stalling at low idle only 1991, 740 GL 164,000

Ron Richison · Post by **Ron Richison** » 13 Apr 2008, 18:14

when I said I checked the sensors, I was talking about the connections only.
Is it possible to pull that coolant temp sensor without pulling the mainfold off? you mentioned a new gasket??
I have had short bursts of ether all over every potential problem area. I have yet to get a reaction. I even wrap the bellows in saran wrap to help stop a leak if there was one.
the only positive reaction I have had since this witch hunt started was when I accidently sprayed carb cleaner on my injecter o rings. No change in idle smoothness until about 10 min. later, then it ran fine for about a half hour only then back to the same old crap.

Post by **jonesg** » 13 Apr 2008, 23:17

Yeh you can swap the coolant sensor without pulling the intake, I don't know how but others say they did it.
You'll need to pull the idle control motor and hoses out from underneath the intake. You'll need some teflon plumbing tape to seal the threads when installing, it doesn't need to be very tight, just a good seal like a sparkplug.

see the faq,

http://www.brickboard.com/FAQ/700-900/E ... CTFailures

what I did was buy everything under the intake and change it all at the same time, oil trap and hoses.

Pulling the manifold back isn't a big job in case you're wondering.

Ron Richison · Post by **Ron Richison** » 22 Apr 2008, 20:55

I'm still fighting this problem. since I wrote last I have replaced the ECT sensor and the manifold now has a new gasket. I also replaced the check valve on the main fuel pump.
I really have thoroghly checked for vacuum leaks in all the problem areas.

There's what apears to be some kind of sensor in the block, next to the oil filter. The wiring is full of oil, but appears fine when I unplug it. WHAT IS THIS? any idea?

How about timing? could it effect idle and not running performance?

I tested the TPS by jumping it. Unplugged and jumped and outside wire to the middle wire, no change.

How can I test internal wiring to these sensors?

I'm really hitting the wall here, I've done evrything suggested by you guys, parts guys and one local mechanic. I want to fix this thing but it's getting desperate here.

Post by **jonesg** » 23 Apr 2008, 05:47

Try reading this.
http://www.brickboard.com/FAQ/700-900/E ... mptoms.htm

Any codes yet?

From your original post,
"Car starts, (rough sometimes when cold) then warms up, drives ok for 4-5 minutes. At full speed, car runs GREAT. Responsive, no hesitations or misfires of any kind. When the car comes to a stop, at idle, it feels and sounds like it's "missing" and will eventually stall. I have replaced plugs, wires, cleaned throttle body, replaced flame trap, air idle control valve and mass air sensor. "

Has there been any change?

When its running rough, thats the time to pinpoint the problem, start spraying ether in the vac line from the FPR and see if the idle smoothens out, if so then its fuel delivery.
Probably pump or injector relay overheating.

If the there doesn't do anything start pulling plug wires til it has no effect.
You can also try unplugging each injector plug to turn off a cylinder.

The idea is to isolate the problem cylinder and its a lot easier to do when the car is running rough.

If its a universal problem that can only be a few things, I would take another look at the idle motor, remove and really drown it w/ cleaner.

Ron Richison · Post by **Ron Richison** » 23 Apr 2008, 17:33

ok, I pulled each plug and inspected and checked gaps, all good. pulled each wire one at a time while enigine was stumbling. each time, each cylinder reacted severely. I pulled each plug from each injector one at a time. each injector reacted, but not as dramatically.
the air idle control valve is new (Bosch) from Volvo.
now, the ether in the vacuum line from the pressure regulater seemed to have a short lived positive reaction (remember, I installed a new fuel pump reg, filter and check valve.
Now, should I be on the hunt for a bad relay? I have the panel out and the relays exposed but can't tell which is which. Fuses are marked, relays are not. I'll check brickboard.
You mentioned overheating, can I bypass these relays? I did that once on a chevy truck to verify my fuel pump was ok. would it work on the Volvo?
Thanks for all the help!
Ron

Post by **jonesg** » 23 Apr 2008, 18:08

" pulled each wire one at a time while enigine was stumbling. each time, each cylinder reacted severely. I pulled each plug from each injector one at a time. each injector reacted, but not as dramatically. "

To me this looks like ignition related because all the cylinders are rough running.
How healthy is the spark?

Post by **jonesg** » 23 Apr 2008, 20:24

relay locations

http://www.brickboard.com/FAQ/700-900/E ... yLocations

Ron Richison · Post by **Ron Richison** » 26 Apr 2008, 22:14

spark is healthy. I replaced both the injector and fuel pump relays, still no fix. ignition related? what next?
I thought I might have had a good car here. Volvos have a great reputation but this one is beyond me.
I'm seriously thinking of scrapping this one. I've been on 3 web sites, talked to 3 parts guys (one from the dealership) one guy from the Volvo proving grounds in Phoenix and 2 local mechanics. There are as many diagnosis as there are peolpe! I've covered everything that's been suggested and NOTHING different. Ignition now?
I'm $2000 into a $1500 blue book car and it runs bad.
Thanks for your patience but I think this Volvo is a lemon.
any suggestions on how to part this thing out to recoup some of my losses?

Post by **jonesg** » 27 Apr 2008, 08:59

"I've been on 3 web sites, talked to 3 parts guys (one from the dealership) one guy from the Volvo proving grounds in Phoenix and 2 local mechanics. There are as many diagnosis as there are peolpe! "

I know its tempting but it doesn't work to diagnose by committee .

By talking to too many people you'll get a lot of ideas but no logical approach. "It could be this and it could be that" isn't a logical approach.
Possibilities are not a diagnosis'

Your car needs compression, fuel and spark.
Fuel mix can be affected by a couple of computer controlled sensors, the AMM , O2 , coolant sensor too.
Its simple enough but figuring out whether its getting each if those in the required set amount is tricky if you don't have certain tools such as fuel pressure guage.

lacking a pressure guage limits you to shooting in the dark with hunches, I went through that and by elimination AND a logical approach that didn't include a multitude of opinions I was able to pinpoint the problem to fuel pump.

I got around the lack of fuel pressure guage by using ether to start and keep it running, that meant the spark was good enough , testing the injectors showed they weren't the problem so that left, by elimination, the fuel delivery. Fuel filter change did nothing so that only left the pump, which although it pumped, didn't have enough pressure to atomize at the injectors.

Ron Richison · Post by **Ron Richison** » 28 Apr 2008, 20:47

ok, that makes sense.
as you may be able to tell, I'm frustrated. (my 2000 Chevy truck is also down) so now, unlike 3 weeks ago, I'm under the gun. I have 4 kids in 3 different schools and 2 adults that need to get to work.
Without a pressure gauge, how would I proceed on the fuel delivery side?
summary of what I've done: replaced orings in injectors, fuel pressure regulator with both fuel and vacuum line, fuel filter, check valve on main pump. I can hear and feel both pumps run (maybe not well, I don't know)
I have done nothing regarding the pump in the tank other than feel and hear it run. Should I pull it and check to sock filter? How about the fuel pump relay?
What now then would be the logical approach? I will be going with you exclusively from now on.
Ron