Car sputters on anything over 3/4 throttle

[Hobart]

OKay i dont have a data logger yet so i figured i would ask to see if any one can give me a good idea i havn't tried yet heres the story bought a 96 gst not running after tracking everything down turned out to be a bad cam sensor so i went ahead and placed a 1st gen hall effect on it and rewired the apropiete conectors car starts runs fine when its cold once it warms up to operating temp i get one of two problems depending on my spark plug setup problem 1 if i gap the platinum plugs at around .28 no stutter under boost but it will faul one plug at partial throttle. problem 2 if i gap them to .30 or .32 the spark seems to blow out under boost as you cant go over 3/4 throttle wich still pulls very hard im in the middle of trying to get a 95 ecu and a dsm link so i can know exactly whats going on but i was hoping to fix this now so its more drivable. The following is what i know about the cars setup 96 gst with 3 inch apex down pipe and exhaust super t 28 with upgraded fuel pump that seems to be all the mods hes done before i bought it any good sugestions would be aprciated as i know i need some datalogging to know for sure.

 

[DSM90AWD]

..very dense reading. may want to structure you posts to be easier to read.

First.. pitch the Platinum plugs and go with std NGK7ES'. I've tried Platinum plugs before and they just don't work well on DSMs.

Second.. sounds like you're running overly rich. Check for boost leaks.

Third.. I'm no expert on this.. but I thought the 2G and 1G CAS were different so would need to invert the signal when using a 1G sensor with a 2G ECU?

 

[unsivil_audio]

OKay i dont have a data logger yet so i figured i would ask to see if any one can give me a good idea i havn't tried yet heres the story bought a 96 gst not running after tracking everything down turned out to be a bad cam sensor so i went ahead and placed a 1st gen hall effect on it and rewired the apropiete conectors car starts runs fine when its cold once it warms up to operating temp i get one of two problems depending on my spark plug setup problem 1 if i gap the platinum plugs at around .28 no stutter under boost but it will faul one plug at partial throttle. problem 2 if i gap them to .30 or .32 the spark seems to blow out under boost as you cant go over 3/4 throttle wich still pulls very hard im in the middle of trying to get a 95 ecu and a dsm link so i can know exactly whats going on but i was hoping to fix this now so its more drivable. The following is what i know about the cars setup 96 gst with 3 inch apex down pipe and exhaust super t 28 with upgraded fuel pump that seems to be all the mods hes done before i bought it any good sugestions would be aprciated as i know i need some datalogging to know for sure.

Okay heres the problem:

Right now we're using Bosch platinum plugs gapped to .028 and no stutter under boost but it will foul one plug at partial throttle (steady state mode). If we gap them to .030 we get both problems, stutter (misfire) under full boost, and fouling at steady state driving. We also have tried just your normal copper plugs (not NGK, Bosh) and it didnt seem to like those. At .030, no fouling but it misfired pretty bad at anything more than like 1/2 throttle.

Okay heres the story:

We got the car not running (96 Eclipse GST spyder) from a guy in NJ. Turns out no spark on 1&4 or 2&3 (I cant remember), but we replaced the Cam angle sensor with a 1st gen one and dialed timing back to zero (to stock).

Mods:

2.5 dp flared to 3"
3" exhaust (no cat)
T28 turbo
K&N filter
9.3mm wires
Walbro(?) high flow fuel pump 255lph(?)
---------------------------------------------------------------------------------------------
Fixed it. Any suggestions would be helpful guys. I've been working on this car with Hobart for like the past month.

 

[DSM90AWD]

^^^ much better

I still think your car is runnign way rich since you keep fouling plugs and are missing under throttle. Typical causes are boost leaks or too much fuel pressure /injector.

Check to make sure all hoses are secure from the MAS to the TB.

Is the same plug fouling or different ones?

 

[unsivil_audio]

The platinum ones will foul at .030 and smaller, the copper ones will only foul at .028 and smaller.

too much fuel pressure /injector

Thats what I think it is. So should we go with a FPR or just get an SAFC II(obviously with a wideband) and back fueling off?

 

[Hobart]

ANy ideas guys?

 

[DSM90AWD]

I meant injector# not type when asking if the same one was fouling.

Unless you're injectors are non-stock (which I assume were stock) or you have the 255HP Walbro pump (flows more than the 255 non-HP).. I don't think that your fuel system at fault.

I'm still leaning toward a leak in your intake btw your Turbo outlet and throttle body. Is your engine throwing a CEL when it's running poor?

 

[unsivil_audio]

It only throws a code if you just start it up and go. One code is for random misfire (which we haven't got that one in a while, and the other is for primary o2 I think (defective heater circuit or something). If you let it warm up for a minute before driving it doesnt throw a code.

Yeah and the injectors are stock, and I have no idea which one of thes plugs is fouling. You cant tell shit from platinum plugs (nor the copper ones for that matter).

Oh one other weird thing that I dont get, the plugs wont unfoul unless you idle down. If you try getting into boost it just boggs really bad. But if you downshift and let the rpms drop in the proccess then you can get right into boost no problems.

 

[Hobart]

I bought the car modded and it does have a aftermarket fuel pump thats quite loud but i have no idea what type as fro the fauling plug i ha vn't been able to find it as the minute you get out of say crusing at 2k on the tach it clears up untill you hold part throttle under load again.

 

[Crawl]

..very dense reading. may want to structure you posts to be easier to read.

First.. pitch the Platinum plugs and go with std NGK7ES'. I've tried Platinum plugs before and they just don't work well on DSMs.

Second.. sounds like you're running overly rich. Check for boost leaks.

Third.. I'm no expert on this.. but I thought the 2G and 1G CAS were different so would need to invert the signal when using a 1G sensor with a 2G ECU?

My car (95 gsx) was stuttering as well, replaced the fuel filter and it helped alittle bit, put in the NGK7es plugs, problem solved.

 

[Defiant]

Let's try one last time.

DO NOT USE PLATINUM PLUGS ON A DSM TURBO.

Get a set of NGK BPRS6ES gapped to .028"

Those cat-turd Bosch plugs should be taken to the nearest lake so their flotation rating can be tested. Over the deepest part.

Do not bump your thread.

 

[ken inn]

you may have more than 1 problem. i would suspect one of them would be the ign wires themselves, breaking up under load, a common problem on our cars. try a known good set of wires.

 

[unsivil_audio]

^---You were right (more than one problem).

Something I hadnt mentioned earlier was that there is a 1g CAS (hall effect) on the car. Turns out Magnusmotorsports had a fix for the stuttering and the CEL (random misfire). So to them.

IF CHECK ENGINE LIGHTS OCCUR! TRY THIS:

(Blake Heisler's Fix for misfire Check Engine Lights (CELs) when putting a 1G Cam Angle Sensor (CAS) on a 2G)

Many people using the 1G CAS on a 2G head have been running into problems with misfire engine codes while at cruise. Many different things have been blamed for this and many different fixes have been attempted.

This fix will keep the ECU from looking for misfires at all. This is the criterion that must be met before the ECU will start to look for misfires:

1. 300+ seconds of steady state RPM less than 80% throttle position

2. Engine coolant temperature -10C or higher

3. Intake air temperature -10C or higher

4. Barometric pressure greater than 76 kPa

Now if we can get one of these values outside of the criteria the ECU won’t check for misfires. The value that would be the easiest to change would be the barometric pressure sensor. We’re going to add resistance to this value so that the ECU will see less barometric pressure than what there really is. This will also lean the car out so you should see a performance increase as well. Depending on the car and altitude you might need to add more fuel with an AFC.

So let’s get started, Parts needed:

A 10K potentiometer (although a 5K would probably do just fine). These are available at any electronics store, if you go to Radio Shack ask for a volume control knob because they don’t know what a potentiometer is

Wire strippers

Soldering iron

Step 1: Remove the access panel on the driver’s side of the center console. You should now see four plugs with a ton of wires going to them.

Step 2: Pull out the top plug, it’ll be the one that’s the hardest to reach. Locate wire #85. It’s orange with a white stripe.

Step 3: Cut the orange wire in half. Solder one end of the wire to the center peg of your potentiometer. Solder the other end to either the left or right leg, it doesn’t matter which. Turn your potentiometer all the way counter-clockwise.

Step 4: Plug the harness back in and start up the car. It should sound like it did before you did any modifications. If the idle is choppy or the car won’t run you turned your potentiometer the wrong way.

Step 5: Add resistance to the barometric pressure sensor by slowly turning the knob on the potentiometer. Drive the car around; if you get a CEL then add some more resistance. Keep doing this until you no longer get the CELs.

That’s it, special thanks to Marco for pioneering this mod and to all the guys on the DSM1Gina2G Yahoo group for all the discussion, ideas, etc.

-Blake Heisler

Also I should mention the stuttering actually turned out to be the injector on cylinder #3 not firing under steady state driving mode, the above fix fixed that and the CEL. (The misfire is still present though, just an effect of having a 1g CAS)

As for the blowing out spark under boost, we ended up switching to NGK (some two-prong bullshit that the guy claimed were stock plugs), I think they were copper. Gapped to whatever they come as right now (since you dont gap multiprong plugs), I think we'll gap them smaller though cause we know that they were not actually fouling but in actuality the #3 injector was shutting down as a result of the CEL (random misfire).

And lastly I want to thank you guys for the help and insight you've given us. I hope this thread helps someone in the future too.