1998 V70 GLT Cyl 1 Misfire only under LOAD

AD_NAPCO · Post by **AD_NAPCO** » 01 Oct 2015, 16:59

Hey everyone. First, let me say thanks. This is my first post here. Over the past few weeks, in my spare time, I have been slowly rescuing my parents 98 V70 GLT wagon using information from this site, and Robert Spinner's youtube channel. Can't say enough how grateful I am for you all that contribute to these resources.

I have replaced the radiator, removed, rebuilt, and replace the turbo, also replaced the complete PCV system and as many of the old crumbly rubber vacuum lines with new silicone as I could find, as well as all the coolant lines/hoses I could get to. It has been quite a chore. Needless to say when I got the car fired up yesterday for the first time and she started easily and seemed to run great, I was thrilled. I let the car idle up to operating temperature and just sit there for about 20 minutes. Never moved above normal operating temperature in that time. So I then took it slowly up to about 2000 rpm from normal idle of 840 or so. Sustained that for 30 sec, then 3000, then 4000... Never got hot. Ran smooth as silk.

I then took it out for a test drive and everything seemed fine. Got it going pretty fast and the only symptom was excessive smoke out the tailpipe, which I assume is normal post turbo failure due to the amount of oil that gets sucked into the exhaust past the seal. I figure it could take a while to burn all that out even with a good dose of fuel system cleaner (Red Line) added to the tank. So all seemed right with the world. I brought the car home, let it cool off completely. No coolant leaks, no weeping oil from the intercooler weep hole. All signs pointed to victory.

Today, I took the car out because I needed to get the battery tested under load and I'm working alone so that's tough to do. On the way to autozone I hit a back road and decided to really stand on it and see how it responded. Initially everything was fine, but as the car hit around 3,500 RPM it started to stumble badly and vibrate pretty intensely. So I let off the throttle and almost immediately the check engine light came one. I went ahead and bought an OBDII scanner and the code it threw was P0301. Cylinder 1 misfire detected. This misfire only happens under load, in gear, on the road... I have now cleared the code three different times and tested on and off the road. I can rev up to redline with no misses whatsoever in park sitting in the driveway but if I try to put the pedal to the metal in gear it will miss somewhere around 3000-3500 RPM's... The miss goes away after I throttle back some.

Any ideas what might cause this?

The car has to pass smog test this month so I need to get it sorted for my parents asap.

Thanks in advance!

Post by **mikealder** » 02 Oct 2015, 01:52

What spark plugs have you got fitted to it? - Mike

Post by **abscate** » 02 Oct 2015, 08:08

Move the spark plug to cylinder 2 to see if the code moves.

How old are the cap rotor and spark plug wires? Over 3 years - replace them.

AD_NAPCO · Post by **AD_NAPCO** » 02 Oct 2015, 08:47

The plugs are stock Volvo. I'm not sure how old the cap, rotor, plugs, and wires are. I will ask my dad when the last time he had them changed was. I'll move the plug to #2 and see if the code moves with it. Thanks.

AD_NAPCO · Post by **AD_NAPCO** » 02 Oct 2015, 15:22

Well, guys, thanks for having me look at the spark plugs more closely. Working in better light this morning I discovered that there was a crack in the insulator on the number 1 plug. Strangely enough, there was an even worse crack in the insulator on #2, but I never got the error for #2. In any case, I changed all the plugs to Bosch double platinum and the car runs noticeably better at idle and I can stand on the throttle with no hesitation/stumble/missing, and no check engine light!

Thanks again!