Engine seems more powerful below WOT?

[allthrottle]

I've been noticing whenever I'm around 80% throttle and floor it for some extra oomph, I hardly(if at all) notice a difference.. I was out on the highway late last night and was noticing that when I floored it (at highway speeds), the engine didn't seem to pull as hard as I thought it should, but when I let up just a hair (maybe down to 85-90% throttle), it would start to pull a little more. Is this a TPS adjustment issue, or something else?

I've tried to do a boost leak test but my pump wasn't building pressure fast enough, so I'll need to wait until I can get to a compressor. In the last month I've changed the plugs(bpr6es), fuel filter, and pump rewire. It runs well enough.

It does have a slight misfire at idle occasionally. Could this be from the lower MAF honeycomb being removed?

Thanks!

 

[Twistaye]

The lower honeycomb removed could be causing you to run lean. Maybe at WOT it will have a worse effect than anything else and maybe you're seeing some kind of timing retard under WOT. If you're above stock boost or you're running an open filter on your turbo with that lower MAF honeycomb out you could be really running lean. To give you an example when I first bought my GST it had some issues. One of them the owner was explaining the car was "really slow under boost" and it was idling horribly. I really didn't think of checking the MAF but when I installed my Wideband I was idling anywhere from 15.6-19.0 and my car had to of been pulling timing extremely bad since a stock 1g n/t eclipse sat right beside me during a little pull. I got some of my buddies to hook me up with the honeycombs. My idle went down to 14.7 and under WOT I'm around 10.8 and it definately feels much better than it did before. Hope this helps some..

 

[Jetrosr]

Sounds similar to the way mine runs. Have you checked your knock sensor? Mine looks like somebody lit it like a candle and the guts ran down the back of my block. By 3000 rpm I'm at 43 knock counts and single digit if not negative timing advance. It's directly under the intake manifold.

 

[allthrottle]

The car had a big 16g and modified MAF/airbox with a OEM air filter when I got it, and I removed the BCS restrictor and rewired the pump, but that's all it has done. Factory exhaust from the turbo-back, factory intake/IC piping. I've taken it all apart, cleaned/tightened everything, and put some rtv/gasket sealant on the throttle body surfaces. Haven't checked the knock sensor yet though. I know with a logger I'd be able to diagnose these better, but I'm still recovering from just buying the car a month ago and doing maintenance, so any new toys/mods are a few weeks away.

 

[PIMking]

What kind of fuel are you useing?

Put 91 or better in the vehicle. Sounds like your getting knock and the ecu is retarding the timeing. It wouldn't hurt to check the base timing.

 

[allthrottle]

I always run 93 octane in it. I haven't checked ignition timing yet. The crank-cam timing looked just about perfect. I better check the ignition timing and get to a boost leak test asap. Where's the knock sensor at?

In the morning when not fully warmed up, it seems like it's either taking out alot of timing or dumping fuel.. it's a little sluggish. Other than that, no problems.

 

[ClevelandDSM]

I would think it would either be Knock , or have someone hold down your accelerator pedal to the floor and make sure your throttle cable is not stretched out.

 

[allthrottle]

That was my first though, so I had a friend hold the pedal down while a checked to make sure the throttle butterfly opens/closes all the way. I checked the butterfly, and made sure WOT was at the throttle stop.

Is it possible to have the TPS adjusted so that when it reads WOT, the butterfly is actually 85-90%, and when the butterfly is WOT/100%, it's reading past WOT? At least, that's how it feels sometimes.

 

[Jetrosr]

I always run 93 octane in it. I haven't checked ignition timing yet. The crank-cam timing looked just about perfect. I better check the ignition timing and get to a boost leak test asap. Where's the knock sensor at?

It's directly under the intake, I had to jack mine up and crawl underneath with a flashlight to look at it.

 

[habitatguy187]

In the morning when not fully warmed up, it seems like it's either taking out alot of timing or dumping fuel.. it's a little sluggish. Other than that, no problems.

This is because you're running in open loop and the ecu is adding too much fuel, you also run in open loop at WOT. Sounds like you're probably running rich, could be timing retard but the "sluggish when not fully warmed up" is giving it away. Pull your ecu out and check for burn marks/leakage. If your ecu caps have never been replaced then they have leaked, it just depends on how bad.

 

[allthrottle]

I checked the ecu a few weeks ago, everything looked almost new. It seemed like either someone bought a brand new ecu within the last 2-3 years, or someone replaced something inside(caps maybe) and cleaned the board. Non eprom though

Thanks for the tips so far

 

[habitatguy187]

That's kinda strange. You can look at the backside of the board and you'll see solder spots where the caps are if they were replaced. You really need a logger to tell you what's going on, you'd be able to see your fuel trims and knock. If it's not picking up knock then it has to be running too rich. It's either one of the two.

 

[spectre22]

I was having the same condition with my 92. I just changed my knock sensor about a week ago and no more problem at all. Just look under the intake manifold with a light and try to see if there is any black goo melting out of it. If so change it.

 

[90redtalontsi]

Sounds similar to the way mine runs. Have you checked your knock sensor? Mine looks like somebody lit it like a candle and the guts ran down the back of my block. By 3000 rpm I'm at 43 knock counts and single digit if not negative timing advance. It's directly under the intake manifold.

damn man you might wanna fix that soon haha i got my knock sensor for 45 bucks from advanced auto its easy enough to change if you have the car jacked up

 

[Jetrosr]

damn man you might wanna fix that soon haha i got my knock sensor for 45 bucks from advanced auto its easy enough to change if you have the car jacked up

Stupid empty fun budget

 

[allthrottle]

So I went out and checked the TPS resistance. It's about .83k closed and 4.97 at WOT. The weird thing is, as I'm slowly twisting the throttle, it goes up to 5k just below WOT, and drops back down to 4.97k at WOT.. just how it feels while driving.

Do I need to adjust it so closed throttle is around .9k, and would this raise WOT back up to 5k? It's getting dark, so I'll have to wait until daylight tomorrow to check the knock sensor.

Thanks

 

[habitatguy187]

Just a heads up, just because the goo melted on the back of the knock sensor, that doesn't always mean that it's bad. When mine went bad it threw a CEL after about 45 mins of highway driving, then it'd go off. It would only come on after being on the highway for a long time. Just some food for thought.

 

[turboglenn]

So I went out and checked the TPS resistance. It's about .83k closed and 4.97 at WOT. The weird thing is, as I'm slowly twisting the throttle, it goes up to 5k just below WOT, and drops back down to 4.97k at WOT.. just how it feels while driving.

Do I need to adjust it so closed throttle is around .9k, and would this raise WOT back up to 5k? It's getting dark, so I'll have to wait until daylight tomorrow to check the knock sensor.

Thanks

This could definitely be worth investigating as i've seen the DSM TPS voltages do this on stand alones where you can always see what it's doing. If i set mine too far to one side of the adjustment, i can floor the car and see 100% TPS then if i push harder it will start to fall back down to 97 - 98% TPS

What you're reading though isn't reistance it should be voltage return IIRC, but honestly the resistance values could match the voltage values and you might be reading impedance, I'm too tired and a bit too lazy to go dig one up and see or go to the garage for my manual.

Some other things i would check would be the coolant temp sensor..when bad it can report too cold of an engine forcing tons of fuel at open loop conditions. But, when you're in closed loop it could compensate through long and short term fuel trims ( to an extent anyway) When i had this same feeling from my car back in the day the logger always showed a massive pull in timing, then i could let off, gun it again and get great timing and a great pull... too much of not knowing what the ECU was going to do and when is a major part of why i just put in a stand alone... This car had me cursing the OBD-II ECU's setup and it's engineers to holy hell righ up until the day i pulled it out and wired in something nice

Another thing is the stock exhaust and timing, it could be as well that the heat and back pressure from the stock pipe is causing the engine to knock easier but the difference between 95 and 100% TPS shouldn't matter at that point when boost is already present

 

[Apeximprt2nr]

I'm having a similar issue. Is it possible an open dump would cause the knock sensor to read knock when the dump is screaming?

 

[Apeximprt2nr]

I'm having a similar issue. Is it possible an open dump would cause the knock sensor to read knock when the dump is screaming?

 

[allthrottle]

I attempted to adjust this out of the TPS today.. got the closed throttle reading up to about .90k and got WOT just about 5k constant. The weird thing is it was no matter how I set it or moved it, just below WOT would always read .02k more than WOT. I'm just going to leave it at that for now and look into a logger. The knock sensor and wiring looked fine, so I'm not going to replace it until a logger tells me it's going crazy.

Thanks!

 

[tegster1]

Interestingly I am having almost the same problem. Full throttle feels more like 50% at times and just below wot it pulls much harder. I have an open dump as well but being 420a, not sure if it could be a related problem somewhere.

 

[big_d]

Yeah it sounds like to me you were experiencing knock symptoms. I changed my knock sensor just so I knew that it was fresh (motor was rebuilt right before I bought the car, so I figured it had been done previously), and take a look what I found:
The factory 90 knock sensor with 180k on it . I went to Advance Auto, ordered a knock sensor, pulled it out of the box, and found a new Mitsu knock sensor with the 3 diamonds on it.

 

[brownfinger]

Most definately adjust the TPS by voltage, not resistence. The ECU thinks that 488mV is closed/10%/idle. .47-.52 V is the spec, but shoot for .49V Use three jumper wires, the VOM set to volts, and, if possible, with the car running. Then start all over again, 'cause it's gonna move when you tighten the screws.
I wouldn't overlook the hacked MAF. Try to find an original one to borrow. It's so quick to swap, and used ones are very plentiful.
Also, don't adjust the throtttle cable for the lever to hit the stop. You need a fraction of a mm. clearence. Otherwise, you'll destroy the throttle shaft bore in no time flat.
Technically, you need the logger to set the throttle perfectly. You need to see 10% on the logger at idle. Some software lets you see it in volts, some as %s. This is done as the TPS adjustment. Then, you adjust the cable untill you see 100% at WOT, and there should be a little clearence at the stop.
Check your coils, too. Incomplete combustion from a poor spark on 2 cylinders has the unintended consequence of making the ECU dump even more fuel into the cylinders It sees the o2 in the exhaust and thinks you're lean. More fuel just makes it worse. This all then conspires to destroy the o2 sensor eventually!
Last fall I had all your symptoms going on: Huge surge in power as you let off the gas from WOT. I had put in a different (used) MAF thinking that mine was bad. At the same time, I had mis-adjusted the TPS using the resistence method. The car ran like ass. Putting the original MAF back in, and properly setting the TPS, helped a lot. It wasn't really right untill I got a new coil pack, replaced injector insulators, and replaced my swiss-cheese exhaust manifold. The cracked manifold lets in even more O2 for the sensor to see and tell the ECU about, just making everything that much worse.
I hope this narrows it down some for you!