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Desperation finally sets in!

C

ctmystique

Hard-core CEG'er
Joined
Jan 2, 2006
Messages
2,029
Location
Enfield, CT
Ok here's my plight...

In the early spring I had spun a rod bearing in my 2.5L mystique so I did a 3.0 hybrid conversion with 2.5 heads and SE intake setup. Ever since then the cars has had a rough time starting. It starts ok when cold but recently after it gets hot it won't restart until it cools back down. I believe this may be due to high compression?? I tried replacing the starter but that didn't help the starting issue. It has also been idling very rough @ 750 rpm. If I bring the idle up to 1500 rpm it runs fine. I'm at my wits end trying to figure this out.

Here's what I've tried and or changed.

1. new plug wires (plugs were new at engine swap)
2. idle air control
3. cam sensor
4. crank sensor
5. engine wire harness(really bad insulation deterioation)
6. new starter
7. coil pack
8. maf sensor
9. SVT computer
10. SVT injectors
11. SVT exhaust

These are not in any particular order just as I remember that I've swapped.


I also am getting CEL codes

p301 misfire cyl 1
p302 misfire cyl 2
p303 misfire cyl 3
p171 system lean bank 1
p174 system lean bank 2
p1401 DPFE sensor circuit high voltage


I have a DPFE sensor that I'm going to swap out soon as well.

If anyone has had the same or similar symptoms I'd be eager to try some suggestions.
 
I did unplug the dpfe sensor today, maybe I didn't get it plugged all the way back in, thought that I did so maybe check that first.


Also I would like to bring this up. I was doing some data logging on the car today with my xcal2. I found that when the car came down to the requested idle the duty cycle of the IAC went to 0. On my SVT it only got down to 0.2. Also I noticed when the car reached idle the spark advance would be at about 10, where as off idle it would be up around 30. I know in past logging I have done that the ignition advance was always around 30 unless the car was idling and at 212 degrees when teh cooling fans would kick on.

oh an before anyone says anything about just throwing parts at it they where all free as Aircougar had extras. We when doing the data logging and trying to reason through everything.
 
ctmystique said:
.... Ever since then the cars has had a rough time starting. It starts ok when cold but recently after it gets hot it won't restart until it cools back down. I believe this may be due to high compression?? ...
Click to expand...
Are you running 87 octane? You should try that and see if it helps.

As for the codes, have you check if the precats, and main cat are plugged. And of course, check SP wiring order again, just to humor me.

Firewall side
4- 6 -5 <--coil pack
3-2-1

1-2-3 <--engine
4-5-6
Radiator side
 
he is running 93 octane in the car...

We haven't checked the precats yet, but we might gut them as brapple and I discussed that a few days ago, too...

SP order IS correct... triple checked by all 3 of us.

ANd, Brian, i made sure the DPFE sensor was plugged in after we swapped the injector harness out... :)
 
Guys, I posted in NECO, but I figure I'll toss it here in case you don't see it over there. I mean, I'm no expert, but as Greg said in his NECO post, the engine doesn't seem to be getting proper fuel. Did you check the fuel pump/filter? Maybe this could be a problem...But Brian, you mentioned the IAC reading going to 0? Would this indicate that air intake is too restrictive and isn't allowing enough air in? I'm not quite sure how the IAC works entirely, just trying to rattle the brains for some ideas. Poor car isn't running up to par :cry: .
 
it may not be getting enough fuel at idle, I am not sure, but it runns great at any enigne speed off idle, and I mean really well as in I couldn't keep up ...


as for air restriction, not sure but the MAF appears to be reading correctly. off idle it was reading 1#/min of air at least, idle was under that but that makes sense to me based on what observation I have done from data logging.
 
With those codes I strongly suspect a vacuum leak on bank 1 (the rear bank). Most likely an intake gasket problem but could be anything on the rear bank side. It's bad enough that it is slightly leaning out the front bank too, but not causing a miss in those cylinders.

Try spraying the intake gaskets with throttle body cleaner spray around the gasket areas.
 
brian and I kept pointing towards a vacuum leak too, but with new gaskets we figured they would be fine.... they look to be seated properly and everything.

Could a clogged or very dirty PCV valve cause this type of condition?
 
ok, we did some data logging last night. As ctmystique was driving around I was watching the injector pulse width, numbers made sense to me, about 350 on both banks and it went up over 1k when accelerating. Injector count said all 6 injectors where active.

I was also watch the spark advance. At idle the advance drops to 5 to 10 degrees. when driving or holding a constant rpm over 1k rpm the advance is around 30 or so. I also noted that at time the spark advance would drop out for a split second, so it would be around say 30 and it would drop to 18 then come right back. I also monitored max spark and bourderline spark ans those number where always around 30, 36 respectively.

Last night we again found codes again for the down stream O2 sensor heater circuit.

As I was watching the O2 sensors (upstream) I noted that they where not that smooth. I also noticed that while idling the voltage would drop very low and it would flat line. The voltage reported while off idle or holding a rpm above 1k rpm looked normal, ie ranging from .1 to 1 volt. I also saw that when the O2 sensors where flat lined at a low voltage the monitoring sensors also where flat lined. For the most part they also responded correctly while driving although I think one is on its way out.

that is what i recall at this time anyway, I have to look at the data logs more, and if anyone wants to look pm me and I will email them to you tonight.


oh almost forgot, Cyl. 5 is also miss firing now also, definately need to check spark plug gap
 
Maybe the voltage regulator isn't working at idle. This could be replaced with out replacing the alternator. But the alternatoer would still need to be pulled.
 
svtavino said:
Maybe the voltage regulator isn't working at idle. This could be replaced with out replacing the alternator. But the alternatoer would still need to be pulled.
Click to expand...


alternator has been changed on the car a few times already, again just recently and it never made a different in how it runs. But we can verify the charging of the alternator at idle.
 
the timing will be redone this weekend if all goes well.

now, would plugged pre-cats cause a rough idle? I do know that one cat monitoring sensor is bad or the cat is bad, the other seems to respond correctly.
 
You guys are planning on pulling the timing cover & retiming it?
Clogged pre cats normally don't cause any unusual idling, or mine didn't.
 
Yeah, If the weather cooperates. We'll throw another set of chains and guides at it too. I would love for it to finally idle correctly. Above 2k rpms it runs really well.
 
Well, Aircouger Brapple and myself just finished retiming my motor and that must have been the problem. It now idles ok and no more misfire codes. At least on the drive home.

I want to give great cudos to Greg and Brian for all the great help they have provided to/for me. If anyone ever needs work done here in New England [size=+2]Greg is Da Man[/size]
 
ctmystique said:
Well, Aircouger Brapple and myself just finished retiming my motor and that must have been the problem. It now idles ok and no more misfire codes. At least on the drive home.

I want to give great cudos to Greg and Brian for all the great help they have provided to/for me. If anyone ever needs work done here in New England [size=+2]Greg is Da Man[/size]
Click to expand...
Glad to hear you guys got it straihtened out!
Back in the old days a sure sign of incorrect timing was trouble starting when hot, of course then you just spun the distributor!!

Do I get some props??? :shrug: :)
 
ctmystique said:
Well, Aircouger Brapple and myself just finished retiming my motor and that must have been the problem. It now idles ok and no more misfire codes. At least on the drive home.

I want to give great cudos to Greg and Brian for all the great help they have provided to/for me. If anyone ever needs work done here in New England [SIZE=+2]Greg is Da Man[/SIZE]
Click to expand...

NICE! I really wanted to stay and see the final result you guys, but I HAD to get back to school :(. You silly guys took so long on you're flippin' hot rod that Lindsey's poor car got neglected :(. Lol jk :laugh:. I guess I can't make fun of you any more for not having a crappy-running car :shrug:. Glad to see things worked out :)
 
zorrex said:
You silly guys took so long on you're flippin' hot rod that Lindsey's poor car got neglected
Click to expand...

but we figured out the brake problem, got the alarm sorted out and found about the car haskeyless entry. You check the plug gap and said everythign was in check. so we did get some things figured out ...

very glad to hear the car is running better :laugh:


oh, there is one remaining question, because of the high compressor should the spark plug gap be alittle tighter then stock spec, or at stock spec? right now they are at stock spec ...
 
On the plug gap. You should be fine with the factory setting. Your ignition system has plenty of reserve power to fire fine with your modest boost in compression. Back in the days that ignition systems were limited in their capacity due to mechanical breaker points and smaller capacity coils that fed all the cylinders you would be correct in closing up the gap a little.

If you had forced induction (turbo or blower), that could be a different matter.

If you really want to try a closer gap, don't close it more than about .05". If it were my car, I would set the plugs where I do now, at the high end of specs. Your engine will tend to idle better.
 
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