Lumina full throttle problem

[GreySVO]

I'm having the same problem with my '98 Lumina with 3.1L. The full throttle issue does not always happen significantly, but there is a power loss at times. If the TPS does have a flat spot, will the computer show codes? Mine has none.

Thanks

[tblake]

the computer will usually not show codes for a low spot on the tps. if you know it has a bad spot, do your self a favor and replace it, its not that expensive, a dn will probably fix your issue

[inphinion]

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

Hi, did you find what was causing this problem?

I am having the same problem with 1998 Lumina 3.1. I replaced cat converter, changed fuel filter but still have the same problem.


The problem occurs only after the car is warmed up. In the morning, the car runs fine for approximately 10-15 minutes but then develops the same problem - it just does not have any power if I press the gas pedal beyond the halfway.


If I keep the car in the first or second gear while pressing the gas halfway, the car would slowly accelerate to high RPM so the fuel pump seems to be fine.

The car does not show any codes.

[GreySVO]

My problem is not that bad. It is intermittent. i.e., when I hit the throttle about 3/4, I start to get misses that show on the tach. This does not always occur. I think it may be the Throttle Position Sensor, but need specs on that to check. I checked output voltage from the TPS, and it is consistent to what I think was about 4.5 volts. Otherwise, I am lost, as the car does not show codes, and otherwise drives flawlessly. I'd check / replace your TPS, then let me know what you find.

[corning_d3]

I didn't see it mentioned, but what about a weak coil, plug or wire. These can act fine until you mash the throttle. This increases pressure in the cylinder, now the coil has to increase spark power to overcome this pressure. This is when mis-fires happen. Also, you say it isn't fuel related, but my book shows a min. of 41lbs of fuel pressure, 47psi highest with KOEO 3 lbs from minimum may not sound bad, but Thats LOW!! On average, an 8% drop in fuel pressure causes a 58% drop in fuel FLOW. I'd start checking for at least 15" of vacuum at the pressure regulator. Next would be to test pressure AND flow..

[inphinion]

Originally Posted by corning_d3

I didn't see it mentioned, but what about a weak coil, plug or wire. These can act fine until you mash the throttle. This increases pressure in the cylinder, now the coil has to increase spark power to overcome this pressure. This is when mis-fires happen. Also, you say it isn't fuel related, but my book shows a min. of 41lbs of fuel pressure, 47psi highest with KOEO 3 lbs from minimum may not sound bad, but Thats LOW!! On average, an 8% drop in fuel pressure causes a 58% drop in fuel FLOW. I'd start checking for at least 15" of vacuum at the pressure regulator. Next would be to test pressure AND flow..

I also thought that this could be caused by either fuel or electrical problem. However, as it was recommended on this forum, I tried to accelerate in second gear to see if there are any problems with the engine on high RPM. The car easily accelerate to 65 mph if the gas pedal is pressed less than halfway. So I guess the pump and ignition should work fine.

But I went ahead and changed spark plugs, spark plug wires and oxigen sensors anyway - although the engine seems to be more powerful now, this replacement did not solve the hesitation problem occuring when engine is hot and gas pedal is pressed more than halfway.

[inphinion]

Originally Posted by GreySVO

My problem is not that bad. It is intermittent. i.e., when I hit the throttle about 3/4, I start to get misses that show on the tach. This does not always occur. I think it may be the Throttle Position Sensor, but need specs on that to check. I checked output voltage from the TPS, and it is consistent to what I think was about 4.5 volts. Otherwise, I am lost, as the car does not show codes, and otherwise drives flawlessly. I'd check / replace your TPS, then let me know what you find.

Hi, GreySVO, did you have any luck with replacing Throttle Position Sensor?

Currently I am thinking about replacing the Throttle Position Sensor and may be looking at Transmission Control Solenoid.

[corning_d3]

The car easily accelerate to 65 mph if the gas pedal is pressed less than halfway. So I guess the pump and ignition should work fine.

There is less requirement for fuel in a lower gear, because the engine isn't straining as hard..

[GreySVO]

Now I am frustrated. I was driving home, playing with the '98 with 3.1L, and floored it... the engine missed and made no additional power. Otherwise, this car drives flawlessly! What can be the problem? I've checked the TPS, changed fuel filter, plugs, wires, and air filter. Any other ideas? Can a coil do this? Any way to cehck the coil? Other checks to perform? Oh yah, and no codes... HELP!

[inphinion]

Originally Posted by inphinion

Hi, GreySVO, did you have any luck with replacing Throttle Position Sensor?

Currently I am thinking about replacing the Throttle Position Sensor and may be looking at Transmission Control Solenoid.

Finally I replaced the TPS but this did not solve the problem.

[GreySVO]

I've not had any luck yet, with any parts replacement, or help!

Anyway, I bought a new EGO Sensor, and will install that this weekend. The car has 136,000 miles on it, so maybe it is worn, as I am starting to smell more fuel in the exhaust... which indicates to me I am not getting good combustion. Idle is good, so I am guessing it is not too high fuel pressure.

The anomoly is also like this... when I floor it, the engine misses as if its hitting a rev limiter... will keep the speed, but will not speed up.

Again, any help from anyone else will be very much appreciated.

[corning_d3]

Tried a new pump yet?

[inphinion]

Originally Posted by corning_d3

Tried a new pump yet?

Nope. But accordingly to the recomendation on this forum, I tried to drive on a highway in the second gear and the car accelerates slowly to ~70 mph (with the gas pedal pressed halfway) and runs stable at that speed. This seems to indicate that pump should work fine, do not it? New pump is quite pricey and I do not want to change it until there is a clear indication that the pump should be replaced.

Originally Posted by corning_d3

There is less requirement for fuel in a lower gear, because the engine isn't straining as hard..

I agree that the load on the engine is not that great but I would think that the load on the PUMP is quite significant if the engine is continously running at 4000 RPM. Is it correct?

[corning_d3]

I can rev my engine to 4000 in neutral, and then in each gear with a flow and pressure guage. There's hardly any flow at all in neutral, but a considerable amount when in gear travelling. Besides, you mentioned you only have 38 psi, which is well short of the 41-47 psi needed....

EDIT: The only way to ACCURATELY test a pump is with a flow and pressure guage, not by acceleration..

[slicktree]

You describe the same issue I had with my 96 3.1 2 years ago when it had about 125,000 miles). It would act as if the rev limiter would kick in. I want to add that mine would only occur under 2 circumstances that you didn't list. The ambient temp had to be above 80 F and the engine compartment had to be at operating temp(3-5 miles to warm up). The revs would continue to come down as the engine compartment got hotter, like when slowing down for a small town, or finding myself behind a slow truck/tractor. If I feathered the foot feed lightly, I could get the car back up to speed and it would seem OK until I tried to accelerate hard.
Anyway, I was able to eliminate the fuel system as the issue. Also eliminated the exhaust/cat as the issue. I had no codes. I checked/swapped all the coils & ignition module. No improvement. I replaced the plugs/wires and found several plugs to be bad (platinum tips gone). FYI, I checked the plug condition regularly as the miles(on the plugs) crept past 100,000, but I only looked at the easy access front plugs. I won't make that mistake again. Anyway, the new plugs/wires helped the rev limiting problem substantially, confirming ignition as the problem. However, I could still get it to act up on 90+ F days when towing my small fishing boat, and accelerating fast. I gave up on trying to troubleshoot any furthter beacause it was so rare that I would drive in that high temp/High load condition.
Chapter 2......
About 6 months ago, the alternator finally failed with 185,000 miles on it. I knew from previous testing that the old alternator charged at a low 12.8 -12.9 volts since day 1. Seemed low to me but the car never complained.
After installing the new alterntor, I observed that it charged at 13.4 volts, but thought nothing of it at the time.

With the hot weather here recently (90+ in fargo, nd), I was towing the boat and wanted to verify that the high throttle rev issue still existed. IT PERFORMED PERFECT AT WOT!!
The theory is that the coils now have more primary voltage to work with, therefore more potential secondary voltage is available at the plug gap. If this theory is valid, I would assume the same result if you closed the spark plug gap slightly.....say from .060" to .055".

Hope this provides some insight/ideas. PLEASE LET ME KNOW if you or anyone else can reproduce these results. I would appreciate some confirmation that low voltage was my issue.