Ok..here it goes. When driving my Firebird I cannot get the RPM's up past 4000. The car has TPI fuel injection with a manual trans. I am (as well as my boss) pretty confident that the motor isnt out of time. Overall the car runs great..starts up no problem..idles ok..I can drive the car fine as long as I dont try to "stretch the gears." I bought the car with the pervious owner paying someone to do a "standard" tuneup on it. From what I can see the plugs..wires..cap..rotor have been changed. Anyway..Im ruling out timing as the problem. I checked fuel pressure a couple days ago (that was somewhat of pain to do!). Heres my results~
Key on-45psi
Idle- 35psi
High R's- fuel pressure gauge goes up
Fuel pressure never dropped below 30 psi
These results are all normal right???

I DIDNT check fuel volume though....dont ask why.
Currently Im "leaning on" a weak ignition coil.. faulty igition pickup..TPS hitting a bad spot (just a shot in the dark)..or maybe the rev limiter kicking in too soon (yet another shot in the dark). BTW..what does the rev limiter kick in at anyway?? I had my boss drive it because he knows a lot more than me about cars and he COULD muscle the car up to 5000 but it engine held back the whole time. What can I say...hes a better stick driver than me. Anyway..what do you guys think the problem is??

TIA..
Later..

 

I'm not sure, but does your car have a knock sensor?? I beleive that tell's the computer to advance or retard the timing. Don't quote me on it but maybe someone can back me up?

 

I believe you are correct.

 

could be a plugged cat. converter.

 

the cats (i have dual cats) are brand spanking new along with borla's exhaust system. Although when I started driving the car I noticed a fair amount of blue smoke outta the pipes. (thinking that i could have clogged them but highly unlikely due to the lack of miles i put on the car) I switched to a heavier weight oil and added engine restorant. I dont think it burns any oil now because everytime I check the oil its full...I dont have to add anything. As for the knock sensor...I'll pass it along to my friends and see what they think. Me personally...I dont think thats the problem BUT I could be wrong...

Later..

 

come on you guys. ...92 people have seen this post but I STILL havent fixed the problem...Can no one help me??

Dan

 

wires? O2 sensor? distributor? plugs?

 

It does sound like plugged exhaust or lack of fuel, either will let the car run at low speed fine.

Try replacing the fuel filter, if it wasn't replaced in the tuneup.

It's hard to check fuel pressure while simulating winding the engine out through the gears. It may deliver enough volume when you blip the throttle but five or more seconds of full throttle at high speed is a different story.

I would tear into the air filter box and air intake ducting, that could be plugged with some mysterious object, maybe a kitten or Christmas decorations, who knows?

 

plugs-wires-distributor-fuel filter-exhaust system are all new...the O2 sensor(s) arent new. Any reason why you suspect them patrickm00??


Thanks for the input rustydawg. Do you know if your cars have a rev limiter? and if so do you know when it kicks in? My boss and I were talking about this a couple days ago and he thought that the computer was "cutting back" on fuel as the RPM's went up. The car has a lean miss at high R's...you hear a "popping" out of the exhaust pipes.


Later..

 

the stock air box is gone and has been replaced with a "ghetto non K&N" open air filter. Dont ask..I didnt put it on there...bought the car like that. I did clean the throttle body a couple months ago and didnt see anything outta the ordinary. But I'll take another look...

Later..

 

Take you hood off and hook up your feul pressure gauge so you can see it while you are driving if you dont have a long enough hose to reach the windshield. Thats what i did when i had a loss of power similar to you.I had the fuel pump replaced and after hours of searching i found the shop put in the wrong one. Once you know whether you have enough fuel ressure under load then you can rule that out. A friend of mine had a bad knock sensor in his truck. He replaced it, as a last resort, and it fixed his problem.
Your sure that there are no other restrictions in exhaust etc. That then leaves the ignition, In my opinion anyways

 

Take your hood off to see the guage??? :sillylol:

Anyway, 30 PSI does seem low, even under vacum. Hook up your fuel guage, and lay it under the hood, on the windshield. There is a rubber weather stripping on the underside of the hood, so this WILL NOT damage the fuel pressure guages' hose.

At full throttle, your fuel pressure should be atleast 42-44 PSI for a stock regulator, and should not go lower than that until the you let off. If it does go lower, then there is your problem.

 

Pull out a spark plug and make sure they are not gapped at .060.
Then stick a new coil on it.

 

Thanks guys fro all your input. Unfortunatly I havent had anytime to play around with my firebird. Ive been too busy to even DRIVE the car let along "tinker" with it. Hopefully I'll be able to "tinker" around with it next week. I hope you guys are still out there so that I can give you some updates...

 

Well I FINALLY hooked up a fuel pressure guage while driving and Im pretty confident that THIS problem is NOT fuel related..... I have about 45psi while the engine is under load. The fuel pressure guage NEVER dropped at all while I was driving on the highway or even on the street. Im 99% confident that the problem is NOT fuel related....Any thoughts.


Later...

 

Metalhead,

You've proven that the fuel rail pressure is O.K., which means the pump, regulator, and filter are good. That still doesn't mean that the injectors are delivering fuel correctly or adequately at higher loads and RPMs. If you're still going lean at high RPM, it could be clogging injectors.

You may also be experiencing poor intake air flow, caused by filter restriction, MAF restriction, an EGR opening at the wrong time, incorrect valve timing, weak/broken valve springs, floating valves, lifters pumping up, burned/pitted valves, or a weak ignition caused by:

• Excessive spark plug gap;
• bad ignition wires;
• Weak ignition coil;
• Worn/weak distributor pickup and reluctor;
• Worn cap/rotor;
• Faulty ESC.

Something on that list may get you closer.

 

Thanks for the info Vader.... Unfortunatly if its not one thing its another.. before HITHERE didnt have the time to screw around with my HITHEREHITHEREHITHEREHITHEREHITHEREHITHEREHITHEREHITHERE now my computer is acting very odd. This limits the time HITHERE have to post on here. Anyway.. could you go into HITHERE little more detail about filter restriction, MAF restriction and HITHERE Faulty ESC? Personally HITHERE think its HITHERE weak coil or pick up coil thats causing this problem. Again..thanks for your input.

Dan

 

Just wanted to thank all of you for your support in my on going problem. I recently got stuck at the gas station...car would not start when the engine was hot. My guess was a bad module because it restarted once I let the motor cool off. Anyway....since I was opting to change the module I figured I might as well change the ignition pickup and ignition coil. I didnt realize it but the coil that was on there was the orginal coil!!! The car has 130,000 miles on it. I really feel that the coil was weak and that was the main source of my "rev limiting" problem. One problem down....serveral more to fix.

Later..

Dan

 

Hey Dan,

If you installed plugs/wires/cap/rotor yourself you might have made mistakes during installation that would cause your car to miss at higher RPMs. It happened to me. Check out my post (click here) to see how to do plug/wires/cap/rotor right

I'll try to send an tech-article to thirdgen soon...