850 driven 1,800 miles on 4 cylinders

speedbump · Post by **speedbump** » 01 Jan 2012, 08:56

Last month I put over 5000 miles on my 93 850 GLT. It now has 265,000 miles on it. The last 1700 miles were on 4 cylinders. No check engine light ever came up.

The first thing I did was to change the spark plugs. The #4 plug was wet while the others were dry, with hard crusts. The problem was still present. Then I thought the #4 fuel injector was bad. After I changed it, the problem was still present. I also changed the distributor cap with no effect. For good measure I also changed the fuel pump relay which didn't do anything.

I don't know what to check next. I'd like to keep this out of the crusher. Your help is appreciated.

Post by **Pauloil** » 01 Jan 2012, 09:26

time to check compression look up here how to do it.

https://www.matthewsvolvosite.com/forums ... =1&t=45387

bigrotch · Post by **bigrotch** » 01 Jan 2012, 11:28

hi did you change the ht leads i had same issue on my t5 no engine light etc my leads was the cause

Post by **erikv11** » 01 Jan 2012, 11:40

Three things to check: spark, fuel and compression.

You have confirmed there is fuel.

Is spark getting down the wire to the plug?

speedbump · Post by **speedbump** » 01 Jan 2012, 11:44

I'm not familiar with ht leads (thus I did not change them). What are they?

Also, I don't know how to verify if power is getting to the plug. Is there a tutorial available somewhere?

Post by **erikv11** » 01 Jan 2012, 11:56

If you pull the plug wire and put a spark plug on it, you should be able to see and hear the spark jump the gap. Or you can place the plug near the top of the head, the spark should jump to ground.

Here is a good tutorial on checking the resistance of the wires, to see if that one wire is bad:
http://www.ehow.com/how_2296047_test-sp ... e-car.html

The other place to look for spark issues is the cap and rotor, what kind of shape are they in?

Spark is easier to check but Pauloil is right - could be low compression, too.

Post by **erikv11** » 01 Jan 2012, 11:59

oh and "ht lead" is "high tension lead" just a technical term for "spark plug wire"

speedbump · Post by **speedbump** » 01 Jan 2012, 12:35

My spark plug wires were only a few years old. I have a new set. I can change them out.
Cap and rotor are in good shape.

gilhuly · Post by **gilhuly** » 01 Jan 2012, 14:21

Compression check is job#1 here. You probably have a burnt valve. If so, unplug that injector so you're not washing all the oil off that piston.

Post by **rspi** » 01 Jan 2012, 16:24

Here is the link to my compression test thread.
http://www.atthetipwebs.com/technologyi ... n_test.htm
I also read somewhere that you should disconnect the ignition coil but I did not.