1989 Volvo 240, 20-30 sec surging at cold start, new MAF & O2, no codes

I'm trying to see what exactly is going on with my 1989 Volvo 240. When warmed up, it runs amazingly well. I'm getting ridiculously high MPG on both highway and city: 27.3 with 75+ MPH and 29.4 in the city (35-50 MPH).

The problem is at cold start. I've recently swapped the MAF to a brand new Delphi unit, as well as a Bosch O2 sensor. No codes are thrown by the computer, but on cold start (65? F mornings), the car surges for about 20-30 seconds (as if it's re-learning the settings). After that, everything evens out and it runs great. While it's surging, there is black smoke coming out of the tailpipe, which eventually turns clear after the 20-30 seconds.

I have swapped pretty much everything in this car, including spark plugs, MAF, O2, new Volvo coolant and an 87? thermostat, in addition to the coolant temp sensor and ECT. With the 87? stat, it runs a little over the 10 o'clock temp position normally (faker board removed and contacts 1-3 shorted).



Not a big deal, but I'm wondering why the car seems to be in "re-learn" mode on every cold start. When I swap the old MAF in, I get codes, but a steady start every time. Is this because the new Delphi MAF uses a different technology (looks way different inside)?

Hi

LH2.4 or 2.2 ?

YS
Jaybee

mrjaybeeze said:

Hi

LH2.4 or 2.2 ?

YS
Jaybee

Click to expand...

there is no such thing as codes on 2.2, trust me.

Yep, it's a 2.4.

Have you completely reset the ECU?

Those economy numbers seem to suggest you're running lean.

I disconnected the battery for about an hour after I installed the new MAF, so the ECU should have been reset. Wouldn't running lean throw a code (even without CEL)?

Based on the engine temperature, I'd be inclined to think I'm running super lean, but I'm not sure how to check this for sure.

akhan said:

I disconnected the battery for about an hour after I installed the new MAF, so the ECU should have been reset. Wouldn't running lean throw a code (even without CEL)?

Based on the engine temperature, I'd be inclined to think I'm running super lean, but I'm not sure how to check this for sure.

Click to expand...

As long as you don't have any other power sources, connect positive and ground terminals together for a minute to drain all capacitors and such. Don't forget to them from battery completely.

This one could be tough. Maybe check the O2 sensor voltage cold and hot and also the temp sensor resistance.

Stock injectors?

Reset the ECU by shorting battery terminals together, doesn't seem to make a difference in the hesitation on initial start.

Checked the O2 sensor, seems to be within spec according to Bentley (I expected this, as it was brand new.. but figured I'd check anyway, since the car was running rich for a while during my earlier troubleshooting of rough idle). I thought that the O2 sensor was fouled up from the earlier experience, but doesn't seem to be the case.

Injectors are brand new Bosch. Swapped those when trying to get rid of the rough idle. FPR is perfect, gives about 42 psi constant.

I was also thinking the in-tank fuel pump might be contributing to this, noticed that the main fuel pump is incredibly loud when fuel gets to about 1/2 tank after driving hard for a while (75-80 on freeway for about an hour). I also burned out a fuel relay recently (no start), but it was a cheap $12 one from Pro Parts, so I didn't think twice about it, just swapped in a new one from my glovebox parts collection.

Side question: what are the drawbacks of running lean? To be honest, I was completely taken aback by the city fuel economy numbers. 29.4 is almost as good as my double clutch auto 2012 Ford Focus. I even checked whether the odometer is accurate using a GPS trip meter—turns out it's very accurate. I also drive the stick hard, usually first one out of the intersection.. so the extreme MPG didn't make sense to me.

I've heard that running lean means running hot (hence, premature head gasket failure), but as long as I'm always 2mm+ under the red in the hot Arizona summers (~90?F daily), I should be good to go? Or am I missing something?

Running lean will mean running hot, but that's much more of an air cooled engine problem in regards to your temp indicators.

I know you said the injectors were brand new, but brand new what? Did you check that they're the correct ones... the amount of misinformation involved in injectors alone is problematic.

What other mods are on the car or is it just stock everything? I would assume you don't have an air fuel gauge? I'll further assume you're running 93 octane?

Hmm.. I actually just relied on "compatible with" information to pick the injectors out. I ended up getting the Bosch "yellow tops" (0280150762).

The car has stock everything, no mods aside from replacing old parts with new (most of the parts were really.. "vintage", never replaced). Some of the stuff I replaced:
- all new vacuum hoses
- rubber fuel lines and fuel return lines, new fuel filter (Hengst)
- new power steering pump and lines
- distributor cap, spark plugs (Bosch 7900 Super Plus), wires, fuel injectors
- new bellows hose, bypassed airbox thermostat (removed preheat hose, closed off both ends)
- Volvo coolant swap (plus RedLine water wetter), 87-deg tstat, new hoses all around, faker board removed
- new MAF, O2 sensor, ECT sensor, coolant temp sensor for gauge
- Mobil 1 hi-mi full synthetic oil 10W-30

I don't have an air fuel gauge, but read that there is a way to tap into the fuel injection computer to get the readings "on the fly" - haven't explored that too much, though.

I'm running on 87 gas, as I haven't seen too much difference between 93 and 87 (aside from somewhat louder piston slap with 87, but that could be my imagination).

No answer here, just wanted to say I'm jealous of those numbers. I get about 20hwy and 12 city in my 245

I am gonna guess injectors are causing it. I have seen 2.4 cars surge with the incorrect injectors. Airleaks cam also cause off behavior.

Need more data. These old cars take longer to diag with no obd2.

Try to develop ways to test what is going on. Does the car pass smog?

My grey car sort of did this after the poly motor mounts started to rattle loose the exhaust manifold studs. I got slightly poorer than average fuel economy though.

Wait sorry. I thought you were turbo.

Those injectors are def just the stock 215cc/mins so should be "fine".

Might be worth testing compression and/or doing a leakdown test. It's odd that you're running lean, but getting black smoke on startup. This leads me to believe that maybe you're cooking a gob of oil or something briefly... though typically "blue" smoke I guess.

Additionally, maybe try some basic copper plugs... these cars for whatever reason get crazy on the weird platinums.

Surging like that at idle during warm up has always led to a bad AMM in my experience. I know you said "Brand New". Don't equate brand new with good. See if you can borrow a known good Bosch 016 AMM and put it on there to see if the problem suddenly disappears.

^^^^^ Yes! I also noticed NEW MAF was listed. During a cold start, the o2 sensor is dead in the water doing nothing until the sensor gets up to temp. Read up on open loop vs closed loop.

Anyways, surging on these cars is generally mixture issues. An aftermarket MAF sure can cause mixture issues.

Maybe try reading the voltage output of it and see if it's anywhere near spec. You can also pry the cover off and mess with mixture, but I wouldn't really recommend it.

I would smoke test it first for air leaks, and then consider that your replacement injectors and/or MAF aren't working on your car correctly.

As we get more experienced, we tend to notice that "New" doesn't mean good. When I see these threads with a pile of parts that have been replaced, I suspect the owners parts or work first. I also see a trans of no diagnostic procedures or data being provided and just a list of parts replaced, which actually means.....NOTHING!

Oh, I see black smoke on start was mentioned and posted about. That is great info. That means, yeah, mixture is way off. Try another MAF. Also, test the coolant temp sensor resistance at an unplugged ECU, and EZK boxes. It's a little work, but required for proper diag.

Redblocks are few and far between at my local pnp... so I always buy the Bosch 016 amm when I get the chance. I'd rather gamble with $40 on a jy part than several hundred on a "reman" part.
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Thanks for the suggestions! After testing the ECT, which checked out to be within spec (at least in the regions that I could test), it turned out to be the MAF. Plugged in a known-good Bosch MAF that I borrowed from a local pick-and-pull with a deposit, car ran perfectly fine. I called Delphi and they agreed to replace my "new" MAF with no problem.

My question is.. should I replace the MAF and sacrifice my currently amazing MPG? I feel no loss of power, but the engine does run a little on the hot side (although never closer than 2mm or so from the red region, even when I am going uphill from Phoenix to Flagstaff with A/C, which is trying on any car in 100-degree heat). I'm just not sure what the long-term effects of this are on the health of the engine.

Good problem to have? Bad problem to have? Thanks again!