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Discussion Starter · #1 ·
hey there i am ne where trying to find a good vette site.
so i have a 99 vette std tranny coupe.
90 000 mile.
well last summer i noticed a slight or flat spot in the rpm range of about 3-3500 only when i hit the throttel about 3/4 and hold it there or wide open... it would climb good untill that rpm range then it kinna flat line or dropped for a mill second and then it picked up and took off ..
well that buged me.. so.
this summer i got it out i put new plugs in it and a new in line fuel filter.. wich i bought off ebay they said it intrechanged with the one i had parts number did anyhow.
well i put it on and about a week it seemed to be the same... but now today i went to get it out and it did not start it just trun over. it did this all day .. to start it i have to trun the key let it crank for a second and then trun off and start aging it fires rite up.... and now i noticed it doesnt pick up very fast wide open .. like frist gear i can hold to floor and dosent seem to get to 50 very fast...

so could it be my plugs .. becase they was advanced auto brand platinmue or the in line filter wich was the cheaper one but it was new.
and is there a filter int he gas tank of my car i wonder if it need replaced ... i am thinkg its a fuel flow problem ????????
any help please.. i hate having a vette and it takes off like a 6 cyl lol..
 

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Aloha, Welcome to the site.
The first step would always be to pull your codes. At the top of the c5 section is a link thats shows you how.
 

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Discussion Starter · #4 ·
i take that back. i just check my codes.
i have few that are ..h... codes wich mean histoyr so no need to worry about those i was told. well
i have 2120 wich said tpm system malfunction...... wich ened in h and c i have no idea what that is yet.
i have a 1236 c wich is low system voltage..
now i had a dead battery over the winter i jump it few times then i bought a ne wbattery wich is in it now...
so can u help[ me on this may its my whole problem.. thanks
 

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Discussion Starter · #5 ·
tpm is the tire pressure mo.
wich makes since becase i put new rims on and never learned the wheels yet... so thats one thing i solved so far lol.
i might do that pcm restet i read in the sticky .. u no i been runnig 87 or 89 octang for last 2 summers
 

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Hum, i would say the octane cold be one reason. I have verified many times with my scanner, even 91 octane will put my PCM into the ". Low octane tables", of coarse dropping power. Knock sensors retart timing to keep the motor from knock. Ive seen my timing drop as far as 18* with low octane gas. Alot of drag racers have the low octane table erased, or rewrite the file so the high table is copied over the low, if that makes sense. This is a quik description. A good book to get is " corvette fuel injection " by charles probst. R.I.P. This book desribes this very well. As well as many other things. Try to fill the tank with 93 octane, reset the PCM, with the fuses, then drive it hard. Post up your results. Good luck.
 

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let me make sure I am understand this correctly. You replaced the fuel filter and then it started not starting/running like ****, correct?

If that is the case, I would look at the fuel filter. You said you got it off ebay. I would suspect that the filter is causing the issue. I really do not like buying off-brand parts from ebay that I cannot completely take apart and inspect.
 

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Discussion Starter · #8 ·
ok i will get new gas and reste the pcm.. that probly is my problem i mean i frist got the car it felt power house then later on it kinnagot lsuggish .. but i will give the fule a shot.
and it ran like that before i changed the in line fuel pump.. the one on the frame..... thats the reson i changed it becase it ran sluggish before and i am trying to elimante the problem.
thanks .
 

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If the problem is still there after resetting the PCM, Actually'i would change the filter anyways, only use the recommended filter, many guy's, my friend included, tried a non recommended filter, a custom tuner actually caught this issue when the car was on a dyno and they were checking the tune during WOT. Suggested a filter change, and bam, the WOT readings changed, the cheap filter didnt flow the same as the stock one.

If theres still an issue after this, can start going thru the troubleshooting steps. You should try to find that fuel
Injection i mentioned, amazon.com its packed with great info
 

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Discussion Starter · #10 ·
well.. didnt clean the ground syet. but i did the restet of the pcm and cleared any codes... well it made it tens times worse i went down the rode today and i mean it will not go fast at all it idels good and revs good but under load it hits about 2500rpm and just falls flat on its butt for 5 seconds or so and picks up slowly if i stomp it down it picks up real slow and doesnt seem to rev out.... after clearing the pcm codes it really meesed things up .. sop i am gogin out to clean grounds now and see what happens tommerw .. any ideas let me no.. oh and i wonder if my plugs could do that ????.. i am leaning toward that junkie ebay inline fuel filter ........... i wonder why resting the pcm made it that much worse its almost und rivable unless you do under 40 and dont hit the gas to fast ..
oh and its real jerky to let of th egas it alomst like hitting the brake kind of
 

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Im at work rite now, no books withe me to start taking steps. Resetting the PCM, sounds like that exposed your proble even more, the car might run a little better soon as the computer will adjust slightly trying to compinsate for your problem. If it was pulgs or wires, i would assume you should get some kind of miss-fire code. But anything is possible. For now, maybe take off your air filter assembly, make sure nothing broke off or whatever and is blocking the air bridge or MAF sensor. Later when i get home, will post the steps you should take to trouble shoot. I would also change that fuel filter.
 

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Discussion Starter · #12 ·
thanks for the tm but guess what now.
i cleaned the ground and hooked the battery back up.. staterd the car and half or wide openit just sits there and spuuters wont rev at all.and to topp it all off iwas doing that for about 5minutes and noticed a smell . so it offf and got out and smoke was coming from the back of car ... the exhuast was so hot under theback it was almost melting the bumper.. so any ideas now. i thought maybe unbrunt gas ?? i no it was hot hot so hot it was smoking....
kinn wished it justbruned up lol.
 

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Discussion Starter · #13 ·
well of course it got sohot i have 2 codes wich is p0137 and p0157 .
wich is oxgen sensers.....
hey i am gogin to take a video rite now and post it on you tube so you can hear what is doing .... becase i am so sick of it rite now i am ready to junk it for parts // but i will post the url for the vid ok
 

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Ok, buT careful, dont let things get to hot. If the cats are plugged, imagine how hot there getting if the rear is getting as hot as you say? Does the car have a ticking or air sucking sound? Is the exhaust white or black? Dont catch anything on fire under the car bro.
 

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You know it to me sounds like if you have cats on it they are clogged. Some of these symptoms here loss of power,flat,heat, etc. Im leaning to the cats if they are clogged up in any way not good at all. The car wont want to run. Of course this would cause you to get 02 codes also. Ask me how i know.:D. Just a thought to check out.
 

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Discussion Starter · #16 ·

ok check out the youtube clip maybe that will help out...
i thought of cloged caddys but why would they clog now after i reset the pcm .. they worked fine before that and only time it gets hot is if i sit there and do what i do in the you tube clip.... check it out and see if any ideas..
me i am thinkg the bad in line fuel fliter.. i hate to waste cash on anther one untill i do ever trouble shooting idea i can get.....
and in the clip i was holding the gas at one spot each time it flat lined..
i might chage plugs tommerw just to do it..maybe the cheap plugs are fouling out under pressure and letting unwated gas flow into the exhast and when i let off the gas they ignit the unwated gas and makes the exhaust extra hot . i dont no i am just guessing ideas here.
 

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Hum, ok. In the troubleshooting guide for , " lack of power - sluggishness - and sponginess".. The first things all relate to fuel.
- check that both injector fuses are ok, and inspect injector and coil grounds. I also just remembered some cars have a tight wiring harness that wraps around the back of the intake manifold and head, eventually cutting thru and grounding the harness. Check that now as well.
- check if fuel pressure is low
- check if fuel filter is restricted
- check for contaminated fuel.
- check for proper operation of column lock system ( or bypass kit if have)
- check for excessive spark retard in the knock system ( Obd-2 scanner required).
- check ignition and plugs.

Under "'cuts out or misses"
- check fuel pressure
- check for restricted fuel filter

If the car is " surging or chuggles"
- check grounds. PCM especially
- check o2 sensors, wires or if any RTV sealants or crap got in the 02 bung somehow.
Then back to the same fuel checks

First thing i would do is check the injector harness wraping around the engine, and get the proper fuel filter in. Nice car bro, dont junk it, you'll figure it out.
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Wow, I've been passed out every since he said he ran 87 octane for the last 2 years. :thud:
 

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Discussion Starter · #19 ·
haha passedout fromthe 87 octang lol... hey at least when i get her gogin i wont be buying cheap gas anymore..
well i am on my way out to do these troulbe shooting tips and see what happens ...
 

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This thread should be made as a sticky as what NOT to do in solving problems !

1. The Corvette does NOT have a "fuel filter" ONLY, it is also the fuel regulator and why they cost about $70 plus.
This was not the problem in first place.

2. Buying from EBAY is a flag in itself, no clue as what really was bought.

3. Prove it is a fuel delivery problem by simply putting a fuel pressure gauge on the fitting at end of left fuel rail !

5. Pressure should stay right around 58 PSI, if not then solve that FIRST !

6. Every time you clear the DTCs you not only erase the history but also force the PCM into a relearn state, do not do that

7. One of the DTCs was LOW voltage, that does not mean OVERALL voltage but what the voltage is at the PCM. Check fuse for O2 heaters.

8. Run engine via DIC watch voltage should be around 14 volts, low voltage will cause PCM to run in a limp mode.

9. If you cannot afford the correct spec'd fuel then sell the car but using regular will **** up the O2 sensors and the CATs

10. Worse is regular with ethanol is ****, it also degrades over a few months and problem gets worse. If in doubt drain the piss out and put in at LEAST 91 octane.

11. Both rear 02 sensors DTC reporting LOW output. Maybe the heater circuit is popped and 02s not getting hot enough OR some exhaust problem which effects the cold start when AIR ( smog pump is ON) or in fact the front 02s are degraded which would effect the difference the rear 02s report.

12. QUIT fricking around, this is a 5 minute task, USE the proper tool and that is a OBD-II scanner which would tell EXACTLY what each feedback sensor is reporting along with all PCM functions.

13. We have no clue what mods the C5 has and that could cause why the engine is in a limp mode.

14. Low voltage overall could be causing PCM or PCM to effect column lock and PCM has gone into safety mode and when it does it limits engine so that it can only go 2 MPH

15. USE scanner!, look for misfires, bad crank or CAM sensor, low oil pressure, water temp, etc, etc.

16. With scanner see if PCM goes into CLOSED loop once water temp is above 160 degrees.

Issues.

1. long term use of piss instead of high octane gas, worse with ethanol has ****ed up the 02s and caked up CATs

2. Use a thermal gun and measure temps, primaries of exhaust should be about 300 degrees. are the temps the same left head/right head.

3.What are temps by from 02s, then before the CAT and then after the CATs.

4. If voltage is low, check via scanner of the ALT is not being commanded to output

5. 02 sensors should be replaced every 40,000 miles, if car has 90,000 and original 02s then blame is on car owner.
How'd you like to like in 800-1100 degrees plus what ethanol does ? At the least change the fronts and later change the rears.
With scanner the front 02s should average out as 0.450 mVolts, IE about 14.7:1 AFR, the lower the voltage output is the leaner the AFR is, the higher is richer.

6. forums are the worse place to get tech and repair as most guys today cannot even change the engine oil ( they can sew though) much less use a simple OBD scanner which pinpoints the problem :smack
 
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