V40 T4 (1.9) Misfire / backfire - running rich
 

Hi guys (and gals).

2 days ago i became the prowd owner of a 98 Volvo V40 t4. Test drove the car and it was absolutely on the money, so handed over my cash, then drove it 50 miles home without missing a beat.

Next day, at anything over quarter throttle it'd misfire, bog down and sometimes die altogether. I checked the HT leads and Coil packs and they were shot, so replaced them (spark plugs looked ok). This made it better, but the problem was sill there.

Then the wierdest problem cropped up. After turning the engine off, the cooling fan would start spinning for about 15 mins then shutting off (yet wouldn't when it's running). I had it plugged in to the diagnostics today, and they didn't give me the fault code, but told me that It reported "L1 Bank Fuel running rich" or something like that.. Basically the car is running rich.
I completely disconnected the MAF, and it improved things a bit yet it's still misfiring (and backfiring) quite Alot.. and now the MAF is disconnected it stalls on idle, but i was expecting that, sometimes it's almost undrivable.

Is it likely the MAF is the cause of all my woes? or am i looking at something a bit more severe... I am on a very limited budget after buying the car, so i have to be as systematic as i can on repairs. I can't just replace bits Just in case (not yet anyways).

Thanks in advance guys :)

the duff maf thing you mentioned makes a bit of sense,

i and gmain have accidently left the maf unplugged on our cars and as well as throwing an engine light until plugged bsck in one mine the rad fan wouldalso stay on after i switched off the ignition

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Ideal. Thanks.. Well i'll try and get hold of another MAF tommorrow and see if that cures :)

Worth a Try?
 

As btsam said, we had issues when the MAF was (accidently), left disconnected.

I decided to remove the MAF and. contrary to some advice, got electrical contact cleaner and gave it a spray. I also sprayed the connector on the top of the MAF unit itself, and poked dead flies off the gauze itself (still not a clue how those got there, but they were)!

Touch wood, things have been fine since. If you are considering a new MAF, worth a go with this - nothing to lose really? Just make sure that it is electrical contact cleaner you use, if you do try this.

Best of luck

Thanks.... The MAF is definately screwed.... One of the 2 elements is missing (the clip is there but no wire in between them) so it's definately had it.

I'll try another one and see if that cures the problems. I'll let you know how i get on.

Assuming its not the MAF or just the MAF, have you checked the condition of your air filter?

There isn't one. THe previous owner put an induction kit in. That's in good condition and letting plenty of air in.

If it's not the MAF, would lambda sensor be the best thing to look at next? if so, which one is most likely to cause the running rich issue?

The diagnostics didn't mention lambda at all, just running rich. but apparently the 98 ones dont tell you whats faulty, just what's wrong?

Aftermarket induction kits can cause problems particularly if the filters are oiled (affect MAF) or are not installed correctly. Recommend you double check this.

As Terminator says, aftermarket oiled filters can contaminate the MAF, which seems to be the case with yours. The standard air filter housing allows sufficient air flow plus it doesn't draw in hot air from the around the engine bay. If you want a performance air filter I suggest you either get a standard housing with a performance panel filter or go for something like the BSR filter which comes with its own housing.

If I'm not mistaken the sensor before the cat will measure if the fuel has been burnt in the exhaust gasses so this could be a suspect.

Another one for over fueling is the engine temperature sensor on the thermostat housing which, if faulty, can send wrong messages back to the ECU. But because yours is backfiring it would suggest the Lambda sensor/s aren't reading the exhaust gasses correctly.

'960kg' or 'Clan' would be the men to explain this more clearly :thumbs_up:

Thanks for all the advise guys.
I had a cheapo aftermarket MAF turn up today (i wanted proper Volvo, but i just didn't have the funds). ANyways. this seemed to massively improve it, but there was still a slight issue.
I checked the Post cat lambda (which was a universal titania job) and the wiring had been bodged. I redid that, and also replaced the spark plugs.
So. Aftermarket MAF, New Coil Packs / Leads , New plugs and repaired the lambda probe.

The Engine light and DSA light have now turned off and she is almost as she should be.
Except when i give her more than 50-60% throttle on occasion she really hesitates, and maybe a slight misfire but not sure on that one.

It does have some cheap induction kit on it, but i did not fit this, it came with the car. The car basically 3 days old to me and a nightmare already .. why didn't it play up on the test drive so i coulda walked away lol :(

None of the local scrappies have any parts (between Newquay and Exeter where i tried) for Any Turbo S/V40's. Is the airbox on the turbo uprated or can i use one from one of the N/A models?

I am wondering if the rest of my problem is due to that cheapy induction kit on the car... i'll continue trying, i spent all day on the phone to local volvo dealer and they were at a loss as well. especially now there is no Fault light showing :\

It also seems to be running a bit better on Texaco 95 ron fuel, i was running it on optimax since i bought it. Could this have any bearing on the remainder of the problem?

ta again.

Mike.