RPM oscillation under load [Archive] - GrandAmGT.com Forum

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BrittsBen
04-03-2013, 09:47 PM
I'm back with another problem (go figure). When going up hills on the freeway this evening we noticed the RPMS fluctuating 1 to 2 clicks at a time(usually from like 2200-2300 or 3000-3100). It seemed to do it whether we were creeping up mountains at 50 or railing on them at 70-80. The trans was bucking pretty badly when we put it into gear but after all the work I did this week that went away. This problem seems to be new though as with all the stuff messed up, it climbed the mountain just fine. I'm thinking TPS, IAC, MAF, or some weird transmission/torque conversion related issue. Anybody ever come across this before? Thanks in advance for any insight.
Replaced the trans mounts, map sensor, map vacuum harness, fuel pressure regulator, and IAT wire (was cut). The car came with a ghetto CAI installed that I'm highly suspect of.

Fireball
04-03-2013, 11:06 PM
Hmm.. I have a similar issue and have never come to a head on it.
with it only fluctuating ~100 rpm it's not the torque converter locking/unlocking...

Could be the MAF? Possibly the crank sensor? Mine got a lot better when I changed that (until it went bad again thanks to headers :) )

I have no definitive answer unfortuantley..

BrittsBen
04-04-2013, 01:24 AM
Which one did you change? The CAT has been deleted but it never gave us issues before we put the new MAP, and FPR on.

Fireball
04-04-2013, 11:22 AM
the one near the crank pulley..?
Needed a re-learn after... not sure if it's a sure fix but it's like $20-30 minus the relearn (which doesn't necesarilly need to be done I think?)

BrittsBen
04-04-2013, 01:13 PM
I will definitely keep that in mind and thank you so much as this forum isn't quite as active as it used to be (most of the tuners graduated to bigger engines and sleeker rides and then new sites). I discovered a disconnected vacuum hose (hoping I just overlooked it before and didn't just now disconnect it and then reconnect after tugging on some wires). It was the tiny little vacuum hose that leads back into the wiring harness by the fuse box so we'll go for a mountain run and see what happens. I'm hoping for the best cause in 6 days we will be attempting to drive across the country lol.

BrittsBen
04-04-2013, 08:04 PM
Still does it, seems less noticeable at 3000 rpm. It's almost as if I can feel the car rocking back and forth as it slightly speeds up and slows down while keeping my foot at the same throttle position.

BrittsBen
04-04-2013, 08:34 PM
I'm going to try the "ask experts" if I get worked out I'll report back should anyone else ever have the problem.

Fireball
04-05-2013, 03:39 AM
Thanks man, sounds good.
I noted mine doesn't do it under heavy throttle or at low rpm!

sleepyalero
04-05-2013, 04:33 AM
ive had the same problem rpms will jump back and forth under load, after i got my 6 speed it was gone. i figured it was the TC

Fireball
04-05-2013, 08:53 AM
I guess it's possible..
I think I've ruled out the TC as it does it (when it was at its worst) in any gear whether the TC was engaged or not.. I also feel that it's not the tranny as mine will spin to 6k rpm and not miss a beat with the shift...

It's one of those pain in the arse issues that has been a nightmare to try and figure out...

sleepyalero
04-05-2013, 09:19 AM
swap tranny ;)

BrittsBen
04-05-2013, 12:59 PM
Ok so the experts had some interesting stuff to share. They thought maybe a lock up solenoid on the transmission. Said a way to tell if this is the culprit is to barely tap the brake pedal while climbing, hitting the brake will engage(disengage?) the lock up mechanism. However I don't think this was my problem (paid the dude anyways since I'm a man of my word). I cleaned the MAF, adjusted the filter on the CIA (it was all the way up on the neck restricting flow by having the pipe inserted halfway into the filter) and most importantly imo replaced the ground terminal (the damn thing literally slid off the ground wires). I start assuming the worst with my lemon only to find out it's small little gremlins (sigh of relief). Thanks to the various members both current and present as I've read so many different pages on here the last few days. It's running like a throat singing champ now :)

Fireball
04-05-2013, 06:44 PM
Nice so it doesn't do it any more?
Another way to test is to drive it in "3" (just for a little bit).
the converter doesn't look up in 3. However since the issue isn't present at higher RPMS you need to be at a speed that's ~2-3k rpms.

Perhaps it was the MAF? Either way, good to see it fixed!

Fireball
04-05-2013, 06:50 PM
Nice so it doesn't do it any more?
Another way to test is to drive it in "3" (just for a little bit).
the converter doesn't look up in 3. However since the issue isn't present at higher RPMS you need to be at a speed that's ~2-3k rpms.

Perhaps it was the MAF? Either way, good to see it fixed!

BrittsBen
04-06-2013, 12:08 AM
It is very possible, from what I've gathered given the nature of CAI they are dirtier especially when using cheaper filters (i.e. ebay type CAIs). Whoever put this one on the car before we had it literally didn't even take the time to make it fit right which makes me assume the car didn't have an intake and this was a quick universal fix to get it sold. The filter didn't fit the straight pipe properly thus didn't make a seal (filter was slightly too small) so I shaved on the rubber mating inlet like hell to make it fit causing the filter to go on too far and causing small chunks of plastic that my banging missed to get sucked past the MAF, on top of the small dust particles I likely created during the hacking. I plan on getting a nice brand name cone type air filter for it and if the issue returns I shall do a big 3 upgrade to alleviate voltage gremlins and add a new MAF. I'm just tired of firing the parts cannon and need as much of a bubble as possible financially lol. She's running tip top though aside from a squeal/squeak when the wheel is turned more than a quarter or so and at low speed (i have a hard time making 90 degree turns at high speed anyways lol). Time to do more research.

Fireball
04-06-2013, 06:59 AM
I hear ya, I've had the urge to just start replacing a bunch of things and to see what happens! lol