jwog666

the egr should only flow at part throttle cruise, at wide open and at idle it will mess up your air fuel ratio and cause loss of power and rough running. about the tps % sometimes the data logger will show a % reading of throttle open, no biggie if it doesnt, your voltages look good. also i forgot to ask before, does your IAT (intke air temp) match your outside air temp? if your iat gets messed up and reads low then it will add more fuel as well

VTX1800N1

Ok, from what I understand, it started running poorly the minute you put the new intake, throttle body, and plenum on? I know it's a pain, but if you have the stock pieces, you may want to switch back to them and the stock tune, injectors, and MAF and see what it does. That would start you on the path to narrowing down the problem. It could also be that you have a vacuum line hooked up incorrectly somewhere?

I'm starting to think it's one of two possibilities or a combination thereof.

1. You have the wrong injectors for whatever injector/MAF kit you bought, or the MAF is screwed up. This results in the injectors dumping more fuel in the engine than the computer knows about, and the computer is at the limit of what it can adjust for.

2. You have an internal mechanical problem causing low compression across all cylinders. This could be cam timing, leaking valves, leaking seals, collapsed or sticking lash adjusters; broken, stuck, or leaking piston rings, etc. A quick way to tell is by running a compression test.

3. To much fuel in the cylinders caused by something under #1 has washed down the cylinder walls and destroyed the ring seal. Does your oil smell like gas?

I tend to think it's not #2 or #3 because you say it doesn't run bad when cold (open loop) and sometimes runs good warm. Mechanical problems wouldn't clear up under any conditions.

When did you changed the O2 sensors in relation to the engine running poorly? I tend to prefer Motorcraft parts for critical sensors like that. They are only $35 each at Rock Auto.

vinny2car

Yeah I wondered about the vacuum lines being hooked up wrong too, but from what I can tell from dozens of pictures I've seen of other cars, they seem to be alright. Yes it only started running badly after the T/b, plenum and manifold were changed. I do have the stock pieces, and was planning to do exactly that so I may be able to isolate better. I'm going to put the stock injectors back in regardless along with the MAF, as they were doing fine before I tore into the car a year ago. I'm going to put the Typhoon manifold back on though, and if it still runs crappy, I'll know it must be to blame. If it clears up, then I'll put the Trick Flow t/b and plenum back on and hopefully be able to isolate the problem by then. I won't have the gaskets for the Typhoon for a little bit as they're on backorder, but for now I'm going to start putting everything else back to stock. It may be a couple of days before I get to it though, got a lot going on right now - but I'll be sure to update as soon as I get any results. Thanks so much again for your input.

dougward1960

have you figured this out yet my 97 cobra was doing like you described ive thrown a lot of money at it and still havent got it. i have a new/used ecu to put in cause of the age of the computer it could be failing im like you dont know what else to do at the moment.

vinny2car

O.k., I finally got it. I apologize for not updating sooner, but it has been a crazy summer. After pulling the intake off again, I realized that the Professional Products and Trick Flow gaskets both suck out loud - used both, and both leaked. Finally went with the stock Ford ones and they are awesome....duh. The problem wasn't just the intake leak though, I found that somehow while putting the engine back in that I had swapped the O2 sensor harnesses up top, so each bank was trying to correct its air/fuel mixture by adjusting the fuel for the opposite bank, resulting in each bank eventually maxing out - really lean on one, and really rich on the other. Runs great now, and I'm having no problems with the Trick Flow 75mm plenum/TB or the Typhoon intake. After I find the time to install the Nitrous Outlet system I'm taking it to a speed shop in Seattle to get it tuned correctly, but for now at least I can have some fun again. Thanks to all who offered opinions, and I hope this may help a few folks out there someday :-)

majrconst

I'm having what seems to be the same issue w my 99 gt. 10-20% of the time it runs fine. The rest of the time I'm fighting dead spots n the throttle most always mid to high rpm range. Got the car and needd a fuel pump, and clutch. I installed new complete drop in module w sending unit, and new clutch kit. it's had the issue since I started and drove it the first time. I've followed many forums and tried everything but I'm finding that not two people reporting the same issue have the same fix. Am I wrong or is this just a hit or miss, you will fix it by luck type problem?? I'm open to try anything at this point! I dnt have alot of cash to throw at it, but love the car and want it fixed. I'm in it now a total of $1800 it's got 136k on odometer and motor only 26k. Like I say I'm willing to try anything, and have done most everything I've seen on these forums plus some. So PLEASE bring on the ideas!!

Drastang

have you checked all the plastic elbows and pipes that lead from your intake to your headers that keep air pressure in the heads? mine all went bad, elbows to pipe rotted at once could smell gas as soon as I crank my car it was so rich... bogged over more than 25% throttle..... they get old and look fine but if you can press them and they collapse a lil feel kinda like a sponge that's where your are losing air pressure.

vinny2car

Hate to reiterate majrconst, but check those 02 sensors - just the forward ones, as the rears only relate to the cats. Those forward sensors are used by the Power Control Module to regulate the air/fuel mixture. My problem was staring me in the face and I couldn't see it for months, but at the end it was just that simple. In the aircraft world we've got a saying when troubleshooting: go where the people have been. Check anything you or anyone else may have laid hands on, and definitely replace all vacuum hoses or anything else that seems suspect.

majrconst

Thanks Vinny but they r all new. Installed when I got the car and put new clutch and fuel pump in it. I'm leaning toward a fuel issue! Like something in the tank being sucked in by the pump. Cause when it acts up, only aftr it's at op temp, the stuttering issue can b fixed temp by push n the clutch shutting the car off coast a bit swerve side to side, cycle the key couple times and it will fire up and run just like a new car sometimes a few second sometimes many miles and then cough cough the stutter is back. And when it's actn up if u push the throttle any it shuts down, let up then it picks up speed. (Like older models w clogged fuel filter n the side of the carb) but never clears up till its shut down a few seconds atleast and it fires up runs like new again.

WJL

Have you done a sweep test of the TPS