JGuy07

Went ahead and replaced the map sensor. Also found a vacuum leak with the pcv valve and hose so replaced those and can tell a significant difference in how the vehicle is running. But, still having the same problem of the vehicle stuttering when temps get up or under load. I'm going to go ahead and replace the wires and a new MSD coil here soon too, can only benefit. I'll keep posting.

The valves on the TB are also sticking, I am going to take emery paper to smooth the surface and buff it down just enough to where the valves quit getting caught on the surface of the TB, would this method be a bad idea?

JGuy07

Alright, replaced the wires with a set of OmniSpark 7mm wires. Car runs quite a bit better but still has the occasional stutter and hesitation. I'm going to replace the plugs to get those out of the way and the coil too. But I was thinking along the lines of checking the injectors, how much of a pain would this be? I've read that once using cleaner such as seafoam or any other injector cleaner, if not used on regular basis, sometimes it can cause them to foul up due to a film in the lines coating the injectors once the cleaner removes this film or build up from the lines. An injector going bad doesn't seem likely, but just in case it's worth a check. So again, how much time and how frustrating of a task would this be or is it even worth it?

Guest47904

Did you disconnect one of the O2s to see how well it ran once warmed up?

JGuy07

No I haven't. The only o2 which had a problem/threw a code was left bank o2 and that has already been replaced. It was running rich then and I notice no problem with that now. So you're saying I should still let the engine warm up and disconnect the right bank o2 to see if there is a reaction or difference? Granted there are no codes or ses light coming on anymore. So it leads me to assume it may just be faulty plugs. The injectors was just a 'what if' kind of thing and possible option to check with during downtime.

Another note, I've seen multiple views and opinions on MSD products on these threads. I am wanting to put an MSD coil on (street fire coil), has anyone had problems with this or any other replacement models for the coil other then the OE replacement ACDelco?

Guest47904

If you are still having the problem, disconnect one of the o2s and let it warm up. See if it's a lot better once it's warm. There can be issues with O2s that will not throw codes but still give you fits during closed loop operation.

As far as parts like a coil, if the one you have doesn't have spots on the insulation like dots and it doesn't show signs of sparking at night, leave it alone until you get the problem resolved.

JGuy07

Ok I understand what you're saying about the o2 now. I didn't know complications without codes on the sensors were possible. I thought all sensors, being an electrical component as they are, would produce a code if faulty or noticing problems.

One thing I haven't understood or sought clarification on I guess is the difference between open and closed loop cycles. I just read up on the differences and it seems pretty basic from the explanation I found. But I'm sure it may be a little more complicated, or not IDK. This is the thread/forum I read on: http://www.modularfords.com/forums/f...en-loop-58339/

So if I just disconnect the right bank o2, let the engine warm up, and then take it for a run I should see a difference if it was the sensor? Instead of the stutter or hesitation wouldn't the unplugged sensor cause it to just run rich on right bank?

Guest47904

First, forget the sensor being the only cause of a closed loop problem. There are several items that come into play, not just the O2s.

When you unplug an O2, the PCM goes into open loop for the entire engine, not just the bank you unplug. This allows you to see if you have a problem all the time or just when in closed loop. It does NOT automatically mean your problem is with the O2s until you do some checking.

JGuy07

Ok, I'm following now. I will unplug the right bank o2 and then take it for a ride. I will let you know if the problem is still there with the sensor unplugged and go from there in following it up with other possible causes again.

JGuy07

Ok, disconnected right bank O2 and let the engine warm up and also took it for a good ride. There was no longer any stuttering/shaking as there was before. The vehicle also idles better and is a lot smoother as well.

But, since you said that it still may not be the O2 causing the closed loop problem what else are you leaning towards or suggesting? And how long can I run with my O2 disconnected without causing damage or whatever other symptoms it may lead to?

****EDIT****
Car sat in driveway for about an hour temps still up, still with O2 disconnected. Went out to swap positions in the driveway and ran spurratic with idle rpm's fluctuating between 700 all the way up to around 1700. This is the first time since disconnecting the O2 that it has done this, I've done several start ups today with the O2 disconnected. Usually it idles down within a 5 seconds back to normal 900 rpm's but not this time. Didn't take it out just parked. Engine was t

Guest47904

Unfortunately it's going to take a scanner to find the problem now. You could replace the O2s but that is not wise as you could simply have a wiring issue.

JGuy07

So should I attempt to track the wiring from the O2? I should probably at least take the O2 out and check/clean it since I haven't touched the right bank O2 at all. I will take it out for a few more runs and check some stuff tmrw just to make sure. Like I said this last start up was the only time out of about 5 today where it fluctuated bad since disconnecting the O2...

Basically I need to just hustle up and get my aldl cable so I can start running scans....

JGuy07

**UPDATE**

Ok now it just seems odd to me. Speedy, I understand the difference of open loop and closed loop now. Like you said, with the O2 unplugged the engine and PCM go into Open Loop and therefor the O2's should not come into play. In open loop the PCM and engine should operate relatively similar the whole time regardless of engine temp correct?

Today I was once again checking it. Upon start up the idle rpm's were once again fluctuating heavily between 700-1700rpm's. I would adjust the idle screw(open) to increase idle and it would slowly correct itself and rpm's would come back down. I kept tweaking the screw, both opening and closing, to get an idea of how the pcm was slowly making corrections. I kept fine tuning and tt appeared to have worked and the idle seemed to relate around 900-1000 rpm's.

Although I got the idle seemingly handled this time, it only seemed to do this once the engine temp hit about 210. I then would kick the a/c on so the second fan would operate and the idle would jump back up and rpm's would fluctuate around 1200-1400 for a short while before slowly correcting and settling back down around 900rpm's.

Also took the car for another run. Seemed to run pretty well. However, I did notice a few hiccups which tended to relate to higher rpm's starting at about 2500. And every so often while in first gear it would also hesitate then jump, this also seemed to relate to higher rpm's beginning about 2000. But overall it was once again a big improvement over what it was prior to disconnecting the right bank O2. And this is why I'm stumped.

Granted I am still going to get my cable when I can since it would be nice to scan, but this is still a bit confusing to me. Input?

So why did it appear that temp played a factor while in open loop?

97WS6SCharged

The computer still calculates fuel trims based on air temperature, manifold pressure, MAF reading and TPS. Without the O2s it just assumes the motor is running at the AFR it is demanding and doesn't try to correct itself.

JGuy07

The only thing that I haven't changed that you mentioned is the IAT sensor, and MAF. Still runs better while cruising then it did prior to unhooking the O2. How long can I run without it connected before it may lead to other problems, if it even does or can? Need to delay as long as I can until I get a good scan...

Not related but I'm also going to be removing the secondary AIR system. Figured I might as well mention that since this can be considered a "PROJECT" thread lol

shoebox

I am not going to get into the middle of this one, since you have some good advice going already, but stop playing with the idle stop screw (I've read two references to you adjusting it). The IAC controls idle speed-not the screw. The screw is only a stop to set the minimum position for the TB blades. If it is out of whack, now, the IAC may not be able to compensate, causing more issues. Use of a scanner is needed to observe TPS position and IAC readings to help confirm the proper stop setting.

It seems to me that most questions in this thread could have been answered with a scanner. Speedy suggested you get one (or some ability to look at data) and so do I. You can't effectively troubleshoot a modern car without one.