87 GTA 5,7 TPI, 100.000 km, hesitates during driving speed. I've DYI-checked what I'm able to myself, but had a local shop to pinpoint my issue. He said there's a vacuum leak by the intake manifold that has to be sorted before he can continue searching for possible other issues. I hope the gasket is my only problem. I dare ask you for wise info what other parts I should consider renew at the same time. As far as I know:

1. gasket set for intake manifold
2. gasket set for plenum, runners and throttle body
3. injectors, please advise me a good set worth it's money. Engine is unmodded for hp and will continue to be
4. 9th injector / cold start valve, what about this? (or is it possible to reach anyday without lifting fuel rail and so on?)
5. EGR? is operative today, but mechanic recommended delete/blocking it to prevent future problems. Is there a kit available for delete, and will ECU be affected, or other mods needed?
6. Distributor, anything I should be aware of?

Hoping for some quick feedback, I live in Europe and has to order parts (which can take forever due COVID-19)

In May/June I took off the plenum and runners to clean them inside and out. I didn' t have tools to loosen the EGR valve without detaching the fuel rails, so I let it sit. Anyway, I've read the DYI-injector swap on this site, and believe I can manage to tear deeper here. Never ever had out a distributor or intake manifold before either, but hey, that is part of the game. Learning by doing to keep it rolling.

 

All the gaskets for the intake/plenum/runners/etc should come as a set. Get GOOD gaskets.

If your injectors aren't bad, leave 'em in there.

Ninth injector is accessible whenever you like.

If the EGR is working, leave it. You can get a block-off plate, but, the ECM will likely be annoyed, and set a code. To prevent that, you would need a custom programmed chip, to delete it from the programming. You could do this yourself, and open up a whole new world of modifications for your car, with the ability to write a new chip, whenever you changed something significant. Learning curve is STEEP for custom programming, but, gives you LOTS of options. (including deleting the ninth injector.....)

If you don't know when the last time the distributor cap/rotor was changed, change 'em. If the ignition system is working properly otherwise, leave it.

I am a firm believer in If it ain't broke, don't fix it.

 

Sounds like you have a solid plan, I followed those same instructions when I did mine and it worked out well. For the injectors I would look at Southbay or Jon at FIC injectors and get the Bosch III. Both are reputable but southbay will likely give you a discount for being a member here.

I would atleast do the 9th injector delete, eBay has plenty of kits and not a lot of $$$ (maybe $30). Blocking off the EGR is just as easy and there are kits on eBay as well, I think there are ones that have both too. These projects will be much easier if you are tearing it down to the intake ( EGR especially)I also recommend Fel Pro for the gaskets and it’s not a bad idea to replace the o-rings where the lines meet the fuel rails.

Another thing to replace/upgrade is the fuel pressure regulator and diaphragm, the adjustable ones are a nice modification to raise the fuel pressure a bit for a small gain. The Holley one is like $125 but has the easiest adjustment compared to others.

The last thing I would recommend is a new PROM chip, If you delete EGR you will constantly throw a code 32. Also if you do the 9th inj delete the new tune can provide you with the 1989 start up which will result in faster/better start ups. I recommend member Tuned Performance for the chip, he can do a few minor things in the PROM to wake the car up a bit and lower fan temps to come on earlier so car runs cooler. www.tunedperformance.com

Why are you replacing the distributor? If you are I would recommend the DUI distributor www.performancedistributor.com , it’s not cheap at $200usd but it’s high quality and many members swear by them. I replaced mine with a AC Delco that was same price but not as high quality but is fine with a stock build. The parts store ones are not that great but are cheap, so you get what you pay for. Do a few searches and you should find some step by step or invest in a used service manual, they are worth their weight in gold on these cars.

If you have everything tore down might not be a bad idea to replace the thermostat, will be very easy with all that stuff off, maybe go to a 180? I did and it works good. I can’t think of anything else at this point, good luck with your project.

 

Thanks a lot, I'm likeminded about "ain't broke - don't fix it". Injectors though, aren't easy for DIYer like me to diagnose for future problems, so I find it natural to replace them since I must tear down the fuel rail at this time. The labour can justify the cost of new injectors (and prevent possible future issues)

Myself, I would gladly leave the EGR valve in there, as built by GM. Or better, replace it with new Delco valve during this step. The chip replacement, ECU codes and so on is more than I want to deal with - if not necessary.

Distributor cap, rotor, ignition wires and plugs were all new this spring.

Cheers!


Thanks for your input. I feel some of your recommended upgrades surpasses the cost and effort I'm looking into for my intended use of this car. I will check out both South Bay and FIC injectors. What flow rates are original and /or recommended for stock setup? I've read both 22 and 24.

I'm not replacing the distributor, but I was told it must be removed before the intake manifold. Is there anything I should be aware of or check for wear while out?

Thermostat was a good suggestion, thanks! I have a few (from Rock Auto wholesaler closeout) on the shelf, but believe they are 195 degrees. How about the thermostat housing, are they prone to break or can it most likely be reused, replacing the gasket? I add 180 degree thermostat and gasket to be bought.

I have Haynes' book, which I find easy to use. I also have Chilton's manual which I don't find easy or logic in use. And I bought the heavy 87 GM Shop Manual a few years back, but prefer Haynes for most DIY wrenching. Nice references these books, but from fellow forum members like you, I get the best advise.

 

22 for the L98 is what you want and if those are factory Multecs they are junk at this point, ethanol gas destroys them.

I’m not an expert on distributors but I know mine was rusty on the top and the pick up was dying so I just replaced it and all the ignition pieces with AC Delco and it worked out well. Just be careful with the hold down, that was tricky to get loose to adjust timing/remove distributor. No other tips and tricks that your manuals do not have.

The housing is pretty sturdy and can be re-used for sure, just let the bolts soak in the PB Blaster to loosen them up before trying to remove. I made sure to sand off the old gasket material so I had a clean surface for the new gasket and no issues.

I still run my EGR too but I had to replace everything with it ( temp sensor on egr, the solenoid , and a new AC Delco EGR valve 214-5538). The solenoid and temp sensor were sourced on eBay from corvette suppliers as the factory pieces are extinct. But finally after all that I cleared up that code 32. Be careful about parts store EGRs, they usually do not fit correctly and require modification, the Delco I mentioned is a direct fit.

I get where your going with the car and keeping it largely stock, mine is pretty stock minus a few bolt ons and suspension pieces to improve it etc. But for under $100 that chip I mentioned will make your car start better, run cooler, and have just a bit more pep. I wouldn’t bother with the 180 t stat if you keep the fan temp at factory setting, it won’t do anything just run the 195. These cars run too hot at factory settings IMO.

 

very helpful of you, I appreciate all your
info and time 😊

 

A new question showed up. The car has some blue smoke at Cold startup which I’ve now learned can be cured by changing valve stem oil seals. Is it possible to do any day later or do I benefit from including it while changing intake gasket?