Volvo 940 rattle/clank plus surge and stumble

[Shane]

Hello everyone this will be my first post and foremost, my trouble thread. And secondly my introduction.

Let’s get to the issue at hand. Tuesday I drove home for lunch and on the way back, I overtook a slow moving car. Afterwards, I could hear a Tinnish sounding clanking while braking for a light.

Upon leaving the light the car surged and stumbled until it cleared 2000 RPM where it began to run normal. Beyond that, it was fine until 3000 RPM when the clanking returned. The car still ran fine, but made quite the racket.

To clarify here are the symptoms.

Idle is stable.
1500-2000 rpm is surging while free revving.
Tach reads 0 rpm at idle at times, idle is rough when in this condition but not normally.

Metallic clanking at 3000 rpm and beyond when free revving or under load.
Clanking also occasional under braking and sharp turns.
Vibration from clanking when present under braking or turning.

Vehicle is a 1994 Volvo 940 Wagon (945)
2.3l inline 4 sohc 8v (b230f) non-turbo
4-speed Automatic (AW71)
171,444 miles

Oil is full and good
ATF is full and good
Brake fluid is full and good
Coolant is full.
No vaccum leaks found.
New belts, hoses, plugs, wires, coil, air filter.
Checked and cleaned MAF.

Any ideas? Planning a TPS check and checking both fuel pumps.

Topic

[Its me]

If you are getting no RPM reading, then your computer is having an issue getting a signal from either the Crank position sender or the Cam position sensor…. I think Volvo may even have a special RPM sensor….. been awhile…. Anyway, based on this you should be getting some OBD 1 code… pull the code and post it here…

Also, lift the hood and observe and listen while raising the rpms… look for any frayed or cut wires by the fan area and elsewhere…

Karl

[Shane]

Thank you for the reply. I will attempt to pull codes, although there are no CELs.
These motors are notoriously noisy runners, but I have listened for leaks and have not heard any.
I did not notice any loose or broken lines or wires.
I will check again though, as once is never enough.

I have narrowed the noisy clanky noise toward the back of the engine. But have not found anything out of place.

These motors only have a crank position sensor. Volvo calls it an “engine (RPM) speed sensor” I have taken that into consideration, but since it does read RPM I assume it is not the culprit.

[Its me]

I was under the assumption you were getting 0 RPM at some times. To me this is a bit of a clue, but I admit I am not that adept with European makes…

Karl

[Shane]

Correct it does read 0 at times. Perhaps i should look into the wiring for the CPS as well.

[Its me]

I would 🙂

Karl

[EricTheCarGuy]

I would also be looking at the TPS readings. If there is an issue there it can also cause that symptom. You can watch it on a scan tool. Just leave the key on and engine off while you depress the gas pedal. The voltage should increase gradually until it reaches it’s max. If not, the sensor could be bad. You also want to make sure the wiring and connectors are good as well. More info on solving performance issues here.

http://www.ericthecarguy.com/faq/solving-automotive-performance-issues

Good luck and keep us posted.

[Shane]

Thanks! I just found out my multi meter is no longer with the living.
I will have to borrow my dad’s Sunday and give the tps a test. I don’t have a odb 1 scanner.

I did attempt to pull codes from the on board LED diagnostic system and got nothing but 1-1-1 which is a code for no codes in memory lol.

I did record some clips of the symptoms and will upload and post them here in a a few.

[Shane]

Here we go.

[video width=550 height=309 type=youtube]mpkxH-sctUA[/video]

[video width=550 height=309 type=youtube]zYDed-fiQ0g[/video]

Checked wiring for TPS and CKP sensor and all looks good. Connectors were pretty clean but i cleaned them anyway.

Disconnected TPS and problem still persists.
Disconnected CKP sensor results in non-start, of course.

I’m wondering, would a cracked or broken flex plate cause these issues?
I only doubt it because the starter operates correctly.
I really don’t have the means to drop the trans. I will try to get a peek into the inspection passage though.
Hopefully a tech at work will help me put it up on a rack.

Did an engine load test.

[video width=550 height=309 type=youtube]gBXjJuWLd1c[/video]

No luck with getting it on a rack. Will try to get it on my ramps tomorrow.

[Shane]

Spent some time under the car watching the flex plate and torque converter.
Fun stuff. Neither have a wobble or made any noises.
Noise seems to come from the center of the car near the back of the motor. I’ve beat on every heat shield i could find and even removed the pre heat pipe because it was missing a bolt.
I’m at a loss there.

As far as the idle issue, i cleaned the throttle body and inspected the intake piping for cracks. No issues found.
Tps checked out ok using a jumped in multimeter.
Was not able to get a reading from the CKP sensor. I will be replacing it later this week.

Update: Got some hints from a Volvo specific board.

I checked the connection to my RSR (Radio Suppresion Relay) DaveBarton RSR

Everything looked good but I will test using the jumping method described on that page.
$49.00 is a bit steep to just replace at will.

I was also informed that there is a heat shield somewhere near the back of the engine or the top of the transmission. I just need to locate it and see if it’s loose.

[Shane]

I am focusing on fuel systems now.
The car is parked, I will be picking up a fuel filter tomorrow.
Based on how it does with that I will then be moving to fuel pumps. There are two and I might as well replace both. One is about $40 and the other is about $60.

On the way back to work from lunch I got about a block from my house and it decided to start acting like it was starving for fuel.
I turned around and headed back home.
Upon pulling into the garage I could smell that the car was running lean.

The car refused to get over 2000 rpm on the way back to my house.
I believe there is not enough volume going through to the FPR.

[EricTheCarGuy]

If you suspect a fuel psi problem the best corse of action is to check the fuel psi. As for fuel volume, I believe there’s a test for that as well but you’ll need to consult the service manual to see if they have information on that. Factory manuals are usually pretty good about things like that.

Please keep us updated on your progress.

[Shane]

So after a lot more testing I found the pump in the tank is not working correctly.

When fuel is low the in tank (pre-) pump helps push fuel to the main pump.
This pump failing explains the starvation symptoms while still being able to run.
Also explains the sudden nature of the problem beginning as I had roughly 1/4 tank as this began.

Anywho, i have ordered a Walbro 255 lph pump to take over for both pumps.
I am going to delete the main pump and overly expensive canister filter in favor of a premium in-line filter.
I will also be installing an adjustable FPR.

Seems like overkill but I will be boosting the car at a later date 🙂

[Shane]

Sorry guys, this has been a nightmare of defective parts and being sick.

The first pump was defective, i sent it back and got another one. Installed it and she fired right up after letting it build pressure.

The car is now running in 1 255lph in-tank pump and an in-line filter. That’s the good news.

It still has the partial throttle stumble and obnoxious rattle. Thats the bad news.

I’m thinking I’ll jump the RSR and see if that stops the stumble. If not the CKPS is the next suspect.

[Shane]

So i jumped the RSR, not the issue. Ckps is working correctly.

Today I managed to get it on a lift. The noise is definitely coming from the bell housing, I’m going to research parts and see what my next move should be.

With the incorrect tach readings I want to fault the flex plate however it doesnt make odd sounds when starting so it doesnt seem like it would be that.

I was told there is a tone ring between the flex plate and torque converter. If the car uses that to read rpms and it has come loose it could cause all of these symptoms right?

Back to work for now, I’ll update on my findings.

[Shane]

So I was curious yesterday and climbed back under the car to take another look into the bell housing. What do I find? A bolt.

It appears to have come from either the crank position sensor mount or the distributor. Now I just need to figure out how to get it out without dropping the whole trans, then figure out exactly where it came from.

[Author]

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