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If it runs like crap the Fuel Pressure Regulator diaphragm previously mentioned by someone is a good possibility. Mine (1991) went bad a couple of months ago and yes it ran like crap it was also very rich, the exhaust was very strong and gassy smelling. Replaced that diaphragm and it ran great again.

 

Good tip, now that I have (for now) verified all cylinders show compression between 170-210 I go back to the
basics.First task is fuel pressure, will keep your suggestion in mind.

 

Its a shame what that shop did... they give a bad name to other good shops.

 

As I was reading through this thread and saw you mention about the fuel pump replacement, checking the fuel pressure was the forst thing that jumped into my head as a potential problem.

Let us know what you find...

 

Will do, hoping to spend part of the upcoming long weekend working on the car.

 

I agree. Check your fuel pressure first. Are your fuel injectors original? If so, I would ohm test them.

 

do the basics first... feul/spark.. cap rotor.. coil... worst thing you can do is start chasing codes when you forget the basics, L98 engines are not exactly high tech ya know. it's still just a glorified small block chevy engine the runs on the same standards as they did back in 1968 compression spark air. not like it's an ls motor.. it's a gen 1 chevy small blocki am still going with spark issue myself maybe even simple as a melted plug wire from touching a manifold? that computer is not even obd 2.. its obd 1.. very very basic stuff. commodor 64 vrs todays intel coffee lake cpu's
not knocking it, don't take it wrong. just saying it's not exactly state of the art tech in there usually some basic problem causes a sensor to read wrong, gives a code out.. change sensor but didnt actually fix the "problem" and you still have the same issue after 600 buckls of new sensors and fuel pumps n so onif you check pressure, dont assume it is the pump. as already said. it could be that goofy looking regulator there in front of the passenger side head.. so check pressure before and after that for sure

 

just went thourhg all that myself and i got myself caught up in the chasing codes crap... 800 buckls after new injectors new fuel pump... it was my frickn cap n rotor.. 50 bucks...and oreileys. talk about feeling like a fool. with 80 grand of snap on tools and a big fancy snap on scanner... i forgot the basics... that was a 98 chevy silverado with vortec but again. gen 1 small block chevy engine.. on the bright side, it runs super, better than it did when i bought it with the new fuel pump and spider injectors.. but ouch on the wallet

 

The injectors were replaced by the PO, I checked all 8 today and they were all exactly 16 ohms. I am slowly taking off the intake manifold, will thoroughly clean the intake
and plenum and then test everything as I reassemble. I found a great video today that demonstrates how to test all the basics


Chevy Corvette - No Start When Hot (The Diagnosis) not my symptoms, the title of the video

 

Hopefully I am not over-sharing my progress, maybe my issue and the eventual fix will help somebody else in the future. We removed
the intake plenum and intake manifold tubes last night, noticed a couple issues. First of all the intake manifold tube bolts were not much more
than hand tight, spec is 35 or 45 lbs depending on which bolt. Also there was a long, 8 - 10 inches, vacuum line laying disconnected under
the fuel rail. This is one of the reasons I am taking the intake manifold off, cleaning it and then piece by piece (per the FSM) reinstalling the
intake and all associated items. I want to feel confident everything is installed as required. More to follow

 

Interesting approach. What led you to tear down the intake system? I dont recall a measurment that was off? Did you check vac at the fpr?

 

I'm not saying that is the only problem, but if the intake runners were likely not sealing and some vacume line(s) were disconnected, that will for sure make the car run poorly so fixing thay should at least help. Check the EGR for carbon build up while your in there too.

 

"I took the EGR off last month when I replaced it and did not blow air through, i did clean out the main
orifices in the intake manifold. Once I get it home I will add this to my list, I hope to have..."

DO you have to remove the runners to replace the egr?

If this were me, and it is not, Id have looked at fuel pressure with and without the vac line connected to the FPR before I spent hours tearing down the runners.

I dont mean to sound like a jackass but this approach is not dissimilar from throwing parts at a problem. Id be taking measurements and id I didnt have the tools Id get them if I planned to maintain the car long term.

Perhaps the OP is like me and very curious.. in which case, continue on with the education.

 

good looking vert, fix it,

 

I understand my approach may seem the long way but there is a couple reasons I am doing this. The first is I have had reoccurring EGR failure codes over the three years I have owned the car. I would normally see the code after an extended drive, the code would go away after the car sat for a while. When my car first acted up this fall I replaced the EGR valve because of the intermittent code and the symptoms pointed towards a stuck open EGR valve.
After exhausting my troubleshooting skills I had it towed, compression tested and then brought home (more details in previous posts). Once the car got home a buddy and I began removing items with the intent of replacing the head gaskets. The shop I took it to said I had head gasket issues. We decided to rest the compression again while we had the plugs out. All of the cylinders are between 150-210, don’t know how the shop came up with their numbers, so we changed our plan. Since we already had removed enough items I decided to go as far as removing the intake, cleaning and replacing what is needed as I put it back together. I have found enough cracked vacuum lines already to know this is necessary. If I was to start this all over, months ago, I would have done the basics first. Live and learn, die and forget it all (shrug).

 

I did not have to remove the runners to replace the EGR, just the plenum.
You don't sound like a jackass, sounds like you are just trying to save me money.
Some of this is curiosity, this is how I will learn more about my car.
I am NOT replacing everything hoping something fixes it, only items I idenmtify
as defective will be replaced. The intake manifold gives me a place to start from
and as I said somewhere I have found enough cracked/broken vacuum lines
to justify my (unique) method,

 

Thank you for recognizing I am not a jackass

Good deal on vac lines.. Im just curious to know what the actual issue is. The drama part of me wants you to storm into that shop and give them hell with the cure in hand. I gotta tell you, the service industry in general really makes my hackles stand up... Im guessing they would have actually done the work, found out during the process what was actually wrong and handed you a $4k+ invoice. I think its likely this shop is practicing this sort of thing often... no one to know the better; the problem albeit was solved. Makes the veins in my kneck stick out.

Will be peace of mind to restore the intake/vacuum system moving forward.."while you are there" I would urge you to send your injectors in to be tested. another peace of mind matter for the future.. might even just consider replacing them. ive been theorizing why old injectors would show low or high resistance.. only thing I can think of is the coil insulation somehow breaks down and shorts.. but perhaps there is something else. Video was very educational though I cant help but wonder "why". Perhaps the pintel becomes "stuck" but I dont think that explains the resistance being off.

anyway.. hope you make progress this weekend.. not sure if you have replacement vac lines or if they are standard off the shelf hoses.

May the force...

 

If you want to see an example of a good mechanic, youtube search for "south main auto".

he verifies every fix, there is usually very little doubt on his diagnosis.

 

He actually quoted his video for the injector testing. South main is top notch imo.