type 44 cis troubleshooting ... im stumped...

[Ed Kellock]

Sounds like ignition, not fuel.

Does the tach needle drop to zero when it bucks/backfires? 

Intermittent hall sender has been discussed.  On my urq, I believe my
ignition foibles were being caused by a weak coil and/or oxidized
contacts at the coil side posts.  The backfire proves you have fuel
and it made it through one or more cylinders without being ignited.

Ed

On 7/27/05, Beatty, Robert <BeattyR at ummhc.org> wrote:
> Patient is an 89 early model (MC-1) us spec 200 tq sedan, its chipped but I
> haven't verified if its QLCC or one of the tuners chips.  Its not the
> resistor/zener mod.  It also has a bypass valve.
> 
> Problems are bucking and afterfiring at all rpm ranges.  When problem 1st
> occurred I did some looking around and found a leak at the throttle body
> which I had replaced previously.  I corrected the leak with a new gasket.
> The bucking actually caused the downpipe to crack because the main exhaust
> system mount was broken.  I rebuilt the mount and swapped out the downpipe.
> In the process, I cleaned out the air filter chamber and the air metering
> plate of dirt and other accumulated crap.  I accidentally cracked off the
> vacum fitting to the deceleration valve, and since I didn't have another
> handy, I simply plugged its port in the U-shaped boot on top of the air
> meter plate and removed its vacuum control line from the layout.  I also
> found the bucking had torn the elbow from the turbo to the metal pipe coming
> from air cleaner assembly.  I replaced this as well.  Verified integrity of
> all of the hoses in the intake path with the exception of the IC itself.
> 
> No codes in ECU either.
> 
> So now at all RPM ranges and under load or not, the car bucks and spits fire
> (which if intentional would be cool, but its not.. heh).  I tried changing
> out the distributor cap/plug wires and all 5 plugs hoping that was it since
> its acting KIND of similar to bad wires when wet.  No difference.  Looking
> through the manual in the troublshooting, it suggests various fuel pressure
> problems causing this type of scenario and since I dont have anything to
> measure fuel pressure with, I haven't really gone down that path yet.  So
> currently I'm stumped.  I was thinking of changing fuel filter, fuel
> distributor and anything else I had spares of in a vain "shotgun" attempted
> at troubleshooting, but I would prefer to narrow things down if I could.
> 
> Briefly looked over SMJ's site, didn't see much that I didn't already know
> or try.
> 
> Anyone got any ideas?
> 
> Thanks!
> 
> Rob
> 
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