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Discussion Starter #1
Well I finally got a code after a couple of hundred miles. It's an 1131. I have read everything about it already and I don't think I have read any real prople's fixes yet. Does anyone out there want to post how they resolved their 1131 or 1151?
I am going to swap my 02 sensors from side to side to see if my 1131 turns into an 1151. I have no vacuum leaks, fuel leaks, or ignition issues that I can find. My maf is cleaned too. So I hope the 02's leave a trail, but in the mean time , other people's solutions may lead to mine too , so please post! By the way, the PI manifold really adds power. thanks in advance.
 

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Discussion Starter #2
My new periodic misfire symptoms.

The engine's habits have changed a little from three weeks ago. Now,when it is first started after several hours, it runs really great across the board.This could last for a long time if the throttle is somewhat constant (frwy). But when there is stop and go,the engine's manners decline after about ten minutes or so. At that point, the idle will be rough,and there will be minor lean surge thru around 1200 to 1500 rpm,but it could after a while clean up and run great again. It tends to take a hundred miles before the P1131 sets in. Here's what I have done: I swapped in another maf w/ no change;I put vacuum plugs on the upper intake connections w/ no change;I measured the ohms at all the injectors (19.5 thru 22.5);I have checked plugs (they all look a normal/leanish);I have disconnected and tested the egr valve w/ no change; I have listened to all the injectors,and they sound the same;I sprayed wd-40 at their base to check for a vacuum leak (none), and I swapped the upstream o2's from side to side. I am still waiting for the new code to set. The periodic rough idle really feels like a lean-misfire,as does the low speed surging I sometimes (not always) get. I am left with the possibility of one or more injectors on the right bank being partially blocked by debris as my only analysis to date. Can someone expand on my thinking?My smog inspection is a week overdue, and I know it will fail.
 

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did you put rtv on the ports?
 

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Discussion Starter #5
I used genuine Ford PI intake gaskets.

And, I used plenty of rtv at the two corners. I have no known water leaks that could snuff out the ignition. During the period of rough idling, I have pulled the corner spark plugs out to check for coolant and have not found any, although anything can change. It really feels like there is a periodic lean surge at off idle.
My cornniest guess is that one (or more) injector has a partial clog that changes while running.
 

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Discussion Starter #7
It gets resolved for a while then sneaks back!

I am sick of this too. I have swapped the injectors and coils from side to side on my '97 bird. I have tightened up the passenger side of the pi manifold a couple of extra pounds. It idled great for sixty miles and just came back to a little rough again tonight going to the post office. The surging is almost gone, but a little is still there sometimes. I just got a code P1131 too. My mileage has dropped to 15 combined from the 19 it used to be. As I stated before, I have run the engine with all the vacuum ports plugged, and to no avail. This is totally periodic, and the idle can and will become smooth for a while , then rough for a while. My next step is to get a wrecking yard model match computer (only because the cost is an easy write-off). There can not be such a thing as a periodic vacuum or exhaust leak. My maf is so clean it shines, the 02's are new upstreams, the wires and plugs are as new. I think nobody that gets the periodics has ever posted because there never was a cure. I really want to like my car, but she's asking for a divorce.
 

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i have the same sorta problem,it idle's fine in park but while in drive and stopped at a light it will drop a from 700 RPM to 600 and then jump back up to 700.i just replaced my pass. side o2 upstream as i threw the 1131 code.the CEL has not come back on since then.my maf is shiny clean,new air filter etc. my mileage is crap...i 've no idea what to do.
 

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Discussion Starter #10
I've got some data.

I hooked up a friend's Actron reader and there is a live data setting. My driver side upstream 02 (the one with no problems) reads from .1V to .85V throughout the rpm range. The passenger side 02 sensor always reads between .25V and
.30V at all times. Just for drill, I hooked it up to my daughter's 1996 4.6 bird and both upstream 02's read between .3V and .8V at all times. Her car does not have any trouble codes. I still get P0171 and P1131 every day ( because I erase them daily). It's strange how the readings are in such constant flux (except for my pass side). I had thought that a good running car would read stabilly between .4V and
.6V at all times. What could my numbers mean? Is my daughter's car running normal or not in your opinion?
 

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your daughter's car is running just fine....the oxygen sensors are supposed to toggle back and forth like that....this is because of the non-linear response of the sensors...they are purposely supposed to have a large voltage deviation from 0.5V with any minute deviation from stoichiometric operation, which is what allows almost instantaneous learning/adaptability in closed loop operation

your driver's side O2 seems fine as well, but your pass. side O2 is telling the EEC that there is an abundance of oxygen on that side, and the EEC has already exhausted all of it's leeway in terms of correctability, which is around 25% maximum....so it is already dumping ~25% extra fuel, and still cannot get that bank to stoichiometric operation.....well since you have new O2s and already swapped them with each other, i'd say you do have a lean misfire....as you mentioned, an injector may be clogged up
 

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Discussion Starter #12
This is strange.

As I stated yesterday, my passenger side reads lean and does not switch as my codes P1131 and P0171 so inform me. Also, my pass side upstream 02 had a range of only between .25V and .30V while the drive side upstream was in flux between .15V and .85V. That was untill this evening. I was running the engine and watching the usual display when I thought I would take the Actron unit out to the running engine and watch it as I pulled pass side injector terminals. No change at all. Then I moved and pulled on the main wiring harness and bam, the pass side 02 suddenly went up to .8V for a moment. I moved the harness from various points in the engine compartment and got an increase in 02 voltage every time. Unfortunately, I cannot single out what portion woke up the voltage, but now the pass side 02 is constantly shifting between .1V and .6V while the drive side continues at the usual. I am really stumped as to what caused the change. Before all this happened, I pulled the pass side plugs and they were equally sooty from the computer's enrichening. This will probably be short lived as whatever the wiring problem was comes back again. What I don't know is whether my surging was actually running lean or over rich missfires, or even insufficiant pulses going to the injectors. All I do know is my harness still has something hidden inside ( I found three shorts several months ago that prevented even starting the car). Has anyone ever had this happen before?
 

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usually a 1131 mend u need to replace the sensor po171 means bank 1 is lean usually indicating a vacciam leaking but a bad sensor can do it since you have the 1131 also swap the sensors if the problem dont move it could be a PCM problem I've send PCM problems on the 96 97 birds with heatercircuit problems so its possible
 

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Discussion Starter #14
Found it, more wiring harness meltdowns.

This time it is a five wire bundle that branches out right by the passenger corner of the intake manifold. I wouldn't be surprised if it was the 02s11 wiring. It currently has all wires bare for about an inch of insulation meltdown. I haven't even started to re-insulate anything yet. It's windy and lightly raining outside.
It's a sticky hot mess right now. I am thinking that the short kept the 02s11 at only .25V. I'll post again after repairs.
 

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or a wiring problem. Be sure to get all straight and hopefully no wires bleeding voltage have messed the PCM up
 

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Discussion Starter #16
All fixed.

The five wires have been repaired. Soldered and coated in heatshrink, then put into a run of that corrogated split plastic. This really bothers me, because a thousand miles ago I had to discover,find, and repair a three wire branch in nearly the same place. Anyway, both upstream 02 sensors now are continously flicking between .05V and .85V , while the downstreamer are from .00V to .5v most of the time. The best part is that all the short term and long term fuel trims are at or just off zero percent. The car finally runs great again. My specs are : 1997 4.6 , pi alum cross over intake, C&L 73mm maf body, cotton/oil unrestricted intake, MSD wires, and a Dynomax cat-back exhaust. The misfires and rough running had to have been from the extremely rich mix periodically fouling a plug. On a daily basis, I was clearing the P1131, and every other day I was disconnecting my battery. Now, I can finally set my radio presets for keeps.
 

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edman,
When you were having the surging, did it suddenly "take off" at about 2500 RPM? I am currently having similar trouble and havent pined it down yet.
 

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Discussion Starter #19
The surging felt like little misfires,then all-clears.

The surging I had felt just like lean surge, but based on finding my electrical shorts, they must have been misfires from periodic fuel fouled plugs.The car ran strong at all large throttle openings, and generally great at light throttle, but had periodic faltering, maybe when the computer corrected to over rich settings.
For the last 100 miles, since the latest wiring issues, the car has been running perfectly. Because I was erasing codes daily, and pulling the ground wire several times a week (because I was constantly thinking I had a fix) the fuel mix was always in a start over then get rich mode. By the way, the shorting wires probably were not 100 percent shorting, they must have been in the clear some of the time or I wouldn't have had periodic problems.
 
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