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Hi all,
Been a while since I have posted here, but still driving Swedish wonders. Can't imagine driving anything else.
Acquired a real nice 07 XC-70 that had only 104K, and never, ever seen road salt. This is a big deal to those of us in upstate NY. Been working my way through some of the things one finds on a used car. (Timing belt, serp. belt, oil change, new spark plugs, IPD belly pan, etc.) One that has me a little puzzled is an intermittent rough starting issue.
The car always starts and runs great. What is puzzling is how it starts. Many times it starts like any good XC-70, a couple rotations of the engine and it starts smoothly. However, sometimes it cranks a bit more and starts a bit rough. Immediately smooths out once it starts. I just began to notice that when it takes more than a few rotations to start, the speedometer will briefly go way up before it starts, then when it starts, it is running at normal idle speed (around 700 rpm). Not the usual 1500 rpm when it is cold. If I give it a little gas, the idle speed will got to 1500 rpm and hold there for several seconds as is normal for a cold engine. The rough starting also occurs with a hot engine, though without the high idle, which is normal on a hot engine. Another symptom is when cranking the engine (both cold or hot), sometimes the starter is fighting against what seems like a strong kick back. The engine rotation almost stops briefly before rotating again. Eventually, the engine starts and runs fine.
Any ideas out there?
Had our first snow today, and want to get this resolved before winter settle in for good.
Gary
2 '07 XC-70s, '72 1800ES (under restoration)
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Gary D
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Greetings all,
It has been a while since this thread had any attention, and I have been living with the starting problem through the winter. Not having a garage makes winter repairs difficult and unpleasant. So, one lives with annoying problems until spring.
While reading up on my starting problem on various forums, there never seemed to be a definitive answer that solved the problem. There were mentions of sensor wires too close to the starting cable, weak crank and cam position sensors, even grounding issues between the engine block and the transmission case. The transmission and engine block are held together with big and tight bolts. How can there be bad grounds there? Also saw on one forum where a dealer (I think) said the engine management computer needed to be replaced. Basically, a lot of shops were shot gunning the problem, and no real solution was presented.
In my attempts to resolve the hard starting problem, I replaced the crank and exhaust position sensors. Low hanging fruit and not overly expensive. No improvement in starting, but at least the sensors were off the table as a possible cause. Then I made an interesting observation. Both my wife's car and mine are '07 XC70s with roughly the same mileage. Both cars have relatively recently replaced batteries, hers being an 3ish year old Interstate, mine being a 3 year old Volvo battery. I noticed her car started with a faster cranking speed compared to my car. Not that my car's cranking speed was excessively slow, but was noticeably slower. Got to thinking that perhaps the starter on my car was getting a bit tired, pulling more current especially when cold, and in the process throwing out more EMI that interfered with the pulses coming from the crank position sensor. Recently I replaced the starter with a new Volvo starter (generally do not do after market anymore, too many quality issues). Immediately noticed the engine cranked much faster, and all starts since then have been perfect. A few fast cranks, engine fires, and off we go. No tachometer bouncing around, no starter fighting against the engine, none of the problems of the past.
So far, it has been over a week since the starter was replaced, and a puzzling problem looks to be resolved. And, did it without shot gunning a lot of expensive parts.
Hope this helps with others that have mysterious starting problems.
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Gary D
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I did some digging in VIDA, and located where the crank and cam sensors are located. Should not be a big deal to access.
Trying to understand how electrical interference can impact the signals from the crank and cam sensors as suggested by VIDA. Especially only during starting. Trolling around a few forums, I found references to electrical noise coming off the starter and the cabling leading to the starter during cranking. I can see the logic to this as the starter is a high current device which can emit nasty EMI. However, if the crank and cam position sensors are sensitive to EMI, then why doesn't the the problem occur on more cars since they are all manufactured pretty much the same. Also, since it sounds like this problem can occur as the car get some age on it, what is changing to cause the problem?
I am theorizing that with miles on the engine, perhaps the sensors are aging, and producing weaker signals. During starting, the EMI from the starter is interfering with the sensor signals enough to muddy the pulses and confusing the computer. If the computer does not have a good fix on crank or cam positions, it can't fire the plugs correctly. Once the engine starts, the EMI from the starter goes away, and the pulses from the sensors are less noisy, enabling the computer to know the crank and cam positions, even if the signals are a bit weak. Solution would be to replace the sensors with the anticipation of stronger pulses.
Does this logic make sense???
Thoughts from others on my thought process are welcome.
Gary
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Gary D
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On 1998 and earlier cars, some people routed the coil to cap wire too close to the CPS wire and the EMI from the coil would mess up the signal from the CPS. Your car doesn't have that, thank you.
The wire from the battery to the starter shouldn't be close to the CPS in any case.
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Keeping it running is better than buying new
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Over the weekend I scanned the engine, and after a little digging, I found the following:
ECM-5000 Engine Speed (RPM) sensor signal. Faulty signal
Possible sources provided include "signal interference, Contact resistance and oxidation, intermittent fault causes in the engine speed (RPM) sensor wiring."
Does not tell me much beyond the obvious. Guess I will try to unplug, clean, and plug in again the wiring. Next question is, where is this sensor?
Any suggestions?
Gary
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Gary D
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On the 5cyl engine the CPS is on the exhaust cam, driver's side of the engine. The wiring coupling is directly below the intake cam, about 8 inches from the CPS body. On my 850T, I had to take out the air filter box to gain access.
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Keeping it running is better than buying new
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I wonder if the 2007 5 cyl has a cam position sensor. If so, check the connector in the wiring and clean any corrosion. Same for the crank position sensor.
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Keeping it running is better than buying new
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Did it start rough both before AND after the spark plug change?
What kind of spark plugs did you install?
Has the throttle body ever been cleaned out?
“...sometimes the starter is fighting against what seems like a strong kick back. The engine rotation almost stops briefly before rotating again...”
Is there smoke out the tail pipe when first started? If so, what color?
Is the coolant level dropping?
I’m wondering about a leaky injector. Here’s something to try - when you shut the engine off, immediately release the residual fuel pressure out of the fuel rail Schrader valve into a rag. Then see if you still experience the cranking “kick back” and rough idle the next time you start it up.
Is the problem worse after it sits all night or after a five minute visit to the store?
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The intermittent rough starting occurred before the spark plug change as well. Thought that the PO may not have had the plugs changed, so I did the change during timing belt change. The plugs are Volvo plugs from a dealership. So, we are talking OE parts, not after market junk.
As for the throttle body cleaning, no idea. Car appears to be dealer maintained by the PO in Colorado, and my son who lives out there (and found the car for me) talked with the dealer who did the maintenance. They gave him the records that remained in their system, and nothing regarding ETM cleaning came up. However, their records only went back about 3 or 4 years.
Coolant level appears steady, and I do not notice any "smoke" coming out of the tail pipe when first starting.
Like I said, the rough starting occurs intermittently. Happens sometimes first thing in the morning. Sometimes when it is warm, sometimes after it has only sat for a few minutes. The intermittency of the problem makes it a bit tricky to track down. Once it starts, it runs smooth and fine. Drives like my other P2 XC-70s.
The wild behavior of the tachometer during cranking (I think I mistakenly said speedometer in my post) has me wondering. Sometimes during cranking the tach will swing up to 2k-3K then drop down. This morning, it swung up to the 2-3k range, dropped back down, and the engine started normal and smooth. However, it did not go to high idle as it normally would with a cold engine. I'm wondering if an engine speed sensor is acting up and causing the EFI to over inject, or something along those lines.
Any other ideas? I figure it is something fairly simple, but what is it?
Gary
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Gary D
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What caught my attention was the part about the starter struggling against the compression. If it were me I would try the free stuff first - clean the throttle body and try the fuel pressure experiment. Then move on to other, more costly, stuff. The jumping tach needle is interesting. Have you scanned the OBD for fault codes?
How old is the battery? How much is the voltage dropping when you crank the engine? What’s the voltage just after starting and it’s running rough?
Sorry for all the questions. Just trying to cook up some food for thought.
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Battery is only 3 years old, and is a Volvo battery. Did look at the voltage when I first noticed the struggle against compression. Nothing raised a flag at the time.
I scanned the car with my DICE box a few weeks ago, and nothing caught my attention related to the engine. I will scan it again this weekend and look closer for engine related stuff.
Gary
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Gary D
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