[RESOLVED] engine revs up and boosts but no power

[spicoli619]

every once and a while when i get on the throttle my car will rev up and boost up at normal rates but there isn't as much power as there should be. but when i let off the throttle for a second and get on it again the problem goes away. Ive done a boost leak test and don't have any leaks. it doesn't do it to often but when it does it makes me nervous. I'm afraid its something major.
could it be crank walk?
i have new spark plugs and wires and some minor mods but nothing to the fuel delivery system or computer.
any help would be awsome!

 

[Bluefire16]

Check the turbo for shaft play....

 

[Bluefire16]

And please fill in your info in your profile....would help out a lot.

 

[spicoli619]

OK cool ill check that out first thing in the morning, and I'm sorry about my profile, when i first registered i filled it out but i guess i messed it up somehow. its now filled out to the best of my knowledge
can shaft play really affect it that much? i guess now that i think about it it does feel as if its a non turbo engine when it does that.
thank you so much.

 

[dragon2144]

I would say it would be your BOV vent to the air is your problem. Unless you have a way to tune or a GM MAF-T set up. You can not vent to the air it makes the car do bad things. It will make the car run rich that could be the problem. so recycle and please take the D cell battery out of your intake. I could not imagine what would happen if you suck battery acid into your turbo and it got in the seals

 

[spicoli619]

oh i know i actually am recirculating now i just havent gotten a good picture of the engine with it just yet. another thing to do tomorrow. and i know its not the BOV cause it did it with the stock one as well. so im hoping its the shaft play, gives me an excuse to upgrade turbos haha

 

[Bluefire16]

I saw his pick and was gonna ask about the BOV, but if you want to get a 14b i got one...needs to be rebuilt but i just want it gone...

But it could be your turbo might be going out on you...any smoke?

If shaft play is minimal to none, do a boost leak test, compression test, make sure spark plugs are good, wires...ect. All the basics. Thats what i start with, but do a boost leak test, most likely a small leak and up high when you get into the boost its loosing the air...

 

[dragon2144]

oh i know i actually am recirculating now i just havent gotten a good picture of the engine with it just yet. another thing to do tomorrow. and i know its not the BOV cause it did it with the stock one as well. so im hoping its the shaft play, gives me an excuse to upgrade turbos haha

Also check your Coils, Wires, and plugs maybe a bad coil or wire maybe cracked where you are getting spark leak from a wire and it just moves when you let off and its no longer close enough to jump to the block.

 

[MAX420]

I also have this issue, only happens when the car isn't fully up to operational temperature.

 

[VETTE_50_TH]

Buy a datalogger and datalog. That will help yourself, us, and make your future a hell of a lot easier. Does, it feel like the car falls flat on its face, does it make any popping noises, or stutter, or do anything out of the ordinary? You said, it works after you let off and get back on, but is this all the time, only sometimes, when you first drive it, after a long time, when?

Let us know. My questions if anwsered will let us know what it is for sure.

James

 

[Bluefire16]

Max that is kind of normal, you should never really push your car real hard if it is not warmed up....

 

[MAX420]

Max that is kind of normal, you should never really push your car real hard if it is not warmed up....

Oh I don't. I have an uphill by my house, driving up that hill without the temps in operational range (Coolant and Oil temps) causes hesitation. I have a drop in piston/rod motor, I always wait till the motor warms before I play with it.

 

[spicoli619]

Buy a datalogger and datalog. That will help yourself, us, and make your future a hell of a lot easier. Does, it feel like the car falls flat on its face, does it make any popping noises, or stutter, or do anything out of the ordinary? You said, it works after you let off and get back on, but is this all the time, only sometimes, when you first drive it, after a long time, when?

Let us know. My questions if anwsered will let us know what it is for sure.

James

I'm in the process of saving for a logger.
it doesn't feel like it just looses ALL power but there is a lot less then what it should, almost like its running without a turbo but it is boosting. there aren't any popping noises or stutters or anything like that. other then the loss in power it runs normal.
when it does the power loss and i let off the throttle and get back on it, it does fix it every time. and the loss in power doesn't happen all the time. i never push the car right when i turn it on. so its more like after a long time the problem happens.

 

[juanpac0]

Sounds like your ECU is pulling timing for some reason, since you said you dont have boost leaks have you checked your CAS?

 

[spicoli619]

ok call me stupid or what ever but what does CAS stand for? i cant find what it stands for haha

 

[juanpac0]

Sorry, cam angle sensor, the big goofy looking thing on the left side of the valve cover.... oh wait do the 96s have a cam angle sensor? I forgot but some 2g's come with them and some don't if I recall correctly.

 

[AWD_FIEND]

When you say the turbo is boosting have you measured with a gauge whether the turbo is hitting full normal boost or if it's less than normal? If the turbo is consistently hitting full boost but not full power you could still have vacuum/boost leaks around gaskets in the intake system that seal when the metals expand during warm-up. You didnt mention if this problem occures during the heat up cycle. Pretty sure the 96+ cars switched to crank angle sensor. 96 or 97 cant remember. You should definetly consider the timing retard path also. Have you run less than premium fuel recently where the ecu will learn to reduce timing?

 

[VETTE_50_TH]

95-96 dont not have the typical CAS like 91-94 or 97-99. Sounds like your pulling timing. I would def like to see a datalog once you get one.

James

 

[jdodds]

Theres a few things that could cause this. First, do a boost leak test. Next, if its a 6 bolt motor, check your base timing. I usually run mine anywhere from 5*-7*. Your base fuel pressure can also affect this. ive had mine set just a little below or a little above 43psi and I was having the same problem you are. Do a leakdown test if you can too. The health of your motor will have alot to do with things like this. Like the other guys said, check coils and wires too.

 

[97gstnick]

every once and a while when i get on the throttle my car will rev up and boost up at normal rates but there isn't as much power as there should be. but when i let off the throttle for a second and get on it again the problem goes away. Ive done a boost leak test and don't have any leaks. it doesn't do it to often but when it does it makes me nervous. I'm afraid its something major.
could it be crank walk?
i have new spark plugs and wires and some minor mods but nothing to the fuel delivery system or computer.
any help would be awsome!

I would put my bet on phantom knock. What happens is your knock sensor hears something (usually not real knock) and pulls timing drastically. Your car will then lose tons of power, almost feeling like its braking. I have had this problem tons of times.

 

[spicoli619]

OK cool. the engine is pretty new actually. it was replaced after an accident so the engine is fine. i did a boost leak test but it never hurts to do it again i guess. and i only put premium gas from chevron in. i don't put anything else in there. ill check my timing soon as well and put it where it is supposed to go if necessary.
if it is that phantom knock will it harm my engine? my engine doesn't click or knock and has new oil in it. I'm actually gonna replace the tranny fluid tomorrow just to make sure it isn't my tranny.
ill also do a run down of all my wires and coils and see if they are in good condition. they should be, cause i replaced all the plugs and wires when i first got the car 5 months ago
also anyone have any recommendations on what data logger i should get? i hear dsmlink is good.
and where would be a good place to get one? (please dont say autozone or kraegen )

 

[dragon2144]

Sorry, cam angle sensor, the big goofy looking thing on the left side of the valve cover.... oh wait do the 96s have a cam angle sensor? I forgot but some 2g's come with them and some don't if I recall correctly.

They to not have adjustable CAS so pull your ECU and you my want to open it up and check for leaking caps that is a real common problem with ecus in the 95-96 my frined had something similar happen to him. all yo have to do is go to radio shack and show them the caps and they will help you get new ones. you will have to soldering them in and that might fix it that is if your caps are leaking. Leaking caps can do funny things to your ecu and if not fix sooner then later you could fry your ecu.

 

[MLutin]

DSMLink/ECULink is the way to go if you really feel like dropping close to 600 bones on tuning. If you just want a logger, I just picked one up from ebay for 80 (hasn't arrived yet). Just depends on how serious you are with your car and budget I guess.

 

[97gstnick]

OK cool. the engine is pretty new actually. it was replaced after an accident so the engine is fine. i did a boost leak test but it never hurts to do it again i guess. and i only put premium gas from chevron in. i don't put anything else in there. ill check my timing soon as well and put it where it is supposed to go if necessary.
if it is that phantom knock will it harm my engine? my engine doesn't click or knock and has new oil in it. I'm actually gonna replace the tranny fluid tomorrow just to make sure it isn't my tranny.
ill also do a run down of all my wires and coils and see if they are in good condition. they should be, cause i replaced all the plugs and wires when i first got the car 5 months ago
also anyone have any recommendations on what data logger i should get? i hear dsmlink is good.
and where would be a good place to get one? (please dont say autozone or kraegen )

No, phantom knock will not hurt your motor. I think it would be more appropriately called pseudo knock seeing as it is false knock. Like I said, I get phantom knock here and there. My motor is still going strong.

 

[corsair231]

My money is on knock retard too. When you make the pull the sensor picks up knock (maybe false, maybe transitional) and pulls the timing. When you get out of it and right back in the sensor o longer picks it up and normal timing restores.

Another problem could be fuel pressure. I'm kinda new to DSM tuning but I'm sure there has to be a boost reference for the fpr. Is your fuel pressure going up with boost?