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Poor running b230ft

R

rjritterjr

New member
Joined
Oct 10, 2010
Location
Waynesville, NC
1989 Volvo 780, b230ft, 200k+ miles (true mileage unknown)

I am completely stumped, so hoping someone has an idea to help.

Had been running great. Driving one day, engine lost power, began stumbling, and stalled. It was extremely difficult to start. Once it did start, the engine ran terribly. Smelled like it was running rich.

What I have done:

- Previously discovered a rod knock, so acquired a 1993 block, had a machine shop go through the block, and installed new bearings and pistons. New head gasket. Retained the original head, so I did not need to change the computer or fuel injection system.
- New tank fuel pump and under-vehicle fuel pump.
- Now that the engine is back in the car, the same problem persists. It's very hard starting, and when it does start, it's constantly stumbling and visible black smoke out the tail pipe.
- Repaired wiring harness to throttle position sensor.
- Repaired wiring harness to power stage; swapped in another power stage.
- Swapped in another MAF.
- Swapped in another ignition coil.
- Replaced distributor with a new Bosch distributor which included pre-assembled distributor, cap, rotor, and cam position sensor.
- New Volvo spark plugs.
- Swapped in another set of spark plug wires.
- Swapped in another fuel pressure regulator.
- Adjusted distributor, so timing is about 11 BTDC.
- New check valve between intake manifold and turbo.

What I have observed:

- Timing light shows spark intermittently drops out while cranking.
- Takes a lot of cranking to start; most of the times, it stumbles and stalls; I have to keep the starter engaged for a long time to help the engine stay running.
- Starting is slightly easier if I unplug the MAF. Engine runs very rough during start-up but then runs as if it is missing intermittently.
- Plugging in the MAF helps once it's running but does not solve the intermittent miss/stumble.
- There is a lot of hesitation when throttling up engine.
- Vacuum is about 5hg. All new vacuum lines, and I cannot find any vacuum lines unplugged.
- Black smoke from tail pipe while idling and noticeable intermittent miss when feeling the tail pipe output.

It seems to me that there is an ignition/spark problem, but I don't know where to look for the cause of the problem.

I have noticed that some of the wiring harness connectors have problems with the connector pins. As I find them, I am repairing them.

If you have any ideas, I am certainly open to help.
 
black smoke indicates too much fuel. Check the vacuum line going to the FPR for gas. If there's gas present replace the FPR. Also verify your CTS is plugged in and check it's resistance to make sure it hasn't failed.
 
On these systems the coolant temp sensor will override going into closed loop. So if the impedance is too high in the coolant sensor circuit it stays rich and is very hard to start. Make sure you have the correct sensor for your fuel injection.
 
I went through all connector plugs and found a few that had damage inside. Replaced the bad terminals inside the connector plugs. Also found a few damaged terminals in the ignition module plug. All of those were replaced. Still no joy.

I went through the green book fuel injection troubleshooting guide. Everything checked out except the engine coolant temp sensor, which was brand new (although I have had it in a drawer for 10+ years). I discovered that the engine coolant temp sensor voltage at the ECU was around 4.8v. I could not get an ohms reading at the ECU. On a hunch, I pulled the coolant temp sensor wire connector and checked for resistance between the ECU and connector plug. Nothing. The ground wire had 0.2 ohms, which seems to indicate a good wire from ECU to the connector plug terminal.

I should have replaced the wire then and there, but I ended up ordering a new coolant temp sensor and a Programa ECU. Still no joy. I ended up stringing a new wire from the connector plug to the ECU, and now it starts fine when hot. So one problem solved. Eventually I will probably have to replace the entire wiring harness. That's for another day.

It still wants to stumble on acceleration under boost. Runs great at idle and if I back off acceleration. Per green book and a Volvo faq page, the oxygen sensor should have around 0.5 or 0.55 volts. Mine is constantly around 0.85 volts which I understand indicates a rich condition. From what I am reading, this would reduce fuel flow.

In testing for voltage, I can get the voltage to read around 0.02 if I remove a vacuum line, which is apparently what it should do. However, on all other conditions and rpm range, voltage sits right around 0.85. I have ordered a new oxygen sensor on the belief that these readings indicate a bad sensor. This is what volvoclub.org.uk's faq page says if readings stay around 0.85.

If anyone has another suggestion, I'm all ears. I've had b230f and b230ft Volvos over the last 23 years, and this has been the most problematic and frustrating of them all. I successfully swapped in an m46 and a squirter block from a 93 940. I'm telling you, this car wants to go and have fun so badly. I just need to get the stumble on acceleration sorted. Will post back once I get the new oxygen sensor.
 
I'll get pics once it's successfully on the road. I first saw the 780 when I was in college, and the 780 was new. From that moment, I had to have one. 15 years ago or so, I read about someone swapping in an m46. Rekindled my desire to have a 780. In 2020, I decided it was time, saw one for sale in TN, and bought it. Needed a lot of work, and previous mechanics ruined the block, unfortunately. Then, we found a pair of non-running 740 diesels, one of which made for a donor car for the m46 swap. Donor block for the engine rebuild was a wrecked 93 940t which turned out to be a squirter block. I should have transplanted the whole ignition module and ECU to convert it to lh2.4, but I didn't and scrapped the 940, wiring harness and all. Oh well, I prefer fewer electronics anyway. Machine shop wanted to bore out the block, so it's got the Mahle overbore pistons. Hoping I can have fun with it soon!
 
Maybe, but I already swapped in a reman Programa ECU, with no change. If my ECU had faults, I would expect to see a change with another ECU. This was the first time I swapped an ECU in 23 years of owning b230 engines, and it seems the ECU was not at fault.
 
I still think you need to measure the impedance of the coolant temp sensor. You need to ohm it at three temps. Cold engine off, warm engine, and fully up to temp. Then after that I'd look toward the mass airflow sensor. Look on the cleanflametrap website for checking the mass air sensor.
 
Update: See ECT ohms in the recap below. Also, new Bosch 02 sensor, and same symptoms. Took it out for a drive, maybe 3-4 miles. My test route us up a slight grade, down a slight grade, through a roundabout and back again. Exactly when the boost gauge needle gets into the yellow the engine loses power. In 3rd gear with throttle, I will lose speed going the uphill. Before the boost needle dips into the yellow, acceleration is normal, and the engine feels great. I can get up to 40mph with ease. But once I give it more throttle to get the boost needle into the yellow, there is hesitation, stumbling, and loss of power.

A more troubling problem is that on my way back home, when starting out from a traffic light, the engine has no power whatsoever, and the car barely moves. The engine sounds bogged down. After 5 seconds or so, it will start accelerate normally, right up until the boost needle dips into the yellow.

I pulled a spark plug, and it appears to show symptoms of fouling. The electrodes look to be fine, but the bottom of the threads are sooted.

One item I am noting is that the red/white wire at the coil only has 11.5v, while the blue wire has battery voltage (13.5v or so). I measured resistance on the red/white wire, and it is normal (0.4 ohms). I measured between the connector at the firewall and power stage, which I believe makes a loop to the coil, into the cabin (fuel pump relay?), and back to the power stage.

I checked resistance between the fuel pump relay sockets and red/white wire at the firewall, and got no reading. Dave Barton's site shows the red/white wire is socket 31b at the relay. If that is correct, perhaps the wire is bad, but I would expect to get some kind of reading.

To recap:

-Swapping in Programa reman ECU made no difference.
-New Mahle fuel injection relay.
-New radio suppression relay, and green book tests all checked out as within range.
-New power stage and fresh silver paste, and multimeter tests all check out.
-Coil resistance is 0.1, so it seems to be ok.
-I tried adjusting the distributor a little just for giggles, but no joy.
-New engine coolant temp sensor shows 1450 ohms when cold, 900 ohms during warm up, and 740 ohms right after the test drive. That all seems to be fine.
-Swapped in another coil, no difference.
-New Bosch 02 sensor installed today, no change in symptoms
-New Bosch distributor which included cap, rotor and hall sensor pre-assembled.
-New timing belt - checked timing today, and marks are right on the money.
-Timing light shows 11 btdc at idle 750 +/- rpm
-Per green book, fuel injectors, ballast resistor, and MAF sensor all passed the multimeter tests
-Swapped in lh2.4 fuel injectors, no change to symptoms
-New Delphi fuel pressure regulator
-New fuel pumps and new fuel filter (fuel filter installed earlier this week).
-New Bougicord wires and Volvo plugs
-New head gasket installed just a few weeks ago after block rebuild (but I have not checked compression)
-Vacuum holds steady at idle at 15 on a hand-held vacuum gauge, and boost gauge shows very strong boost (halfway into the yellow) under heavy throttle
-Swapped in an off-brand MAF sensor I had laying around, and symptoms seemed to get worse; I cannot confirm replacement MAF sensor is good, and I do not have another Bosch to test.
-Unplugging the Bosch MAF sensor results in very poor idle. Plugging it in again smooths out idle.
-Hard hot starting problem solved with stringing a new wire from the ECT to ECU.
-It is no longer emitting black smoke on acceleration.
-All grounds I could find were cleaned, re-seated, and resistance in wires were all 0.1 to 0.4 ohms.
-Overboost pressure switch is connected electrically but not current tied into the vacuum hoses
-Turbo plus system is not currently connected electrically; I disconnected the wiring at the coil, but this made no difference to symptoms; turbo plus system is also not tied into the vacuum hoses.
-New fuel line routed from tank to pump when I installed the tank pump.
-Checked all the connector plugs and replaced multiple damaged terminals, still no joy.
-Found a couple damaged terminals at ignition computer, replaced terminals, and no joy.
-All new vacuum hoses, including to boost gauge, and all new air/intake/intercooler hoses. Old hoses showed signs of significant wear.

Symptoms:

-Under heavy throttle when boost gauge begins to dip into the yellow the engine stumbles, hesitates, and loses power. Uphill, I will lose speed.
-From a traffic light, there is no power at all, engine will not rev for about 5 seconds, and then it will begin accelerating normally until gauge gets into the yellow.
-On the first leg of my test drive, I can easily get up to 40mph if I keep the boost gauge out of the yellow, just on the edge of the yellow.
-At idle, I am getting visible vapor from the exhaust, and with today's rain, the visible vapor was worse.

Really, I am at my wits end. My daughter heads off the college in 2 weeks, and I promised her a day trip before she leaves. I'm losing hope that I can enjoy this car before summer ends. Any ideas are appreciated because I don't know what else to try.

I did rent a fuel pressure test kit today, but did not have a chance to hook it up. I also plan on replacing the feed line from the pump to the rail because it's original and looks to be in rough shape.
 
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So an update is that Programa confirmed my MAF sensor is dead. I sent it down for repair, and they said it is dead and not repairable. I have a new Delphi in temporarily. After installing the Delphi, I had to readjust the timing. It's still not running great under boost.

I also discovered this week that there is dirty fuel at the under chassis fuel pump. In spite of flushing the system out and pumping in fresh fuel, it seems I have dirt and yellow fuel in the lines. Once I have time to refresh the fuel system, we'll hope that and a reman Programa MAF sensor will do the job. If I don't any updates, that was the whole problem.

I was able to enter the 780 in the Maggie Valley Euro Fest today and am posting pics as others requested.IMG_2312 (1).jpgIMG_2313 (1).jpgIMG_2314 (1).jpgIMG_2315 (1).jpg
 
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BTW the 740 ohms at fully warmed up is too high a reading for the engine coolant sensor. Fully up to temp it should be around 290 ohm or so. So maybe there is still some extra resistance in the circuit or that sensor is slightly off.
 
dl242gt, thank you for the observation. I believe I was reading conflicting info on the ohms. Green book service manual indeed says 290-364 ohms.

I found that the new Delphi MAF sensor and new Delphi fuel pressure regulator I bought are not up to snuff. Also found loose wiring on the in-tank fuel pump. Discovered the wiring issue when I was cleaning the tank, which had a lot of rust debris apparently from the coating on the sending unit. The Programa MAF is working good, and a used Bosch fuel pressure regulator helped. I still have some low RPM hesitation, but once that clears up, the turbo boost makes me smile!

Perhaps the low RPM hesitation is related to the engine coolant temp sensor resistance. I will test it more. I currently have timing set to 15 btdc and it seems to want a couple more degrees of advance, which suggests it is compensating for a lingering problem.
 
That being an LH2.2 car. You can try to fine tune the system with the led setup and the mixture screw on the Maf sensor. Make sure you have a fresh air filter and fresh oil for a mixture adjustment.
 
I believe I have finally resolved the poor running issues I was having. First, I adjusted the CO screw on the MAF. I found detailed instructions on Saab and Porsche forums, bought an analog volt meter, and dialed in the CO screw. I had trouble finding instructions on building a test light, and I wanted to understand the operation better. The analog volt meter was very useful.

Then, I suspected the idle air control valve may be at fault and contributing to the poor idle. I left the IAC plugged in but removed the hoses and installed caps on the air tube and manifold. The idle is perfect now, and drivability has greatly improved. I know it may not start or idle well in the winter, but this will not be a winter car.

Now I just need to decide whether to transplant the rear axle or look for a T5. I am finding that the M46 with a 3.73 setup is not as much fun as I was hoping to achieve.

Entered the car to the Autumn in the Mountains British car show yesterday, and won second in class! Then took a run through the mountains on the back roads. It is definitely a lot of fun, more so than the automatic slush box.
 
Terrific! As a fellow m46/3.73 haver, I feel you on the ratios. First is a bit of a bummer and cruising at 3k on the highway is a bit much.
 
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