't see how that would cause intermitant idle fluctuations or no-start conditions. I should do a compression check.</P>


There is no lights on and no codes in the diagnostic.</P>


Admrudder</P>

 

Ah, the Regina system! I read about it last night in my beloved Haynes manual, which i've been spending far too much time reading!</P>


I'll see if the 740 Haynes covers 1991 cars.</P>


Well, the big test comes for me tomorrow when I service my car to see if the idling problem disappears...nervous! I'll be replacing spark plugs, air filter, oil filter and oil. The latter won't matter with regards to the idling problem, but are certainly required. My good friend Graham who is helping me to service the car, studied a degree in Motorsport Engineering degree in Swansea, so he's pretty clued up. Hopefully, collectively, we'll come to an agreement over what it could be!</P>


Adam.</P>

 

The Haynes manual covers cars up to 1991.</P>


Hope this helps!</P>


Ads.</P>

 

I'd also recomend a full engine cleaning. I had tons of little problems with my 87 GLE, and i got it professionally cleaned, and it worked so ----&gt;o much better. Hopes this helps.

 

Hi Guys,</P>


Well, I finally bailed out. I got rid of the 740. Way too many problems and some that would not solve! I am now a believer in the true "unfixable Lemon" car! Not only the above mentioned problems, but since it got warm here a month ago, on hot days (over 80) the car would run until it got fully warmed up and then die - not to run again until it cooled off. That was it! I even got stuck trying to drive it to the charity donation center! But it is now only a tax write-off. I have to confess I went out and bought a Honda... I need reliability in getting to work. I still have the old faithful 1982 240 - that is reliability! Why do manufacturers have to always "improve" the product and make it more complex and less reliable? Only older Volvos for me!</P>


Admrudder</P>

 

I have a Regina 740 1990 and I wondered why there is not a mention of the alternator belt being loose? Sometimes I forget and the belt gets to wobbling and little loose and it seems to cut down on the amount energy coming from the alternator and sometimes will cause it to stall because of not getting enough voltage to rest of the components.