1986 Volvo 760 Turbo underpowered when cold
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NEW UPDATE
So, I did replace the O2 sensor and to my disappointment... Nothing changed!
Frustrated, I went to see a mechanic, asking if he could diagnose the car, test drive it and give me his report.
He did and here is what he said:
He seemed to have noticed that the timing marks were not steady. He suspects that the timing is off and that I need a "timing belt tear down and inspection of belt and crank pulley fpr damage or missing keyway".
In my opinion, that could explain the problem when warm, but not when cold. The timing belt has only 40 000 kms, still a lot of life left!
The car is super sluggish when cold, it gets better when it warms up but still sluggish. I also recently noticed that my gas mileage was not good.
I changed and cleaned important sensors and nothing changed. So in my mind, the ECU would seem to be the problem.
The mechanic quoted the timing adjustment at 250$, but I doubt it will remain the same after repair. And who knows, maybe 250$ is the cost of inspection and not of fixing....
Decisions.... Getting a new cheap ecu VS adjusting the timing for a costly price but taking the risk that it will not fix the problem.
So, I did replace the O2 sensor and to my disappointment... Nothing changed!
Frustrated, I went to see a mechanic, asking if he could diagnose the car, test drive it and give me his report.
He did and here is what he said:
He seemed to have noticed that the timing marks were not steady. He suspects that the timing is off and that I need a "timing belt tear down and inspection of belt and crank pulley fpr damage or missing keyway".
In my opinion, that could explain the problem when warm, but not when cold. The timing belt has only 40 000 kms, still a lot of life left!
The car is super sluggish when cold, it gets better when it warms up but still sluggish. I also recently noticed that my gas mileage was not good.
I changed and cleaned important sensors and nothing changed. So in my mind, the ECU would seem to be the problem.
The mechanic quoted the timing adjustment at 250$, but I doubt it will remain the same after repair. And who knows, maybe 250$ is the cost of inspection and not of fixing....
Decisions.... Getting a new cheap ecu VS adjusting the timing for a costly price but taking the risk that it will not fix the problem.
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yes, you can definitely get in over your head. transmission issues are often fairly clear. The ones used for 940s/740s 760s were very high quality and if maintained correctly (change fluid every 25000 miles, filter every 50K and no nasty towing, they were very hard wearing. The AW-71 I had lasted 255K and was still functional when the 760 GLE I had was scrapped. I have ZF4HP22 and that is fine too after 27 years. However, my water pump failed yesterday and I find I could only get a gasket for my spare from ebay..in the process of changing it now (when it stops raining)
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From: Orlando FL
It seems to me that you are shopping around for an opinion that you want to hear. Your mechanic gave you a diagnosis yet you come here to debate same.
What was the point of going to the mechanic?
What was the point of going to the mechanic?
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I think try the ECU first which is a cheap and easy fix...generally at a garage they will check fuel line pressure and also timing with a strobe...If the belt has lost some teeth it would throw out the timing, but it would be cold as well as hot and would not improve...Changing a timing belt on a red block engine is not very expensive or difficult..they should last about 80K Km but mine at that mileage was in really good condition...yours being a turbo and depending on how lead footed you are, it might be worn, but you can inspect the belt and see if there are any obvious missing teeth on it. Take the cover off (three bolts and a screw) and turn the engine via the pulley nut..easier with the plugs out obviously..seems unlikely though...also you could check compression at TDC for each cylinder and see if its OK..the guages are not very expensive..if the valve timing is a long way out, then compression will not be within the correct range at TDC
before any of that ECU change is the smart move I think
before any of that ECU change is the smart move I think
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The point is, I am rather lost! I am just starting to get a little bit of experience on those cars. With different opinions and suggestions, I can have a better idea on what is going on.
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I don't see how the transmission would be to blame, It shifts smoothly and the oil has been changed regularly.
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I think try the ECU first which is a cheap and easy fix...generally at a garage they will check fuel line pressure and also timing with a strobe...If the belt has lost some teeth it would throw out the timing, but it would be cold as well as hot and would not improve...Changing a timing belt on a red block engine is not very expensive or difficult..they should last about 80K Km but mine at that mileage was in really good condition...yours being a turbo and depending on how lead footed you are, it might be worn, but you can inspect the belt and see if there are any obvious missing teeth on it. Take the cover off (three bolts and a screw) and turn the engine via the pulley nut..easier with the plugs out obviously..seems unlikely though...also you could check compression at TDC for each cylinder and see if its OK..the guages are not very expensive..if the valve timing is a long way out, then compression will not be within the correct range at TDC
before any of that ECU change is the smart move I think
before any of that ECU change is the smart move I think
I have found some good ecus matching mine (0280000541) on ebay. No more than 50 bucks.
But before I do that, I wanted to ask you something about the TPS sensor. I checked all the sensors the other day and I came accross one particular detail.
My TPS is a 3 pins sensor. But I noticed that the connector had only 2 slots... One was missing somehow... There is still 3 wires : one is going in the first slot and then 2 wires together go in the second slot. Would that explain something?
Would a bad connection in the tps sensor cause so much trouble??
Again, thank you for all your help!!
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The TPS has three wires, one is an earth, one goes to the ECU and another is linked to the temp sensor..if two are together, it may be linked to one being an earth and the other is linked to the temp sensor. there is no reason why anyone would change this and it is likely to be how it left the factory. .I don't think it would affect things, but this is beyond my experience..the TPS output tells the ECU what you are doing, but it is mainly about maintining the right idle...decent power is about correct valve and ignition timing and the correct fuel air mix (correctly metered air from the air mass sensor) and decent line pressure, plus iin your case, boost from the turbo...there is a turbo overpressure switch that could be checked, but I never had a turbo, so I am limited on that,
.it might be worth testing the knock sensor, as it that is telling the ECU there is lots of detonation it might retard the timing too far so you lose power, but that seems a long shot.
try the ECU and see what happens..you can always keep it as a spare...
It took me a while to work out why my car was running so rich..I went through all the sensors etc, until I changed the ECU and took the old one apart..water ingress had damaged it so that it ran as if it was -40C....I could see where the water had got in..these things do take a while and you learn plenty while you do it. These cars were very advanced for their time and the tech is usually Bosch so its excellent quality and longevity.
.it might be worth testing the knock sensor, as it that is telling the ECU there is lots of detonation it might retard the timing too far so you lose power, but that seems a long shot.
try the ECU and see what happens..you can always keep it as a spare...
It took me a while to work out why my car was running so rich..I went through all the sensors etc, until I changed the ECU and took the old one apart..water ingress had damaged it so that it ran as if it was -40C....I could see where the water had got in..these things do take a while and you learn plenty while you do it. These cars were very advanced for their time and the tech is usually Bosch so its excellent quality and longevity.
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From: Orlando FL
Another thing that came to mind is whether the harmonic balancer has slipped and gives a false reading for engine timing. Removing the balancer and checking the base timing belt timing would be in order.
I would start with base timing as your mechanic suggested.
I would start with base timing as your mechanic suggested.
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Like one of these?
https://www.partsgeek.com/mmparts/ha...volvo/760.html
not sure how that would have such an impact on power..valve/ignition timing, fuel air etc, yes, but not sure how the balancer will have such an impact?
See what happens with another ECU..I think that will do it, although I was wrong about Brexit, Trump, the downturb in 2008 ...etc etc etc
https://www.partsgeek.com/mmparts/ha...volvo/760.html
not sure how that would have such an impact on power..valve/ignition timing, fuel air etc, yes, but not sure how the balancer will have such an impact?
See what happens with another ECU..I think that will do it, although I was wrong about Brexit, Trump, the downturb in 2008 ...etc etc etc
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Like one of these?
https://www.partsgeek.com/mmparts/ha...volvo/760.html
not sure how that would have such an impact on power..valve/ignition timing, fuel air etc, yes, but not sure how the balancer will have such an impact?
See what happens with another ECU..I think that will do it, although I was wrong about Brexit, Trump, the downturb in 2008 ...etc etc etc
https://www.partsgeek.com/mmparts/ha...volvo/760.html
not sure how that would have such an impact on power..valve/ignition timing, fuel air etc, yes, but not sure how the balancer will have such an impact?
See what happens with another ECU..I think that will do it, although I was wrong about Brexit, Trump, the downturb in 2008 ...etc etc etc
Alright, I checked the belt condition yesterday and after putting the cover back on, I started the car. But it did not start.
The engine turns over and cranks intermittantly but it is a no start situation.
I did not touch anything while inspecting the belt so I don't know what happened.
Now, is it a bad battery, starter solenoid, fuel pump or relay?? I don't know... I doubt the ecu is to blame.
One thing I do know now is that I have to fix a new problem before dealing with the actual one lol!
This car must be doomed... Or maybe I am!
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no i got you there, mine was all started cause my sunroof drain was clogged and the watter then rain down the interior panel onto the computer and down to the carpet.....who knew lol
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OK..check that the fuel pump runs (open the drivers window and listen for it buzz before you start..check number 1 fuse also..if you have cranked it a few times, the pump may not buzz as it has already primed the system. , the next fast way to find out what is going on is to cheat and squirt some Quickstart into the intake and crank it then. if the engine catches but then dies, then you have a spark but no fuel... also, check for a spark (just pop a plug out and rest it on the engine and crank to confirm.
On the 80s cars there is a risk that the ignition barrel contacts can fail and you get strange dashboard light combinations and a no start...if you waggle the key in the ignition you can sometimes get the contacts to work. The first place to start though, if you are getting intermittant cranking, that is you turn the key and it cranks a bit and then stops, is check the earths (grounds) to the battery and the body...the cars are earthed near the battery onto the body and at the back of the engine also into the bulkhead (firewall)..Check the earths first I think...
If the quicksquirt test fails and you can't get the pump to run, then it could be the relay. You can remove it and bypass it with some wires (instructions are on the net) and the pump will run continually...if the car starts then its the relay...
See how you get on...at the end of the day, its a 32 year old car..some people don't even live that long...this morning I fixed my water pump and primed the system for ages and then found a nasty oil leak..you get no probs....then probs...Don't give up..when they are running well the turbos are still even by todays standards a pretty fast car and they are a decent size, not like some pathetic little economical globby car..
On the 80s cars there is a risk that the ignition barrel contacts can fail and you get strange dashboard light combinations and a no start...if you waggle the key in the ignition you can sometimes get the contacts to work. The first place to start though, if you are getting intermittant cranking, that is you turn the key and it cranks a bit and then stops, is check the earths (grounds) to the battery and the body...the cars are earthed near the battery onto the body and at the back of the engine also into the bulkhead (firewall)..Check the earths first I think...
If the quicksquirt test fails and you can't get the pump to run, then it could be the relay. You can remove it and bypass it with some wires (instructions are on the net) and the pump will run continually...if the car starts then its the relay...
See how you get on...at the end of the day, its a 32 year old car..some people don't even live that long...this morning I fixed my water pump and primed the system for ages and then found a nasty oil leak..you get no probs....then probs...Don't give up..when they are running well the turbos are still even by todays standards a pretty fast car and they are a decent size, not like some pathetic little economical globby car..
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OK..check that the fuel pump runs (open the drivers window and listen for it buzz before you start..check number 1 fuse also..if you have cranked it a few times, the pump may not buzz as it has already primed the system. , the next fast way to find out what is going on is to cheat and squirt some Quickstart into the intake and crank it then. if the engine catches but then dies, then you have a spark but no fuel... also, check for a spark (just pop a plug out and rest it on the engine and crank to confirm.
On the 80s cars there is a risk that the ignition barrel contacts can fail and you get strange dashboard light combinations and a no start...if you waggle the key in the ignition you can sometimes get the contacts to work. The first place to start though, if you are getting intermittant cranking, that is you turn the key and it cranks a bit and then stops, is check the earths (grounds) to the battery and the body...the cars are earthed near the battery onto the body and at the back of the engine also into the bulkhead (firewall)..Check the earths first I think...
If the quicksquirt test fails and you can't get the pump to run, then it could be the relay. You can remove it and bypass it with some wires (instructions are on the net) and the pump will run continually...if the car starts then its the relay...
See how you get on...at the end of the day, its a 32 year old car..some people don't even live that long...this morning I fixed my water pump and primed the system for ages and then found a nasty oil leak..you get no probs....then probs...Don't give up..when they are running well the turbos are still even by todays standards a pretty fast car and they are a decent size, not like some pathetic little economical globby car..
On the 80s cars there is a risk that the ignition barrel contacts can fail and you get strange dashboard light combinations and a no start...if you waggle the key in the ignition you can sometimes get the contacts to work. The first place to start though, if you are getting intermittant cranking, that is you turn the key and it cranks a bit and then stops, is check the earths (grounds) to the battery and the body...the cars are earthed near the battery onto the body and at the back of the engine also into the bulkhead (firewall)..Check the earths first I think...
If the quicksquirt test fails and you can't get the pump to run, then it could be the relay. You can remove it and bypass it with some wires (instructions are on the net) and the pump will run continually...if the car starts then its the relay...
See how you get on...at the end of the day, its a 32 year old car..some people don't even live that long...this morning I fixed my water pump and primed the system for ages and then found a nasty oil leak..you get no probs....then probs...Don't give up..when they are running well the turbos are still even by todays standards a pretty fast car and they are a decent size, not like some pathetic little economical globby car..
Despite the car wanting me to give up, I am not! I kept it out of my sight for 2 days so I could have a clearer mind and more motivation to spend time on an engine.
I checked for sparks first and all good, I've got sparks!
I check the fuel pump, it buzzes, the relay clicks. To be sure, I took off the pipe that goes into the fuel injectors rail, put it into a bottle and there was fuel coming out when cranking.
I checked the negatives and they seemed fine. The wires were in good shapes, nothing was loose...
The air filter is clean, the mass air flow sensor as well. Jumpstarting the car does not change anything.
So, I have sparks and fuel.
The funny thing is that I squirted some quickstart in the intake and nothing happened.
I am kinda puzzled by the sound the car makes when it tries to start.
The engine turns over and will catch intermittently but it doesn't start
It seems to me that the engine is not cranking enough to start.
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First thing...is the engine turning over fast enough to catch..(check battery status, charge if necessary so you get 12.8V on a meter)
Next, since you have the fuel and air, might mean that there is another electrical issue going on...check your crankshaft position sensor..if that is open circuit the car will not run...it should read a resistance of 200-500 ohms...if the ECU does not know what the crank is doing then no go..
Try that next, it is not hard to find and is easy to test...
I fixed the water pump yesterday, today I have a broken spring!!!!!
AAREGH!!!!
Next, since you have the fuel and air, might mean that there is another electrical issue going on...check your crankshaft position sensor..if that is open circuit the car will not run...it should read a resistance of 200-500 ohms...if the ECU does not know what the crank is doing then no go..
Try that next, it is not hard to find and is easy to test...
I fixed the water pump yesterday, today I have a broken spring!!!!!
AAREGH!!!!
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First thing...is the engine turning over fast enough to catch..(check battery status, charge if necessary so you get 12.8V on a meter)
Next, since you have the fuel and air, might mean that there is another electrical issue going on...check your crankshaft position sensor..if that is open circuit the car will not run...it should read a resistance of 200-500 ohms...if the ECU does not know what the crank is doing then no go..
Try that next, it is not hard to find and is easy to test...
I fixed the water pump yesterday, today I have a broken spring!!!!!
AAREGH!!!!
Next, since you have the fuel and air, might mean that there is another electrical issue going on...check your crankshaft position sensor..if that is open circuit the car will not run...it should read a resistance of 200-500 ohms...if the ECU does not know what the crank is doing then no go..
Try that next, it is not hard to find and is easy to test...
I fixed the water pump yesterday, today I have a broken spring!!!!!
AAREGH!!!!
Sorry about your spring mate... :/
I don't think my volvo model has a crankshaft position sensor. I read it was within the distributor??
I tried to jumpstart the car and it did not work. The battery is not the problem then.
The fuel pump buzzes for 3 seconds when turning the ignition key.
Should I test the injectors one by one?
Also, I am not sure if I am right but when I unplugged the vaccum hose from the FPR, it tasted like fuel. But just a bit, not much. However, there is no fuel dripping out of that vaccum hose when turning the key on. Is there any other ways to test a FPR?
Would the FPR be the culprit? I mean, I was not getting a lot of power before and now the car refuses to start. What if the car was running too lean all along because of bad fuel pressure? What if that was why I had no power? I could fix two problems in one shot! Man that would be neat...
For now, I have a few culprits:
-The FPR (Will check the pressure)
-The injectors
-Bad timing