Various engine problems - advice?

It seems my car is getting slowly worse and various things have occurred with the engine, which aren't so good. In fact its all quite annoying. I have various ideas and things to fit to try and improve matters, but I thought I would post some stuff here about the problems. Not so much because I am expecting "the answers" from anyone, but just in case someone else has experienced anything similar or has any suggestions. You never know, many heads are better than one

(Car is 2000 MY S40 T4 + mods as described in my sig).

So, the symptoms. Well it all began with:
- generally seemed a bit less responsive under hard acceleration / boost
- occasional "stutter" under high boost (so > 3000 revs)

Also I noticed:
- this seemed to occur more after a hard run
and
- if you declutch after hard acceleration, and let it drop to idle, the revs drop right down to about 500rpm before settling back to normal 750 to 850 rpm

Hmmmm.....

Now my thinking for the first couple of things was that it needs a new fuel pump. Also the fuel pump is very, very loud at the moment it whines like a good 'un. This also makes me think it needs a new fuel pump asap. And sure enough a new one is on the way (I've had some problems with getting hold of this due to some g!ts I ordered it from messing me about - described in another thread), anyway it is an uprated 255 litres/hour walbro one and should arrive tomorrow.

My feeling was that the car was getting starved of fuel under sudden, high demand conditions. But to further try and check things I rigged up the diagnostics on the computer and checked out various things whilst driving along.

I discovered that at idle, all the measurements for everything where in spec. Driving along, everything seemed fine the usual stuff like coolant and air temperatures etc. (Edit) also should point out the boost gauge says boost is fine, holds boost fine, boost pressure all as expected.

What was interesting though was that the front o2 sensor readings seemed to go and stay particularly low voltage = weak a/f mixture under hard acceleration and high boost. Now the diagnostics only updates every 1/2 second but you can kind of get readings at different instants if you monitor the same parameter on more than one channel (won't explain this further). Even so, under low acceleration / no boost the front o2 sensor showed switching between rich/weak/rich/weak etc. as expected but under high boost it remained quite weak for a bit. I forgot to monitor injector opening during this time though.

Anyway that made me feel like my diagnosis was sound.
Although I'm not so sure it can explain the idle speed dropping like it does. Note that I have very recently given the idle valve and throttle body a good clean out, note also that the throttle potentiometer readings are in spec and the idle control valve opening at idle is also in spec.

But then I changed the spark plugs earlier. Although the current NGKs had only been in about 2000 miles I had got some of those denso iridium ones.

I was very suprised to see that the plugs were very carbonised. It indicated to me that the engine was running rich, which wasn't particularly what I expected to see!

I wondered if this could solely be explained by the presence of the dump valve and the fact each time I throttle-off there is a realease of metered air into the atmosphere hence the engine gets less air than it thinks it does. But this only happens briefly when you close the throttle, can it really explain everything? (Edit) Thought I'd add that I have been using a lot of "add to tank" fuel additives lately, some redex to clean up the fuel system and some octane booster. Dunno if these could make a difference?

Perhaps it is still a fuelling problem? If the engine runs weak under high boost due to low pressure then maybe it overcompensates when going back to idle? could this explain the idle dropping thing as well? Perhaps the fuel pressure regulator is also knackered? I have tonight cleaned the vacuum hose to it, was a little oily but not blocked. Will see if that makes any difference.

The other bad thing that happened... after the new plugs, took it out and was stuck behind something but when the road cleared I accelerated but all I got was what felt like a serious rapid sequence of misfires at about 3000 revs til I backed off somewhat. This happened repeatedly but then it was all alright again?! One possible explanation was that there was a bad contact between the HT end of the coil pack and the plug on no. 4 cylinder. I checked it out and on this one the spring had lost its "springyness" if you see what I mean, I have ordered a "new spring and rubber" kit. I mean the spring in the end of the coilpack lead. The 2 HT leads are new BTW and no. 3 seemed alright, although I thought I'd get that one a new spring as well. Even from volvo they can't be much!

Now the funny thing was there was NO FAULT CODE saying "misfire" nothing at all, once again as per usual the car is convinced everything was a ok which is just plain frustrating. What makes the car detect a misfire? Does anyone know? Can it only detect it from the sudden spurt of unburnt fuel emission? If so, how is it sensitive enough to know which cylinder it came from - can it be that quick to respond? Perhaps there was just a low spark and the car cut the fuelling drasticly to one of the cylinders, I don't know. Either way you'd think it could've been ar*ed to raise a fault code, but no it couldn't be. Anyway since then I've pulled the spring out a bit. And is hasn't come back. But the other faults remain.

Will report more when new fuel pump fitted but that might not be for a bit.

Any advice / info is appreciated, thanks for reading

In the constant conflict of me vs the car, it looks like the car has started winning a few battles. But I'm determined to win the war, but I might need a little help from you guys

Cheers,
Pete

[johnswlondon]

very puzzling problem,the temptation is to start replacing everything in sight only to find the problem remains!

i think the condition of the spark plugs will always give the best indication of whats going on and its cause.

one way or another the fuel isnt being burnt cleanly,with the mixture being too rich.if its your fuel pump,which you suspect due to the hesitation,i would have expected fuel starvation and the plugs to be pitted.

i would be very interested to hear the co2 reading from the exhaust to know if your lambda probe isnt playing up,because this increases the fuel to ensure the cleanest burn and minimum co2.

the wrong spark plug gap can also cause hesitation at certain rpm,it can usually be spotted by a slight misfire at idle,with your ear near the exhaust

ive never bothered to look but i assume the car has points in the distributor cap even though its contactless,this can also cause hesitation if worn or dirty

[scottishvolvo]

Pete have you tried a compression test on the cylinders to check if any might be passing.
Chris

before condeming the pump have you tested its output pressure at the fuel rail test port?

Thanks for the 3 replies so far chaps... keep them coming, people

To answer some of the points you all raised:

1) chow: No I haven't checked the fuel pressure due to lack of a fuel pressure gauge but the new pump is winging its way here hopefully now (didn't arrive today )... anyway it is making lots of noise and getting worse so one way or the other, it ain't right!

2) chris: No I haven't done a compression test. I do not have a fitting which is small enough for the small spark plug hole on this car.

But I think this would tell me all is ok. The plugs are the same for all cylinders. The engine starts, idles and generally runs ok just a bit hesitant at hard acceleration I feel and the other minor things mentioned above.

3) john: On these cars there is no distribution of the HT there are two coil packs each feeding 2 cylinders so at any one time there are 2 sparks one of which is a "wasted spark".

Yes it is possible that the front o2 sensor is faulty, I do not have an exhaust gas analyser so I cannot easily check the emissions from the pipe.
But the car reports no emissions faults, and so I presume that this would mean either both o2 sensors were faulty or the cat was strangely knackered which all seems a bit unlikely otherwise the car would detect a problem by comparing readings before and after the cat. If I can find one cheaply e.g 2nd hand I might invest in an EGA - could be worth having. Would be more useful to use if I could read the CO before the cat though.

I was thinking of posting up a picture of the plugs, and also a picture of the previous set which were in the car up to about 2.5kmiles ago. Of course this means finding both sets - they will both be in the garage somewhere, but no doubt somewhere amongst all my junk!

IIRC the previous plugs (which had no doubt been in there for eons) looked all ok. It would seem strange for the car to have a sudden major mechanical failure recently, and all of a sudden, so it would seem like perhaps a sensor failure or something I have done. Since I last changed the plugs - over the last 2k miles - I have done the modifications shown in my sig. The only other significant thing to do with the engine has been new cambelt done at same time as the plugs. And well, if I'd got that wrong the car would either have introduced the pistons to the valves or would just plain have run like sh!te. Plug gaps on the previous set of plugs I am sure would have been set by me to be within tolerance; on these ones they are 0.75 to 0.8mm (spec is 0.7 to 0.8mm).

So, I am now wondering if the rich running is solely down to using an atmospheric BOV? It would be good if someone else with one could tell me how their plugs look. I am getting a bit fed up with this thing (despite having a photo of it in my avatar) not only is it not too loud, but it was potentially giving me gyp to do with the fluttering air noise (see another thread somewhere) and it wasn't exactly free to buy either!

Wasn't able to investigate anything further tonight; now it is too cold and dark I'm fed up of going out there in the cold and freezing my bowl-lax off, car been running as ok as normal today (i.e no more dodgy misfire type things).

Thanks again, any more suggestions welcome esp. re. spark plug condition in those with an atmospheric BOV.

Cheers, Pete

[johnswlondon]

when you say you changed the spark plugs earlier,did the fault arise at the same time?i only ask because on my last volvo i changed the original volvo spark plugs and it never ran the same again so i put the originals back in.

in total they covered 160,000 miles!

Originally Posted by johnswlondon

when you say you changed the spark plugs earlier,did the fault arise at the same time?

No, was alright after that well same as it was before doing that and the belt. The only difference was I didn't "bottle out" of revving it hard, which I had been doing before I did the belt as I had this fear that if I stressed the engine the (old) belt might be more likely to snap. Bit silly I know, but you know how things can go... that's why I did the belt sooner rather than later, just so I wouldn't get worried about it!

Then a few weeks after that I did some of the mods, and obviously each of those increased performance to varying degrees.
And then I suppose I started noticing some of these problems happening, maybe first of all a bit occasionally and then a bit more often and I suppose the only thing it correlates with is the noise from the fuel pump increasing.
I couldn't say there was "a moment in time" when the faults all started. I think I might've noticed the odd stutter at one point, then there was one day when it seemed a bit less quick in acceleration, then seemed a bit ok again, then I noticed the stutter thing happen more and more often, and somewhere around this point it began to occur to me that the fuel pump was sounding louder... then the idle thing (which might actually be nothing who knows) I noticed that...

you know how these things go, they sort of creep up on you don't they. So it's not like anything failed, but in a very short space of time (like maybe 2 to 4 weeks tops) something has occurred. That's why I was/am thinking fuel pump (which STILL hasn't arrived come on mr. ebay power seller deliver the effer!!!!). And why I don't particularly just want to have it get worse in case it does then suddenly fail.

The misfire thing hasn't happened again so I think that was "a blip" explainable by the coils thing.
Even the heavy fuel consumption I can't be sure when / if it suddenly started going up because I don't actively monitor it (and the car has no facility to do it for me)... but bear in mind my mods would naturally worsen the mpg plus I've no doubt been driving it harder lately too.

Forgot to look for the old (i.e "original") set of plugs but will hopefully get a photo up soon.
The only other thing I did the other day was disconnect the EMS ECU ground connector and clean it up... well you never know! Anyway I thought a "reboot" might help. So at the moment the ECU is still learning the car again, so any current "results" are a little bit skewed from before for a few miles yet.

Ah well, it's all a bit of a pain in the bum really.

Be good if someone could answer my "plug condition" -> "rich running" -> "people with atmospheric dump valves" question... anyone?..... c'mon some of you must change your own spark plugs????....

Pete

Wanted to answer some stuff from pyaap which was started in this thread but is best discussed further here....

Originally Posted by pyaap

Our cars run open loop at full throttle, so if anything is wrong with the mixture, I would look at the MAF sensor as the first port of call; either get it cleaned or replaced. If its not the MAF, then you need to start working down a rather extensive checklist for other possible causes.

Hmmm.... MAF I cleaned it some while back, and the readings are ok at idle.
I must say "extensive" also = "expensive" so hopefully and faults won't be too difficult to resolve.

Certainly the rich running is only something noted from the colour of the deposits on the spark plugs.

Originally Posted by pyaap

On a stock ECU, a T4 tends to run quite rich at high revs so if its lean, something's wrong somewhere; BTW, how lean are we talking?

It's difficult for me to say, but it does not seem to be running right under high revs/hard acceleration (see symptoms above).
If I say accelerate midly at lower revs (under closed loop control as you mentioned and as indicated by the VOL-FCR) then the lambda (looking at front HO2 here) will fluctuate between rich and weak as I would expect in a fair old short bit of time (e.g 4.XX Volts, 1.XX Volts, 4.XX Volts, 0.XX volts etc.)
But in a short bit of time when flooring it at high boost the reading from the same sensor remains < 0.1V or so e.g 0.04V, 0.06V etc. etc.
During this time it is in open loop as you mentioned.

Originally Posted by pyaap

If the dump valve is in good order, then it should be tightly closed the moment it senses any boost, hence it would not explain a rich condition under boost, or at least a boost leak due to the BOV itself; the engine will undoubtedly run rich in overrun though (I have detailed and accurate pre-cat wide lambda data logs on this and can discuss them with you)

Yes, under boost I do not think it is rich but weak as mentioned above.

I notice that in the overrun as you infer it goes to open loop control and so with the atmospheric BOV I think here this is where it is running rich. And that makes sense. Could it explain the fouling of the plugs? Maybe. Loopy who posted in the spark plugs question thread seemed to think so.

Certainly from a "how does it drive" point of view the ONLY time I have any problem is under hight boost / full-throttle type conditions APART FROM the thing I mention above where the idle seems to drop quite low when you throttle off. But then again that could just be a "nothing" thing and something it is meant to do if the car is moving since it is not something you would normally do if you were changing up or down a gear. What is "quite low" revs well it doesn't seem to be below 650 rpm I would say, before picking up to 775 rpm again. If it wasn't for the fact I was "looking" to figure out what is wrong with the car then I doubt I'd have noticed this "feature".

I think what I will do is to change the fuel pump and then reassess the issue and see how it is, and post further then. Might be able to do the pump on wednesday if a) I can get a day off and b) it isn't raining that day. It would certainly be a bit of a coincidence if the amount of aural grief being chucked out by the pump is not connected with the performance issues I've been having. But the only thing is the car has had a number of mods in a short space of time: the exhaust, the air intake, the MBC and the dump valve have all come within the last couple of thousand miles.

Re. the exhaust gas analyser, this might be a good idea anyway and I've been thinking about getting one in the back of my mind for a while now (before got the volvo, when there was something wrong with other cars I sometimes work on). There was one on ebay cheap t'other day, although I am a bit put off ebay at the moment from the fuel pump experiences (even though that prob. was not an ebay problem)......

Cheers,
Pete

[loopy]

i had my dump valve on for 2 year know covered 30k it did run rish and chucked a nice flame out of my s/s exhast but i turned my boost up to 14 psi and my plugs and car realy good. interpro said a bov would make it run rich just when you change gear ane at tick over they said it ok on turbo it better to have it runing like it cause it wont go bang for runing lean ring them the good in the modyfing sceen their good with turbo 01454412777 their roller are the best ask them hope it help my

Well now....

Today I fitted the new (the uprated) fuel pump. Now the inside of the car smells of petrol but hopefully that'll clear soon.

In terms of noise, well the new one is quieter - but it is not silent. In fact the noise it makes is particularly annoying as it is very high pitched (even though is quieter). But maybe it will "bed in" and improve. I am a bit concerned though, because like a fool I dropped it on the ground the other day when I was startled by the neighbour's cat (DOH! You couldn't make it up, could you!). However in terms of being a fuel pump, it seems to work fine.

For sure it has made a difference. Now, it is difficult for me to say at this stage exactly how much difference because I disconnected the -ve lead on the battery before doing the job (due to lots of fuel vapour everywhere) so right now the car will still be re-learning the engine. But assuming that is not relevant, I noticed the following:
- as yet (touch wood!) no evidence of any sort of "holding back" or the dreaded stutter / backfire (!!) or anything horrible like that under hard acceleration
- the car has more "urge", if you see what I mean.
- during the open loop fuelling control (non-lambda active) the car seems to "give 110% commitment" which it didn't do before (or at least hasn't done for a while). And it does this right up to 6,000 revs without any sign it is having gyp.

So basically performance isn't exactly a massive improvement, but it is better at least it is a lot better than it has been for a fair while (if ever).

One thing I noticed which I am not sure I can explain, is that turbo boost (measured by the gauge at the manifold) was suddenly increased.
- previously was 1.2 bar
- would now peak at 1.4 bar!!

Perhaps someone can explain this?
It must be directly related to the new fuel pump, because:
- "atmospheric conditions" tonight are same as last night (not too cold, damp)
- nothing else whatsoever changed on car (no I didn't accidentally change the MBC setting!)
- no new fuel added (at the time I noticed this)

Note: I have now backed off the MBC back to 1.2 bar again.

Also, re. the idle issue it still seems to do this. It will drop to about 600 revs before picking back up to 775rpm. Well, I always expected this would have nothing to do with the pump.

I might post some info on doing the pump. I took a couple of photos but I was in a bit of a rush as darkness was falling (unfortunately I was later than I expected starting the job).

Interestingly enough, all 3 pumps were Walbro and all were different. Of the two new ones the uprated GSS342 was actually a better swap than the other one which was billed as being "a direct replacement"! Also the instructions for the "direct replacement" one were complete b*llox, but it was obvious what to do although I wish I had not changed the supply hose because so difficult to get the old one off and new one on, and in doing this I of course snapped the thin wires from the sender unit to the terminal block and hence had to bring my soldering iron back into service. But I managed not to set the gaff on fire so that's a bonus

But no-one light a match in the back of my car for the next couple of days

I shall monitor how it gets on, fingers crossed that it gets quieter and the car continues to perform without previously mentioned problems.

Cheers,
Pete