'95 T5-r Misfiring 3 way Cat Codes

Post by **erikv11** » 02 Apr 2016, 15:17

Fuel pressure will bleed back down, I think that's not going to tell you much. I would monitor psi from right after priming then across the next few (up to 10?) minutes. If it stays high it is ok, if not then maybe a leaky FPR or fuel pump check valve. Did you check the vac line to the FPR, does it stink of fuel or just a faint whiff? I also don't think 34 is far enough from 40 to be an issue, but let's see what others say.

warmblood58 · Post by **warmblood58** » 02 Apr 2016, 15:52

Hi, thank you for such a complete description. The good news is, I think I may have discovered the issue, the fuel pump pressure at the rail is only 34 psi. My understanding is the fp is supposed to be in the low 40's, correct? If this is true, it explains why the car drives so well around town but misses when you start to put your foot into it. I purchased this fuel pump used just to get this car running . . . On to a compression check next. I am curious to see if fuel pressure holds for the next half hour while car sits. Thanks again for your advice!

Post by **JDS60R** » 02 Apr 2016, 16:22

Never put in a fuel pump without a new filter first.
Install filter first - recheck pressure and flow.
Then proceed to pump diagnostics. You must confirm it is getting the voltage ( ground and B+ needed) You should have a ground resistance test to battery ground as well as a voltage drop test from battery to pump. Don't forget to make sure the relay and fuse are corrosion free as well.

For it to break up at higher rpm and load due to bad fuel pressure it would then recover and lower rpm and load.

Post by **JDS60R** » 02 Apr 2016, 16:30

I don't know if you have diagnostic equipment or an OBD port. I would take a volt meter and backprobe the front oxygen sensor. ( 2 wires same color is heater. remaining two wires include the signal wire and a ground. The sensor is not grounded through the exhaust pipe. Backprobe signal wire with positive and batt ground with negative. Place on lowest dc volt scale. .1 volt is full lean .9 volts is full rich.

Steady state driving should be .6 ish. When you floor it you should see the car get rich and then level out.

warmblood58 · Post by **warmblood58** » 02 Apr 2016, 19:15

Fuel filter was changed yesterday and front O2 sensor went in over a week ago after throwing a fault code for that sensor. Still curious if anyone knows if reduced fuel pump pressure could cause misfire - my understanding is these pumps put out 40psi plus, either way, ordered a Bosch replacement today. Fuel pump pressure remained at 34 psi throughout RPM changes and it sat with gauge attached for at least 10 running and held pressure for 20 plus minutes after shutdown. Compression cold readings were 155, 155, 150,155, 160 . . . pretty even!

Post by **abscate** » 03 Apr 2016, 06:18

Good compression, excellent. I think that fuel pressure is low, so the FPR would be the first thing to check

warmblood58 · Post by **warmblood58** » 03 Apr 2016, 14:41

I have some spare relays, I will see if I can get a change with a different relay

Post by **JDS60R** » 03 Apr 2016, 15:52

Yes - low Fuel pressure or flow can get you to a misfire or no start.

This would be a lean misfire which can be detected on the Oxy sensor signal wire . Have you backprobed that wire yet or checked for an OBD port under coin holder?

Has new ignition coil gone in yet? It is your prime culprit for misfire under load When wires and plugs are new

Put in the good coil before pulling the fuel pump.

FUEL SYSTEM
WARNING: Always relieve fuel pressure before disconnecting any fuel injection-related component. DO NOT allow fuel to contact engine or electrical components.

FUEL PRESSURE

Fuel Pressure
1) Before disconnecting, cover fuel line connector using shop towel to absorb any fuel spray. Connect Fuel Pressure Gauge (5011) between fuel line and fuel rail. Seal free end of hose using Plug (5266) or use Fuel Drainage Unit (981 2270, 2273 and 2282).
2) Lift cover on central electrical unit located in engine compartment and remove fuel pump relay. See Fig. 1.
3) Connect a jumper wire between relay terminals No. 1 and 3. See Fig. 2.
4) Turn ignition on. Fuel pump should start. Fuel filler
cover can be removed to determine whether main pump is operating. Fuel pressure should be about 43.5 psi (3.06 kg/cm ). If pressure is too low, pinch return hose by hand and check whether pressure rises. DO
NOT allow pressure to exceed 86 psi (6 kg/cm ).
5) If pressure rises rapidly, pump and lines are okay. Replace pressure regulator and recheck line pressure. If pressure rises slowly, fuel filter, fuel pump strainer or fuel lines are blocked. If pressure does not rise, fuel pump is probably faulty.
6) If pressure is too high, remove jumper wire between relay or fuse terminals. Remove return hose from pressure regulator. Blow in pipe. Remove vacuum hose from pressure regulator. Blow in pipe. If
volvo 850 s70 v70 c70 fuel pressure test service manual
both hoses are open, pressure regulator is defective. Replace regulator and recheck pressure.
Fig. 1: Locating Fuel Pump Relay
Courtesy of Volvo Cars of North America.
volvo 850 s70 v70 c70 fuel pressure test service manual pin layout
Fig. 2: Identifying Fuel Pump Relay Terminals
Courtesy of Volvo Cars of North America.
CAUTION: Ensure ignition is off when connecting or disconnecting ECU
connector.
Fuel Pump Circuit
1) If fuel pump does not operate with ignition on, remove fuel pump relay. See Fig. 1. Connect jumper wire between fuel pump relay terminals No. 1 and 3. See Fig. 2. Turn ignition on. If fuel pump does not start, go to next step. If fuel pump starts, replace fuel pump relay.
2) Turn ignition off. To check relay ground, connect ohmmeter between ground and fuel pump relay terminal No. 2. See Fig. 2.
Ohmmeter should indicate about zero ohms. If ohmmeter does not indicate about zero ohms, check wiring between fuel pump relay and ground.
3) To check fuel pump relay voltage supply, connect voltmeter between ground and fuel pump relay terminal No. 1. See Fig. 2 . Turn ignition on. Battery voltage should be present. If battery voltage is not present, check wiring between fuel pump relay and fuse No. 2.
4) Turn ignition off. Connect ohmmeter between ground and relay terminal No. 3. See Fig. 2. About 1.5 ohms should be present. If about 1.5 ohms are not present, check resistance at fuel pump
connector to determine whether fault is in pump or wiring.
5) To check fuel injection control signal to fuel pump relay, connect voltmeter between ground and fuel pump relay terminal No. 4. See Fig. 2. Operate starter motor. If voltmeter indicates about 3 volts, replace relay.

Read more: http://www.volvotips.com/index.php/850- ... z44m8c1ER4

warmblood58 · Post by **warmblood58** » 04 Apr 2016, 10:45

Thank you for the procedure, have not swapped coils as of yet but will do so today. Are all coil interchangeable for the 850 series? Thanks!

Post by **JDS60R** » 05 Apr 2016, 16:36

the 850 should only have 1 coil on the driver side fender apron in front of driver side strut mount.

Are they all the same shold be a yes but some aftermarket coils make you use the converter on the mounting bracket and just give you a coil.

A quality new coil should have the bracket, convereter and coil all mounted toghether and ready to plug into the harness and bolt to the apron.

I never got you answer on what happens if you are misfiring and you take your foot off the gas pedal ( coast) . Does it continue to misfire of does it even out. This answer is important as it guides you betwenn sensor and coil failure diagnostics.

The way I'm reading your post is that if you back off the pedal it smooths out. This means a spark is escaping under load. This would make coil the likely culprit. Please remember someone else will have this issue next week and if they can match your symptoms to theirs they may be able to match your sucessfull repair to theirs as well.