RedTRex

Recent purchase taht had been sitting, have completed major tune up, checked fuel press (replaced sock and dampner), was running decent. Suspected injectors, I have two that are at 8 ohms, rest at 16.

Like I said was running decent.

Higher priority (funding wise) was to replace was waterpump which I just finished.

She fired right up and ran fine for 15 minutes, shut off for 30, decided I wanted to do a quick ride around the hood, fired up threw it in reverse and she wouldn't stay running in gear, back to P started, rev'd a little seems very sluggish and letting off gas she stumbles below 500 rpm and then dies. Now feels very rough when reving.

Coincidence? or did I muss something up? not sure how as waterpump and all doesn't touch fuel or ignition.

had her idling and turned lights on seems like heavy elec loads drop idle speed too. Is alternator going bad maybe? Guage shows volts smack in middle, didn't try multimeter yet.

pear

You'll be surprised how much of your symptoms will be cleared up by replacing the injectors. That process may also uncover a couple of vacuum leaks when you take off the plenum and reassemble. It will be almost like having a new car…injectors play a big factor in just what you described. "pear"

RedTRex

That is reassuring to hear since I have been through everything else. Just waiting until payday to order a set.......
Thanks!

navy_vette

I think those 2 injectors decided to give you the big fat middle finger. They watched you as you fixed something else while they were screaming for repair. They are now angry.

Also,
Vacuum lines can cause issues too. If you can't repair and refit, then replace.

leesvet

The most common cause of poor general performance is bad or worn fuel inject ors.

Its been said that fuel inj do not wear out. They just get dirty and stop working well. Thats not entirely accurate. Your stock injectors will wear at the nozzel and cause poor spray patterns, like dripping and wet spray which does nothing for combustion. Wet fuel/air charge does not burn worth a crap. An inj in good shape sprays fuel so fine that its more like a fog than a wet mist. It instantly mixes with the air that carries it to the combustion chamber.
Knowing that your model does NOT spray fuel IN the combustion chamber, or not even at an open intake valve, this mixed fuel charge becomes even more critical. If half of the fuel is wet and clinging to the wall of the intake passage then its not getting sucked into the cyl as the valve opens. Poor performance.
The other BIG (biggest clue) is the well known fact that the stock inj are TRASH and WILL go bad for whatever reason over time, miles, sunrise, whatever. They just go bad like cheese left out in the sun....

The good news is that FIC seems to have figured all this out and will sell you some recon inj all tested, cleaned and flow balance checked for around $200. That includes all the gaskets and O-rings (very critical). Go to You-Tube for a bunch of how-to videos and some tips and tricks on doing the work. I did it in the driveway in 5 hrs...taking back-ache breaks often. But I also had every possible tool that I might need....Call it a Saturday job..Call it whatever you like, just be sure to call Jon...@ FIC.

The ONLY other thing that you want to check is the condition of the CATS. When they plug they cause the engine to not want to rev, burp backfire and run very bad until it just won't run at all. Thats usually a progressive thing t hat gets worse and worse over 50 to 100 miles. Easy to test by taking out the o2 sensor and checking the back pressure. System should only have 2 psi unless the cats are dead/plugged then it goes WAY up.

frenchyoliver

I changed all 8 with FIC bosh 3-21. get the fresbee out, march performance pulley, replaced all spark plugs, wires with 8.5. added slp runners polished inside for maximum flue speed with perfect bosh 3 fog spray, 160 alternator, all gaskets changed, relocated IAC, 180 thermostat, tpis air pump delete kit, ceramic hooker longtube, perfo cats, magnaflow catback. changed all sensors (all), TPS etc. New EGR with Elcamino 87 egr solenoid, adjustable AFPR set to 48 psi (best we found to be for bosh 3, especialy at start and best according to bosh 3 cycles to stich to 128 ), added a Pcmforless with logs sent to them accordingly then finalised it at the dyno. My L98 is working like a beast as it can do with the stock cam. push really strong until 5100 rpms and it really is like GM should have it done at the first place. Gas milage is amazing too. I have Z07 auto with 3.07. Smoking tires all the way and go way stronger than LT1s, hands down.

change to bosh 3 but dont forget to add the extras too.

RedTRex

LOL - probably so......


Has long tubes, 3" pipes, and hi-flow cats to Flowmasters. I'd say backpressure not an issue.....

RedTRex

Ordered injectors, started disassembly. Found 1/2 the intake runner bolts barely more than hand tight. Tstat gasket leaky - will fix that while I am here.

Question - The vacum valve under throttle body that is attatched to Tstat bolt has a double vac plug and elec connector (for evap canister I believe). It has a port on the opposite side with a clip to hold another vac line in place. Mine doesn't have a line on it. Should there be one and if so where does it go to?

navy_vette

Post a pic of it. They are worth a thousand posts

Mikky89

The vacuum valve under throttle valve bolted to the t-stat should be the egr solenoid.
There should be two vacuum lines connected - one to the egr valve and one to a source vacuum that tee-ed into a hose that run from the underside of the throttlebody to the evap canister stuff. If you see a third port - that simply relieves the vacuum to the egr valve when the solenoid goes to the off position - there is no hose on it. There may have been a "filter" on it when the car was new, but at least on mine it was long since gone.

By the way, this part was one of the many reasons my 89 was running crappy. It would stick and cause the egr valve to hold open. Make sure it operates correctly and the egr valve works properly - especially now that you have the plenum off. This part was obsolete for quite a while, I had to mod one for an Lt1, but I see new ones are now available through the corvette suppliers.

As well my car had a couple of injectors that were bad. The new FIC injectors made a world of difference. Good luck!

leesvet

NOPE....

That vac valve is a solenoid for the EGR control. The 3rd port is not a vac fitting. Its just a vent so the valve can exhale and have free movement and operation. You might want to relocate that solenoid to the backside of the alt on a bolt so you can have access to the EGR vac line. The EGR is often the culprit in many performance issues and when you have easy access to the vac line running to the EGR valve and the EGR solenoid you can quickly test and rule that out as a cause of problems as they arise.

Test and clean the EGR and ports when the plenum comes off. I'd also replace all the vac line while you can see and get to it all. Might want to do some house-keeping on top of the intake and just organize, inspect and repair anything thats not 100% with the harness, lines, check bolt torque (actually very important as some intake bolts WILL work their way loose)(retorque based on pattern in FSM) and just do a good PM check while you have it apart.

If you have not already done so, utilize the access and get a good adjustable fuel regulator so that is ne and able to be set for your engines needs. The difference between 22lb/hr injectors and 24 or 26 is simply a very few lbs of fuel pressure. Adjustment allows you to dial it in for your driving needs. Also, the regulator CAN leak internally and cause the system to starve for fuel even though it shows pressure and flow. The inside can pass fuel under the spring plate and leak it into the return side of the system instead of maintaining that pressure on the rails where it gets to the injectors. Gauge still shows pressure but the flow is being lost to the return side. Its difficult to detect because the return side always has something going thru it, so you have to look at the parts of the regulator to see if there is a good even seating surface just like lapping in an intake valve in a head where you look for the ring around the valve seat. If the ring in the reg is irregular or broken in appearence then there is a chance that its been leaking internally. Besides, adjustable regulators look nicer than the stock. Polish the new one and its even better.

Hope this inj upgrade solves the problem.

RedTRex

Excellent tips guys - thanks.

The car already has an adjustable FPR installed - cool.

RedTRex

Groan......all back together, but won't start ??????? WTF.

Well - It will fire with some starting fluid (I know bad, but rules out ignition)

Can't hear fuel pump run. Jumped test connector. still didn't hear pump, but have some fuel in rail. Swapped relays, no change. Verified I reconnected everything right.

Pulling pump shortly to test directly.
- Could it be failing, which is what it showed me the other day with the very rough running and low idle?
- Anything else I should look at?

RedTRex

Update......
Fuel pump was only getting 2 volts......ended up being fusible link H. Behind battery - it's right after the long connector you pull to clear ECM.


Next issue. Disconnected tan/blk wire near booster. Set timing to 6 deg before was at 8 after, shut off car and reconnected. Idle is at 1300 rpm.

navy_vette

Is it throwing any codes?
How does the exhaust smell now?
Is it at least running smooth?

Your car may be good now, you might just have to do an idle relearn.

RedTRex

Code 42
Exhaust smells normal
runs very smooth.

How do you do idle relearn----looking through service manual now

RedTRex

Code 42 cleared.
I did BLM reset - no change to high idle speed. runs great.

Now what? Idle air valve?

navy_vette

Relearn is something different I was confusing myself...
I'm on a REALLY boring watch right now. Has anyone noticed I've been on the computer for almost 8 hours? Yep.

Code 42 is EST.
I think a disconnected timing advance wire can cause that... Check distro wiring.

Adjust screw on the throttle body arm while it is running until you get it where you want it. Shut it down and disconnect the battery long enough for a reset. Reconnect battery and start her up. She'll run higher RPMs until she hits closed loop and should come back down to the normal RPMs.

Check exhaust and codes. Post