'99 s70. Misfire

taiga · Post by **taiga** » 21 Oct 2007, 00:23

I'm getting a misfire but not sure how to locate it. I've gone through some simple troubleshooting by removing the ign. coils from the plugs, one at a time and then seeing if the engine runs differently or not. (not - would locate the misfire) with no result (each time the engine ran worse). I purchased a new ign. coil ($98) and I have tried it in each cylinder but i get a misfire on ODBII every time. I am in the process of putting the new ign. coil in each cylinder and leaving it there for a day of driving and monitoring it. Still haven't had any luck.

How can I find which cylinder is misfiring? I have some oil around the plugs on number 2 and 3, could that be a problem? I use dielectric grease on my plug/ign coil connections. Could that be causing a problem? I'd appreciate any input.

Thanks

cyclmck · Post by **cyclmck** » 21 Oct 2007, 12:44

Is the check engine light coming on? Chech for misfire codes if you have a reader. Since you could not pin it to a cylinder by pulling each coil it seems to be something affecting all cylinders. Have you checked the condition of the spark plugs? Also you should check for vacuunm leaks.

flynscot · Post by **flynscot** » 21 Oct 2007, 17:11

Had a similar issue on my 2000 S70 a while back (should be a related post a couple of weeks old).

Did you get the CEL with a 030# code? Mine had the CEL with 0305 code (cyl 5 misfire). I do have the oil drippage problem (from bad oil filler cap gasket-- seems common), but didn't see much oil in the plug holes themselves.

I bought a new coil and put it on #5 with the same results you describe. I even went through the same troubleshooting pattern you describe. I could only get it to clear and run correctly after the following steps:

1. From a cold engine, start car and run for a minute or so. Shut down. Then, as quickly as possible:

2. Remove turbo intercooler plumbing over the top of the engine.

3. Pull all coils in sequence. Clean boot and metal "spring" that makes contact with the plug.

4. Pull related plug in sequence, check gap. Note if one plug seems "wetter" than the others with a more pronounced raw fuel smell (this should be your mis-firing cylinder). Reinstall plug and coil. (Repeat for all 5 cylinders).

5. Moved #5 coil to #3 postion. #3 to #5. Probably not necesary for you, but I had a couple of reasons for this, mostly on a whim.

6. Reconnect intercooler plumbing.

7. Do not attempt to start car yet. Remove negative battery cable and wait about 15 minutes (even better, disconnect the batt before you start all this). Re-connect the cable. (Seems to reset OBD computer and possibly other PFM boxes).

8. Start car and pray. Check CEL light out and drive a bit. Hopefully should clear the issue.

taiga · Post by **taiga** » 21 Oct 2007, 20:39

Thanks for the feed back.

This problem came to my attention when I had a check engine light come on. I hooked up the OBDII sensor and found a bad o2 sensor. Replaced that and then found that I have a misfire.

Before I did anything else, I replaced ALL of the plugs. Then I started in on the above trouble shooting sequence. I'm worried that it is a compression problem and not an ignition problem.

Post by **MadeInJapan** » 21 Oct 2007, 21:30

What codes if any do you get now?
What 02 sensor did you put in? Some have had trouble with the Bosch generic sensor. It is also notable, that if you bought what you thought was the correct proprietary sensor, (as far as I can remember) some on-line sites as well as Volvo literature had the wrong sensor listed for some 850's as well as early 70 series Volvos.