UPDATE! MISFIRES, SURGING, AND HESSITATIONS!

[shortstuf212559]

1990 SSE

NEW ICM/ Coils (the newer style with the seperate coils)
NEW plugs and wires (AC DELCO brand)

car is hessitating hard from a stop, and backfiring out the exhaust. also surging and misfiring when in lockup.

i just replaced the Harmonic balancer yesterday and it was not doing this before i replaced that. could i have done something wrong?

[Jrs3800]

Did you replace it with a new balancer?

[shortstuf212559]

yes, put on a new balancer

[shortstuf212559]

also, it is idling around 1000 to 1200 in park, idles at 1000 in drive. (according to the tach) it was idling much lower prior to the HB replacement.

[chemicall]

The high idle would first point me towards vacuum line leaks. Check for any disconnected, cracked, or if they turn to sut in your fingers then they are bad. Sometimes an old line can just become disconnected(its happened to me), and cause surging and bad/high idle.

If you put the car in drive, hold the brakes good, and floor the gas, this loads the engine up, does it sound normal? or does it spit/sputter? If it spits/sputters I would make sure of proper gap on the plugs, and no corrosion within the coilpack. Also if it spits/sputters under load it would be a good idea to test the primary/secondary resistances of the coils.

Here is how to test the resistances if need be; http://www.pontiacbonnevilleclub.com/fo ... =48&t=1683

[shortstuf212559]

i put new vacuum lines on last year, and i checked them all over again. all are fine.

the coils and ICM are all new. i swapped it out with another one(older magnavox style) and still ran the same way

car spits and sputters only under 1500 rpms.

will barely stay running at idle when coming to a stop in drive. almost stalls when puting into gear from park. alot of vibrations and surging at 45-55.

plugs are new, and gapped at .060

also fuel pressure is at 40psi and stays pretty constant between 38-41

[myfirstbonnie]

When was the last time the MAF, TB and IAC was cleaned?

[wjcollier07]

I'm thinking MAF. Do you have a code 34 SES light by any chance?

Mine had about 5 different codes, all of which were triggered by the bad MAF, which was only one of the codes. They ALL went away with that replacement.

Can't hurt, just grab another with the same code (from the same year) out of a junkyard. Even one from just another LN3 will work fine, I know I used one from a 90 on my 89 and got no difference.

Also, it could be your TPS as well. I went on a wild goose chase with all those codes, which IIRC, included a code 21, for TPS voltage out of range. Make sure your TPS is at (IIRC) .45v with the throttle plate closed. You'll have to check this with a scantool or with a voltmeter probed into the sensor plug. Both of these things directly cause the problems you're experiencing.

[shortstuf212559]

i swapped out the IAC, MAF and TPS with ones from a known good running car. so its not any of those things

computer shows no codes at all.

i cleaned the TB yesterday

[RJolly87]

Is it possible that the rings on the back of the balancer that the crank sensor reads are differant on this one? Perhaps even damaged? Is it hitting the crank sensor? We all know that crank sensor issues don't throw codes, but usually result in stalling/no start conditions. thoughts?

After all, we are assuming that the harmonic balancer that was put on was the correct one for the car.

[shortstuf212559]

its a GM Brand one.

could a leak in the exhaust be causes this? there is a hole in the muffler causing a louder'ish exhaust

[shortstuf212559]

well got a new fuel tank, new lines, and new cat and muffler. still has a bad hessitation from a stop, and surging/misfiring above 45. i only get the misfire/surging at low RPM's once the TCC kicks in. I'm at a loss....

[RJolly87]

Were the ICM and coils done at the same time of the harmonic balancer? Or was the car running fine before?

[shortstuf212559]

i replaced the plugs and wires prior to the harmonic balancer. i replaced the ICM after.

its really hard to say how the car was running prior to the harmonic balancer replacement. the balancer was so bad the car would barely stay running. (it was extremely loud) also the car sat for 9 months after failure of the balancer before i put it back on the road and replaced it

[shortstuf212559]

anyone? *bump*

[bs009]

could a bad crank sensor be the cause of this?

[shortstuf212559]

i havent replaced that, anyone know if this is something that could cause it?

[shortstuf212559]

UPDATE: i noticed something i hadnt before, the TACH is jumping around like crazy in park idling and when driivng. it isnt anywhere near what the engine is actually doing.

[myfirstbonnie]

How many miles are on this car? Do you notice it hesitating or surging on hills or down grades?

Check the coils by the techinfo section and take a look at the crank sensor. It is actually adjustable and needs to be centered on the rings around the balancer. They make an expensive tool for this alignment, but most people just eyeball it. Some have even used a feeler gauge.

Also, if you have access to a fuel pressure gauge, see what the fuel pressures are at idle and if possible extend it out far enough to be seen while driving during the moments of hessitation. Another thing to check is the fuel pressure regulator on the fuel rail. They are fairly cheap if you want to go ahead and replace it. One bolt and a good tug and it is off.

[RJolly87]

UPDATE: i noticed something i hadnt before, the TACH is jumping around like crazy in park idling and when driivng. it isnt anywhere near what the engine is actually doing.

1 of 2 possibilities. Either something is up with the cluster, or something is up with the ICM...