Update:

I had the car out on the interstate on Friday during some unusually warm February weather (almost 60 degrees). I had just gotten the transmission fluid changed on Wednesday, and the car ran smooth as glass for my whole trip back home. Not once did I experience any kind of surging or hesitation. I'm starting to think the Intense PCM had the effect I was hoping for. With the stock computer in the car I had experienced multiple occurrences of surging during 60-degree weather last November, and the only thing that has changed since then is the addition of the Intense product. The motor/tranny pulled strong up several hills while in overdrive, keeping the car at the same cruising speed without downshifting. Needless to say, I'm very pleased with my findings so far. I'm not going to declare anything for sure yet, but it seems that whatever Intense modifies in the tranny/torque converter parameters fixes the problem in the stock PCMs. I'll do some more digging and find out what the differences are.


EDIT: By the way, is it possible for an Admin to change the title of this thread so the word "Bonnaville" is spelled correctly? It'* no biggie... just a little bit of an eyesore.

Tried ignition fixes and trans flush simultaneously. No help. Also if there'* an ignition miss while the TC is engaged you wouldn't see a 200-500 rpm jump. An ignition related chuggle at highway speed with 4th gear/TC engaged can be felt but won't be seen on the tach. A 500 rpm jump corresponds to a large speed difference on the tall geared Bonneville. A 200-500 rpm fluctation caused by ignition issues would correspond to huge speed differences to cause whiplash or seat belt bruise marks.

If there'* a chuggle and no big rpm jump it'* ignition or other stuff.

If you feel a surge/chuggle and you see a 200-500 rpm difference, it'* the transmission TC unlocking/locking.

A local trans guy explained that these higher mileage 4T60-Es have some added clearances between the accumulator and accumulator bore. On hot days, there'* some leakage between the bore and accumulator causing the TC to lock/unlock. Does this make any sense? I don't know transmissions to know. This explains why it happens on older transmissions and it explains why some after fluid changes/flushs notice some improvement due to different fluid properties of fresh fluid although I didn't notice any difference.

I am contemplating rebuilding the valvebody. But interestingly after fall of 2004, it has never done it again. Anybody notice such intermittency?

I know that intense does not modify any of the TCC routines on their Standard PCMS (I talked to Scott Cook about this -- I have a standard PCM on my 97 n/a). I had the same problem you had, replaced the transmission, and now do not have a problem. I had the TCC shudder/chugging intermittently, and it always ended up coming back.

my car also surges only at idle and sometimes when i step on the gas it hesiates alittle (like turbo lag) then i give it some more gas then it like downshifts and goes, kinda wierd, other wise the car runs well, i did a complete tune up only thing i haven't done is replacing the wires, cleaning the maf senor, iam thinking it may be a mass air flow problem or maybe a TPS sensor?, has anyone cleaned up their mass airflow sensor and solved their surging problem? would a TPS cause something like this?






1995 bonneville se, 192,500 miles

zo6, it sounds like the problems you're having are different than the problem I'm referring to. There are definitely different symptoms that can be described as "surging," but I would refer to your problem of "turbo lag" as bogging, rather than surging. I'm not sure what would be causing your car to hesitate under light throttle. You should certainly try cleaning your MAF and replacing your wires, because those are relatively cheap, easy things to do and they get some of the no-brainers out of the way. Just make sure you use electronics cleaner on the MAF, and keep it away from harsh stuff like carb cleaner. You don't want to damage that sucker.

In reference to the TC surging issue, would the increased line pressure of the Intense PCMs have anything to do with their effect on the surging problem? My car hasn't surged once since my installation. Maybe the weather hasn't been warm enough to tell whether it'* cured or not? I'm just throwing out ideas here.

If your 97 is naturally aspirated (I'm not a bonneville trim specialist, SE must be 3800 series II n/a), then it has the 4T60E. The 4T60E is hybrid hydraulically/electronically controlled. Line pressure is regulated via VACUUM-REFERENCED HYDRAULIC means. The computer DOES NOT control the line pressure. Therefore you could not program the ECU to increase the line pressure even if you wanted to! The Intense Standard PCM changes the shift/kickdown points on a 4T60E but your line pressures are still stock right now!

Argh.... I totally overlooked that aspect. Thanks for pointing that out.

For the record, I still need to check my RPO codes to make double sure I have a 4T60E. There was some speculation that maybe the late model year '97 NA models got the 4T65. I checked my tranny pan, but there was nothing stamped on it to indicate its identity.

There'* a REALLY easy way to check if you have a 4T60E (likely if you had/have TCC issues) or a 4T65E. Only the 4T60E will have the huge vacuum can on the front for the line pressure modulator.This is located on the airbox side of your engine compartment, on the transmission, facing the front of the car. It'* big -- like 3" long and maybe 2.5" diameter, with one vacuum line going straight in the top side.

I'll check it tomorrow if I remember.

Hehehe, well it'* been a while. I've verified the 4T60-E, and I think I've also verified the definite source of my surging problem. I took the car out for a scan yesterday, and drove it VERY hard on some winding back roads. After about ten minutes of high speeds and WOT acceleration runs I'd had enough and headed back to the highway. Wouldn't you know it, the thing started surging in a terrible way. Uphill, highway speeds, TC lockup, the surges were ~400rpm and extremely obvious. The tranny must have been way too hot. But after about 20 minutes of easy driving on the highway and city streets it cooled down and the surges totally disappeared. I let the car sit for about an hour and a half to cool down even more, then drove 3 hours of interstate on my way back to college. It didn't even surge once.

If all I've done is confirmed the need for an auxilliary cooler on the 4T60, at least it seems to be an obvious diagnosis. I think this is pretty good evidence of troublesome heat buildup in the tranny/TC. I'll be adding a cooler without a doubt. Let me hear some of you guys' thoughts on this one. BTW, I'll also be posting my scan results in a different thread for help with the "interpretation."