BOTTLEDZ28

iTrader: (9)

My car will not rev past 4800 rpms. I just put in a new motor with all new sensors. It sounds and feels like a a rev limiter but my MSD box has a 7000 pill in it. What else can cause the motor to just stop climbing past 4800 rpms. My fuel pressue reads 40psi at idle and has a new Holley intank pump. i also added LT1 fuel injectors with 50K on them. No codes are being set.

Mark_ZZ3

4800 is about the range a stock TPI will pull to, although it should still climb.

Is your car stuck at 4800? As in all acceration stops as if you took your foot off the gas?

I would suggest that if you have a stock RPM gauge, consider that it is not correct, so +/- 100 rpm is not unusual.

Are you using a 350 knock sensor? The 305/350 is different. I don't think that would cause your problem, but it might retard the timing.

Is your chip made for your 350 or is from the 305?

Have you put a scan tool on it? It would be worth monitoring your sensors and see what is going on. Pretty hard to trouble shoot without one.

Mark.

86TpiTransAm

Yes it should still climb, my 355 revs toi 5500 all day long with a 6,000rpm pill in the MSD.

Yes they are different knock sensors but that wouldn't cause the engine to stop. The ECM retards the timing and once it has retarded all it can then you start hearing audible knock.

His signature says stage 2 Ed Wright Chip. Same chip I have and again, I'm revving to 5500 rpms.

I don't know what your problem could be. Possibly your cam. I know with my stock TPI 305 the engine would die right about 4800-5000rpms like yours does. When i installed my 355 I put in a comp cam, 50,000 volt coil, MSD 6AL, and stage 2 Ed Wright chip and can now rev to 5500 rpms (with a balanced engine and 6" rods).

Maybe your MSD pill is mislabeled and it's a 5,000rpm pill. Try switching the pill and see what happens.

Mark_ZZ3

Just for clarification, Ed Wright chip can be for a 305 or a 350. Stage 1,2,3 means nothing either, just one persons interpretation as to what mods qualify for stage 1 or 2 or whatever.

Mark.

86TpiTransAm

True Ed does make a 305 and 350 chip but I assume if someone was switching to a 350 like this guy did he wouldn't buy a 305 chip. Guess I shouldn't assume but I did.

Stage 2 doesn't mean anything other than Ed put in more changes to the spark and fuel curve than he did with the Stage 1 so the Stage 2 requires a 160 thermostat. I wasn't making a reference to the fact that it's a stage 2 so it shouldn't affect the rev limit, I was just simply typing what he put in his signature.

I'd still say that even with a 305 Ed Wright chip it wouldn't cause his engine to shut down at such a low rpm. The problem lies somewhere else and not in the chip.

Mark_ZZ3

Agreed. Unless the chip is programmed incorrectly for a cut off ... I recall there is a high rpm cuttoff. The problem is most likely elsewhere.

Mark.

86TpiTransAm

Yeah, there is a high rpm cutoff. Even in the stock chip though it's set to something like 10,000 rpms. I don't think I ever got a verification of exactly why GM did this though.

I do suppose it's possible that Ed messed up somewhere in the chip programming but I think it's highly unlikely.

Zepher

iTrader: (1)

Maybe the tach is wrong, if it is the stock one.
Some people have problems with the MSD box and stock tach, gives incorrect readings or jumps all over the place.

You could be revving to 5500+ but the tach is only showing 4800.

Just my $0.02 worth.

Vader

If you are using a stock valve train, especially stock springs with exhaust valve rotators, the vales can easily start to float at that RPM.

To quote an educated source, "Once the valves float, the party's over..."

BOTTLEDZ28

iTrader: (9)

Vader,I am using the stock valve train. I have had 3 other 350 tpi motr and know whatt hese things can do and what they sound like. My motor here just stops climbing at 4800. It feels like a rev limiter. I have hit the rev limiter plenty of times on my last 97ws6 so I know what it sounds like. I have been using the same msd box in my last 3 cars and never had this problem,. it still does it with the stock chip in it. The tach is correct. I ran an Auto Meter tach right off the MSD box and both where within 100rpms of each other through the power band. I do notice that my stock tach jumps about 2K once in a while on it own. Could the timing be getting messed up at this rpm. There ia a new MSD pro billet dist. in the motor with a bronze gear. no matter how much more gas i give it the motor just wont go past 4800. how could the valves be floating. the motor is brand new from the dealer. how can you determine if the valves have floated. could it be from not seating right on intial startup for the first time

88 WS6 TransAm GTA

iTrader: (1)

Get that fuel pressure up to about 48-50. That might not cause your problem, but 40 psi is way too low. Try that, and see what you come up with.

86TpiTransAm

Bad Idea. He's running LT1 injectors which are rated at 24#/hr and the chip he's using is programmed for 22# injectors. He would be running WAY rich at 48-50psi. Even at the stock 43.5 psi he would be running rich. I'm running same injectors and same chip that he is and I'm running 42psi and that's still too rich.

88 WS6 TransAm GTA

iTrader: (1)

86TpiTransAm, Good point, but the reason I said that was that the earlier Lt1 injectors were 22's. BOTTLEDZr28, what size Lt1 injectors are you running?

86TpiTransAm

I did not know this. Mine are from a '96 if I remember correctly so I'm sure mine are 24# injectors.

88 WS6 TransAm GTA

iTrader: (1)

Yeah, 96's were 24's. I think they changed over in 94 or 95. Have you checked you coil or ignition controll module? The stock ICM's blow goat! :sillylol:

superrammed

check your grounds i had the exact same prob and it was my ground wires on back of my head came off ill bet its a ground mine would hit 4800 and act like the rev limiter on my msd kick in check all grounds good luck

BOTTLEDZ28

iTrader: (9)

i am running 96 lt1 injectors and have a new msd pro billet dist in so i know all the crap for the ignition is good. ifit was a ground then why wouldnt it do it all the time, how can a ground only do that at high rpms

88 WS6 TransAm GTA

iTrader: (1)

To answer that last question, when the engine revs up, more electricity is being taken to give it spark. If you have a bad ground, or too weak a ground, the engine will only get the spark that can be disipated by that ground.

Its like a funnel... you can pump as much water as you want into it, but only a cartain amount is gonna come out, unless you make that hole bigger.

Now Im not sayin that thats your problem either, but if you do have a bad ground, that could definatley be why.

superrammed

trust me it kinda of boggled me to but i would look all over for a bad ground the post above makes sense

BOTTLEDZ28

iTrader: (9)

how can i find a bad ground ground? everything else works fine on the car.

88 WS6 TransAm GTA

iTrader: (1)

Bad grounds arent all that hard to find... The major ones you probably missed are the ones on the back of the heads. There is a ground strap which bolts to the back of each head. Their kinda a pain in the ***, but they need to be there. Check them first.

86TpiTransAm

I have 3 grounds on the back of one head and 4 grounds on the back of the other head. You might want to start there on your car. Also, check your negative battery cable for corrosion and clean off any corrosion or replace the cable/ends.

Another thing you might try is finding someone with a similar setup as yours and borrow their chip and see if that changes anything. If it does, send yours back to Ed and have him fix it.

BOTTLEDZ28

iTrader: (9)

The chip is not the problem. I have tried 3 stock chips in the car and it still wont rev past 4800. The grounds in the back of the heads are good. I will keep looking though

Steve10

Have you changed the coil wire? Bad one will show up at higher revs.

BOTTLEDZ28

iTrader: (9)

No I have not changed out the coil wire. I got a set of MSD wires but the coil wire was way oto long and I have ot have it cut down. I am using the stock one for now. I will look into that this week. Thank you

Steve10

I had that problem on my '94 TA. I lost a couple of races and couldn't figure it out. Finally I found I could repeat it by flooring it in first and it would cut out around 5000 everytime. The connection on one end of the wire was all corroded. New wire fixed it.