1999 V70 odd miss

[mafulcher]

Hello everyone, this is my first post on this site and I have a question. I have a 99 v70 2.4 non turbo from the southern US. I bought the car with a bad engine and just replaced it with a 120,000 mile used one. I had already replaced the ETM with the XeMod with the old engine and it ran perfect minus a bad knock. Here is the problem. When I first started it with the replacement engine, it ran perfect for a while. Then the next day, I started it again and it has a miss. I pulled the injector plugs one by one and there is no change when I unplug the no. 5 cylinder. All others cause it to run worse. I have spare parts from the other engine, so I replaced the coil with no change and the plug with no change. What could cause this to miss on the 5th cylinder only after running so well when first started. Any help would be greatly appreciated.

[Ozark Lee]

Welcome to MVS,

Do you have lifters clacking? If the replacement engine had been parked for a while that would not surprise me and it may just need to get run for a while to re-build the lifter oil pressure.

Any codes?

If you unplugged the #5 injector and there was no change that is where I would start - Swap out the injector from from one of them on the other engine and see what happens.

Normally with a bad injector I can use a long screwdriver and literally hear the difference but that is not always the case.

...Lee

[mafulcher]

The lifters were clacking when first started, but now they are quiet. I forgot to say that I put another injector on it too and that did not help. I was thinking about that on my way to work today. Have not checked codes but there is no engine light on.

[jblackburn]

It may be a stuck lifter or a burnt valve. I believe my next test would be to run a compression test on that cylinder.

[mafulcher]

I will, then I will get back to you. Thanks

[mafulcher]

compression was good in no. 5 cylinder. Still running bad. I had not put in new plugs, so I did that. I did not expect a change and there wasn't. There is still not an engine light. Checked miss by pulling injector plugs again and 1-4 cause it to stumble terrible and there is no change with no 5 just like before. Is there a way to check and see if the no 5 is getting a firing signal?

[jblackburn]

Connecting a noid light to that injector plug should do that trick. The wiring for the injectors gets especially brittle over the years.

[mafulcher]

Well, got a noid light and injectors are firing correctly. Kindof back to square one. Really not sure what's going on.

[jblackburn]

Remove the plug and coil pack and ground it to the top of the engine block while the car is running. IS the plug actually firing? The wiring up there on top of the engine can get into some pretty bad shape after all these years.

[mafulcher]

I will try that. But, if the noid light flashes like it's supposed to, the wiring should be ok, right.

[jblackburn]

To the injector or the coil pack plug?

I thought you'd just tested the injector, but yes either way.

[mafulcher]

Oh yea, sorry about that. I did just check the injector. I'm out of energy with the new baby in the house so I broke down and took it to one of my local volvo specialists. Thanks for the help and I will update when I find out.

[mafulcher]

Well I'm back,
Long story short, I took it to a local Volvo repair place. They said I had a couple bad coils. Replaced them and it ran perfect. Drove it and then developed a miss again. No. 1 cylinder was leaking down like a stuck or burnt valve. We were guessing it was stuck since the engine has prob been sitting a while. Had them put old coils back in. I unplugged the no.1 injector to drive it home so it would not wash down the cylinder with fuel. I stopped halfway home after driving it as hard as I could and plugged the injector back in. Half mile down the road it started running perfect. I have driven it @ 175 miles since and is running great with the old coil packs. Could the valves have been slightly sticking all along to cause an intermittent miss and now they are just freed up?
Anyway, I'm happy, looks like I don't have to replace the engine again.

[jblackburn]

It happens! The good old Italian tuneup will usually do the trick if it's just a stuck valve.