1993 z28 will not rev past 3000

[brandon_wilson7588]

I have a 1993 z28 six speed and it will not rev past 3000 I put in a new opti, plugs, plug wires, fuel pump,and Icm and nothing changed. Checked fuel pressure and it is right. Anyone have any clues what it might be?

[Fastbird]

What does it do when it hits 3000 rpm?

[brandon_wilson7588]

Sounds like its hitting a rev limiter.

[popo8]

U said fp is "right." What is "right," as far as ur diagnosis?

[Fastbird]

Mods? Tune? What is fuel pressure under a load? Can you free rev past 3000 RPM or does it happen whether or not it's being driven?

[brandon_wilson7588]

It was at 42 psi idling when I started Reving it dropped to 38 but at 3000 it's at 40. Mods long tube headers 2 1/2 exhaust and magnaflow muffler, Egr delete, air pump delete. It will not rev past 3000 in gear or not. I have even had in 3rd at 3000 and dropped it in 2nd and it locked the back tires up.

[brandon_wilson7588]

Also can not get any coded to come up.

[firebird_1995]

Sounds like someone put a "valet" tune on it. You probably don't have access to another 93 pcm or chip do you?

[brandon_wilson7588]

No i dont

[tleed]

Check your tps voltage should be around
.60 at key on and 5volts at wot

[brandon_wilson7588]

Yea I checked that to. And I also cleaned up the iac valve and made sure the map sensor was not leaking air

[popo8]

Sounds like someone put a "valet" tune on it. You probably don't have access to another 93 pcm or chip do you?
Not a bad idea. See if u can borrow another computer amd see if thats ur issue.

Did this just happen or is there some back story u can tell us to let us know more?

[Revolutions]

Have you verified that the throttle blades are opening fully.
Intake restriction? (pull intake tube off)
Exhaust restriction? (drop y or disconnect and pull O2 sensors)
You replaced everything in the ignition system but the coil. Can you borrow one?

[popo8]

Im on tapa amd cant see if there is a signature "build" of the car. Need more details on the car tho.

[brandon_wilson7588]

I bought the car from a guy who said it sat up for 2 years for doing this and he could never find out what was wrong. here is a video of whats its doing
https://youtu.be/0O0J4ntRVdM324453244632447

[popo8]

What code is the check engine light being triggered by?

[brandon_wilson7588]

I Cant get any to flash

[popo8]

Go have it scanned.

[Fastbird]

Just making sure, how are you trying to flash the codes?

[brandon_wilson7588]

I would take it to someone but no one near me says they can. I have been using a paper clip to short out a and b terminal

[popo8]

Mechanics in ur area dont know how to scan it?

Is there a GM dealership?

[jaysz2893]

93 had a limp mode iirc. Where is op located?

[popo8]

93 had a limp mode iirc. Where is op located?
That would make sense with the ses light on...

[jaysz2893]

Mine went into it one time and the ses stayed on but I couldn't pull a code. I have an aldl to USB cable and tunerpro. I have been thinking of a "free" rental service for my cable as it sits around alot. I was thinking of a deposit that would cover the replacement of the cable and the cost of shipping. I would return the deposit as soon as I got the cable back.

[popo8]

Mine went into it one time and the ses stayed on but I couldn't pull a code. I have an aldl to USB cable and tunerpro. I have been thinking of a "free" rental service for my cable as it sits around alot. I was thinking of a deposit that would cover the replacement of the cable and the cost of shipping. I would return the deposit as soon as I got the cable back.
I do something very similar with my tuner laptop...

[brandon_wilson7588]

the dealership in my town isn't know for great service. I just bought a obd1 12pin connector to usb. so maybe I can find out what's happing.

[brandon_wilson7588]

What could cause one to go into limp mode. Knock sensor

[popo8]

Great service or not... scanning a car is about as basic as dealership can get.

[popo8]

What could cause one to go into limp mode....

Get that code and ull have ur answer. Lol

[brandon_wilson7588]

Well I just got my car back from the dealership they could not get the codes to read and their best guess was the tps which I replaced this afternoon and still no luck

[Jayz28]

Acts like a rev limiter cutting spark. Does it have an ignition system with wrong pill or another rev limiter system?

[brandon_wilson7588]

No it doesn't have a 2 step and it's the stock ignition set up

[popo8]

Im still staying with... we need the codes. Gotta find a place to make it happen. I have a hard time believing the dealer cant do it. Maybe they dont want to cause they caught the vibe from u that u just want the diagnosis... not the fix.

[brandon_wilson7588]

Well I would say that but they did it for free since they couldn't give any codes. The only sensors I have left that have not been changed are the o2's map and knock the guess the computer and epprom chip.

[popo8]

Hate to see u blindly throwing parts at it...

[brandon_wilson7588]

It's either that or sell it and I love it to much to sell it

[popo8]

Someone has to be able to scan it. If u were in Pa... id say come to the garage and get it done.

[brandon_wilson7588]

I have the Aldo cables and I may buy tts datamaster so I can see exactly what's happining

[brandon_wilson7588]

Aldl cables

[Jayz28]

That's a nice car to just up and sell. Looks good.

[Jayz28]

You can get a free trial of datamaster. 20 uses.

[brandon_wilson7588]

I thought it was $119 for authorization code. But I get payed tomorrow and downloaded it to my laptop and I will see

[Jayz28]

You can download it for free off the tts datamaster site. When you do, you get 20 free datalogs.

I just did this last night on my new laptop. When you go to log it will tell you how many times you can use it before having to buy the authorization code.

[brandon_wilson7588]

got everything going no I have this problem any clues?32683

[popo8]

Maybe Jayz28 can help u.

Are u sure u have it set for ur car?

[Jayz28]

I think each time you download it you have to click the one for your car. Are you 100% sure you clicked for LT1?

[Jayz28]

32694

[brandon_wilson7588]

Yes it said that on two laptops

[brandon_wilson7588]

I called obd diagnostics ins were I bought my cables and they said it could be because my computer is bad and their is low voltage on the serial port and that could be why no one has been able to read the Codes

[Jayz28]

I called obd diagnostics ins were I bought my cables and they said it could be because my computer is bad and their is low voltage on the serial port and that could be why no one has been able to read the Codes

Never heard that before. Guess it makes sense.

[brandon_wilson7588]

well I finally found out what was wrong the tune chip was cracked and not making a good connection.

[Jayz28]

And this solved the problem? Connection issues and revving issues???

[brandon_wilson7588]

Yes runs like brand new.

[popo8]

Yes runs like brand new.
Well thats great news... simple fix once u can find it.

[Jayz28]

I'm glad you got her running good! I always hated lookin for crazy problems like that. Something simple but hard to find.