What does it mean if...
Discussion
...Your Impreza turbo stutters under full throttle when it hits around 4000rpm?
My new Scoob seems to have a bit of a cough. It feels much like my old 200sx when the fuel cut tripped because it was running too much boost. It's only a momentary cut in power, but it hits like a hammer and then the power comes back. It doesn't seem to do it if you accelerate softly, only when you try to press on.
The car is a last-of-the-line classic Impreza turbo, and as far as I'm aware it's standard so don't know why this would be happening. It's going into the garage for a service tomorrow so it would be good to have some suggestions to put to them as to what might be causing it.
Cheers
My new Scoob seems to have a bit of a cough. It feels much like my old 200sx when the fuel cut tripped because it was running too much boost. It's only a momentary cut in power, but it hits like a hammer and then the power comes back. It doesn't seem to do it if you accelerate softly, only when you try to press on.
The car is a last-of-the-line classic Impreza turbo, and as far as I'm aware it's standard so don't know why this would be happening. It's going into the garage for a service tomorrow so it would be good to have some suggestions to put to them as to what might be causing it.
Cheers
Out of curiosity, anyone know where to buy a new MAF other than direct from Subaru? Don't want to go with a secondhand one as they are a complete unknown as to when they will give up the ghost, and they're not cheap either - I put a quote in on 247spares and was quoted between £70 and £90 for a secondhand unit!
It's going in to SCC Performance tomorrow evening for a full service, cambelt, all the fluids etc. The plugs will be changed as part of this. They will also be fitting a Scorpion exhaust system and a Bailey DV. I'm not hanging about trying to bankrupt myself, only picked the car up on Saturday! It's already got new indicators all round and a new stereo, hehehe.
Got to get it sorted for the annual pilgrimage on June 10th though... so I'm going to mention the hesitation to the garage, they are fairly familiar with Scoobs so hopefully they'll be able to diagnose the problem and sort it. Just thought I'd ask in case this was a known fault with a straightforward solution.
Got to get it sorted for the annual pilgrimage on June 10th though... so I'm going to mention the hesitation to the garage, they are fairly familiar with Scoobs so hopefully they'll be able to diagnose the problem and sort it. Just thought I'd ask in case this was a known fault with a straightforward solution.
My 1994 import wrx sti is doing the same thing. Changed the fuel filter, plugs, checked the coil packs for cracks, cleaned out MAF with air compressor, replaced air filter, tried different fuels and still it does it when you really push on...Boost is fine.
Done a manual read of error codes and nothing thrown up, reset ECU...still there....
I think it could be one of the following:
Internals of a coil pack knackered
MAF problem not shown in fault codes
Fuel pump problem
Timing issue from when I had Cam belt changed (when I bought it so don't know if its that)
Report back if you find out.... might get mine on rollers to try and diagnose the problem.
Done a manual read of error codes and nothing thrown up, reset ECU...still there....
I think it could be one of the following:
Internals of a coil pack knackered
MAF problem not shown in fault codes
Fuel pump problem
Timing issue from when I had Cam belt changed (when I bought it so don't know if its that)
Report back if you find out.... might get mine on rollers to try and diagnose the problem.
TAS1981 said:
My 1994 import wrx sti is doing the same thing. Changed the fuel filter, plugs, checked the coil packs for cracks, cleaned out MAF with air compressor, replaced air filter, tried different fuels and still it does it when you really push on...Boost is fine.
Done a manual read of error codes and nothing thrown up, reset ECU...still there....
I think it could be one of the following:
Internals of a coil pack knackered
MAF problem not shown in fault codes
Fuel pump problem
Timing issue from when I had Cam belt changed (when I bought it so don't know if its that)
Report back if you find out.... might get mine on rollers to try and diagnose the problem.
Compressed air not a good way of cleaning a MAF as far as I'm aware. It could damage or break the sensor wire, and if contaminants are firmly on the wire you need to dissolve them with a solvent, air won't shift them.Done a manual read of error codes and nothing thrown up, reset ECU...still there....
I think it could be one of the following:
Internals of a coil pack knackered
MAF problem not shown in fault codes
Fuel pump problem
Timing issue from when I had Cam belt changed (when I bought it so don't know if its that)
Report back if you find out.... might get mine on rollers to try and diagnose the problem.
Also check the turbo up pipe, mine did a similar thing and it was caused by the a split in the turbo up pipe. This meant that when the engine rocked back underload it opened up the crack and the turbo wasn't getting the gasses it needs to create boost so it would jump and stop for a bit until the engine settled into position.
I just had another google session on it and I am going to try some electrical contact cleaner on the MAF sensor as I read that although the air compressor shouldn't harm it it wont get the dirt off as it will be bonded on pretty tough. I gather as long as you don't touch it its fine....
Also read that at high revs the MAF sensor dominates the Lambda sensor in terms of reporting back to the ECU and therefore if it happens at high revs = MAF, low revs = lambda...this may or may not be true but ...
I will give this a go and let you know.
Also read that at high revs the MAF sensor dominates the Lambda sensor in terms of reporting back to the ECU and therefore if it happens at high revs = MAF, low revs = lambda...this may or may not be true but ...
I will give this a go and let you know.
Not rulling out any of the other suggestions but it could be compressor surge.
Turbo may be overboosting thereby trying to feed the engine more air than it can consume for the given RPM/Load. Most commonly happens inbetween 3000-4500rpm on part or full throttle. Too much air pressure builds up back to the turbo and induces compressor stall thereby creates your stuttering. Too much compressor surge long term can kill turbo bearings in the end.
Turbo may be overboosting thereby trying to feed the engine more air than it can consume for the given RPM/Load. Most commonly happens inbetween 3000-4500rpm on part or full throttle. Too much air pressure builds up back to the turbo and induces compressor stall thereby creates your stuttering. Too much compressor surge long term can kill turbo bearings in the end.
Well, I bought some MAF cleaner off ebay (which I could swear from the look and smell was Isopropyl alcohol, in which case it could have been bought much cheaper and in larger quantities from a chemists... ah well) and gave the MAF a good drenching with it, put it back together and the problem has gone away for the time being. Good job too, as they don't seem to be easy to come by (without paying through the nose).
If it's a late classic (1999/2000) then the MAF shoud really be replaced since they tend to not like being cleaned. I have known Subaru engine failures caused by dead MAFs. They cost £80 from the right places, not the £200+ figure most dealers used to quote...
My thoughts are that the boost control hoses & solenoid have slowly filled up with waste oil and the "controlled leak" type boost control system fitted as standard doesn't cope, and the ECU cuts the fuel when it detects what it thinks is an overboost. Simply cleaning all of these pipes and the solenoid with the isopropyl alcohol you already have would work, failing that carb cleaner works well. Chances are you'll have disturbed these pipes to clean the MAF.
My thoughts are that the boost control hoses & solenoid have slowly filled up with waste oil and the "controlled leak" type boost control system fitted as standard doesn't cope, and the ECU cuts the fuel when it detects what it thinks is an overboost. Simply cleaning all of these pipes and the solenoid with the isopropyl alcohol you already have would work, failing that carb cleaner works well. Chances are you'll have disturbed these pipes to clean the MAF.
Hi lummox / dnb, sorry for hijacking the thread -again.
I completely dismatled the air intake and boost solenoid pipes and gave the lot a good blast with a can of carb cleaner, spraying the cleaner into the boost solenoid whilst in diagnostic "clicking mode".....did an ecu reset and the problem is still there but I think i made it better...maybe.... its most evident around 90-100 leptons upwards.... slightly emabrassing when a Focus ST225 started to pull away because mine had a wheezing fit...
I think the boost solenoid looks to be the culprit though ...maybe....
I cleaned the main bottom pipe by blasting through with the carb cleaner, I noted it has a restrictor in the end, I think I cleared that one the goes to the resonator, ran out of time for the other ones, may blast them through as well but the larger bore means that it would have to be some build up to be blocking it....
I completely dismatled the air intake and boost solenoid pipes and gave the lot a good blast with a can of carb cleaner, spraying the cleaner into the boost solenoid whilst in diagnostic "clicking mode".....did an ecu reset and the problem is still there but I think i made it better...maybe.... its most evident around 90-100 leptons upwards.... slightly emabrassing when a Focus ST225 started to pull away because mine had a wheezing fit...
I think the boost solenoid looks to be the culprit though ...maybe....
I cleaned the main bottom pipe by blasting through with the carb cleaner, I noted it has a restrictor in the end, I think I cleared that one the goes to the resonator, ran out of time for the other ones, may blast them through as well but the larger bore means that it would have to be some build up to be blocking it....
dnb said:
If it's a late classic (1999/2000) then the MAF shoud really be replaced since they tend to not like being cleaned. I have known Subaru engine failures caused by dead MAFs. They cost £80 from the right places, not the £200+ figure most dealers used to quote...
+1 for where are these 'right places' please?I have an MY00 classic and probably ought to change the MAF before it goes.
If you need a new MAF why not just buy one 2nd hand from somewhere like Grade A Subaru, they do mail order. That's what i did a couple of years ago and it's still going strong. Been cleaned a few times too with brake cleaner. No issues thus far and only cost £45 back then.
To be on the safe side why not just buy one, keep it in the glove box as they're not very big together with a small cross head screwdriver. If you suspect your MAF has broken down it takes just a few mins to swap and you're away again.
Simples!!
www.comparethemaf.com
To be on the safe side why not just buy one, keep it in the glove box as they're not very big together with a small cross head screwdriver. If you suspect your MAF has broken down it takes just a few mins to swap and you're away again.
Simples!!
www.comparethemaf.com
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