When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
...I agree with ya'll that a bunch of changes at once may be a recipe for disaster and to that end we've made changes/repairs one at a time. So here goes from beginning:
Found car where it had been sitting in backyard not running for 2 years. Supposedly in shop for brakes when damaged by a tornado. Engine and trans allegedly had been recently shortly before then but no documentation. Other potential buyer had tried to get it to run to no avail.
1. Purchase car for $500. Trailer home. Charge battery. Turns over but won't start. Dash lights up but instruments don't work. Warning lights in center console do appear to work (SES, abs, low coolant etc.).
We'll come back to this once the Vette is running; but for info for research, did any of the instruments on the driver's side work in either switched position (with the exception of the speed display and tach)?
2. Will start with starting fluid. Discover fuel pump fuse missing. Replace but fuel pump dead. Replace fuel pump, fuel pump sock, and fuel filter. Gas appears fairly fresh since someone put fresh gas in it trying to start in few weeks before we bought. Tank and old sock seem fairly clean. Car starts with difficulty but runs rough and once warm idles fast. Can't drive since brake lines rusted out.
Are you saying that the engine fired briefly on starting fluid then died? Have you checked the fuel rail pressure (the Schrader valve on the passenger side fuel rail)? The fuel pressure should be at least 40.5 psi at start up. The stock pressure is 43.5 psi at WOT (zero engine vacuum). The stock pressure regulator is the domed unit on the crossover fuel rail facing the firewall. (If someone replaced it with an adjustable fuel pressure regulator, there will be some type of adjusting screw at the top of the unit.)
3. Rebuild brake system. Begin gutting. Remove window regulators, electric door solenoids, etc. All worked prior to removal, Test drive. Fast idle, stumbles when you give it gas but once clear up accelerates fine with no miss all way to redline. Shifts crisp, kicks down on hard acceleration. etc. Car wants to overheat. Fan doesn't come on. Discover hidden manual fan switch under dash. Turn on fan. No more over heating.
Sounds like a vacuum leak at this point in time if you have a fast idle, but a noticeable stumble upon acceleration. Finding the source of the vacuum leak requires looking at all the usual suspects, e.g., loose intake manifold & throttle body bolts, vacuum takeoffs for brake booster, cruise control, fuel pressure regulator, vapor recovery system, and EGR system.
Be careful when accelerating to the "redline" indicated on the instrument panel. The L98 doesn't have an automatic fuel cut-off rpm like the LT1, LT4, or LT5. Some have suggested that the automatic fuel cut-off is just north of 8K rpm with tongue in cheek. Sounds like some of the instruments are working now. Is this correct?
4. Discover car has wrong plugs and although new appearing one plug wire seems bad. Replace plugs. Doesn't cure stumble or high idle. Began removing air pump mess. Throws SES light. We don't pull code because quite honestly we didn't know how without scanner. Thanks to this forum we now know. Runs same
Think this one is OBE now.
5. Relocate battery to behind passenger seat. Remove air pump and AC units. Install regular flow water pump...THANKS Matt! Install 160 degree thermostat (had 195 in it). Take out for test drive. About 4 miles in begins to un rougher. Decide to turn around and gets rougher sand rougher running....stumbling....does not want to run when push on accelerator. Limp home. Does not overheat. Did backfire a few times on way home.
Normally rough running like you describe is the result of the fuel pump acting up and/or the fuel pump replay going bad and cutting off the flow of fuel. Again, please check the fuel pressure at the fuel rail and advise. The backfiring could also be the result of improper timing. Did you have the timing problem corrected when you started the run or was that later? The four miles during the summer weather seems long enough for the ECM to shift from open loop (fuel table look-ups based upon engine rpm, coolant temp, throttle position, MAF data, and manifold air temp) to closed loop (measured fuel trim values and oxygen sensor input data plus engine rpm, coolant temp above 167F, throttle position, MAF input, and manifold air temp). The knock sensor comes into play during closed loop and interfaces with the Engine Spark Control (ESC) module (flatpack module located on the outside of the evaporator airbox on the passenger side). Knock counts are sent to the ECM which retards the timing for a set period of time before allowing normal spark advance. Code 43 is set if the ESC module sends a low voltage signal (knock detected) for more than five seconds, or if the ESC module fails the start up test. Without a functioning knock control in Closed Loop, I imagine that the ECM advances the spark very slowly if at all. (I have no data on this. The shop manual gives plenty of data on testing the ESC module, but no specific data on what the ECM does when after setting Code 43.) The knock sensor wiring needs to be fixed/replaced. If you still have a Code 43, then I suspect that the knock sensor itself is damaged and should be replaced.
6. Won't start without aid of fluid. Replace plug wires. Drain all fuel and replace with fresh...no trash in filter or sock. Same. will only rough idle Once running if you constantly feather throttle. Check timing. Discover distributor is loose. Did not know to do ignition disconnect to set static timing. Now we do thanks again forum. Pull code....43 Knock sensor.
This should be OBE too.
7. Check knock sensor. Discover wiring insulation burn fro contact with exhaust manifold and ceramic connectior broken on wiring loom. Still will plug in though. Replace wire to knock censor with new wire. Notice O2 sensor wiring is ratty. Replace O2 wire. Clear codes. Try to start. Same. Get started with stating fluid, PROPERLY reset timing to 8*. RECONNECT DISTRBUTOR wire. Runs same. Pull codes. Get 43 And now 42. Note...timing jumping all over when checked at rough idle. Clear codes and try again. No JOY....runs same.
Based upon the re-occurrence of the Code 43 (knock sensor), the sensor itself may be bad. (The ECM doesn't use the knock sensor's input during Open Loop so this isn't the source of the rough idle.) Again, try connecting a fuel pressure gauge to the fuel rail to see if the pressure is steady or varies after the engine fires. (Just want to eliminate the fuel pump replay as a source of the rough idle.)
Once you reconnected the distributor, the ECM will clear the Code 42.
Where do we go from here....looks like throw up hands and yank FI and go to carb. There goes GRM challenge budget. LOL
You may want to do that after the GRM Challenge is over; however, doing it now will eliminate you as a competitor plus cost a ton of money for a carb, intake, new distributor, re-wiring the ignition to by-pass VATS, and adding new gauges, etc. Best stick to getting the TPI to work.
Maybe try dist modules since I can get some cheap at junkyard?
Don't think that the distributor or either of it's modules are at fault here. Check to see if there's a strong spark between #1 spark plug and its plug wire with some type of metal conductor inserted in the plug wire. If the spark is strong it will be white and jump the gap easiy. If it's weak, it won't jump the gap or will just jump it it you narrow the gap. The color of a weak spark is normally yellowish.
ADDENDUM....one thing that seems to keep coming up in the back of my mind is that it seemed to go south with the way it land immediately after I relocated the battery. I spliced into existing cables and use a heavier cable to go to the back. I spliced boat positive and negative leads. maybe it's something to do with that?
If you have battery voltage at the alternator, you should be okay.
Oh yeah...distributor has not been removed. With exception of timing changes it is still where it was originally when the car was running
In a previous post, I recommended checking out the coil in the cap. Has this been done? (Usually the coils go out completely at one fell swoop, but a weak coil on the verge of collapse would allow the Vette to idle, but would cause misfires as the engine accelerated.) It would give you a chance to checkout the condition of the cap and rotor at the same time too. Carbon tracking is bad as are burned/pitted contacts or rotor blade.
Finally...The Code 42 has now disappeared. May be because we plugged distributor back in
If nothing else, this has been one Corvette Adventure so far! We shall prevail!
If nothing else, this has been one Corvette Adventure so far! We shall prevail!
Thanks MrBeach...
Will comeback when I get a chance and reply in more detail. We it seemed to make a little progress today. We finally got pressure testing equipment in place and discovered it is booting up when key is turned on but before starting to about 45 PSI.
once the engine starts to run pressure drops back to 23-24 PSI. We checked wvacuum lines and replaced a suspect line that might have been leaking to the fuel pressure regulator. On the recommendation of another mechanic we tapped on the pressure regulator and we're able to getthe pressure to come up to about 30 PSI. It ran somewhat better.
would start without starting fluidat this point.when you shut it off it would not hold pressure and would slowly leak down to about 12 to 15 psi.
My partner in this emdeavor, Larry, who is the better mrechanic will be joining this thread with his comment and observation.he is also an old geezer who preferred carb to fuel injection. LOL
to answer one of your questions no instruments work from the outset.so we're Flying Blind so to speak.
Will comeback when I get a chance and reply in more detail. We it seemed to make a little progress today. We finally got pressure testing equipment in place and discovered it is booting up when key is turned on but before starting to about 45 PSI.
once the engine starts to run pressure drops back to 23-24 PSI. We checked wvacuum lines and replaced a suspect line that might have been leaking to the fuel pressure regulator. On the recommendation of another mechanic we tapped on the pressure regulator and we're able to getthe pressure to come up to about 30 PSI. It ran somewhat better.
would start without starting fluidat this point.when you shut it off it would not hold pressure and would slowly leak down to about 12 to 15 psi.
My partner in this emdeavor, Larry, who is the better mrechanic will be joining this thread with his comment and observation.he is also an old geezer who preferred carb to fuel injection. LOL
to answer one of your questions no instruments work from the outset.so we're Flying Blind so to speak.
thanks for all your suggestions.
Either regulator pump or filters. Regulator most likely if tapping makes it better. Idle should be around 36 or 37 psi if starting at 45.
Either regulator pump or filters. Regulator most likely if tapping makes it better. Idle should be around 36 or 37 psi if starting at 45.
looks like we're going to have to take off plenum and fuel rail off to get at the pressure regulator. Oh well I guess we can work on intake with dremel while it's off and cap off egr to allow us to run headers.
Don't think its filter....we just put new one on as well as fuel pumps sock.we sure hope this solves our problem.this will tap out challenge budget
everybody agreed that it's fuel pressure regulator?
looks like we're going to have to take off plenum and fuel rail off to get at the pressure regulator. Oh well I guess we can work on intake with dremel while it's off and cap off egr to allow us to run headers.
Don't think its filter....we just put new one on as well as fuel pumps sock.we sure hope this solves our problem.this will tap out challenge budget
everybody agreed that it's fuel pressure regulator?
From what you've reported for fuel pressure readings, the pressure regulator needs to be replaced. The initial 45 psi is close to the 43.5 psi recommended for WOT, but the running fuel rail pressue of 30-32 psi is too low for a stock L98.
Before you take off the plenum to change it out, try posting a picture of your fuel injectors and post their part numbers on this thread especially if you have an adjustable fuel pressure regulator. ( I use Ford Bosch injectors rated at 24 lb-hr @37.5 psi instead of the stock Multecs rated at 22 lb-hr @43.5 psi. My max psi at WOT is 36 psi, and my running fuel rail pressure is 32 psi.) Just want to make sure that aftermarket injectors didn't replace your stock Multecs. (The Multecs have a light gray upper body cap while Ford Bosch injectors can be pink, blue, orange, etc. but now gray.
From what you've reported for fuel pressure readings, the pressure regulator needs to be replaced. The initial 45 psi is close to the 43.5 psi recommended for WOT, but the running fuel rail pressue of 30-32 psi is too low for a stock L98.
Before you take off the plenum to change it out, try posting a picture of your fuel injectors and post their part numbers on this thread especially if you have an adjustable fuel pressure regulator. ( I use Ford Bosch injectors rated at 24 lb-hr @37.5 psi instead of the stock Multecs rated at 22 lb-hr @43.5 psi. My max psi at WOT is 36 psi, and my running fuel rail pressure is 32 psi.) Just want to make sure that aftermarket injectors didn't replace your stock Multecs. (The Multecs have a light gray upper body cap while Ford Bosch injectors can be pink, blue, orange, etc. but now gray.
I haven't seen original Multec injectors on an '89 in years; however, it appears that you have the replacement Rochester Multec injectors with the black top. In fact, it appears that you have two different types - one with a green body stripe and the other w/o the green stripe. (89 was the first year for Multec injectors, and they had gray tops.)
While you're replacing the fuel pressure regulator, go ahead and remove the electrical cap on each individual injector to check the internal resistance on it's coil. It should be nominally 16 Ohms cold or hot. I've found most measure between 15-16 Ohms when relatively new, 14-15 Ohms when used (>80k miles), and 12-13 Ohms when in need of replacement. Here's a link to a good video on the forum regarding Ohming Injectors.
If anyone following this topic can shed some light on what a green stripe Multec injector is, I'd appreciate it! Thanks!
Last edited by mr.beachcomber; 07-26-2016 at 09:11 AM.
Reason: Corrected "link" to "topic"
Larry, team torque wrench supervisor, and I have come to the conclusion that a rebuild of the pressure regulator is inevitable. we have a few questions.
does the Runners, plenum , fuel rails have to come out? Or can we access the fuel pressure regulator without tearing all of the intake off?
if the pressure is correct when you turn the key on initial why does it not start up? it would seem that if it reached 47 psi it would start and then die if the pressure droped down to 25 psi.
What is significancexpected of fast idle when it was running?
if we do have bad injectors what are most economical replacement options?
what if any fuel pressure rebuild kits do you recommend? Are there any Brands we should stay away from?
Larry, team torque wrench supervisor, and I have come to the conclusion that a rebuild of the pressure regulator is inevitable. we have a few questions.
does the Runners, plenum , fuel rails have to come out? Or can we access the fuel pressure regulator without tearing all of the intake off?
I've replaced the fuel pressure regulator diaphragm & spring assembly just be taking off the plenum and throttle body.
1) Unplug the Throttle Position Sensor. Remove the throttle, cruise control, 700R4 kickdown cables as well as the hoses for the vacuum port and fresh air for the PCV system from the throttle body.
2) Remove the inlet hose from the heater box and outlet hose to the intake manifold. (Good time to go ahead and by-pass these two hoses by taking a length of heater hose from the heater box directly to the intake manifold. The OEM design is to prevent icing during the winter, but I have had any problems after removing it with our Virginia Beach winters.)
3) Remove the bolts holding the runners to the plenum. (You may have to loosen the bolts holding the runners to the intake manifold just to lift the plenum straight up after unbolting the power brake vacuum source and unpluging the Manifold Air Temperature (MAT) sensor and vacuum feed ports (one goes to the regulator). (Don't forget to plug in the MAT sensor when you're putting the plenum back on. I learned the hard way that's there no way to re-connect it once the plenum is bolted in.)
4) Remove the torx screws holding down the top of the regulator. Replace the diaphragm and spring assembly and reattach the parts in reverse order.
if the pressure is correct when you turn the key on initial why does it not start up? it would seem that if it reached 47 psi it would start and then die if the pressure droped down to 25 psi.
Could be weak spark, wrong initial advance, or touching the accelerator while cranking the engine. We've covered the first two conditions in previous posts. If the accelerator is depressed even a little bit during engine cranking, the ECM interprets the increased throttle opening as an indication that the engine is flooded and cuts off fuel flow while the engine cranks to clear the flooded condition.
As for the low fuel pressure (25 psi) killing the engine, the ECM reads the fuel tables for the engine while operating in Open Loop. There is no feedback from the oxygen sensor, so the ECM looks at the table value and batch fires the injectors one side then the other based upon the tables which were developed for around 37 psi. The result is a lean condition that won't support even an idle.
What is significancexpected of fast idle when it was running?
Normally, I've experienced this fast idle condition when there is a vacuum leak providing more air to the engine past the MAF. (The air/fuel mixture is slightly rich in the stock tables to preclude lean misfires.)
if we do have bad injectors what are most economical replacement options?
I would contact John at Fuel Injector Connection. His located in Georgia and has done a lot for this forum. Good people. He will probably work with you if you let me know your prepping for the GRM Challenge. He can rebuild your injectors or offer warrantied new or rebuilt injectors.
If your injector Ohm out okay, I would try using CRC Intake Valve Cleaner. (I like this better than Sea Foam which is a great product also.) I inject the cleaner through the fresh air takeoff on the passenger side of the throttle body. I put a rubber cap on the takeoff. Drill a hole large enough for the applicator straw and then just follow the instructions. This will remove carbon deposits on the intake valve and combustion chamber. Use Techron (see post below) to clean injectors.
what if any fuel pressure rebuild kits do you recommend? Are there any Brands we should stay away from?
You've expressed some concern that your injectors may be bad. I've thought about that as a possible cause for your hard starting issue. Looking at your pictures, I see that you are using replacement MULTEC injectors plus you indicated that you were able to run the Vette to redline and that it pulled strongly. Partially clogged injectors or non-functioning injectors would have given you a ragged ride in that situation. Plus you haven't reported any lean misfires other than the time your drove the Vette back in the limp home mode.
Doing the Ohmmeter test only verifies that the internal coil is strong enough to open the injector's disc to allow fuel to pass through. You have to bench flow the injectors to find out how well they're working.
I think that you're okay in the injector department; but adding the recommended amount of either Techron Fuel Injector Cleaner or Fuel System Cleaner to the gas tank at each fill out will take care of any built-up gum or varnish the injectors have accumulated over the two year period that the Vette just sat.
Note: Clinking on link with result initially on notification of undefined variable. Click on "OK" to continue to the web page.
Last edited by mr.beachcomber; 07-27-2016 at 06:09 AM.
Reason: Added link to Techron products that can be added to gas tank
Time to jump in and say hello. I'm the other part of this racing venture and want to thank yall for the info on the preceding pages. It has been a huge help. My auto experience began in the Chevy dealership where my mom worked and I've been a Chevy guy ever since. Along with some others!
Unfortunately I've have not had the opportunity to learn much about TPI. Till now! I can't say that it's been the easiest row to hoe mainly due to a complete lack of knowledge. All the alphabet seem to be used in this system!
The consensus in recent posts feel that we have a FPR problem. So, yesterday we took the thing apart and learned a lot but the experience also raised a lot of questions. If you guys are game I'm going to post some questions and try to include a few photos.
First, removed everything needed to access the FPR. Why didn't someone tell us about tamper-proof torx? Trip to AutoZone! There was no visible issue with that thing. The pressure gauge readings were, IMO, a little odd. 45 at key-on around 25-6 at "idle" which is very high on this car. There was no movement or bounce in the gauge with changes in rpm. I am assuming that the FPR must be stuck in an open position. Is this common?
I'm going to post each question in a new post. Thanks for the help and please remember I'm a TPI beginner and am truly this clueless!
We are trying to clean up the engine space and want to eliminate any source of leaks, unneeded hose, etc.
So we yanked the EGR Valve and the tube from header to manifold. We are getting a plate to block where the EGR mounts, have blocked the port from the header and closed the tube from the header. The little sensor that was attached to the tube? I've got it taped to a safe place but what should be done with it?
We found that someone had already tampered with the EGR valve. It was blocked with what appeared to be silicon, non-functioning at best.
Can we expect any issues from this?
This photo shows (I hope. This is my first photo effort) the vacuum line that was attached to the EGR. It started at the vacuum port located on the left front of the Throttle body. The Y went to the EGR and to the PCV on the right side. Can this now be eliminated? The PVC on the right has two tubes, the forementioned and another going to the right side of the Throttle Body.
In previous posts my partner has mention the high idle condition that has been with us since the get-go.
When I removed this It had no coolant, having been blocked by me, before I knew this was idle related. I have also seen/viewed stuff where this was bypassed. Bad Idea? Keep in mind we give no hoots how well the car cold starts, but do need to get the idle under control, if nothing else to try and get accurate timing. Additionally the IAC looks like carp and I really don't want to hit the budget for an unnecessary part. can I block the flow internally? Make a Blockoff plate? If I have to re-plumb where is the best place to run the outlet/inlet ? One goes to the water pump, the other ?
That vacuum port on the bottom right was where the EGR, discussed in a previous post, was plugged.
This thing was, essentially laying on top of the engine. It has what appears to be a couple of vacuum tubes and is wired. It is not an attractive thing and we would like to see it gone.
One of the vacuum ports on the right side goes to the FPR. The other leads to a Y with one tube going nowhere and the other disappearing off behind the motor. Where is it going?
A couple of non-related question if yall don't mind.
I check the injectors and ALL of the said 16. Not 16.4, 15, 17, 14. That lead me to question my procedure of setting my V/O to 2000 and touching the two injector connections. Does this sound OK? Note of interest there are at least two, maybe three, kinds of injectors.
Things are not where I expected. Some of my info has come from Camaro/ Firebird forums which must account fot the differences.
I expected the Manifold Air Temp to be at the front of the plenum, it's at the back. I expected the Coolant Temp sensor to be left front on the manifold, it's right front block. Is this correct?
...The consensus in recent posts feel that we have a FPR problem. So, yesterday we took the thing apart and learned a lot but the experience also raised a lot of questions. If you guys are game I'm going to post some questions and try to include a few photos.
First, removed everything needed to access the FPR. Why didn't someone tell us about tamper-proof torx? Trip to AutoZone! There was no visible issue with that thing. The pressure gauge readings were, IMO, a little odd. 45 at key-on around 25-6 at "idle" which is very high on this car. There was no movement or bounce in the gauge with changes in rpm. I am assuming that the FPR must be stuck in an open position. Is this common?...
First Welcome to the Forum! Second, mea culpa regarding the anti-tamper torx screws I forgot that they were used in this application. (The factory service manual states that the FPR must be replaced as a unit and cannot be worked on.)
Your overall fuel pressure of 45 psi at start up is fine. The 25-26 psi at idle is the problem. (You should see ~ 37-40 psi at idle.) The fuel pressure regulator essentially operates on engine (manifold) vacuum to by-pass more fuel into the return system during cruise conditions. During no vacuum situations such as WOT, the spring holds the by-pass valve closed. I'm guessing that the diaphragm's spring is fatigued. It's strong enough to hold down the by-pass valve at WOT, but not strong enough to prevent the diaphragm from by-passing too much fuel at idle and cruising.
07-23-2016, 10:16 AM
