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Hello I've got a 1990 Volvo 740 Turbo, it was running great up until a week ago when it started to hesitate on take off. I would give it gas and it would start to bog down and then pick up all the sudden and go. Now it's gotten even worse, and when I first fire it up in the morning it will hardly go past 10mph (bogs and jolts, bogs and jots), once it gets going it'll start to go faster but I still can't get it past 50mph (shifts very late) and it's redlined at that point. As it's accelerating I can hear the wastegate popping and I've never heard that before, it sounds pretty bad. Idles fine, starts perfectly despite outside temperature.
I've tried:
Changing out the AMM with a good one.
Swapped FPR with an old one.
Changed the Radio Suppression Relay.
I pressurized the intake system using the brake reservoir cap and installed schrader valve, seemed to just push air right back out the turbo, so I couldn't tell much from that.
Any Ideas would be awesome, this is really getting on my nerves!!
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Re-reading your post, that sounds a lot like my car when it has a massive intake leak.
The hose that failed on mine was the hose from the intercooler to the metal intake tube. It failed on the underside and it was a long time before I found the cause.
Any news?
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1990 740 Turbo, on its way to stock specs, maybe beyond
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Hey Will,
I haven't had a lot of time to fiddle with it, I plan on spending a good chunk tomorrow and see if I can figure it out (I have to fix it, I can't borrow the vehicle I've been using anymore!)
Update: Yesterday I took all of the bigger intake hoses (from Airbox to Throttle body) and pressure tested them with 15psi and they all held up just fine, I spun the turbo while I had everything off and it felt very smooth.
Discovery: Turns out there are two Engine Coolant Sensors, one that sends temp to the gauge in the instrument cluster, and another one that is mounted farther back against the firewall than I was looking. My last post I said I disconnected the ECS with no change, well I just unplugged the one that goes to the dash.
I must have confused the two while looking at the FAQ page, they're VERY similar!
Hopefully I'm going to determine for sure if the ECS is really the cause, I have a sneaky suspicion it's the fuel system... but I really hope it's something easier! (I was hoping it would be a hose)
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Can you check your timing?
When you're trying to drive it like this, does your turbo/manifold glow red?
If your valves are closed, I think the pressure should stay solid, and not blow through the combustion chambers and out the exhaust. It may be easier to seal one end of the intake tubing (with packing tape even) and pressurize the rest of it.
Have you considered the engine temperature sensor being bad?
Good Luck
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1990 740 Turbo, on its way to stock specs, maybe beyond
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Will -
I haven't checked my timing yet and the turbo/manifold doesn't glow red either. I bought a new engine temperature sensor but it has the wrong connector so I'll need to exchange it for the correct one. As I was attempting to change it I unplugged the current one and ran the engine, absolutely no difference. I also plugged it back in with the engine running with no change.
Does this mean it is absolutely bad, or could there also be a problem with the ECU ? I've had to switch it out before.
I was reading only 2k Ohms at 0 degrees Celsius and it should have been reading 6k so I figured it might be time for a new one.
Thanks
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I haven't had a failed temp sensor myself, but if it made no difference in the engine running, that might be your problem.
Is there any voltage to the connector? Is it the one nearest the distributor or nearest the water pump?
Good Luck
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1990 740 Turbo, on its way to stock specs, maybe beyond
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"I pressurized the intake system using the brake reservoir cap and installed schrader valve, seemed to just push air right back out the turbo, so I couldn't tell much from that."
Not sure what you mean by blowing back out the turbo.
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Post Back. That's whats makes this forum work.
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Can you rev the engine cleanly in neutral? In other words, does being under load make a difference? What is the history on the O2 sensor in the cat?
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Aleekat - I was trying to pressurize the intake so I disconnected the hose from the turbo and intercooler and put air through the system find leaks in other hoses. The air was going through the intercooler > intake manifold > engine > and out the turbo. I couldn't really tell if any of the hoses were leaking.
Efrat3 - Yes being under a load makes a huge difference. With the car in neutral it revs fairly smooth, when I switch to drive it begins to bog at low RPM's. I can floor it and it will bog and then smooth out, but it won't rev as high as it should and there's no power. The O2 sensor is less than 4 months old, I replaced it after experiencing very poor MPG (~16mpg) and hoped it would help, no change though. The cat was removed prior by the previous owner, the O2 sensor is located just below the exhaust manifold.
Hope this helps
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FWIW-- The symptoms match an odd fail on my B230 FTI. The turbo pressure hose attaching to the throttle body had deteriorated inside and was generally leaking on the bottom, however, not in one place, but in between layers and through small cracks. It split after being squeezed to reveal why without load, things were better, but on loading, the engine failed to perform. The failing hose just looked a bit "oily" inside until it split revealing a much larger deteriorated area at the bottom bend. Before that, it acted like a random pressure relief valve. You can monitor the boost gauge to see if boost level is affected or has an effect.
Also, I have been blindsided by non-Bosch O2 sensors enough, even new ones, that I only use Bosch O2 sensors on my Volvos. HST only way to know for sure is swap in a known working sensor.
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To use the reservoir cap/valve assembly:
Disconnect the turbo hose on the front of the turbo (output). Loosen the other end and turn it up to easily insert the cap/valve. Tighten both clamps- the one on the cap and the one you loosened on the intercooler.
Apply about 15 psi to the valve. Any leaks in the system between the input and throttle body will be apparent with the sound of escaping pressure.
Randy
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Sounds like your cat is falling apart, or you have a hole in the hose from amm to turbo. Check for a hole in the hose right below the breather hose. Pauli
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