Engine Stutters When on Load

[neoviper]

I've been trying to track down my cars problem for MONTHS now and have officially run out of ideas. I will try to describe the symptoms as best as I can but please feel free to probe deeper as I am desperate to finally get this thing running right.

Right now I have the car running in safe mode with the MAF unplugged because the car bogs and stutters violently under the slightest load when its plugged in. Now you're all probably saying "Your MAF is bad", Wrong because i've changed it once and it didn't fix it so i figured maybe i bought one that was broken, changed it again and it still didn't fix the problem. So i've ruled out the MAF. I bought a new coilpack, wires and spark plugs and still no fix.

Now when I turn the car on with the MAF plugged in it runs very smooth, but as soon as i get on the throttle it starts stuttering and choking violently, than when i get off the throttle it struggles to stay on. If i turn the car off and turn it back on, again it runs smooth but than shows the symptoms as soon as i get on the throttle again.

I know I'm probably not giving you much to work with but again feel free to ask any questions. I'll also mention that im in no way a newbie when it comes to working with cars, i've diagnosed some pretty hard to find problems in many of my friends cars, which makes this all the more frustrating that i cant figure out what it is. PLEASE HELP ME!!

 

[97gsxturbo97]

First thing that came to mind was check the engine coolant temp sensor, then I was thinking CAS, and then TPS. Mabye this helps.

 

[Boosted3s]

Have you checked for boost leaks? The TPS is also a very good idea.

 

[jen_cairo]

What did you gap the plugs to0? And have you done anything to your car recently thats not listed in your profile? And does your boost gauge go above 0 at all? I would start by making a boost leak tester.

 

[neoviper]

First thing that came to mind was check the engine coolant temp sensor, then I was thinking CAS, and then TPS. Mabye this helps.

I had the same thoughts, I actually replaced the coolant temperature sensor today and there was no change, I checked the tps with a voltmeter and it read fine, my current thought is the cas, however, the car runs fairly good in safe mode, granted that it runs pig rich dumping way too much fuel, but still driveable, if it was the cas wouldnt it run like crap either way?

 

[Boosted3s]

The cas can give problems kind-of like what you are describing. Have you checked the wiring to the MAF, maybe there is a broken wire or loose connection somewhere.

 

[neoviper]

What did you gap the plugs to0? And have you done anything to your car recently thats not listed in your profile? And does your boost gauge go above 0 at all? I would start by making a boost leak tester.

with the maf plugged in no the boost gauge does not go over 0, in safe mode the car will boost but obviously make no power, its absolutely positvely definately not a boost leak i've done about 15 (literally) BLTs

 

[neoviper]

The cas can give problems kind-of like what you are describing. Have you checked the wiring to the MAF, maybe there is a broken wire or loose connection somewhere.

Yes I peeled back the wrappings on the wires and checked connections, all the wires going to the sensors in the thermostat housing are soldered on directly to the prongs since the old connectors were corroding

 

[neoviper]

Since my current theory is the CAS maybe someone can give me a little more detail on what kind of syptoms a faulty CAS would cause

 

[Boosted3s]

I would try a different cas then ecu if cas is not it.

 

[generalu]

O2 sensor?

 

[neoviper]

Ok im ressurecting this thread because i have a new clue to share. Apparently when the car is cold it runs fine, It makes power revs up and the whole nine. when the car warms up however (guessing it has something to do with the car going into open loop) Thats when all the above mentioned symptoms start. Hopefully this sheds a little more light on the situation because this problem is really starting to get on my nerves

 

[projekt1]

I had a similar issue although you probably already ruled it out for your DSM. My car would stutter when under load especially when it would start to boost after I did and injector swap. It would run like shit and sounded like a subie driving at low throttle. My problem was a simple fix, turned out to be one of my injector clips kept coming off with so much vibration under the hood. I purchased some pigtails with new clips, soldered them in and fixed my problem.

 

[neoviper]

yeah i checked the injectors twice already. Another reason why i wouldnt think its injector related is because the car is fine when its running cold, it only gives me problems once its warmed up

 

[350war]

ECU could cause this. Have the caps. been replaced?

 

[neoviper]

just to update this thread in case it turns up in someones search, the problem was my ecu. the capacitors leaked onto the board. i removed the old capacitors, cleaned the corrosion and soldered in some new ones and now the car running stronger than ever! thank you to everyone who helped me narrow this problem down