UNSOLVED MIStery. For those who want a challenge, I need major help.

[Sean Roe]

Hi John,
Any news?
On an interesting note, I recently ran into this problem when testing AKovacs PCM, VEC2, MAP sensor assembly recently.
I finally got my car to start missing at 5188 RPM (logged on the dyno).
The problem occurred only after the car (and PCM) got hot. Once I got it to do it, I started changing back to the original parts from my car. When I changed back to my PCM, the problem stopped and never returned.
I know you've tried a couple PCM's, but have you tried the '96 alternate part # PCM?
It took us a few hours of testing his parts to get it figured out, but that's what it was on his car. We mailed his parts back to him and he was buying a PCM from another individual that had one sitting. I have not heard back from him yet.
If the cam sensor didn't do any good, you may want to give the PCM a try. I can loan you the one out of my car when we go to VOI (the car will be sitting while I'm gone).
Regards,
Sean

 

[J DAWG]

Sean, the sensors were sent out yesterday so I expect them today or tomorrow and will give them a shot. Car still misses around 5600 under load and 5100 while parked free revving.

What exactly is the "'96 alternate part # PCM?"


I appreciate your offer and will talk to you next week after I change sensors. Thanks for keeping me in mind and for all your help. I really wanna get the VEC2 back on the car, but need to pinpoint what happened.


John

 

[tommygun]

Sean, the sensors were sent out yesterday so I expect them today or tomorrow and will give them a shot. Car still misses around 5600 under load and 5100 while parked free revving.

What exactly is the "'96 alternate part # PCM?"


I appreciate your offer and will talk to you next week after I change sensors. Thanks for keeping me in mind and for all your help. I really wanna get the VEC2 back on the car, but need to pinpoint what happened.


John

96 alternate is the replacement pcm that Mr. Roe offers to replace the stock pcm on later model gen II's. It is a pcm that will eliminate misfire trouble codes and O2 heater codes. The only down side to this pcm is no odbII, so no misfire monitor. Excellant product and kudos to Mr. Roe for coming up with it, the man amazes me every time I see one of his product.

 

[J DAWG]

installed cam sensor - still missing


installed crank sensor - still missing



going outside to put o2 sensors in for the hell of it.



John


ps - drove a buddies stock GTS and - no missing......hmmmmm

 

[99 R/T 10]

did you replace the stock PCM with a 96?

 

[J DAWG]

did you replace the stock PCM with a 96?

not yet....spoke with Sean and will be trying his alternate 96 pcm while he is in Dallas.



May have it in prior to V10 nats or it may be later next week.....dunno yet.


otherwise I will just yank Tony's off his car and try it.


John




ps - puting in the injectors right now as well. Don't think they will make much difference, but nothing else here to try at the moment. Thanks for the package.

 

[AJ]

nothing in the front should affect your fuel pressure (as somebody else mentioned). so it is something in the fuel supply system- you might have a bad impeller in your fuel pump that cavitates and loses pressure. the wild fuel pressure is very indicative of such activity.

its fuel.

alex
few cars

 

[J DAWG]

AJ


would my air fuel stay rich with a fuel delivery problem or should it go lean or would there be no effect on a/f? It consistently stays in the low 11's.



John

 

[AJ]

dont know and i dont think it matters in this case (i assume you should go lean btw). your pressure depends only on your fuel system and nothing else.

your problems (as i see them ) might be:

1. fuel pump (replace to test).
2. fuel pump relay (replace to test)
3. sticking injector(s)- test
4. bent/ clogged fuel supply line - visual
5. bent/ clogged fuel return line - visual
5. dirty fuel pump pickup - visual
6. general electrical problem that affects the fuel pump voltage - hook up (long wires) a voltage meter in the cockpit to the fuel pump and run the car.. observe meter- if it moves more than 2 volts - this is your problem.
good luck and let us know...

alex
few cars

 

[J DAWG]

ran the car again last night and whether or not I gave it 10%, 50% or 100% throttle, when it got above 5500 rpms it missed.


I have an RT, so I really don't feel like taking the pump out, but if I have to I will. Just trying to understand because when the car is sitting still and revving it up, the pump essentially doesn't have the load or under the stress as it does when it is actually under load?


Parked and revving it up aren't the pulsewidths in the single digits?


I appreciate your time
John

 

[AJ]

does your engine miss when revving it in neutral above 5500 rpms?

also, you sure your tach is not slow/wrong and you are hitting the rev limiter? just a thought...

alex
few cars

 

[J DAWG]

does your engine miss when revving it in neutral above 5500 rpms?

also, you sure your tach is not slow/wrong and you are hitting the rev limiter? just a thought...

alex
few cars

in neutral when I rev the motor it actually misses around 5100.

while in motion under load it misses around 5600.


go figure.

 

[Renan]

i have seen the same problem with 2 cars, 1 was the cam sensor the other was the crank sensor

 

[J DAWG]

replaced both of them and no luck. I was hopeful it was one of them as well.



replacing injector clips now.

 

[AJ]

you sure your tach is accurate? they are kinda slow- mine at idle can hit the rev limited at indicated 5500 rpms.. however, i know it is really at 6000 rpms..

other than that- as i said before- see if your fuel pump voltage fluctuates, and replace all injectors (one at a time if you wish) with a good working one...

alex
few cars

 

[J DAWG]

car misses at 5100 when parked and clears up above that rpm, so I don't think it is the tach.



-replaced injectors with another set of stock injectors and - still missing


new injector clips - still missing

tried pacm modified with more timing and fuel - still missing

tried Sean's 96 alternate # pcm - still missing

 

[J DAWG]

visually inspected coil packs and they look ok, but plan on getting a new set as well as MAP and TPS sensor.


took the car to a dealer while at the V10 nats in Shreveport and the tech only had a minute, but he hooked it up to the DRB and the misfire counter showed #8 and #7 cylinder misfiring(for whatever that is worth).


#8 plug color looks appropriate, but the metal perimeter was wet.

#7 plug was as white as snow.

I put number 7 plug in the 8 hole and put number 8 plug in the 7 hole and ran the car hard. The dark plug(old 8) was now much cleaner after being in the 7 hole and the old #7(snow white) was white on the upper part of the plug and dark around the bottom after being in the 8 hole.

 

[J DAWG]

Added headers/cat back since last dyno of 503/535(january - 40 degrees) and dynod car in shreveprt(80 degrees) and car made 521/536.


Dyno graph dipped at 5600 rpms when miss occured everytime just as it misses at 5600 everytime on the street.

 

[InjectTheVenom]

Speaking of the MAP sensor... I've posted this issue in the technical section of the forum I have more than 3000 posts on, and someone said it might be a bad map in your ECU. Does this sound like something possible to you?

 

[J DAWG]

Where is this posted?



Don't completely understand, but wouldn't trying several other pcms rule out that possibility?


Thanx
John

 

[InjectTheVenom]

Where is this posted?



Don't completely understand, but wouldn't trying several other pcms rule out that possibility?


Thanx
John

Technical section where I posted your problem

Maybe there's still some kind of fault in the ECU

 

[InjectTheVenom]

You might want to get in contact with the guy who has this screenname:

matt frost

When reading his answers to technical problems in that forum section, it sounds like he knows a very good deal about technical issues

 

[J DAWG]

Mistery solved.

It was the vavle springs.

I had Greg Good modify my heads that were already modified.

Picked up some significant power and the mis is gone. The car will run to 6 grand all day long.


John

 

[TOOOFST]

Ofcourse watson.
Glad you got it Johnny,are you coming out to chi-town this summer?

 

[J DAWG]

Scotty

I will definetly be heading up that way. Waiting for PC to get that beast running.

 

[99 R/T 10]

Hey John,
have you gotten a chance to dyno the new setup yet?