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'Hope this is not what I think it is' - New info - still a quest! 700

posted by Andrew in AL on Tue Jun 29 03:53 CST 2004
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last visit: Fri Oct 24 06:17 CST 2014

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Thanks to all who gave good info on my other post - same topic.

Went this AM - the mechanic pulled the fuel rail - swapped out #1 & #4 injectors. Same thing - #4 missing at idle. Tried a spare plug wire to that plug - nothing new.

Mechanic suggested a local Texaco lube spot that does a top end clean - under pressure. So I am there - watching the guy pour two cans of cleaner into the cylinder that feeds it - insert the spray head under the boot - shooting straight into the throttle body. He puts an extra can in the tank - then runs it at 1500 rpm for about 30 minutes. It does seem to be a bit different - but still a definite miss at idle.

So my quest continues. My thoughts are to go like this for a spell - and maybe give a good fast hard workout on the freeway (been driving way too easy lately trying to save fuel). If nothing changes (or I discover nothing new) - then on down the road I will probably pull the head and check the valves. Is there a way to check the compression rings at the same time - I wonder?

Before I do this - I will find a good Volvo shop and get a proper compression test done.

One good thing about all this today is that neither place charged me a dime. The top end clean was to be 79.95 - but he just wrote it off.
--
'94 940T (160K) , '92 745T (200K+)

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Sorry if this has already been covered---- 700

posted by Rolyak on Tue Jun 29 06:04 CST 2004
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last visit: Fri Oct 24 08:03 CST 2014

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but is the injector "clicking"? You know, put a long screwdriver on the injector put the handle on your ear (mechanics stethoscope would be good too) and compare the sound to known working injectors.
I once had a bad connection at the injector ballast pack that gave me a dead miss.
Pull it apart and clean the connection and apply some dielectric grease. Also use your test light to test for continuity.
Worth a look if you haven't already checked it?

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Sorry if this has already been covered---- 700

posted by Andrew in AL on Tue Jun 29 06:20 CST 2004
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last visit: Fri Oct 24 06:17 CST 2014

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I actually have an automotive stethescope I have never used - until now.

Man - that thing works great!

New tool jubilation aside - they all sound good - same tempo. There could be a slight variation as far as actual sound - but even if there is - it is across all four of them.

Worth a try. Thanks.
--
'94 940T (160K) , '92 745T (200K+)

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'Hope this is not what I think it is' - New info - still a quest! 700

posted by Aye Roll on Tue Jun 29 05:32 CST 2004
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last visit: Tue Oct 14 21:08 CST 2014

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I agree, not only a compression test but a "leakdown" test. This applies high pressure air to the cylinder in question through the plug hole, then you listen for where it's escaping: intake manifold (intake valve) exhaust pipe (exhaust valve) oil cap (rings or burnt piston) or another cylinder (head gasket).

Good luck with it!
--
Rob Bareiss, New London CT ::: '87 244DL/M47- 229K, 88 744GLE- 218K, 82 245T-181K Also responsible for the care and feeding of: 88 745GLE, 231K, 87 244DL, 239K, 88 245DL, 246K

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'Hope this is not what I think it is' - New info - still a quest! 700

posted by Andrew in AL on Tue Jun 29 06:01 CST 2004
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last visit: Fri Oct 24 06:17 CST 2014

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Thanks Rob
Just got off the phone with Franklin Automotive ,an independent in the Birmingham area. They used to fix nothing but Volvo - now Volvo and Lexus.

He said they do a leakdown test, and then he talked to me for a good spell - saying that my model was one of the toughest to track down as far as a bad idle. Gave me some ideas - cap/rotor, suppression relay, coil, do a good check for vac leaks with starter fluid. All this - of course, I have seen on the brickboard.

Sometime between now and when I would take it in to him - I am going to swap the cap/rotor and coil from my wifes 940, and just see what happens. Then I will do a really good check again for vac leaks. Maybe I will get lucky.
--
'94 940T (160K) , '92 745T (200K+)

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'Hope this is not what I think it is' - New info - still a quest! 700

posted by someone claiming to be JimL on Tue Jun 29 05:16 CST 2004 [RELATED]

Common way to find a leaky valve is first run the compression check. Then squirt some oil into the cylinder to improve ring sealing. Re-run compression check. If the numbers go up you have leaky rings, but if they don't go up, you have leaky valves.

Have you replaced your dist cap and rotor? What about the O2 sensor?

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'Hope this is not what I think it is' - New info - still a quest! 700

posted by Andrew in AL on Tue Jun 29 05:39 CST 2004
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last visit: Fri Oct 24 06:17 CST 2014

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I replaced the cap and rotor last year - and now that you mention it - I did that because it was running really badly. I have not replaced the O2 sensor.

Some of these things - like the cap/rotor - would seem to have a direct link. Could a bad O2 sensor affect only one cylinder?

Fire from the cap is getting to #4 at idle - but is there such a thing as a weak spark that would not make the plug fire at idle?

Thanks for that good info on a compression check. I may end up getting me a tester and trying it myself. Just trying to judge where to spend the dollars I have.
--
'94 940T (160K) , '92 745T (200K+)

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'Hope this is not what I think it is' - New info - still a quest! 700

posted by dick on Tue Jun 29 04:38 CST 2004
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last visit: Sun Aug 3 15:24 CST 2014

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Anyone check for a broken valve spring on that cylinder? You are getting spark?

Good luck,

dick

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'Hope this is not what I think it is' - New info - still a quest! 700

posted by Andrew in AL on Tue Jun 29 04:55 CST 2004
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last visit: Fri Oct 24 06:17 CST 2014

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Yes - spark is there. It runs good at speed - and when I put it down she pretty well will fly.

I am not quite ready to give up and pull the head just yet - as it was rebuilt about a year ago after an overheat.

BUT ...I would not have to pull the head to check the spring - just the cover - right? If I had a bad spring - would it still run good at speed?

I do wonder - since vacuum seems to an oft-times culprit in probs like this - if a vac prob can influence only one cylinder like this.

Please keep in mind that all the pulled plugs looked the same, and looked good as far as diagnosing the cylinders.
--
'94 940T (160K) , '92 745T (200K+)

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