This is in regards to my '89 IROC (rebuilt L98, mostly stock).

I hear a rapid tapping sound roughly in time with the engine coming from the engine bay under heavy acceleration or excessive throttle. The sound goes away when I ease up on the accelerator (even if the engine speed doesn't slow). Sound like pinging to you?

This is the only car I've ever worked on and it's never pinged in the past, so I'm not entirely sure how to fix this. Alls I know is that engine ping is not very good for the engine...

I can say that I did just recently swap out the original Rochester injectors (~145,000 miles) with some "pink" Ford injectors (~10,000 miles) which I understand to be 1 lb/hr higher than what they replaced. I do plan on getting the PROM reprogrammed for the larger injectors--if for no other reason than that they're killing my gas mileage. The exhaust does smell rich with these injectors (makes sense)--could this be causing the ping? I wouldn't ask, but I was always under the impression that a lean condition caused ping--not rich.

Thanks

Does it have the same tick at an idle?

I know some people here have though a rod was going but it turned out it was injector noise!

Dont know much about the injectors in use but make sure that the origional units and the replacement ones where rated at the same pressure. If there is a difference in rating (new ones rated at a greater pressure), then it can cause the detonation as the car will be lean when in power enrich.

I know what you mean about injector noise--I've heard that before, and these injectors are no different. However, I've never heard it from inside the car before.

As for the actual injectors, these were off eBay and as with everything else off of eBay, I can't be totally sure that I got what I paid for. However, these definitely had pink tops and were Ford. To my knowledge, the pink Ford injectors are fairly popular are fairly popular and distinct.

What do you mean by "car will be lean when in power enrich"? You mean when the ECM tries to tell the injectors to dump more fuel in, but they don't actually dump in as much as the ECM thinks they are?

True. You may need an adjustable fuel pressure regulator.

What is the part number for your new injectors?

Ford Pinks are 21lb/hr which is 1lb/hr less than the 22lb/hr in the TPI 5.7L.

If the old injectors are in fact Rochesters, they are probably worth cleaning and flow matching. For $11 apiece, you can get them serviced while you limp along on the Ford injectors.

http://www.cruzinperformance.com

Oops! They're now twelve bucks apiece. Better hurry.

Well I'd love to pull up more detailed specs or a part number on these things, but I'm having a heck of a time finding any of that information. I've been trying to fish-up a record of the eBay purchase on their site, but the purchase history only goes back so far. And since the injectors are already in the car, pulling the PN off of them is a P.I.T.A. . It shouldn't be, but when your car has to live in a dimly-lit parking garage and your hood struts won't keep your hood up, doing any engine work is a pain. As of right know, the only thing I know to tell you is that the bases of the injectors are black and the top plastic connecter parts are pink. The guy said they were from a Mustang GT (forgot which year) and, as of this moment, that's all I know.

I'm going to be pissed if these really do flow less than what I pulled out, though. My car doesn't run like it used to with the old injectors (plus it takes like 3x more cranking over to cold start the thing), and the exhaust is definitely rich.

Vader: Ideally I would have liked to do exactly that and have the originals flow matched. That's when I learned I had Multitecs that I should "go find a deep river and let them sink to the bottom." (quote from the guy at Cruzin'.) From what I hear about Multitecs, that's pretty good advice.

And it you heard it from Rich @ Cruzin' it's probably good advice. That's why I mentioned that if you had pre-Multec Rochesters, it may be worth doing. I guess not.

What pressures are each rated at? Theres enough extra fuel for preserving the cat during WOT that the 1 lb/hour flowrate difference wouldnt really be noticable, if they where both rated at the same pressure. The easy solution if theyre rated at different pressures is to install an AFPR and set the base pressure to at, or just above, what the ford injectors are rated at.

"Yes, Ford rates their injectors at about 37 PSI, GM does it at 43 PSI. Ford injectors are the cheapest way to go that I have found in most cases as long as you just keep the different rating scheme in mind."

This was a quote from another thread here. FWIW, that would put the peak flowrate at just over 22 lbs/hour for the ford injectors @ the GM pressure, which would be close to perfect for your app. Id still try to get the specs from ford or whoever makes the injectors and find out for sure what they actually are rated at. If the above is the case, then the injectors may not be the cause of your problems.

Bosch made a lot of injectors for early EFI systems. Rochester picked up many for GM, while Bosch continued for many other applications. Denso started taking over after a few years. The later Ford injectors may be Denso units, but I'm not sure. That may help your search, however.