Bog at WOT

[birdman]

It seems like 2/3 throttle is better that WOT. its extremely evident from a stop, if i stomp it, it bogs for 1-2 sec then goes with reduced power if i let up while at wot i feel the power come back when i reach about 2/3 throttle. what could cause this??

[DiscoStudd]

Sounds like it could be a faulty Throttle Position Sensor. Are there any trouble codes being thrown?

 

Have you tuned up your car recently? Make sure your plugs, wires, fuel filter, air filter, and O2 sensor are all fresh before investigating further.

[birdman]

Ive replaced the air and oil filter, new tps and iac, new plugs and wires. I havent got to the fuel filter or o2 sensor yet. do you think that could be the problem?

[88Regal Limited]

get a K&N air filter. IMHO its worth it.

[digitaloutsider]

I'm putting my money on a fuel filter.

[RareGMFan]

Fuel pump beginning to fail can cause this, too. It can start at WOT, and gets worse and worse as it goes, till it just won't turn over. So I'm going to go with fuel pump in this little bet. Who's got the odds?

[GP1138]

get a K&N air filter. IMHO its worth it.

 

If he's having a problem accellerating normally, I doubt throwing a K&N at it is going to help.

[Canada]

I would check fuel preesure......you should have AT LEAST 30 psi, 38-45 ideally.

 

Why do you guys replace TPS sensors?

[RareGMFan]

Because they're cheap to replace, and can display the same symptoms he's describing. Due to the sensor reading the throttle plate opening wrong if it's malfunctioning, or has wiring issues (thinks it's more or less open then where the plate actually is), the computer takes the incorrect reading, and throws out the amount of fuel needed for that reading, instead of the correct figure. This can cause random bogs at different points in acceleration depending how bad the problem is. But I'd agree, as I said earlier, to check for fuel related problems first, especially if WOT is your only problem area.

[Canada]

Thats fine and great....BUT....

 

I've NEVER seen a replaced TPS sensor actually fix anything.

 

I've NEVER replace one.

[RareGMFan]

I'd never had issues with one, either, up until I got the turbos. I was going through, replacing ALL sensors (whether it needed it, or not), and chaning the TPS actually made the idle WORSE. It was only AFTER I changed the TPS that I finally started getting codes.....which coincidentally turned out to be "TPS Voltage Low". :shock: I think there's a wiring issue which I haven't had time to track down, yet. But as I said, there should be more, spurratic problems if the TPS is the issue at hand. Mine bogs at many different points, and can idle normal some days, while idling at 2K RPM plus on others (intermittent SES will come on for the TPS voltage problem), or accelerate like a bat out of hell at times, and then choke most others..

[DiscoStudd]

I had a horribly intermittent "stumble" on 2 of my old Grand Ams (at different times, of course,) and both cars threw the "TPS Malfunctioning" trouble code. Changing out the TPS on them both solved the problem. FYI, one was an 85 with the Iron Duke, and the other was a 94 with the 3100. The problem felt like there was a dead spot on the TPS at a certain position of the throttle. As soon as I would move the accelerator past that spot, the motor would spring back to life...

[havikx]

i'm having the same problem. WOT sucks..2/3 kicks ass. cept now you can feel the spot getting a little up higher on the throlttle where it chokes. like raregmfan, i also can fly on some days..and be a boat on other. if it was working right..it'd be pullin some sickly burnouts.

 

where exactly is the throttle position sensor and how hard is it to change? i have a LQ1. i hope to god its not the fuel pump. if its that easy..i'll take it off the euro.

 

oh by the way..as for earlier posts..i did a complete tune up..wire, plugs, coil pack, oil change, oil filter, fuel filter. didnt do air filter as i already have a high flow intake. everytime i did something..it made it work a little better..but thats a gimme. if you every do anything like basic up-keep..its obviously going to run better. put i still had the problem.

[havikx]

scratch that. i just changed the throttle body sensor and i didnt do the job. we're going to change the fuel pump tommorow or in the next few days..and i hope its that. if not..what else could it be?

 

my crews ideas were maybe bad injectors. i had run-rite done at my local mechanic..so i figured it wouldnt be that. we're going to try some injector cleaner. if not..i'll change those too. the other idea is possibly tranny related. one of my buddys said it sounded like a crimped or punctured tranny pressure line. not pressure line..vacuum line. we're going to look at that eventually.

 

any1 else have any ideas?

[RareGMFan]

Along with the fuel injectors, and pump, perhaps the FPR, as well. I'd get the injectors checked for ohms before a cleaning. I don't think it's a tranny issue.

[birdman]

Ive been told fule pump/filter and plan on doing the filter soon and the pump when i run into extra money any way iv also thought about the injectors and all 91-93 lq1's have faluty injectors that cause "phantom stalling". gm recognized it as a problem and put out a report but did not make them a recall. you can either go to gmpartsdirect.com and get them for around $70 a piece or you can find a 94+ LQ1 and get the injectors off that which is what i did. im going to have them professionaly cleaned, rebuilt,spray pattern tested and flow tested before i put them in. ive also thought of a clogged cat??? any other ideas??? Thanks.

[RareGMFan]

You mean someone actually checked the fuel pump for you, and told you that was it? Or someone is suggesting it as a possibility?

[RareGMFan]

*Edit: Not sure why it double posted. That's the first time I've had THAT happen. :?

[birdman]

suggeested that was a possibility but i was thinking it would be more of an rpm based thins becuase if i start at 2/3 throttle and coax it down a little more at higher rmps it will go to 6500k still pulling ok, not the best but ok.

[radman3120]

Along with the fuel injectors, and pump, perhaps the FPR, as well. I'd get the injectors checked for ohms before a cleaning. I don't think it's a tranny issue.

I've been having the same problem lately and thats exactly what I've narrowed it down to as well. It always seemed to run better when I put fuel injector cleaner in it but of course that has other treatments in it too so thats sort of a given. I'm leaning towards FPR and once I get the chance I will be checking the fuel pressure both before and after the regulator in hopes that it is the FPR or fuel pump which are much cheaper than six $70-$80 injectors.

 

If none of that I, too, would say check the cat. It's worth a shot. My dads '02 GP GT bogged similar to that when the cat was clogged up but thats an auto. Is yours a manual or auto?

[birdman]

Its an auto, i wish it was a manual buts thats a differens story. i just replaced my fuel filter today and it made no difference but that was expected. where is the temp sensor for the ecm because i belive there are two temp sensors, one for the ecm and one for the gauge correct??? the next project im going into is to replace the o2 sensor, thermostat and temp sensor in hopes of solvine the problem, but my book doesnt show a pic of where my temp sensor is, i think its somewhere under the rear head??? anyone know? thanks.

[havikx]

birdman..i had the same problem as you. dude..i ran my z at the track and ran 17.9 all because my 60' time was like 2.9 i had it checked out.

 

check the engine mounts. seriously. if your car is shaking or anything that you notice..you got the same problem. whats happing is the engine is moving more when you get down lower on teh gas. the movement of the engine crimps one of the gaskets in the exahust system. i think the one coming from the heads to the exhaust pipe. its not allowing exhuast through at hard accelerations.

 

just to be sure though..i'm also getting my engine re-timed and replacing the injectors. lol. i want it to run perfectly.

 

but seriously..check it. if not..pay your local mechanic to put it on the scanner..even if your not throwing a light. it could still coem up with something.

[birdman]

i know its not the engine mounts becuse i have put a crowbar in the lift point on the motor and tried to torque it forward to get to the rear plugs and it wouldnt budge. ive also put it in gear and held the brake and torqued the motor to check the mounts and it had hardley any movement at all. but i can see what your talking about. how much does it usually run to get it scanned??

[havikx]

i know its not the engine mounts becuse i have put a crowbar in the lift point on the motor and tried to torque it forward to get to the rear plugs and it wouldnt budge. ive also put it in gear and held the brake and torqued the motor to check the mounts and it had hardley any movement at all. but i can see what your talking about. how much does it usually run to get it scanned??

 

i couldnt move my engine when i tried to get to the plugs but the engine creates alot more power than we do so whats hard for us..maybe too easy for the egine itself. i had it scanned at AAMCO for around 40$. i think mieneke will do a quick check on it for free if i'm not mistaken. i brought it over to them and they looked at it..showed me..and was free of charge. i would get it scanned just incase though. it might come up with an exhaust code..which is what i had.

[birdman]

Thanks ill have to call my local mieneke and see if theyll do it for free, if not ill pay someone to check it out after i do my temp sensor, thermostat, and o2 sensor.