car stalls while driving - NOT hall sensor

[Brian C]

Lately I've had this problem where my '88 Volvo 740 (non turbo 8valve) stalls while I'm driving. The first time it happened I was on the highway going about 55 and all the sudden my tach drops to almost 0 and jumped back up to around 3k then 5 minutes later the car died altogether.

I let it sit 15-20 minutes and it started up like nothing had ever happened and I went home. It did this several times and a few times in town in traffic (and to my horror my emergency flashers are currently not working so driving my car is not an option right now ).

First I looked here and found that my symptoms almost exactly matched the hall sensor problem that a few ppl seemed to have here. So, I got a distributor pretty cheap from a volvo mechanic I knew and changed it. This had no effect whatsoever.

So, I thought maybe it's a fuel problem. Vapor lock...(probably not in january but what the hell)? So, I put a bottle of HEET in with the next tank of gas I got and it seemed to completely cure the problem! I drove it for about 250 miles (or about one full tank). I tried filling up and adding HEET again and my car ran pretty well for awhile.

Now, however it will sometimes die if I just let it idle for 5 minutes and the other day it died before I got halfway out of my apartment's parking lot...

So maybe it running well with HEET was just a coincidence?

This is very frustrating. Any ideas?

[Guest]

fuel injected cars do not vaporlock. Try ign module on drivers front fender or fuel pump relay.

[85 760 turbo]

i had the 760turbo w/stalling problems caused by the hall sensor.

your problem does sound like the ignition module(ignition amplifier),or fuel pump relay. my ign. amp. is mounted inside the drivers side fender wall, 'behind the battery, beside the ballast resistor;2in.x2in. w/clip you push in to 'unplug' it. my fuel pump relay is on the relay panel behind the ashtray assembly, left middle plug on panel board. mine is an '85 760t w/ b230ft 4cyl. 2.3L by the way.

from what i've learned over the past year, the ign. module will cause it to stall if bad and you would have the erratic idle as you do. the hall sensor , when bad, causes the tach. to drop to zero immediatly, car dies, and the tach doesn't move while trying to start, and the needle wouldn't be 'jumping" before it died, mine never did.

there are other components that would cause stalling and/or erratic idle. the air mass meter(plugs into air filter housing), pressure regulator, fuel pump itself. i just started with the small stuff and kept going till it worked, with the distributor (w/ hall sensor of course) being the last.

GOOD LUCK!

[LaRy]

Keep looking at the ignition. I have the same experience as "760 turbo". If you have an ignition module made by Bosch, you should be happy that it has survived so long. It should have been dead for at least 10 years. It had some problems.
Back to the problem. If the tach is dropping while the engine is still rotating (because you have it in gear and the car is still moving), you have an ignition problem. Tach is connected straight to ignition coil. That means no rpm on tach = no ignition. Check also all connections and especially the grounding. Close to the ignition module you will find a grounding bar. Loosen it, clean it by a steel brush, put it back. Clean the flat connectors, especially the one going to the igniton module. Check that it has a tight connection!

[yosef7]

Brian, I have the same trouble now with my 87 740 gle. What was your final solution? I could sure use the help.

[brian c]

Yosef7- I got a message from you about the 87 gle. Oddly enough I didn't make the original post here .I see it was back in 06!! Must have been another brian c in the forum at that time.

however....I did have an 87 this past year with similar trouble. the car would die and not start back up. But then after a while It would start again. After much fiddling around I decided it was a fuel issue and checked the fuel pump. It was fine. I checked the filter. It was good too. I checked the fuse in the fuse box next to the drivers door it was fine.I replaced the fuel relay under the dashboard (passenger side i think). Still no start. finally we called the volvo shop to have it towwed in. He asked if i had tried replacing the fuel FUSE. I thought he meant the relay or the fuel fuse in the standard fuse box next to the drivers door but it turns out there is another fuse under the hood that feeds the fuel system! That was it! I put a new fuse in and presto! it somehow had worked intermittently. Corroded I guess. Anyhow, after a day of searching and crawling under the car and standing on my head under the dashboard ...all it was was this stupid fuse under the hood which the owners manual doesn't mention nor does any other research I did that day online! I can't recall now exactly where under the hood it is. Got rid of the car a while ago. but look into it.

[billofdurham]

The fuse mentioned is not fitted to the 740 but it is fitted to the 240.

One of the items that can cause this problem on the 740 is the Radio Suppression relay. This relay is badly named as its task is to provide power to the injectors whilst blocking any interference to the radio from the injectors.
On the '87 740 this relay is mounted on the coolant reservoir strap. It is the same type of relay as the cooling fan relay so you can interchange them to test if one or the other is not working.

Bill.

[prb00a]

Has exact same stalling issue and constant Check Engine light. OBCII Computer read Mass Air Flow Sensor at 0.04. It had same reading even after disconnecting MAF Sensor from wiring harness. Installed 're-manufactured' MAF Sensor and all problems were immediately resolved. At idle, MAF sensor reads 0.48 with reading increasing to 9.8 while under moderate/heavy throttle. Check Engine display is no longer lit.