AUTOFIX.COM.AU

If you're new here, you may want to subscribe to my RSS feed. Thanks for visiting!

 After reading my post on how to clean throttle bodies, John Rhook, e.f.i. expert and all round nice bloke had a few things to say regarding the cleaning of throttle bodies on late model vehicles. This is what he had to say;

Hi Craig, just discovered the blog. well done on getting involved in ICT. I find most in the motor trade are reluctant to adopt technology. I would like to add to you post a word of caution. Late model throttle body’s are coated and cleaning with solvent based cleaners is not recommended. There are some detergent based cleaners now finding there way into auto parts suppliers. Also some sensor failures have been linked to the use of Propelant type solvent cleaners.
Regards,
John

 As I have been off the tools since 2005 and have only seen a handful of vehicles where throttle body cleaning is not recommended, I asked John to clarify this information further.

HI Craig, yes, throttle body coating is pretty much the norm now, especially since drive by wire has been adopted. Some dealers have been caught out (Ford,Mitsubishi) cleaning throttle bodies and then upsetting base idle functions (by removing laquer), which then requires back to the factory bench calibration. I am still happy to see throttle bodies cleaned, It just needs to be done with caution. I like you have been off the tools now for 5 years, after 23 on the body has had enough so I have moved into education. Look forward to more postings.
Regards,
John

 If you own a late model vehicle and are considering cleaning the throttle body please check with the manufacturer before carrying out this operation. I have successfully cleaned throttle bodies on cars ranging up to the late 1990’s and early 2000’s however I would recommend checking first before doing the job on any vehicle younger than this.

 I would like to take the time to thank John Rhook for his input on this subject and with any luck we will be hearing more from John in the future. He ran a successful repair business before his body gave up on him (sounds familiar!) and is well educated on automotive subjects. Good on ya John!

Craig

 Cleaning the throttle body on a fuel injected engine is one of the most effective ways of restoring idle quality, performance and fuel efficiency. It is a simple job for the DIY’er and should be carried out every 10,000km if you want to keep your engine running at it’s best.

 The tools and supplies required are;

• Screwdriver or spanners/sockets for removing air intake at the throttlebody
• Can of throttle body cleaner. There are dedicated Throttle Body cleaners and Carb. Cleaner, either will do the job as the majority of carby cleaners available are sensor safe.
• A Toothbrush. Preferably an old one, I do not recommend ever putting it back in your mouth after doing this job!
• A rag to be placed under the throttle body to prevent spills on painted surfaces.
• Eye Protection is recommended, see below.

 PRECAUTIONS - Throttle body and Carb. cleaner is corrosive and must be used with caution. It will strip paint so imagine what it can do to your eyes and skin.

 Step 1 is to remove the air intake where it attaches to the throttle body. Depending on your vehicle it may be necessary to remove the air intake duct further to allow access to the throttle body. Place the rag underneath the throttle body where the cleaner is likely to run out.                                                                                    

 The next step is to locate the throttle lever and while holding the throttle plate wide open, spray the cleaner into the throttle body bore.

 Now the fun part, grab the toothbrush and start scrubbing. Pay particular attention the the underside of the throttle plate and around the bore where the throttle plate sits when closed. The spray and scrub steps may need to be done a few times before all of the deposits are removed.

 Once all the black gunk is loosened and removed it is time to refit the air intake and start the engine. The engine will turn over quite a few times before starting and may missfire and carry on once started, this is perfectly normal. It may take several minutes for the cleaner to pass through the engine and white smoke from the exhaust until all the cleaner is burnt is normal as well.

 After the idle returns to normal I recommend a couple of quick wide-open throttle openings to ensure all the cleaner has passed through the engine. That basically sums it up, if you found a lot of build-up in your throttle body take the car for a drive and I think you will be pleasantly surprised.

Craig

I would like to tell you of a car that we had in our workshop, going back around 3 years ago. The anti-christ was a 1990 Toyota Camry fitted with a 3S-FE engine, essentially a 2.0 litre, 4 cylinder engine fitted with electronic fuel injection.

  The car came in on a tow truck with the owner telling me that for some reason it kept ‘flooding’ itself. It had been to a handful of workshops before coming to us and needless to say the owner was ready to solve the problem with a box of matches and a can of fuel!

  The last mechanic to look at it had replaced the fuel pressure regulator and it behaved itself for about a week before this latest dummy-spit. Numerous litres of fuel had worked their way past the piston rings and into the sump, so the first thing to do was drain the oil and change the filter.

  With that taken care of it was time to go hunting. It was first necessary to figure out whether it was a fuel pressure issue or perhaps leaking injectors (unlikely due to all cylinders being over-fuelled and the amount of fuel present in the sump.) or an issue that was causing the injectors to stay open.

  Fuel pressure was hard to guage as the engine would only run for a few seconds! From what we could see the fuel pressure was within specifications, a tad low if anything, not likely to cause over-fueling on this scale. I had discounted the leaking injector theory based on the reasons stated above. So the only logical theory left was the injectors staying open for some reason.

  Testing the electrical controls of the injectors is a simple procedure. On one side of the connector we have constant power. On the other side the computer provides an earth that is controlled by the computer. Signals from various sensors around the engine combine to dictate when the injector is opened and for how long.

  Out with the test light and with the ignition switched ‘on’ we found we had the constant power and by reversing the polarity of the test light ( clipping the lead onto the positive terminal of the battery instead of the negative ) we found we had a constant earth supply as well. Not good! Even with the engine running the earth would show as a ‘pulsing’ of the test light and with the engine stopped we had a constant glowing test light.

  The first thing that came to mind was a faulty computer. A call to a friend of mine who is a master-mind with electronics revealed that the Toyota computers are on of the most reliable around and it was unlikely to be the cause. Time for a head scratch and a finger and thumb rub of the chin. They make thinking so much easier! Just like having your tongue half out when doing something difficult!

  Things were starting to get confusing. I couldn’t help wonder why the fuel regulator had been replaced, was I missing something? After a longer than usual head scratch we decided the only logical next step was to check the wiring from the connector to the computer. Easier said than done when the it twists it’s way in and around the engine…..

  Then the penny dropped, the wiring was quite tight going around a sharp corner of the cylinder head. Funny enough it was close enough to the fuel pressure regulator to be moved around a bit when replacing the regulator! So we connected the test light again in reverse polarity and while probing the negative side of the connector we wiggled the wiring harness around where it contacted the cylinder head and surprise, surprise the earth dropped in and out. Four hours just to find a short to earth!!

 I spent the next couple of hours repairing and re-insulating the wire that had it’s insulation rubbed through and beefed it up with a piece of bike tube and plenty of insulating tape. Kicked it over and what do you know, ran like a champion! We replaced the fouled-up spark plugs and the car hasn’t missed a beat to this day. The previous mechanic probably thought he’d hit the jackpot with replacing the fuel pressure regulator and for a week or so he did!

  I thought I would share this story to highlight how the smallest things can turn into big headaches for us mechanics, and how diagnosis can sometimes be the most expensive part of the job. If you get charged what you think is an un-realistic amount for tracking a problem down, please think of this story and the amount of hours it took to find such a silly little problem.

Take care and be safe on the roads.

Craig