98 V70 T5 Crap Idle/Performance after engine is warmed up

850n00b · Post by **850n00b** » 30 Dec 2014, 18:11

Good Evening! I'm about at my wits end and close to sending in my wagon to the local repair shop. I haven't touched a repair in years and this issue is beginning to rethink my sanity.

Here's the issue:

Once the car's engine is fully up to temp the idle starts dropping, chugging, looping, whatever you want to call it. It's getting fuel just absolutely dumped. It performs like it's running on 4 cylinders. It smokes, smells like unburnt fuel/sulfur. O2 voltage is north of .800v according to my OBD2 scanners live data when it's chugging, then fuel trim jumps to -25%.

Before it's fully up to temp and not in closed loop mode, the car runs beautifully as it should. Great power, great idle, everything as it should. As soon as it enters into closed loop, is when the issues start happening.

Here are my engine mods:

ARD Green Tune
Blue injectors
AEM Dry Filter
Silicone IC Hoses
SAS Removal

Maintenance Done:

PCV System
Front O2 Sensor
New Iridium Plugs
New Wires
New Cap, Rotor
Cleaned IAC

Other Mods unrelated to motor:

Koni FSD Struts
IPD Blue springs
Volans

Car ran perfectly before/after mods and maintenance. Only shot gunned ignition parts, thinking this was the issue. It wasn't. I have a 95 850 that I was swapping parts to see if that fixed (MAF, Coil), and that didn't solve it either.

I thought maybe it was a bad fuel injector, as I had a plug that was absolutely fuel fouled. So I picked up a set of blues and then drove to ARD to have the ECU retuned. It has the stock whites previously.

Only other thing that is coming up is possible CT Sensor. I purchased one from AZ, but is has the wrong plug, I think for the 99-00 models. Have to exchange it and see if they have the correct one. I checked my torque app and the live data on my OBD2 reader, and it's reporting temp correctly, so I'm not sure if that is the problem.

I've posted this problem to other forums and I'm getting tons of views, but nothing more than check your coil or injectors.

Much appreciated in advance for any directions you guys have. This site helped me a ton when I lurked after getting my 850 in the summer of '13

Post by **jblackburn** » 31 Dec 2014, 07:42

Yes, I think the coolant temp sensor might be a possibility...but if it's reporting the correct temp, then who knows.

Have you double-checked and tugged on all intercooler air hoses? I've had em blow off before even though they looked still connected and the car can hardly even run.

Post by **Ozark Lee** » 31 Dec 2014, 10:05

I'm not sure which fuel pressure regulator system you have but if it is the type with the vacuum line that controls it the regulator diaphragm can rupture and cause raw fuel to get sucked into the intake manifold through the vacuum tree. That isn't temperature dependent but it may be a slow leak that takes time to get flowing.

Pull the vacuum line off of the regulator and see if there is any fuel in the line. It should be bone dry.

...Lee

850n00b · Post by **850n00b** » 31 Dec 2014, 11:27

Ozark Lee wrote:I'm not sure which fuel pressure regulator system you have but if it is the type with the vacuum line that controls it the regulator diaphragm can rupture and cause raw fuel to get sucked into the intake manifold through the vacuum tree. That isn't temperature dependent but it may be a slow leak that takes time to get flowing.

Pull the vacuum line off of the regulator and see if there is any fuel in the line. It should be bone dry.

...Lee

I checked when I swapped injectors and it was dry. I'll let it idle again this morning and see if that's still the case. The regulator is housed between injectors 1 & 2 with an S hard line to the vacuum nipple on the #5 side of the manifold.

jblackburn wrote:Yes, I think the coolant temp sensor might be a possibility...but if it's reporting the correct temp, then who knows.

Have you double-checked and tugged on all intercooler air hoses? I've had em blow off before even though they looked still connected and the car can hardly even run.

How many coolant sensors are there on this car? All the parts places are quoting me two different sensors. The one that I know of, apparently is the gauge sensor, with the two bullet male connector at the tstat housing. The other one they have has two a female connector end...Haven't been able to locate that one anywhere.

Post by **jblackburn** » 31 Dec 2014, 11:33

How many coolant sensors are there on this car? All the parts places are quoting me two different sensors. The one that I know of, apparently is the gauge sensor, with the two bullet male connector at the tstat housing. The other one they have has two a female connector end...Haven't been able to locate that one anywhere.

I am only aware of the one at the thermostat.

850n00b · Post by **850n00b** » 31 Dec 2014, 14:52

Ozark Lee wrote:I'm not sure which fuel pressure regulator system you have but if it is the type with the vacuum line that controls it the regulator diaphragm can rupture and cause raw fuel to get sucked into the intake manifold through the vacuum tree. That isn't temperature dependent but it may be a slow leak that takes time to get flowing.

Pull the vacuum line off of the regulator and see if there is any fuel in the line. It should be bone dry.

...Lee

Bone dry. Plugged it the manifold side up so motor still ran, and let it warm up and nothing coming out of regulator line. So that's a good thing.

Post by **JimBee** » 31 Dec 2014, 15:13

I have a '96 850 that was behaving that way. The coolant temp sensor in the t-stat housing was the main cause, though I think the MAF was a little flaky, too (I swapped it for a used one), and a couple of the vacuum hoses were slightly porous. Changing out the ECT sensor made a big improvement. The engine ran even better when I changed the front O2 sensor.

screwdriver · Post by **screwdriver** » 31 Dec 2014, 15:23

I cant believe there is no check engine light/mil codes. If you have access to a cheap obdII scanner you can check all your values these are fairly cheap on ebay and are priceless in your tool box. I picked mine up for $40. runs the real time data.

850n00b · Post by **850n00b** » 31 Dec 2014, 16:03

screwdriver wrote:I cant believe there is no check engine light/mil codes. If you have access to a cheap obdII scanner you can check all your values these are fairly cheap on ebay and are priceless in your tool box. I picked mine up for $40. runs the real time data.

I have bluetooth obd2 with torque app on my phone. Everything looks normal. That's the thing that is cooking my noodle.

OK..Even though CLT looks normal, going to swap it anyway. The sensor itself is green from corrosion. Couldn't help.

If this doesn't do it, then I'll have to give a shop a call, unfortunately.

Btw, most of vacuum lines are new/good. That's one of the things I did when I did the PCV system.

850n00b · Post by **850n00b** » 31 Dec 2014, 23:48

Going to swap out the CLT sensor and see how it does. Then disconnect the new O2 sensor I installed to see if there are any changes.