Hi everyone,

I have a project 1989, Irocz, 5.7L TPI, that my son and I are working on. The car runs but runs rough and seems to be misfiring. I have gone thru most diagnostics and replaced a few components, and now I'm down to figuring out if it's the fuel injectors themselves or the fuel pump. The car has only 88K original miles, but it was sitting for long time. This is what I've done so far:

- Replaced plugs and wires

- Replaced rotor and rotor cap

- Replaced fuel filter

- Replaced Ignition Coil

- Visual inspection of ignition module- looks in great conditions

- Verified power to injectors with Noid lights- good to go.

- I also noticed while I was testing the injector plugs, when I unplugged some of the injectors there was no discernible difference on how the engine was running, which makes me thing those are the bad injectors? Could a V8 still run with multiple bad injectors?

- Verified fuel pressure in rails with pressure gauge. So, I verified this with a loaner gauge from oreilly, and I think it was a shitty gauge. At first it read 0 Psi, while the car was running and after while it slowly went up the 40PSI range which is where it should be.

- I did a compression test and verified there are no head leaks- good to go as well.

Any ideas of what to check next? I was going to go for replacing all 8 injectors. Any thoughts/ideas are welcome.

 

Worth checking over your firing order/plug layout just to make sure they all went back right.

Another thing I would do is look over all the vacuum lines and really look them over well. Worth grabing a good vacuum pump and checking each tube, hose, connector etc.

Fuel pressure sounds okay at 40psi.

Something worth investing in is a Moates ALDL cable, Tunerpro RT, a laptop and some time. Being able to live data log all the sensors will quickly help identify any trouble areas to include fuel trims and O2 readings should fuel be a concern at the injectors.

 

Ohm check the injs cold and hot. The gray/silver rochester injs are know to short and fail.
also check dist components for rust broken parts. Ohm the pickup coil

 

If the car has the original Rochester Products Multec injectors they ARE bad. They should be replaced with a set of 8 brand new Delphi fuel injectors from site sponsor South Bay Fuel Injectors. If they need replacing then there are multiple other things you have to do while you are in there too. We 3rd gen members get a discount at South Bay.

Your car can have multiple things wrong with it but I guarantee you if it has the original factory RP Multecs they are bad. They are retroactively defective by design.

Where the injector connector plugs into the injector on the injector will be a stylized RP logo and they are a greenish greyish color about 3/4 way down the injector from the top and aluminum on the bottom. Post a pic of them if you can.

 

I just checked out their website. How do we get their discount at checkout? Is there a discount code I should know for being a member of the forum?

By the way, here are the pictures of the injectors. It looks like they are a mix. 3 out of 8 are that greenish/grey type you described.

 

Iirc it’s tg11

 

Agreed 100%. With these cars, this is almost becoming a must-have. With a windows laptop (which pretty much everyone has) and a ALDL cable (with TunerproRT being free), it almost seems silly to not have it.

 

looks like a multec from tpi and a lt1 injector. Definitely not a matched set

 

Btw get the delphis

 

Agreed.

You'll get a known-good set of injectors.

 

Yes you car has a mismash of original RP Multecs and later replacement injectors. This was typical of how things got done back in the day before people knew better. They tested all of them and only replaced the ones that tested bad. In hindsight it was a bad idea because all 1989 to 1992 RP Multec injectors are defective they just might not have tested that way at the time. They are little hand grenades with the pins pulled so far out it's just about to let go and it will let go sooner or later.

Now you just identify them as being 1989 to 1992 RP Multecs and throw them in the trash. No testing needed. Replace with a matched set of 8 Delphi injectors.

I will make you up a list of what you need with links so you can get it ordered tomorrow. Will be South Bay and Amazon links. TPI gasket set, O-ring rebuild kit for the fuel rail, O-ring kit for the fuel lines. fuel pressure regulator diaphragm, special Torx bits, and what ever I didn't remember right now.

 

I don't think I missed anything you will need.

The long Torx bit makes it easier to get to some of the TPI runner bolts while clearing the runner tubes. The Torx security bit set is needed for the TR10 bit for the screws holding the two halves of the fuel pressure regulator together.

1989+ TPI will only use 7 of the 9 O-rings in the fuel rail rebuild kit.

South Bay's promo code for members here is TG11 and is for 10% off. They are also having a March sale too with a promo code for 10% off. You can't combine both promo codes.

South Bay - DELPHI 22 LB/HR 5.7L TPI Fuel Injectors
South Bay - TPI Fuel Pressure Regulator Diaphragm







.

 

thank you for much man. This is way beyond what I was expecting help wise. I really appreciate you.

 

No problems. I don't think I missed anything you will need as far as just doing the TPI related stuff.

While you have it tore down this far you might also want to do the valve cover gaskets too and replace the rubber grommets in the valve covers for the passenger side CCV and driver side PCV system and the 36 year old molded rubber hoses for them. It's a lot easier with the TPI system out of the way. I'll post links for these too.


The molded CCV and PCV hoses are only needed if yours are in bad shape or you want to replace them because they are 36 years old. You wont need the one for the driver side of engine if you upgrade to the 90+ TPI driver side valve cover.

88-89 Camaro/Firebird TPI Crankcase Vent Tube Hose - Passenger Side of Engine | eBay

87-89 Camaro/Firebird PCV Valve Hose - Left Side of Engine | eBay

.

It's the correct grommet. Same as a Dorman HELP PCV Grommet PN-42062

General Motors, GROMMET, 3989350 - 2 Required

I like to use plain jane Vaseline petroleum jelly to lube the O-rings.

Don't use abrasive discs, wiz wheels, or wire wheels to remove the old gasket material. Use razor blades, gasket scrapers, chemical solvents and good old back and neck breaking elbow grease to get the mating surfaces spotlessly clean. TPI systems are prone to vacuum leaks anyways when reassembling so don't compound things by making the mating surfaces uneven by using aggressive cleaning methods. Someone has been in there before so who knows what they did. Maybe easier to get the gaskets off because they haven't been baking themselves on for 36 years.

 

if I were to replace the valve cover gaskets thus removing the covers, would you recommend replacing the stock valve covers with anything aftermarket, or just clean and keep the oem ones?

 

The stock valve covers work just fine. Aftermarket valve covers are normally for appearance reasons or maybe to clear aftermarket valvetrain components. Lots of aftermarket valve covers aren't properly baffled inside for the CCV and PCV system.

If you wanted to change something swapping to the 90+ TPI engine's driver side valve cover will relocate the oil fill to the front of the engine and the PCV valve to the rear of the engine making oil changes easier. This is how it should have always been on the F-body TPI driver side valve cover. It also gets rid of the molded PCV hose too. You can just run a short piece of normal hose to the PCV port on the lower intake manifold to the PCV valve at the rear of the valve cover.

You could paint or powder coat them for appearance to suit you. Extreme caution should be exercised if media blasting the valve covers to make sure no media gets into the internal oil control baffling and that it is thoroughly flushed afterwards to make sure any errant media that might have gotten in there is removed. Sand or glass beads in your oil doesn't play nice with your engine's internal parts. You could also chemically strip the valve covers instead.