1998 V70 - Engine Runs Rough After Sitting (ECU replace,ent) Topic is solved

whirligig · Post by **whirligig** » 01 Oct 2014, 23:08

This past month I replaced a myriad of fuel related items on my 1998 V70 with over 180K miles. The fuel pump relay/controller failed and it was replaced with a Kaehler unit. Sometime later the fuel filter was replaced with a new Bosch because it was due. After this, I encountered rough running sometimes stalling if the car sits for more than one day. Subsequent starts for that day, the car will run fine like nothing happened. I then checked the fuel pump.

I conducted three pressure tests on the old fuel pump. The priming (i.e. turn the ignition key 3 times without starting) came out about 40 psi. The running pressure was 45 psi. But the fuel leak down test was showing a pressure loss from 38 psi to 27 psi in 36 minutes. So I replaced the old fuel pump with a Hella unit. It runs fine for the most part but I'm encountering the same stalling and rough running if the car sits for more than a day. I get an occasional stumble if it sits for 12 hours. I get stalling and rough running if it sits for more than a day. I have not done a leakdown test since installing the new pump but I suspect a leak somewhere. I just can't find it or smell it (yet). Is the rough running due to air in the lines? Could it be a leak around the injectors? Would a check valve work? Any clue?

By the way, this fuel system does not have a return line nor a pressure regulator.

Post by **rspi** » 01 Oct 2014, 23:23

Is the car turbo?

Sounds like a cold start issue which would point to the ECT.

whirligig · Post by **whirligig** » 02 Oct 2014, 13:19

Mortitia (my V70) is normally aspirated. There is no ECT on this car. It's a mechanical throttle. There is a throttle positioning sensor though.

I'm about to take her out for a drive just to make sure she starts tomorrow. Later on, I may get the Torque software and look at the fuel trim. The best thing I should do is crawl underneath and sniff for gasoline. I may have disturbed something in the EVAP/fuel system when I replaced the fuel filter.

Post by **erikv11** » 02 Oct 2014, 14:42

ECT = Engine Coolant Temp sensor

I agree with rspi, that's a good place to start.

whirligig · Post by **whirligig** » 03 Oct 2014, 12:50

rspi & erikv11, you may have hit the nail on the head. I replaced the ECT and thermostat this morning and the car appears to be running fine in this 100 degree heat. I did test the old ECT in a pot of heated water measuring water temperature and sensor resistance and it appears to look OK but I have no specs or curve to compare. Maybe the curve is off due to age.

I thank you both for steering me in the right direction. I had my acronyms mixed up between ECT and ETM. I also thought this was a fuel related problem due to recent failure of the fuel pump relay and an aging fuel pump.

whirligig · Post by **whirligig** » 09 Oct 2014, 15:46

The problem is still there. Replacing the ECT and thermostat did not fix it. The car sat all day yesterday. It started fine this morning. About a mile out at a stop light, it hesitated and stall. After restart, it would idle rough then stall. It became difficult to restart but when it started again with engine misfires and a the check engine light on with a bunch of P030x faults. After this rigmarole, the engine will eventually run smooth again. I just took a drive and all appears to be normal, hah!

Any clues? I have yet to replace the crank sensor and ignition coil, should I? I have not open up the EGR valve (if it has one) yet. Come Monday, I plan have it towed to my mechanic after it sits all Sunday.

Post by **abscate** » 09 Oct 2014, 22:54

What's the status of the ignition parts on this car...plugs wires cap rotor coil? How old are they?

Post by **rspi** » 10 Oct 2014, 02:40

Grrrr, I really dispise intermittent problems. A buddy had an issue like this and it turned out to be his fuel injector relay. If it starts to sputter, get a screw driver and pop it a few times.

Post by **E Showell** » 10 Oct 2014, 08:28

Make sure you check the battery cable to the starter -- in particular, the ground that bolts to the front subframe cross-member. I had a cable corroded completely through there and the cable appeared intact until you went and tugged on it. This can cause intermittent starting/stalling issues that can take quite a while to diagnose.

Post by **erikv11** » 10 Oct 2014, 08:33

rspi wrote:... A buddy had an issue like this and it turned out to be his fuel injector relay. If it starts to sputter, get a screw driver and pop it a few times.

What does that mean, "pop it," are you saying to whack on it with something heavy, or to somehow jumper the contacts with the screwdriver? Something else?

Definitely sounds electrical/electronic, something with poor conductivity that gets even worse when it heats up. Now to find it ...