$200 reward: Hesitating above 4500, loss of power, no cel, help!!

[swarm]

a little history about this problem.
I bought this car with 70,000 miles on it. it's a '95. when I bought it, it did not boost properly, or so the previous owner thought. turns out, it is boosting fine, because i installed an autometer boost gauge and it reads 14psi until it drops off in the higher RPM's down to 11psi.

Anyhow, here's the problem:
i accelerate, first gear seems fine, above 4500rpms in any gear, it feels like it's no longer pulling under boost, but it still accelerates like it's N/A.. boost gauge never drops below 11psi. Air/Fuel gauge goes really lean. here's a log. i can't read this log on this computer so i can't just paste it here. www.icehouse.net/turners/firstlog.db1

I know what the car SHOULD feel like because i used to own a properly running one, but it didn't like it's own flywheel, and decided to launch it out the hood.

With MAS plugged in, it does this bad running, with MAS unplugged, car runs rich as hell. this means my MAS is good, right?

I have also done a boost leak check with negative results.

mods:
MBC@14psi
Walbro 255HP
K&N filter
BPR6ES, taylor 8mm wires


Here's what I'v replaced:

Walbro 255HP FP
Reinstalled honeycombs
Fuel Filter
Fuel rail
coil pack
MDP sensor
front 02 sensor


I have owned this car for 5 months now, and have never felt it run properly. I am willing to pay someone a $200 reward if they give advice that fixes the problem. I just want this car to run properly stock before i MOD it. =(

 

[green92gsx]

Check base timing, look here . If base timming is too high set to stock at +5. If problem continues try retarding to +2 and see if it helps.
The issue you describe sounds like pulled timming advance from too much knock. Try also running a few gallons of pure racegas and see if the problem disappears.

 

[green92gsx]

Did you ever check your knock senser?

 

[86MCSS]

I will check timing and stuff again

I have stock exhaust

Defiant, I have 6es's gapped to .028 and taylor 8mm wires.

nelapse, sorry if you were offended, it was not my intention. i was tired and cranky when writing the post. I can't take it to any local mechanics, because they are all morons x10. they all lie and try to make tons of money.

90AWDTalon, can you please post that log in a more traditional format? i am unable to open it, but it seems you can. I checked my TPS, at idle it was at 1, so i adjusted it to 10, now at WOT it reads 82, but i will fix that soon too. it didn't seem to help the problem at all though.
Yes, i checked for boost leaks with a compressor

i guess i need to check timing then. the logger, at idle, says my timing is at 6, is that the same thing as checking the marks?

Its obviously your TPS. If it is not working properly it will give the computer false readings and screw up lots of things. Hence sputter above 4500 at wide open throttle, I had the same problem. Replace the TPS.

 

[90AWDTalon]

90AWDTalon, can you please post that log in a more traditional format? i am unable to open it, but it seems you can. I checked my TPS, at idle it was at 1, so i adjusted it to 10, now at WOT it reads 82, but i will fix that soon too. it didn't seem to help the problem at all though.

That was the first time I ever used that program so I don't know if I can convert it to any thing else. I'll see if I can figure something out.

I assume when your quoting tps readings your doing so from your dataloger. The tps should read 100 at WOT. I just looked up the testing procedure in my chilton. It says;
"With the ignition off detach the tps connector"
"Measure the resistance across treminal #1 and #4, should be 3500-6500 ohms"
"Change the probes to teminal #2 and #4, slowly operate the throttle from idle to WOT, the resistance shown on the meter must change evenly and in proportion to the throttle movement."

Also check to make sure the throttle cable is adjusted properly

 

[5150DSM]

Its obviously your TPS. If it is not working properly it will give the computer false readings and screw up lots of things. Hence sputter above 4500 at wide open throttle, I had the same problem. Replace the TPS.

Have to agree with 86MCSS here, sounds like the TPS is the core of your problem; however, you are also going to need an AFPR with that 255 pump. Your fuel curve is compltely non-linear when you start overrunning the stock FPR, which can leave you dangerously lean under boost.
Change out the TPS, get an AFPR and you will find your car runs better and is much easier to tune.
Aloha

 

[90AWDTalon]

I couldn't convert that log to any else, and the way that program works doesn't lend itself to posting pics, try using mmcd instead. http://mmcdlogger.sourceforge.net/#Download

 

[swarm]

I have not checked my knock sensor yet. don't know how yet.

I will replace the TPS and see if things change.

The injectors are not from an auto

MMCD is 1g only -- i wish it would work on my 2g

i was under the impression i could run the 255 without rewiring it and be fine without a afpr?

ok, i have a few things to check and i will get back to you guys.

if it's the TPS, 86MCSS will be paid.
if it is the timing, CheckMe will be paid.

 

[90AWDTalon]

if it's the TPS, 86MCSS will be paid.

I thought I was the first one to suggest the TPS?

 

[swarm]

Actually, sorry - 86MCSS PM'd me with that diagnosis first; he just didn't do it on the main forum

 

[98spydert]

Actually, sorry - 86MCSS PM'd me with that diagnosis first; he just didn't do it on the main forum

Before you go and replace it, adjust it so WOT is 100 no matter what off throttle is. If it ends up low 25% and WOT 100% it'll run like crap when you're not WOT but you can still see if the 100% signal at WOT fixes your problem.

since I can't see your log, what's peak timing at?

 

[swarm]

i'll try adjusting to 100

hehe i can't see my log, either.
i can get back to you on that, but i think it's around 34

 

[86MCSS]

Before you go and replace it, adjust it so WOT is 100 no matter what off throttle is. If it ends up low 25% and WOT 100% it'll run like crap when you're not WOT but you can still see if the 100% signal at WOT fixes your problem.

since I can't see your log, what's peak timing at?

If you do this the car will have trouble starting. If you move the entire OHM band so it read properly at wide open throttle then it will read higher than normal at idle [since urs is messed up obviously] and cause the computer to inject more fuel into the engine and run super rich at start up and may not start at all. This is the same problem I just had. I had to use starting fluid in order to start the car because it was flooding right away and the spark could not account for all the extra fuel. You need to replace the TPS plain and simple.

[Broken record off. ]

 

[swarm]

If you do this the car will have trouble starting. If you move the entire OHM band so it read properly at wide open throttle then it will read higher than normal at idle [since urs is messed up obviously] and cause the computer to inject more fuel into the engine and run super rich at start up and may not start at all. This is the same problem I just had. I had to use starting fluid in order to start the car because it was flooding right away and the spark could not account for all the extra fuel. You need to replace the TPS plain and simple.

[Broken record off. ]

under the hood, when i watch it, at idle=10, then when my friend pushes the gas, it shows 82, but i can pull on the throttle cable and get 100; so i should just be able to tighten the throttle cable, right?

 

[90AWDTalon]

under the hood, when i watch it, at idle=10, then when my friend pushes the gas, it shows 82, but i can pull on the throttle cable and get 100; so i should just be able to tighten the throttle cable, right?

Sounds like you need to adjust the throttle cable. You can loosen the two bolts that hold the cable to the intake manifold to adjust.

 

[2.4 turbo Hyped]

What are your compression numbers??

Tell me how you did a boost leak check. I prefer using a compressor and soapy water in a spray bottle. Did you perform the boost leak test this way??

One other thing that hasnt been mentioned , are you getting a good solid ground on your throttle position closed switch?

Another thing that really makes power drop at high rpms is an overly rich running condition. Check these things and get back to us.

 

[kelvinb]

im having the same problems as you, but my fix was spark plug wires. magnacor spark plug wires. maybe try those?

 

[spades_gsx]

my cousins 98 gsx has the same problem we have checked everything, plugs, wires,injectors. he took it to the dealer and they just changed the plugs and wires. the car still spits out "random misfire". we haven't tried to replace the fuel pump, but after reading this thread it sounds to me like it could be the tps

 

[CatchMe]

You have to check that timing on the cams and crank - the ECU will always tell what it thinks it should be from its pre programed timing maps. Line the marks up on the cams and if they match up then go check where it is on the crank. Zach

 

[GsX-666]

I would really check the ecu and ecu wires/ wiring i Know this might not be applicable BUT, it could steer you in the right direction. I had an alarm recently installed. I have the apex s-afc. my Fuel / air wire was cut / pulled out when the installed the alarm dont ask me why but car toys is retarded. but unless I floor it it would bogg down horribly at 3500 - 4000 +. now i now a pulled or cut wire prob isnt the issue but mabey a pin or something with your ecu is holding back / over compensating your fuel / air mixture. even thats not the problem it's always somthing to check out. to make sure everything is running properly.

 

[canada22]

Hi i'm new, but i've had the exact same problem. Thing is it was the alternator, motor was totally rebuilt and what not but the alt was on the way, does it feel like fuel cut like the car wants to go but totally loses power? Check the alt i know it's crazy but just for fun. Sounds like the motor is ok.

Joe

 

[mastadogg2]

You said you removed your battery? .. Check on the negative terminal on the battery make sure you have both wires connected I had this issue already and I forgot to connect a negative terminal up and it caused alot of hesitation so check your battery and make sure you dont got a negative connector unhooked

 

[97gstnick]

hey SWARM. my friend had a 97 gst with that exact same problem.!! we called it the naturally aspirated turbo car. i also have a 97 gst but mine ran awesome. we did all kinds of things to try and figure out why his car would hit full boost and in the upper rpms is was an n/a car. i logged it at everything was normal. boost was normally. new wires, no boost leaks. its something that to this day we just couldnt figure it out. he sold it though. if you ever figure it out, please tell me. i need my mind to be at ease. i dont want to be stumped by that forever.