If anyone can help me solve this problem it be greatly appreciated.
I'm new to volvo and have a 1990 740 GL 291,565 miles with the Regina system.

Starts up idles fine, then after about 6 seconds, in park, it starts becoming very unstable. Sometimes seems like might be ok, so you go to drive and has horrible intermitant acceleration, as if you took your foot off the pedal completely for 1.5 seconds then smashed it again over and over.

About month ago, when just started randomly dying most of the time at slowing down to a stop, but couple times at 40mph and 60mph- just stalls. But always restarts after about 30seconds. Next it started having this idle problem, but then would stabilize and I'd drive off and it would have the acceleration problem but it would eventually go away.

Now it is really undriveable, the idle is intermintantly jumping around between 500-1500rpms and if you try and drive, if does stabilize, it has jerky, hestitant, intermitant acceleration - usually will die at some point.

I had given it a tune up thinking just needed one, bought used with 289000miles
new timing belt, water pump, tensioner pulley
new fuel filter and air filter
new distributor cap, rotor and sparks plugs - wires seem good
cleaned out the TB by removing it and replaced flame trap

Drove good to work - 10miles, but barely made it home (jerky acceleration problem)and died as i pulled into the drive way.

Question 1:
fuel related problem?, but not sure what - if the regulator or pump or relay were bad,the carwouldn'trestart would it?

Question 2:
the Power Stage/coil pack(regina) - if that was faulty, the car wouldn't restart would it b/c the coil is part of the power stage?

Qustion 3:
Could be vacuum line leak?
I was wondering if anyone could tell me what lines these are in the pictures in the links below- thanks in advance- I've circled the items in red on the pictures
[ http://i60.photobucket.com/albums/h1...a/whatisit.jpg]
[ http://i60.photobucket.com/albums/h1...vacuumline.jpg]

Thank you very much in advance.

 

At first I wanted to say sparkplugs, but you changed them.

Now I suspect vaccume leaks.

Purchase a spray can of starting fluid, and while the car is running spray the fluid where you think there may be a leak.

The rpm's should climb as the starter fluid is pulled in by the leak.

Sorry that I can not help on the hose id's.

Let us know what you find as the answer.

John

 

So far, here is how things are going:

1. I looked for vacuum leaks, but we are fairly certain there are none.
-also the car seemed to be idle fine now again.....
-however, if you rev it up in park to like 1500, it kinda sticks for a second at 1200 then 1000 then goes back to 750, but before use to go up and back down with no lag in between.

2. we unplugged the MAP sensor on the air intake from the airfilter box and started thecar
- it actually ran fine, we plugged it back in and pulled the fuse #1 and put it back in then started it up stilled seemed fine
- now I've driven probably 10+ miles and haven't had any trouble, except that hiccup of the rpms coming down.

Does this tell anyone what might be the problem here? should I be looking into a relay, sensor, or something like a faulty pump? for it to go from stalling - horrible idle and stalling - to fine again

 

Would anyone know about the Radio suppression relay, before it goes bad to the point of not restarting when hot, can it make the car act up alot. Also, are there two of these? [ http://www.fcpgroton.com/product-exe...nd_Cooling_Fan]
says 2 per car, one under my hood on the passenger side above the wheel looks new the one next to it looks original.

Thanks in advance

 

Have you checked the Mass Air Flow sensor or the Throttle Position Sensor (might be called Idle Control Sensor...it's been awhile since I delved into a volvo) could also be the Crank Position Sensor?

 

I'm not sure what I'm looking or how to test it for certain. We unplugged the MAP sensor on the air intake from the airfilter box and started thecar and it actually ran fine, we plugged it back in and pulled the fuse #1 and put it back in then started it up stilled seemed fine. I drove about 10 miles since then.

And today I drove about 25 miles total just fine, except had two idle surges. One after start up about a minute passed and surged up for just a second. Then at a stop light, it dropped to 500rpms and surged up to 1200 about.

Idle Control Sensor - I'm not sure how I'd know if that's bad - the idle normally is at 750rpms
Also on here if you scroll up slightly shows some abbreviations.[ http://www.volvoclub.org.uk/faq/Engi...#BoschvsRegina]
Is there sure ways to know if things are good or bad such as:



IAC

Idle Air Control solenoid valve
B/c atleast on like GM cars when stuff like coils went bad, there is no state in between, it is bad and the car doesn't run or it is fine.

From the sounds of it, relays can act up, before they go completely bad.

Any help will be appreciated. THanks