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Engine Misfiring...

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Zerocygnal

20+ Year Contributor
641
1
Jul 1, 2002
Springfield, Ohio
It never ends...

Okay..if I start the engine it stays in the 1500RPM range at idle (Doesn't surge) and just misses like you wouldn't believe. Once at operating temperature it idles 800RPM to 400RPM almost stalling and missing every time. Knocks a little, not too bad when you rev the engine.
All readings on the Pocketlogger look normal except the ISC will sometimes bottom out to 0 steps to keep the engine running. (again normal for under the stalling condition, it's trying to keep the engine running)
I cannot get a proper vacumn reading because the engine is missing. it stays about 14inHG with this problem. Before it was at 17 to 18inHG, and 22 to 23inHG at full clutch downshift.

-I have done the following to attempt to resolve the issue-

-Inspected and cleaned tips of relatively new NGK plug wires
-Installed BPR7ES @28gap (Old plugs had a white tint to them/lean condition didn't look too bad)
-Replaced O2 Sensor (did this to resolve a prior problem, it wasn't responding on the pocketlogger it now works.)
-Performed injector disable and engine balance test. Every injector was at 2.3 Pulse Width@ 5% Duty Cycle and reacted normally.
-Found a black wire w/ yellow (probably white) stripe disconnected from the plug that goes into the alternator? ( I wasn't sure what it was for, but I saw the plug it had separated from. I replaced the entire wire because of heat damage, shrinktubed, heatsheilded the harness and reconnected it.)
-Tested ISC coils all between 28 and 30ohms
-Replaced BISS Screw and O-ring (Again, this was done for a prior problem and the engine was operating properly with it afterwards.
-Removed TB Elbow and cleaned the hell out of the TB and TB Plate (it is now polished aluminum).
-Checked all wiring connections and inspected harness integrity.
-Replace Fuel Filter on 11/02/02
-Cleaned Air Filter
-Changed Oil...(at this point I was at my wits end..)


I DID NOT...
-Check Fuel Pressure
-Check for Fuel Contaminants
-Test the MAF (The Karman was reacting normally with the pocketlogger and showed 95 Barometer I assumed it was working and within spec.)

Bad Ignition, Bad Fuel? What?

Any ideas? 10 years of Automotive experience and I'm stumped. Pathetic...
 
No CEL, Sensors are all good. Most are new
Perhaps we should also have an Extreme Problem Forum LOL....
 
i seen you tested the isc motor. did you take a 6 volt battery and test it?or did you just do the ohms? mine had good ohms on all. but if you hooked a 6 volt battery up to it. it would just click once,and it supose to vibrate or move if you have it out, did you check your ecu caps, i did not get a cel when mine leaked, no fish smell at all, good luck
 
The only reason I didn't do the battery test was because the pocketlogger shows the ISC steps. It was able to move from open to close positions, it saved me the trouble. Would the ISC even cause the engine to miss? I would think the construction of the device would make it reactive only, and not informational.

ECU caps huh? :sigh: I was hoping it wouldn't come to that. Time to get back to I-level repair. I will take a look inside next opportunity. You mentioned you were getting no other symptoms...would it necessarily be clicking or show symtoms at all? I.E. screwy logger readings?
 
i had no clicking,nothing and it was a surprise, i knew all the signs,had none,and had already ordered caps, just to be safe,and my car started acting funny one day before i got the caps in the mail,and i tried to read codes, even without a cel, and it said evereything was fine, and i took mine out and was realy surprised,and pissed, tha they were leaking, so know that our tcu leaks it starts to act like a woman, and tell you what you want to hear.
 
my cars doing the same thing sorta.. i've checked all my sensors, my ISC was bad, i replaced that with a good one.. went to a few mechanics, their all saying its my coil because when it heats up its breaking down.. hmm.. but its a nice day outside, so ima go rip open the ECU and see if the caps are leaking or not.. 200,000km on it, and i don't think they've ever been checked .. but i've never heard a clicking or fish smell.. son to find out.
 
I failed to mention that I have replaced every vacumn hose, and the emission system has not been installed for some time now. Yes, the coilpack does need to be tested. I'm trying to make a list of things to try tonight.
Thus far I have:
1. Test fuel pressure
2. Check fuel pump voltage supply (fuel volume)
3. Disassemble and check for OOT resistors and damaged capacitors in the ECU
4. Fuel Contamination (water, jello, sugar, piss, etc...)
5.
6.

Still have a bit more time in my budget tonight to go father than what I've listed so far.
 
When you yank the ecu you might as well pull the fuel pump relay that's by it and test that. When you test the coils you might want to test the power transistor also. Only other thing I could think of is maybe somehow the MAS is telling the ecu to lean you out but your logger is saying otherwise. Maybe timing is off a hair, I heard it's easy for the CAS to get a little off.
 
I tested the fuel pump relay. It energizes (done with logger diags)
I didn't pull the ECU just yet...there was a few more things I wanted to look at.
Fuel pump was getting good voltage, coilpack tested good, tested ISC again good, timing marks good (just replaced belt about 2 months ago.)
I disconnected the MAS and ran the engine, boy did it really run like shit then..LOL. It's readings seem fine. FPR was good.
I'm lost guys...

NOW everything is doing exactly the opposite. It's running pig rich, so rich the smell makes you nauseous. The O2 shows normal...but it can't be. I'm going to pull the O2 again..it looks like it was sweating around the O2 bung on the manifold....
I even tried adjusting the timing..

I'm not one for giving in, but it's my daily driver. I might have to take it to a shop and atleast get the diagnosis done, I don't have the time with work and kids. Whatever the repair may be, I can do myself.

Any last minute ideas?
 
Okay so it wasn't the remnants of my ex-girlfriends scent in the car. I opened up the ECU and guess what. Smells like rotten seafood by the capacitors. However...I did notice something interesting. This is a 92 model Talon..yet plainly sitting there in the corner on a large chip...E931 EPROM
I was under the impression that the EPROM wasn't put in till 95? :confused:
 
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