I know there are more than a few of these threads floating around but I'm struggling with ideas on this one.

My 1990 Volvo 240 has been running very rough. I have never registered it and been working on it for quite a while since the head gasket blew the day I purchased it. It ran great at that time. The head was skimmed professionally and reinstalled without issue. I just had my second kiddo and can't fit two car seats in my 77 F-150. Therefore I've been spending more time trying to get this thing ready for daily driving.

It currently requires a small amount of gas pedal to get started. Otherwise it just cranks. It runs really choppy once it starts. Most of the time it dies right away. If I'm on the gas it will sometimes hold a very rough idle for a few minutes.
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I pulled the plugs and they were all dark black but not wet. My thoughts are it is running very rich. I replaced them with four brand new Bosch plugs. There was no change.

Im getting codes 1-1-3 and 1-3-3 on my LH2.4 system. This appears consistent with the symptoms I observed.

I unplugged the MAF and restarted the car. It didn't run any worse or better. Not sure it can run any worse without stalling. I plugged her back in afterwards.

Where should I begin? My suspicions from other threads are maybe a bad MAF (not convinced), vacuum leak before O2 sensor (nothing obvious seen), or something else entirely.

 

I'd look at the coolant temperature sensor, the one under the third runner of the intake manifold but even more Iikely you have a bad MAFS. These MAFSs really are the issue in many mysteries with our cars these days. There are hard to diagnose, can't really be tested and create quite a number of running issues, the codes are of little use...

 

Thanks for the quick reply. I'm not against replacing the MAF...they're just expensive. From my understanding, there is no reliable test to see if they're good?!?

I actually replaced all sensors on the top of the engine when I did the gasket. The Engine Coolant Temperature sensor was replaced with a new Bosch unit. The Coolant Temperature Sensor was replaced with a genuine Volvo brand sensor.

How would I check the sensor? I believe you are referring to the ECT sensor, no? The one that has a plug into it not just the single wire.

 

I just did some more checking for exhaust leaks. I discovered a leak where the exhaust manifold and header pipe connect. It's coming out the back pretty significantly. Not sure how I missed it. That gasket was put in when I did the head gasket. Any tips on getting it sealed. Both mating surfaces were smooth and fairly clean if I recall.

Any chance this could cause a lean reading at the O2 sensor causing the car to compensate with a rich condition? Would be nice if this fixed it.

 

That leak won't cause running issues unless really big.
The front sensor is for the temp gauge, the back one is the CTS for the injection, the one that matters.

 

I replaced the MAF with a known good Bosch one. Didn't fix the issue. Glad I have a spare. Not sure what is next. Probably gonna check the post MAF section for air leaks. I also got some high temp gasket stuff to stop the leaks in the exhaust manifold. I'm not convinced I'm running on all cylinders. I need to verify this next time I get a chance. All suggestions still welcome.

 

These problems may be more involved considering this car's recent past. The failed HG, how did it fail? Was the motor overheated? If not, why skim the head? How much was skimmed off the head? Then the subsequent installation, it could be something minor related to that. Then it could be something fatal like an undetected head damage if there was overheating, crack, valves, etc. You can start with a compression test now, go from there... (Sorry, I skipped over the bad HG part in your original post. It should have been addressed fro the beginning.)

 

Lev,

No need to apologize. I appreciate the help.

I had the head skimmed because I was unsure how the head gasket failed. I bought it that way unknowingly. It never overheated for me on the 1.5 hour drive home. I had the local engine shop that did it check the head for cracks. I believe they checked the valves too (it's been a while...I'm not 100%). Everything came back fine.
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I have not checked for compression. I'll have to find my compression tester or snag a new one.

If I have time tomorrow, I plan on fixing the exhaust leak. I'll also check that hose after the MAF for leaks. I think I have a new one somewhere I may swap out.