My service manual, (don't ask) mentions it is well worth trying fuel system additive in the petrol tank before going to the trouble of servicing/changing the fuel injector themselves. (fault = very occasional engine hesitation). I just wondered what is actually in this additive stuff and how it works to clean persumably partially blocked injectors? Must be pretty potent stuff to do much in 1/60th dilution and one pass through. Thanks
servicing/changing
Halfords sell it. Best every 4th fillup use BP Ultimate petrol, which has it in.
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You're right. Proper injector cleaning rigs use very aggressive chemicals, and also usually involve replacement of some parts of the injector to get the correct flow. However, it's most unlikely this is the problem in your case. If an injector was blocked, then it would remain blocked and not be the cause of an occasional hesitation.
The ad man's dream...
I agree. Its more likely you have a worn/sticking air flow meter or summat. Or worn throttle pot if it's fly by wire.
What you need is a good independent place that knows about injection systems.
Alternatively get the manual and try stripping and cleanng the air flow meter or replacing it.
Sticking meter will give you momentary weak mixture when you stamp down on the accelerator.
Haynes 'Automotive Engine Management Systems' is well worth a read. That in conjunction with a decent DVM that includes dwell will test most EFI system sensors that are likely to go faulty.
Is the book any good? I might get a copy. I've a Peugeot 306 that drives like a dog when cold, particularly around 1500 rpm. I'd certainly like to know which of the 86 sensors and actuators might be screwed before paying out cash to replace them. I don't get an engine management light on, so I haven't bothered attempting to retrieve service codes from the computer, although I suppose it might have recorded some without sticking the light on.
Christian.
IMHO, yes, as is their Automotive Electrical Manual which is of even a higher standard. Way above the usual Haynes crap.
There are about a dozen 306 models covered according to the index. Of course many common problems are similar despite the make of injection.
I bought a Peake Research code reader for my BMW and saved its cost on the one occasion I needed it - an intermittent crank position sensor. Labour cost at a main dealer - including diagnostics - far exceeded the purchase price, even for an easy fit part like this.
I have a relative who runs a fleet of 4 stroke motor bikes and will only use BP Ultimate or Shell Optimax. He never has any problems of crap around injectors, spark plugs etc, which he did before. When the bikes are down it costs money, and his down time is less using those petrols.
Before taking your car for an MOT it is worth filling up with Ultimate and running the car until about 1/4 empty then have the test. It improves the emissions slightly. If you are borderline the petrol may just scrape you through.
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i missed the begining of the thread, is your car petrol or diesel? if petrol the problem of ocasional hesitation is often associated with the early signs of the ignition system 'breaking down' under load, i.e ht leads, distributor, or coil etc.
And he has run a control using other *current* makes to prove this theory? Because most businesses would be very wary of paying the extra costs involved. Unless, of course, these bikes demand 97 octane petrol.
FWIW, I have an early EFI car which passed its MOT recently with emissions well below the requirement and has never had the injectors cleaned or replaced.
A car in decent condition will pass ok using any UK petrol. Optimax is a waste of money - unless you have an engine which can make use of the higher octane rating.
Dave Plowman (News) wrote :-
Dave - did you get it direct from the states or do you know of a UK supplier ?
Regards Jeff
We had a pug 305 that drve fine when cold, but would flood when hot.
Took me ages to FIND the water temp sensor,but a quick poke with it in a pan of boiling water showed the problem up. No resistance chage cold to hot.
If yours is shorted, will be like running with no choke.
Yes, obviously water temp sensor must be a prime candidate. However, I'm sure there are plenty of others that could cause similar symptoms.
Christian.
Direct from Peake and they accepted my credit card. Postage costs were low,and I didn't get stung for import duty. Took about 2 weeks to arrive - as I wasn't in any hurry.
The Haynes book gives the resistance at ambient temp, and if faulty it is likely to go open circuit.
The 'standard' Bosch sensor is approx 2K5 at 20C, and 350R at 80C. If the vehicle starts ok from cold it's likely to be open circuit. Once it's warmed up a bit, substitute a 150R resistor for the sensor - this will tell the ECU the engine is at normal temp. If it then runs ok, you've proved it.
A faulty water temp sensor will cause very poor running indeed - if at all when the engine warms up. Remember it acts like a choke, and has the major influence on the mixture setting.
The problem is that it runs fine when warm. It is dodgy when cold. Nothing untoward on fuel economy, either, so I don't think it is running excessively over rich.
All academic at the moment, though. The starter won't completely disengage, making it somewhat undrivable! I can't believe how difficult they made it to access.
Christian.
Twas ever thus...the number of bits that are bolted on engines BEFORE they put them in, that require you to dismantle half the car - or take the engine out - to fix em...
Wouldn;t be teh first time I have had to remove a raidiator, unbolt engine mounts, slpt engibe from box and slide it forward a couple of inches to get at a clutch cyliner etc..
It used to be standard practrice on Minis to simply remove the front subframe and engine complete - wheel the body off it - to do dire things to the front part of one.
The sensor may still be the problem, if its failed S/C rather than O/C. I.e. shorted wires.
I think there are in general three temp sensors on teh average injection system. But only one that monitors engine temp.
OTOH lots of components in the ignition and fuel flow system may be temperature sensitive - a duff spark plug or lead can fail to fire a rich start mixture, but be fine on a weaker one.
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