Lumina full throttle problem

[jaybur_racing]

1992 lumina Euro 3.1
My car runs decent at up to 3/4 throttle, if you smash the gas pedal down, it loses power and slows down, let it back to 3/4 throttle and it picks up speed again. if I keep it at 3/4 throttle in second gear it will continue to pull up to high rpms, so I am kinda ruling out the fuel pump, or filter. I have 38 PSI fuel pressure. I cleaned the IAC valve which cured my idle issue, and did the re-learn procedure, it will idle fine, no probs when stopping. ANYONE have a guess or similar experience? I know these cars have injector probs, but it wouldnt make sense that only at full throttle it dies out. I am going to do the ohms test on the injectors later on to rule those out, but just looking for some advice in advance! thanks

[jaybur_racing]

Originally Posted by jaybur_racing

1992 lumina Euro 3.1
My car runs decent at up to 3/4 throttle, if you smash the gas pedal down, it loses power and slows down, let it back to 3/4 throttle and it picks up speed again. if I keep it at 3/4 throttle in second gear it will continue to pull up to high rpms, so I am kinda ruling out the fuel pump, or filter. I have 38 PSI fuel pressure. I cleaned the IAC valve which cured my idle issue, and did the re-learn procedure, it will idle fine, no probs when stopping. ANYONE have a guess or similar experience? I know these cars have injector probs, but it wouldnt make sense that only at full throttle it dies out. I am going to do the ohms test on the injectors later on to rule those out, but just looking for some advice in advance! thanks

Want to add, I have a brand new battery, NO SES lights, NO stored codes, NO bad vacuum lines, I have researched as much as possible, but I need help on this one, the car also has new plug wires.

[jeffcoslacker]

Leave the fuel pressure gauge on it and tape it to the windshield if you have enough length, watch it when you go WOT.

[jeffcoslacker]

Might wanna do a vacuum test to rule out a cat restriction, etc.

[jaybur_racing]

Originally Posted by jeffcoslacker

Might wanna do a vacuum test to rule out a cat restriction, etc.

Well I know its not the cat, because I had to fix an exhaust leak, and when it was out I put a vacuum cleaner hose on one end and turned on the vacuum and it had no restriction whatsoever.

I just remembered something else, I had a 1998 chevy pick up that died on me, replaced fuel pump, filter relay, and it happened again! I ended up running a higher guage wire to the pump and it never had another problem, I might try that too, I will update this post if that cures it! GM likes to run tiny wires to the fuel pumps. I actually did that on my 97 grand prix as preventative maintenance, and that car has almost 220k miles on it! That or the fuel injectors is my guess, but keep the posts coming! thanks!

[maxwedge]

Your cat test won't work, the element in the cat can move with exhaust pressure, partially blocking the outlet. A pressure test on the o2 port at 1500 rpms should not be over 1.5 psi.

[jeffcoslacker]

Or a vacuum gauge connected to manifold vacuum should hold steady when running at high RPM, slow drop indicates restriction.

[jaybur_racing]

Originally Posted by jeffcoslacker

Or a vacuum gauge connected to manifold vacuum should hold steady when running at high RPM, slow drop indicates restriction.

ok did the test, NOT the cat, and actually it looked pretty new (car has 185K ,iles on it)

I ran a new wire to the fuel pump, it didn't seem to change the effect.

now if I shift into 1st gear from a stop, slowly take off and at about 10 mph nail it, it falls on its face like you lost all power, bring it back to 3/4 and it keeps going, this is getting annoying! I bought the car from an auction, and it looks like someone else has already tried numerous things to try and fix it. It has a new EGR also. I guess I will just check the injector values so I can rule those out.

[jeffcoslacker]

Get an ohm meter reading on the throttle position sensor , then sweep the throttle open and closed slowly and look for a dropout in reading.

[jaybur_racing]

Originally Posted by jeffcoslacker

Get an ohm meter reading on the throttle position sensor , then sweep the throttle open and closed slowly and look for a dropout in reading.

Checked all injectors, had 12.7 ohms across the board, and replaced the fuel filter for the heck of it. Cleaned the EGR ports while intake plenum was off, egr valve is NEW. They were not horrible, but a little carboned up. I will check the TPS next, but I am running out of things to check!

The trans will downshift at full throttle, so I cant see it being the TPS either, but its worth a check!

[jaybur_racing]

Originally Posted by jaybur_racing

Checked all injectors, had 12.7 ohms across the board, and replaced the fuel filter for the heck of it. Cleaned the EGR ports while intake plenum was off, egr valve is NEW. They were not horrible, but a little carboned up. I will check the TPS next, but I am running out of things to check!

The trans will downshift at full throttle, so I cant see it being the TPS either, but its worth a check!

TPS ohms are in check too, This must be an odd thing or something, I was hoping this was one of those things that just happens and there was an easy fix, guess no!

[zephram22]

Originally Posted by jaybur_racing

1992 lumina Euro 3.1
My car runs decent at up to 3/4 throttle, if you smash the gas pedal down, it loses power and slows down, let it back to 3/4 throttle and it picks up speed again. if I keep it at 3/4 throttle in second gear it will continue to pull up to high rpms, so I am kinda ruling out the fuel pump, or filter. I have 38 PSI fuel pressure. I cleaned the IAC valve which cured my idle issue, and did the re-learn procedure, it will idle fine, no probs when stopping. ANYONE have a guess or similar experience? I know these cars have injector probs, but it wouldnt make sense that only at full throttle it dies out. I am going to do the ohms test on the injectors later on to rule those out, but just looking for some advice in advance! thanks

It may have something to do with built in over rev protections or a throttle governor. Or you may not have enough fuel flow to make it work at high engine speeds.

[jaybur_racing]

Originally Posted by zephram22

It may have something to do with built in over rev protections or a throttle governor. Or you may not have enough fuel flow to make it work at high engine speeds.

Nothing to do with an over rev limiter when its in "d" and you are doing 40 and hit full throttle and it slows down.

and not fuel related either

[jeffcoslacker]

I got nuthin.....

[NeonKnight]

is it possible the transmission is acting up, you say its fine in second gear... but in third it loses power. and since you have the Euro im sure you have the 3 speed no overdrive TH125c like i do.