Alan

Charley - If the injectors are dirtly they will flow less per duration, usually they vary injector to injector - so the ECU thinks its delivering a certain amount of fuel but in fact are delivering less to some cylinders = lean.. ECU should try to compensate - but not good for power.

You can get the injectors cleaned & flow tested on a bench to get them banchmarked before & after cleaning - goal is to get them to spec and at least better balanced for flow.

Some of mine were almost 10% off flow rate, some only a few %

Alan

worf928

In addition to what Alan wrote...

Not only can a 'dirty' injector flow less fuel per pulse, but a dirty injector can (will usually also) have a poor spray pattern. The poor spray will result in poor mixing of the fuel/air charge with a resulting loss of power and poor emissions too.

andy-gts

my 93 pinged like crazy when I got it in 2003. Then I heard about the fuel injection cleaning my mechanic could hook up and run for 30 min. whala!!no pinging for 2 years.. now the ping is back when stepping on it (auto) Guess it is time to clean the injectors again.. I hope!

PorKen

Has anyone gone with colder plugs? Run the coldest plug you can!

When I was running a whole lot of cam advance in the '86, I was having trouble with pinging, so I switched from the factory WR7DC to WR5DC, the coldest plug Bosch makes in the 'D' style, AFAIK. I've had no trouble with fouling.

(Actually, they are WR5DC+, the plus is the newer, fancy V-notched ground electrode.)

928ntslow

Yea Ken, thats what I think the problem is with some of the cars that are pinging. The chamber gets too hot and ignites the mixture before the valves are closed and plug fires. Anytime I have ever had a pinging problem with a vehicle, I changed out the plugs to a cheaper, simpler copper plug and it cured it every time. I think I said this 3 or 4 times in this thread and no one has done it yet as far as I know...at least no one reported back. Might be too simple of an answer.

John Speake

If one injector is not flowing as much as it should, the weak mixture does not burn as fast as the correct mixture will. So incompletely burnt fuel will arrive at the O2 sensor, which is just measuring the average of the exhaust gases. So this may cause the O2 loop to lean out the mixture even more, contributing to the possibility of detonation.

derporsche928

Keith,
Which Bosch Copper single electrode plug are you using?
Hope to wrap up TT Rebuild this weekend and will try and then post results.....
Thanks,

cfc928gt

Keith and Ken, interesting what you say about the plugs and I'd add that anyone suffering with pinging would be foulish to not try following your advise since it's so simple and cheap. My question is why does this work? I don't understand the concept of a 'colder plug'.

PorKen

Silly me, I never wanted to think about spark plugs, and 'heat range' until I started messing with my '86. I put my toe in slowly, going from the stock (85-95) WR7DC, to WR6DC, and finally WR5DC. Each time checking to see if the devil 'deposits' formed. None did.

I would have gone even colder, but 5 is the coldest that Bosch makes in this style plug - there's no more room in the plug to lengthen the ceramic. The pic below is very close how the plugs tips look like, hot/7 versus cold/5.



(Wikipedia, spark plug heat range)
(More spark plug tech)

I found the hard way that you need the resistor, 'R', plugs, non-resistors mess with the ignition amps, and cause stumbling.

The Bosch coppers are fine plugs, you really don't need anything fancier. (This took a bit of mental discipline on my part to get over this fact!) Just change them every year or two. The only thing better would be the silver tipped plugs (WR5DS) which last a looong time, but cost 3x. Or get the '+' plugs (WR5DC+), which have a groove in the ground electrode.

Randy V

OK, so can you tell us which exact plugs you are using, Keith?

928ntslow

Bosch "Super" (R6 385). These look like the newer version. BOSCH SUPER PLUS

PorKen

Keith,

That looks like part of a NGK number, but not the one for the 928? (The stock NGK for GTS is BPR6ES.)

Note that Jap spark plug heat range numbers are opposite of Bosch, IE colder is a higher number, versus Bosch, lower.
...

It looks like the colder plugs will give you a tiny compression ratio boost, with the smaller gas space around the electrode.

928ntslow

I read the R6 385 numbers off my spark spark plug.

I can't make any comments on the SUPER PLUS.

ROG100

My fuel pump finaly bit the dust today - I changed out both the internal and external and I am pretty certain the internal was toast also. Came apart as I extracted it.
New pumps and I cannot detect any pinging, however my hearing is not brilliant so I will take Zane for a ride tomorrow and let her listen.
I will let you know if my pinging has gone.
This was the fix for pinging on Shockis car.

worf928

Just pulled a plug out of our GTS.

Bosch Super R6 665, WR7DTC, which, if I read my Bosch plugs (in German) correctly is a copper three-electrode plug.

Plug was grayish with some carbon buildup. (As in, normal for a 928...)