All cylinders misfire, chugging, rich.... - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 10-30-2007, 06:45 PM   #11
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...it'* amazing how good the car actually runs with the SE pcm...

The issues I've been having were not due to the PCM (they are fixed now, re-read my above post?)

The stock PCM also ran the Series 1 supercharged great.
The SE PCM isn't running an entirely different motor by the way, same motore, just boosted. That'* like saying I'm trying to run a V8 with the PCM, now THAT'* an entirely different motor.
I understand the PCM is restricting it, don't get me wrong, but none of my (major) problems have been due to the PCM.

I had an electrical issue with a broken ground. Bad plugs/wires. Bad injector(*)...but never a problem with the computer causing malfunctions.

Although when I first put in the Series 1 supercharged, a lot of guys who "knew what they were talking about" said it wouldn't even run with the stock PCM...2 years later...

I've compared videos of those with beefed up cars on here and must say mine is as fast as most, faster than a few, but slower than those who have very very evil cars (...yours is one of those evil cars if I'm correct).

Anyway, yea, I know the SE pcm isn't what we would call the best choice, but considering this project was built up from a scrapped car, I'd say it'* pretty damn impressive...don't worry - a new PCM is coming soon. If anything, a stock SSEI would do...yes, I do have one of those too but it'* for a 99 ssei - it won't run my transmission.

Any suggestions on a good aftermarket PCM?
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Old 10-30-2007, 06:59 PM   #12
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INTENSE is the PCM of choice here, I don't think you will find any arguement on that
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Old 10-30-2007, 07:59 PM   #13
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After you put the new SC on, it ran great. Then it began to misbehave. Your scan showed all cylnders mis-firing. I'm guessing that'* due to fouling of the injectors due to the rich mixture caused by the stock PCM. Hopefully, this will be cured with the correct PCM.

But you also mentioned fuel. On our cars ten years and older, you really have to pay attention to filters, fuel pumps, fuel tank corrosion, etc. Especially, if you run low or out of fuel, debris and air bubbles can come in and wreak havoc. May not be the case for you, but something to keep in mind.
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Old 10-31-2007, 05:12 AM   #14
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I didn't even know an l36 pcm would run an l67 due to the small differences in design. I wouldn't think it'd even know how to start it upr. Isn't the trans different, too? Surprised shifting isn't goofy.
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Old 10-31-2007, 10:09 AM   #15
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Ok..so you have the 97 4T60 trans and the SC'd motor.

I haven't looked at the various tables etc..but you would most likely benefit from getting the correct engine control tables in place.
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Old 10-31-2007, 12:58 PM   #16
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I have a 974t60 trans and a 2000 Series II L67 motor being run by a stock 97 SE PCM...it'* a hodgepodge that actually works...

Shifting is fine because the 4t60 doesnt' rely solely on the PCM to shift it via-tables, rather, it incorperates the need of load to shift - it'* the stepping stone between cable shift and electric shift...sort of a hybrid.

But yea, I'm aware it'* not running at full potential. A new pcm will get all my tables to their proper set point(*), but for now, it runs like a champ.

Slug - I'm not sure your analogy makes sence to me...the fuel injectors are run on a set range. Their job is to put fuel to the cylinders, and how much/frequent, based on the cal of the PCM. I'm not sure the injectors would be "fouled" by this, seeing as they only deal with fuel....spark plugs can be fouled because of a bad mixture, but I don't believe injectors can...they can cause a bad mixture though...
Someone else comment on that - I may be confused.

My fuel pump/filter were replaced a couple months back - the fuel tank looks like new for being 10 years old. I'm not concerned with anything back there being the issue.


Anyway, I do plan on getting an Intense PCM - it'* only logical that since I have a lot of work done internally to the engine (ported, polished, beefed up), I might as well have a good computer running the silly thing...

By the way, this is probably the best car-oriented message board out there...I've been a member for a long time under a different name (didn't post much, just read), but this place rocks...

Thanks everyone
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Old 10-31-2007, 01:32 PM   #17
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You cannot run an INTENSE PCM with your setup. I believe they will tell you they don't support the L67/4T60 combination. I may be wrong on that, but it'* something to check on.

So you have a non-HD 4T60 trans under a Series 2 L67 running off an L36 PCM.

I smell all sorts of problems. Most notably the durability of the wrong trans, and the MAF/AFR tables which aren't calibrated for the flow of the L67.

You have a mess on your hands. Until you get CONTROLS right, we can't help you much with your problems.
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Old 10-31-2007, 02:25 PM   #18
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Quote:
Originally Posted by willwren
You cannot run an INTENSE PCM with your setup. I believe they will tell you they don't support the L67/4T60 combination. I may be wrong on that, but it'* something to check on.

So you have a non-HD 4T60 trans under a Series 2 L67 running off an L36 PCM.

I smell all sorts of problems. Most notably the durability of the wrong trans, and the MAF/AFR tables which aren't calibrated for the flow of the L67.

You have a mess on your hands. Until you get CONTROLS right, we can't help you much with your problems.
Actually he could run on a custom INTENSE PCM. Most likely it will be along the lines of what was suggested for justav6 recently. An L36 pcm for starters with the L67 information updated into the appropriate engine control tables. Leave the transmission alone and all is well. HP Tuners, which INTENSE works with has support for 1997 Bonnevilles. PDXGTP uses HPT to assist BigNews in tuning his car.
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Old 10-31-2007, 02:52 PM   #19
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Quote:
Originally Posted by blazingranny
Slug - I'm not sure your analogy makes sence to me...the fuel injectors are run on a set range. Their job is to put fuel to the cylinders, and how much/frequent, based on the cal of the PCM. I'm not sure the injectors would be "fouled" by this, seeing as they only deal with fuel....spark plugs can be fouled because of a bad mixture, but I don't believe injectors can...they can cause a bad mixture though...
Again, this may not be the case with your engine, but this is how injectors can be fouled by a rich mix:

An engine'* intake valves can never seal perfectly. If you're running rich, you're generating incompletely burned fuel (well, you're always generating some, but now more than usual). If there'* enough incompletely burned fuel, you can see it from the exhaust in the form of black smoke, or soot.

Some of this soot inevitably can back up into the intake manifold for the reason mentioned above. It then can deposit on everything, including the injectors. Modern gasolines now contain fuel injector cleaner additives for this as well as other reasons. But sometimes it'* inadequate if there'* too much deposit, or too much crud that'* come into the injectors.

You can always find a little "soot" in the intake ports when you open up the intake of an engine that'* been run for a while. And it'* coming from the combustion areas.

Good luck on your car!

(edited -- the technical term for this, I believe, is "blow-back" [different from "blow-by"])
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Old 10-31-2007, 02:54 PM   #20
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I'm wondering how the heck your L36 PCM is giving your L67 engine enough fuel...
I'm also, like Will, wondering how long your non-HD trans will hold up...

Anyway, I agree with Bill that a re-programmed PCM could be made to work with this setup; however, I have one big concern: It is virtually impossible that a mail-order PCM will get your MAF table just right for your modified TB...close, maybe, but not perfect.
(To properly tune your "one-of-a-kind" modded TB, you'd need a tuner, or perhaps a dyno tune at the vendor).

If you were to go with an unmodified post-less L67 TB (or a Northstar, or some other TB with a known calibration curve), you'd have much better luck with a mail-order PCM.
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