Need help please before I loose my mind 88 model camero 5.7 tpi new rebuild been running fine for 8 months stock except for 10.5 flat top pistons new everything sounds like valve float at top of shift points checked timing still at 6deg btc new 02 sensor cleaned mass air flow check valve adj still in spec checked plugs it has been running a little lean by look of plugs that why I replaced o2sensor tps is correct no vaccum leaks hasn't had a knock sensor on it since build due to block hugged headers removed egr valve all pollution crap removed motor ran great for years spun a rod bearing that's why I had to rebuild any ideas I'm at wits end !!!!!!!

 

How are you running it with no knock sensor then? It should be throwing a code 43 and barely run.

 

Just check the usual. Make sure fuel pressure is ok, make sure timing is set to spec.

 

Timing is correct fuel pressure is 46 haven't run a knock sensor on it for four year in this jeep and two years on a 96 lt1 in another jeep has always ran perfect on both small oil return passages and high rev got my tpi after four years spun a rod bearing had to rebuild I know knock sensor retards when sparknock happens just never has guess iv been lucky on both I going to retard to 8 btdc and hope this fixes it I notice happening to when I lift out of the throttle too think do u guys think it could b maf going bad looks like it been running lean

 

No codes idles like a champ runs smooth no throttle lag quick snappy eng !!!!!

 

8 degrees BTDC is more advanced than 6 BTDC.

 

You haven't really explained how it's acting. What exactly is happening?

 

Starts easy idels perfect when u get it on the highway sounds like the valves are rattling at the top rpm right before it shifts gears when it shifts rpm drops rattle goes away till u wind out next gear at highway speed 60 65 lift off gas sounds like valve rattle just a little then goes away running 700r4 trans same set up had for years

 

Could the maf be going bad making it lean out at high rpm same maf has been on it for twenty years , but the throttle respond is good and snappy

 

no offense, but are you sure thats not spark knock? You did lower the timing? Have you pulled your valve covers to make sure nothing is loose or broken?

 

Pulled covers readjusted valves eng running 0 lash plus 1/2 turn valve train is all new even put new rockers and push Rods in it when I rebuilt it replaced every sensor on motor I didn't reuse old stuff cause it always bites me n the *** it's a all new engine crank pistons connecting rods I've always ran this motor on 6 btdc never had a problem out of it do u think with the different pistons 10.5 I need to adv or retard over stock and the maf be possibly causing the lean condition which is causing the spark knock

 

What octane gas are you running? That is high compression you have there.

 

93

 

What are you doing about a knock sensor.

 

Been running a little seafoam with it when I have to run that ethnol crap but mainly run 93 ethanol free

 

Never ran one on either of my motors guess I've been lucky never had issues with out them

 

Knock sensor won't fit due to block bigger headers

 

Block hugger header ($&&,:.,( auto correct makes me type like a retard lol

 

The Tpi computer should be looking for a knock sensor signal and setting a code 43 if all is functioning correctly(knock sensor not hooked up) ,but who knows i could be wrong.. Did you change anything recently around the time this noise/problem starting occuring?

 

No it just started one morning the only code the computer has ever set was a tps to high right after I started it and set everything hasn't set a code since never set a 43 the whole time I have ran this engine after I put it in the jeep

 

Why dont you datalog that thing man. Hook up your laptop to the aldl port and download one of the many free software programs out there.

 

Disconnecting the neg. battery cable for a few will clear any stored codes. How did you set the timing? Did you disconnect the EST and set the timing?

 

You said earlier that you did adjust the valves hot? If so that is prob the best way. I would datalog that thing and take a look at what the ecm is doing. Anything else unusual? Are your fans stuck on? I remember when i had a chip go bad once. The car was stuck in diagnostic mode and the fans ran constantly and it would ping real bad at anything over 3k rpm.

 

Electric fans are on a different cuircut from the computer it's all b cool stand alone on at 185 of at 180 never dat log one before with a laptop I have a snap on scanner that I use It has data log on it Yes disconnected the est before I set base timing have you ever heard a maf causing this plugs indicate it has been running a little lean ohmed the inj all r at 16 or 16.1 pulse lighted all the inj wires they r all good

 

Mass air is the only thing on this motor that is not new????

 

Older MAF bins will not set a code for unhooked knock sensor.

Your description of the problem is still unclear to me, but I'll assume you know what spark-knock sounds like and that it's happening.
You need to watch your fuel pressure while this problem is occurring, - not just sitting there idling or revving with no load on the engine.

I would look over every spark plug for clues. Are they all running the same and knocking? If so then it would seem to be a global problem with the tune.
It could be explained by a loss of fuel pressure with the engine under load (fuel filter blockage), or a problem with the function of the ignition system, - actual spark advance exceeding what is commanded.

When you're talking about the knock happening at the top of your gears, do you mean normal part throttle driving shifting at 3000 RPM? or are you talking WOT runs?

 

I have no codes set in the ECM never has set a code for anything I thing the motor is running lean by the indication of spark plugs would a bad mass air sensor cause a lean condition I live in Nashville tn

 

my plugs are whitish too,not a big deal. should still run good

 

Changed mass air flow sensor with new one runs like a champ again no rattle at high rpm like it was doing thanks for all ur help think old mass air flow was not sending correct data at high rpm low air flow reduced my fuel curve causing lean condition which caused my rattle

 

awesome man

 

So it's fixed now?