I have a question, with the stock 1998 pcms in the fbody's. Are the stock untuned, pcms failing at a good rate, or is this all heresay? I have heard that everyone stays away from the '98 fbodys because of this and I do see quite a bit for sale online. Will retuning a stock '98 pcm cure the issue or is it the pcm of that year itself? Would really like to know if anyone has an answer this question. Thanks.

 

I can't tell you for sure, but that is what I've heard also. My tuner blames my shitty idle on the computer being a 98. He'll tune it and it runs fine. For a day or two. Then the fun begins. It'll start getting a real bad lope at idle especially when cold. Then, putting it in drive elicits a choked down engine response and it dies. Just great. I've had him redo it 4 times. Everytime, it's fixed for a couple days. Then it starts back up again. So, I don't know. But I'm leaning towards it being correct.

 

I would lean towards hearsay.

 

Ive had lots of wierd issues with mine but its consistent. I do believe quality tuners have no issues but they are just more difficult to tune.

 

I still use the original PCM on my 98 TA and have literally flashed it countless times without a problem.

 

You can certainly get them to do what you want, but that doesn't mean that it's not ok to hate them at the same time

From my end, besides a little extra time involved, after tuning piles of 98s in cars and many in swaps, there are all of these stupid little things that are unique to 98s. P0121 has caused people to rebuild trannies thinking they were at fault because when it sets in a 98, the trans can act in several foolish fashions such as just leaping through the gears, refusing to downshift, etc. The default setup for a failed MAF in a 98 is full trans line pressure (ugh). At about 10.0 VDC at the PCM, the IAC just STOPS... falls out of closed loop and just stays at whatever value it was last at when the voltage dropped. If it dies high, at least you idle. If it dies low, the engine dies at closed throttle. The have miles and miles of false knock and you have to use a dyno to see what is real and what is not... Etc.

 

Damn I need to get a new pcm. For F/I especially. Either my tuner sucked or my pcm needs help, because he couldn't tune out the surge on my 232/240 G5X2 below 1800 rpm. Kinda lame for a mid size cam IMO.
I've got a stand alone 98 fbody conversion harness on a 2000 346 block. Do I just need to get a newer pcm and repin it? OP-Sorry for the hijack.

 

Are the pins different if say I have a '98 TA 6m and and I have a computer or get one out of a '99 with the same options. This is all hypothetical, but looking at possibly acquiring a '98 TA 6M, and I don't want issues, even though its bone stock (its for my dad. I want him to have something good here and no issues).

 

It's all hearsay I do believe. I know for a fact that they are a bit harder to tune than the 99-02's but can be done. They just take some patience. Mine has been tuned and reflashed several times as well and never an issue. The only way I'd consider swapping over to a new pcm is if I was doin a rebuild and was goin FI just for simplicity of tuning. I agree with frost on the tuning also. Alot is different on the 98 pcm's but very tuneable. I wouldnt hesitate to buy another 98 if given the oppurtunity.

 

Man there is something about that X2 cam though... I have had it tune very easily in a car or two, and it has been a memorable PITA in one or two as well. There is something about cams in that size area... The trouble in the end is finding a balance. If you get rid of all of the buck, you end up removing so much airflow from different places that it impacts return to idle (while moving, not sitting still) and causes some dips. You get rid of the dips and the buck is back. It's a fine line and that line is usually easier to find in the later model PCMs. There is some irony to the fact that many people pick 'mid sized' cams (232-234deg of intake dur and 112LSA's) because they think they are retaining driveability vs something larger. Some of them are cake, and some of them want to buck and jerk and act the fool (require more time and knowledge to get straightened out). I have had an X1 car or two that was also a pain and it's even smaller. The X1 cars also had heads, so DCR is up as well. ALL of the X3 cars are actually easier to tune and easier to get rid of the issues such as bucking/dipping when goes against the grain of conventional thought related to driveability. The smaller grinds of course make more tq down lower and in the middle than the X3.

Sorry for the ramble, just relating past experiences.

 

Why would my car be fine for a couple days and then go back to the huck and buck? It makes no sense to me whatsoever. You'd think if it was fixed, it'd stay fixed. Oh well. I've just about learned to live with it by now. Just kind of sucks. And I went with a baby cam to retain driveability. 224 224 581 lift on a 112 lsa. Its a comp cam.

 

It shouldn't; not with that grind.

Do you know notice that it follows outside temps at all? For instance, when cold out you get more buck and when hot less or vice versa?

 

Not really. It goes by the amount of time after its been tuned before it goes to total ****. I know the guy who's doing it is doing it right. Because like I said, it runs fine for like 2 or 3 days. Then it just goes bad. Its crazy. Idle becomes erratic. Hitting and letting off the gas elicits the rpms to drop to less than 800 and then bounces back. Its just crazy. I'm swapping to a T56 soon and I have a feeling that will help. I hope so at least.

 

Well it's either in the tune or in the physical setup, but you certainly don't need to swaps trans to help the issue. Bucking is worse in M6 cars because of the constant direct coupling of the drivetrain. The tq converter itself covers up many cam problems while it's unlocked.

 

Well, I'm not swapping because of tuning issues. I'm swapping cause I HATE AUTOMATICS. I shouldn't have bought the car but I got a good deal on it and always wanted an LS1.

 

I like the 98's, But as others have said, They are a PITA to tune when you do major upgrades.
I had a similar issue with my 98 Z with a 403 LS2 Stroker when tuning it. Ran great for 3 days and then went to total $hit! After EXTENSIVE tuning, Chad at GLM got it straightened out for me...
My brothers 98 did it too!

Some are ok, some are a PITA!

James

 

I was able to eliminate this problem by downloading the kncok sensor files from a 2000 bin into the 98 PCM & then dampening the sensativity a bit. Before doing this, that bitch would pull timing any time a bug splattered on the windshield. Not really, but, could have been the case since it was mostly due to false knock.

 

'98s do have crappier knock sensors and prone to
degrade. Possible that even cold clatter could bug
them.

The worst thing about '98s is the number of different
OSes out there, all cross-incompatible. Easy to ruin
one by writing the wrong data file to it.

As to why so many are out there, think about what
model & year is going to the most affordable to your
high school aged "tree seeking missile" sort of kid....

 

Very true, I've tuned a couple of 98's that would get 4* of KR for no reason

For the most part this doesn't affect many people other than those wanting to go to a custom os...personally when I was tuning I never needed to change the operating system to it never affected me and for the average user likely would never affect them either.

lol very true

 

the 98 pcm is rock solid, the 2 bar sd tune raped mine though, after a few writes (and only 1 file on my computer as this was the only car i was tuning with that laptop) it threw a code... i upgraded to a 2002 ecu, 2 hours rewiring, never gonna look back, ever.