• Hello Guest, welcome to the initial stages of our new platform!
    You can find some additional information about where we are in the process of migrating the board and setting up our new software here

    Thank you for being a part of our community!

760 '87 760T no power, low rpm

The replacement Bosch 007 AMM changed the driving response a little, but it's still darn near dead off a start from stop, when warmed up. The initial start, then die issue did not recur.

I am wondering if the temperature sender for the ECM is bad. It is nicely buried under the intake manifold! Repaired the aux fan wires and it operates.

I have to see if Haynes has how to the set the plate and calibrate the TPS.

The aux fan is used with the A/C. The ECT can be replaced in about 15-20 minutes.
 
Thanks for all this. BTW, this engine is a replacement, from Sweden, per the mechanic who read the tag on the block. Seems the original overheated.

The coolant leak was most likely the heater control valve. The ECT is temperature sensor for LH2.2, not for the gauge.
The HCV had been replaced and was dry when I felt around it. That loss has not recurred. Am I wrong that there are two temp senders, one for the gauge; other for the ECU?
LH 2.2 is not self learning. The plugs for turbo engine do use a smaller gap. NGK plugs are good. You didn't mention the plug wire brand. Okay, yes you did mention Volvo wires. Do they have a class letter and date?
I'll check tomorrow.

The aux fan is used with the A/C. The ECT can be replaced in about 15-20 minutes.
Yes. I was surprised that it didn't also activate with high ECT. It works great with the repaired wires and A/C on.

I'm going to re-gap the newish plugs to .028" and see if I get more improvement. The mechanic who worked on this car said he adjusted the boost during the three visits. I'll recheck it against the manual's procedure. It's set too low or this turbo is getting tired. At least there is upward progress after all the discouragement.
 
Last edited:
Bosch plugs are gapped to .028", but someone had stripped the threads in #3. I got a kit for the M14x1.25 threads at a chain store(not the cheapest, but here) and followed the procedure, though I used Thread locker, not hi-temp silicon on the insert. The plug was torqued in to the spc 8 ft.lb. and low end power is better, but somehow most of the boost is gone.

I'd shortened the actuator lever but witnessed less boost. Today, I undid that, plus 1 1/2 turns, which is supposed to be about .6 psi, but the boost is even less! The valve leer moves freely so I wonder if the actuator is failing.
 
the regulator controls the wastegate which stays closed when boost is not in demand and opens when the boost level needs to be controlled, if that regulator fails (= internal membrane torn) the boost will spike high. (as opposed to staying low). In other words, i doubt that the wastegate actuator is at fault.

if the boost is down/too low you should look into where boost is leaking away. A strong suspect is the CBV (compressor bypass valve) , if that CBV has failed (= internal membrane torn) it basically causes a short circuit in the boosted airstream. If that happens the turbo can not make boost eventhough it is spinning.

Other possible leaks: check air hoses for tears, sometimes they are hard to see but they can open up whenever boosted air flows through them.
A good way is to test the hoses and intercooler by pressurising the intake system with compressed air/smoke but if you do not have access to that kind of tools you can often find the leak by manipulating the hoses by hand and visually look for cracks.
 
Last edited:
Thank you for your time and knowledge

:cool: Wow, that's great info. I have my homework assignment, after I reset the wastegate to where it was! I thought the prior boost was lower than 'normal', and combined with the seeming normalcy of the turbo, the CBV deserves inspection.

My pal's shop did a smoke test and found very little leakage. I know there's vacuum loss in the cruise control and linked circuits b/c the aux pump runs quite a lot, but think it's not affecting the engine power much.
 
What do the plugs tell you?
Plugs are near new and slightly light brown.

Volvo wires. Do they have a class letter and date?
403 F, from France.

The coolant loss is ended so I adjusted the waste gate longer for later dump, which raised the Boost meter to about 1/5 deflection; still too low. Having the improved compression on #3 helps the engine accelerate below 1500, where the boost creeps on, but it's hardly a screamer! My wife thinks it is too slow for safe entrance onto 50 mph streets.

I changed vacuum ports for CBV control to the lower (slightly larger) of the two adjacent ones pax side, intake. The other is capped with a clamped rubber plug. Using my hand vac, I pumped the CBV open; saw it move. It very slowly lost that pressure. I have no idea if that is normal or indicates a compromised diaphragm. That hose is new. If so, where on earth does one find them parts for the CBV?

I still find no leaks in any hoses and tomorrow, after it cools down, I'll lengthen the wastegate arm another turn. Perhaps it'll get to 1/2, like it used to, with attendant power increase.
 
Last edited:
Plugs are near new and slightly light brown.

403 F, from France.

The coolant loss is ended so I adjusted the waste gate longer for later dump, which raised the Boost meter to about 1/5 deflection; still too low. Having the improved compression on #3 helps the engine accelerate below 1500, where the boost creeps on, but it's hardly a screamer! My wife thinks it is too slow for safe entrance onto 50 mph streets.

I changed vacuum ports for CBV control to the lower (slightly larger) of the two adjacent ones pax side, intake. The other is capped with a clamped rubber plug. Using my hand vac, I pumped the CBV open; saw it move. It very slowly lost that pressure. I have no idea if that is normal or indicates a compromised diaphragm. That hose is new. If so, where on earth does one find them parts for the CBV?

I still find no leaks in any hoses and tomorrow, after it cools down, I'll lengthen the wastegate arm another turn. Perhaps it'll get to 1/2, like it used to, with attendant power increase.

I'd guess that the 403 is 4th month of 2003.
 
adjustment screw on the connector side of the housing
that setting requires a gas analyzer but I have the other things; cannot do

fuel pressure test kit
I could do this IF there was a port to connect to. Seems I have to make one due to unique Volvo design.

LH 2.2 is not self learning.
This is a head scratcher. How does the ECU optimize A/F ratio, if it cannot learn? Then, there is the issue of an aging car, as components age and alter that ratio. The ECU must adjust to optimize to maintain emissions, especially for the many years required by law.

After another adjustment of the wastegate ( think it's real close), I drove it some miles today, street and freeway It is improved, except the boost is rather low. I need to reread and understand what can be limiting the boost.
 
Last edited:
I changed vacuum ports for CBV control to the lower (slightly larger) of the two adjacent ones pax side, intake. The other is capped with a clamped rubber plug. Using my hand vac, I pumped the CBV open; saw it move. It very slowly lost that pressure. I have no idea if that is normal or indicates a compromised diaphragm. That hose is new. If so, where on earth does one find them parts for the CBV?
.

The CBV should hold that vacume/pressure . the CBV is a spring loaded valve that is attached to a pressure/vacume chamber. The membrane inside it should hold pressure or vacume. If not it is leaking and not functioning like it should.

What brand/type turbo is on the engine? If it is a mitsubishi tdo4-13c then there are aftermarket upgrade kits available. I once bought one from IPD. The kit came with 3 different rate springs as well.

For other turbo's i have no idea if you can get aftermarket CBV's. But you could make a block-off plate and replace the CBV by a dump-valve . They serve the same purpose.
 
that setting requires a gas analyzer but I have the other things; cannot do

I could do this IF there was a port to connect to. Seems I have to make one due to unique Volvo design.

This is a head scratcher. How does the ECU optimize A/F ratio, if it cannot learn? Then, there is the issue of an aging car, as components age and alter that ratio. The ECU must adjust to optimize to maintain emissions, especially for the many years required by law.

After another adjustment of the wastegate ( think it's real close), I drove it some miles today, street and freeway It is improved, except the boost is rather low. I need to reread and understand what can be limiting the boost.

Oxygen sensor. Open and closed loop.
 
The CBV should hold that vacume/pressure . the CBV is a spring loaded valve that is attached to a pressure/vacume chamber. The membrane inside it should hold pressure or vacume. If not it is leaking and not functioning like it should.
I think this is the case, as idle vacuum is only 15-16 psi, while 19 +/- is normal on other engines. Using a MAC (quality) gauge, the reading varyied slightly, as did idle speed (750+/-). When the A/C was shut off, the reading increased 1-2 psi, so there is a small leak in that control system. I knew there was a small draw somewhere in those hoses, however, I don't think this causes the turbo problem.

That MAC gauge also showed 1-2 psi boost maximum, when the turbo activated, agreeing with the low dash reading. This, even flooring the throttle at 35mph, while riding the brake or when just accelerating. I find this congruent with your comments about the leaky diaphragm not allowing more boost, plus the fact that there is less now than 2 months ago.


What brand/type turbo is on the engine? If it is a mitsubishi tdo4-13c then there are aftermarket upgrade kits available.
I don't know. I cannot read any label, as one Garrett description says exists. I have looked at the offering from ipd.

I took 3 pics but cannot add them here.

For other turbo's i have no idea if you can get aftermarket BV's. But you could make a block-off plate and replace the CBV by a dump-valve . They serve the same purpose.
I read that and ipd also offers a plate. The car is subject to CA smog so the legality of that change is a question.
 
IIRC 88-89 Volvo 760 sedans used Garrett turbos and Wagons used Mitsubishi TD05-12b turbos. Not sure of the earlier years.

Maybe this will help you identify your turbo:

https://www.volvoclub.org.uk/faq/EngineTurboIdentification.htm
thanks for that link; useful indeed.

ipd thinks it's a Mitsu, but has nothing. Chatting with their rep, he says the problem is more likely the low vacuum, which should be a 20, but seems worse each day; now at 13.5! I used propane at every junction I could reach and along most hoses, with no change in RPM. ipd said use brake cleaner; same result. While I thought it was the HVAC system, no temporarily disconnected, and after replacing the big how to the aux vacuum pump, after testing them, it's still below 14!

This is a big leak, but the car idles great with no detectable miss. I guess the ECU is masking it with more fuel.

I wish I could find a vac hose diagram, as there's a lot of them and plenty of ports; hence lots of room for errors, mine or another's!

This piece on diagnosis w/ vacuum gauge, is helpful: http://www.onallcylinders.com/2015/05/08/quick-tech-how-to-read-a-vacuum-gauge-to-pinpoint-engine-problems/
 
Last edited:
This is a big leak
Or not. Mulling that article, I was drawn to the low reading causes and wondered about late ignition and valve timing, neither of which I had touched.

After checking the spark strength with my tester, all looked good, eliminating poor plug wires and weak spark.

Attached the Snap-On timing light, read idle at 740-770 but the timing was off. Knowing the ECU controls it, I loosened the two small bolts and rotated the distributor back and forth, watching the vacuum drop, then increase, along with changed engine smoothness and RPM. Having tuned an old MB230 engine by ear, including syncing the two carbs, I maxed out the advance, which gave a better sound and smoothness, plus the most vacuum:17. Timing is 9-10 degrees, but I think it needs a bit more. Interesting is the ECU's adjustments to the widely varying distributor position, improving idle, to some degree.

The car has a more power and throttle response seems snappier. Well, sure. If the timing is too retarded, both will suffer. Now I am wondering if whomever replaced this engine, timed the belt close, but off, which would drop vacuum via late valve and spark timing.
 
Or not. Mulling that article, I was drawn to the low reading causes and wondered about late ignition and valve timing, neither of which I had touched.

After checking the spark strength with my tester, all looked good, eliminating poor plug wires and weak spark.

Attached the Snap-On timing light, read idle at 740-770 but the timing was off. Knowing the ECU controls it, I loosened the two small bolts and rotated the distributor back and forth, watching the vacuum drop, then increase, along with changed engine smoothness and RPM. Having tuned an old MB230 engine by ear, including syncing the two carbs, I maxed out the advance, which gave a better sound and smoothness, plus the most vacuum:17. Timing is 9-10 degrees, but I think it needs a bit more. Interesting is the ECU's adjustments to the widely varying distributor position, improving idle, to some degree.

The car has a more power and throttle response seems snappier. Well, sure. If the timing is too retarded, both will suffer. Now I am wondering if whomever replaced this engine, timed the belt close, but off, which would drop vacuum via late valve and spark timing.

The timing can be adjusted on the 87 B230FT by moving the distributor. The timing belt timing needs checking. Also the crankshaft pulley outer ring may be slipping resulting in the timing moving around.
 
The timing can be adjusted on the 87 B230FT by moving the distributor. The timing belt timing needs checking. Also the crankshaft pulley outer ring may be slipping resulting in the timing moving around.
I had a slipped outer ring on another car and plan to check the belt timing after I swap in a new CAT.

After a smog pre-check, I learned:
1- NoX was high,
2- HC was high, thought the CAT was not well heatedup, prior,
3- the CAT mounted is aftermarket, which often means cheaper and much shorter life, due partially to less catalyst inside.

My amazing car pal suggested slapping it and listening for any rattles plus flashlighting inside, looking for a lack of hoineycomb. Both existed.

The continuing low vacuum led me to a refresh of causes; restricted exhaust is among the possibles. New CAT coming soon and possibly new O2 sensor. The newish wires on this one lead me to believe it's been changed not too long ago.

Ran out of gas with gauge indicating just barely touching the red. After refill, no start so towed it home. After a nose low sit overnight, it fired right up. I'd feared a ruined pump and got lucky, for a change, given my history with this wagon. No fuel= no lube for pump, and it ran so, for about 5 minutes as we coasted downslope to the next station.
 
I had a slipped outer ring on another car and plan to check the belt timing after I swap in a new CAT.

After a smog pre-check, I learned:
1- NoX was high,
2- HC was high, thought the CAT was not well heatedup, prior,
3- the CAT mounted is aftermarket, which often means cheaper and much shorter life, due partially to less catalyst inside.

My amazing car pal suggested slapping it and listening for any rattles plus flashlighting inside, looking for a lack of hoineycomb. Both existed.

The continuing low vacuum led me to a refresh of causes; restricted exhaust is among the possibles. New CAT coming soon and possibly new O2 sensor. The newish wires on this one lead me to believe it's been changed not too long ago.

Ran out of gas with gauge indicating just barely touching the red. After refill, no start so towed it home. After a nose low sit overnight, it fired right up. I'd feared a ruined pump and got lucky, for a change, given my history with this wagon. No fuel= no lube for pump, and it ran so, for about 5 minutes as we coasted downslope to the next station.

Less than 1/4 tank of fuel usually results in an overheated pump.
 
Less than 1/4 tank of fuel usually results in an overheated pump.
So far, so good, but for a battery on its last legs.

Been waiting for 5 days for a reply from volvowebparts place about CA legality of the catalytic converter they sell as OEM replacement. Gee, that place is screwed up (from my dealings with them).
 
So far, so good, but for a battery on its last legs.

Been waiting for 5 days for a reply from volvowebparts place about CA legality of the catalytic converter they sell as OEM replacement. Gee, that place is screwed up (from my dealings with them).

Three-way catalytic converter:
Volvo Part number 1326481. But, Bosal 099-941 not legal for sale in California. What brand of converter did you ask about? Most of this info is available.

Volvo 1326481 has been replaced by 8602955 $558.22

Magnaflow 23949 is not legal for CA.


Benchmark D-193-86 is direct fit and 50 state legal.

You may have to buy a universal CARB compliant catalytic converter.

D-193-86 is the CARB EO number.
 
Last edited:
Three-way catalytic converter:
Volvo Part number 1326481. But, Bosal 099-941 not legal for sale in California. What brand of converter did you ask about? Most of this info is available.

Volvo 1326481 has been replaced by 8602955 $558.22

Magnaflow 23949 is not legal for CA.


Benchmark D-193-86 is direct fit and 50 state legal.

You may have to buy a universal CARB compliant catalytic converter.

D-193-86 is the CARB EO number.
I checked ipd, FCP RockAuto, VolvoWorld and NAPA. Bosal is not okay, and some MagnaFlows are approved. VW shows a 4605, but has no comments and searches were of no help to find the manufacturer. ipd will not ship theirs, a Bosal, to CA and suggested FCP.

IIRC, FCP and NAPA offer legal cats, for $50-60 more than VW's. NAPA's looks like a rebranded Bosal and, sadly, they're earning a reputation here of lesser quality than what built their brand. As a customer of all those places with typically excellent e-commerce, VW is many steps below the others, sadly. The genuine Volvo cats are the most expensive which so far, leads me to FCP, My concern with virtually all aftermarket versions, is minimal catalyst, w/short life a result; a big drawback. MagnaFlow has a good reputation and is local, but their specialty is performance (low restriction) which means minimal catalyst. They vend approved and non versions. That stuff is pricey, so one might get what is paid for with costlier choices. Some shops weld 'illegal' cats onto the stock flanged pipe, which has the smog cert stick-on. Experienced testers know an aftermarket regardless.

Appreciate the leads, which I'll shop.
 
Back
Top