CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Light tapping while accelerating

i have a manual 1992 ford ranger V6 with a 3.0L and for a while now i have been hearing a VERY light tapping sound while accelerating. its so quiet that most people can barely hear it when I turn off the radio and A/C. For about a year or so I could only hear the tapping when I was going up an incline in fourth or fifth gear, but recently I can hear it on flat roads but only occasionally, Again I can only hear it in forth and fifth gear and only when i first get in the gear,when i speed up it goes. I don’t Know if this helps but I change the oil and spark plug regularly.

Has the gas and air filter been changed according to the manual? Try a treatment of sea foam and the next grade higher in gas. If that does not work take it in for analysis.

It sounds like you’re describing pinging. This is usually caused by an EGR system fault.

If the EGR system is fine then the possibiity of too much timing advance should be considered on the offchance that someone has dinked around with the distributor for whatever reason. This truck should be a TFI model and if the timing is not set properly with the SPOUT connector being unplugged the timing will be off quite a bit.

If it is a slight tapping is it erratic or like a drum beat. You could be having oil pressure / tappet issues. If you normally are using the same gas as always try a half tank of 93/94 octane. Tappets are pressurized by your oil system and move the valves. A bad valve tappet will make an unsymmetric sound. A little random. Pinging will go away with a change to high octane. But this car has had a life. The other comments are good but the engine analysis at this point is a timing check and a compression check.

We have a family member with a 93 Ranger same 3.0L V6 motor and it pings a little under load. Seafoam in the tank cures if for a little while but I am not sure how to get rid of it either. I believe on ours it has to do with her driving habit. She is very easy on the vehicle which in turn causes a build-up of carbon on lots of engine parts. This also causes hot spots sometimes in the motor and causes this detonation. The issue I have is I cannot do a upper engine cleaning easily because the vacuum port is far enough back on the intake for me to be sure it gets to all ports on the engine. Can anyone confirm if this would be an issue also?

I regularly inspect and change my oil, oil filter, pcv valve, fuel filter, and air filter. And when I first heard the sound I thought it might be the fuel so I started to use “Gumout fuel treatment” and upgraded to mid-grade fuel, that is until I read my manual and my Chilton repair guide which specifically says only use 89 octane. During the four months I was using mid-grade I could still hear the tapping. And recently I had the spark plugs, wires, distributor cap and rotor changed.

The tempo of the tapping is symmetric and speeds up as the rpm go up.

Also you can hear the tapping if the truck is under load. The more load there is, the more noticeable the tapping is and the longer it takes to go away.

If the tapping is not present with the engine idling and vehicle stationary then my guess is still an EGR fault or too much advance in the ignition timing if someone has incorrectly set the distributor for whatever reason.

You might pull the codes and see if an EGR code comes up.

If you are ambitious you could check the valve adjustment, I am sorry but at this point there are so many variables the ford dealer might be the best place to go.

Here is a somewhat far out possibility that I hesitate to post but until the problem is solved, anything is possible. It could be a marginal exhaust valve hydraulic valve lifter that is partially collapsing under the load of opening the valve at the beginning of the exhaust stroke. At the time that an exhaust valve begins to open, there is still around 100 psi residual pressure in the cylinder. If you have a 1-1/2 inch diameter exhaust valve, its area is 1.76 square inches so at 100 psi residual pressure, the valve lifter must push against 176 lbs and a marginal lifter could leak down a little under mechanical pressure to leave some lash that makes a ticking sound. Increasing acceleration increases power to make higher residual cylinder pressure to make more lash and therefore more noise.

Oil pressure should uncollapse the hydraulic lifter to reduce lash back to zero when the valve is closed but might not do this quickly enough.

Another possibility is a little piston slap but this often goes away when the engine warms.

Either of the above situations is harmless for now but will need attention if the noise gets louder. If the noise gets louder and more persistent, that should make it easier to determine the cause.

Fm the post it’s difficult to know whether the noise is a mechanical tap or pinging. Of course if pressed hard pinging will cause piston slap and rod noise. The 3.0 engines were prone to lifter noise but pinging was also an issue. The ECU allows for tuning to suit the fuel and it would be worthwhile to get a good mechanic to identify the noise and if it is pinging/detonation/spark knock get the ECU reset.

My uncle has a 1990 model Ranger with the 2.9 V6. It’s rattled for the last 20 years but still runs good. Maybe the 3.0 is the same engine with some modifications. Most 2.9’s that I see have the same exact problem.

You could also have an exhaust leak near the manifold that only leaks under pressure, such as when the engine is under load. An exhaust leak can make all kinds of funky sounds. My friend had an old car that sounded like a Vietnam-era chopper under load.