Shuddering in 2nd gear under boost?

[z284pwr]

Now that most of the running problems with the TGP are taken care of, a new one has arisen. In 2nd gear, and 2nd gear only under boost ~7psi or higher up there is a bad shuddering, not like shaking from speed or suspension, but power related. Its totally fine in every other gear except 2nd and only under boost. It gets somewhat better when its not as warm outside, but still does it. It also seems to smooth out alot on top end of 2nd gear as compared to middle, and it doesn't seem to be load related or anything because it doesn't do it at all in 3rd gear it feels like.

 

This problem started after we replaced all these:

New Injectors

New Plugs/wires

 

I had a problem like this after we broke the EGR tube, but replaced it with another one and it seemed to fix it, and there is no signs of any gross stuff coming from it, or any exhaust leak. Oh, and this problem also arose when one of the plug wire's boots came off the conductor, hence why we replaced them, the old one worked fine when I pushed the boot on good and hard, but when it came loose it did it. I have checked all the wires and they all feel nice and tight on the coils and spark plugs, so I'm at a lose. Oh and datalogging it shows no signs of anything bad happening or out of place or odd looking?

 

For more info....

This is a built "3.2* Engine, basically custom everything, FAR from stock

Jeff M Crossover and TopGun 160 Chip

All new sensors, new AC-Delco Plugs and new wires

New Full 2.5" exhaust all the way back

 

Oh yeah, it gets shitty ass gas mileage if I'm lucky 15 MPG 50/50 highway/city with conservative driving. Oh oh yeah, I don't even want to get into how terrible the off idle/bottom end is....

 

Anyways, if anyone has any ideas I'd appreciate them, luckily the car gets driven very often now so I can take it apart if needs be.

[DaveFromColorado]

I'd assume it's an automatic

 

with that in mind, I'd say that the second gear clutches are starting to go out - you step on it - provide boost, extra power, and the clutches can't hold it anymore.

 

without going for a test ride/drive it's really hard to figure out drivability problems.

 

--Dave.

[OldSkoolGP]

With a screen name like Z284pwr, he could have a manual. If it is a 5 speed, that's really odd. All I could say is if you did new plug wires, double check and make sure they're snapped on good. I don't think your injectors could be a problem. Also check for arcing, especially if your new wires are routed any differently.

[z284pwr]

With a screen name like Z284pwr, he could have a manual. If it is a 5 speed, that's really odd. All I could say is if you did new plug wires, double check and make sure they're snapped on good. I don't think your injectors could be a problem. Also check for arcing, especially if your new wires are routed any differently.

 

The screen name has nothing to do with anything about these cars actually, was the license plate on my dad's '79 Z28......

 

Anyways, I'll check the arching thing, I don't think they would be but its worth a shot....

 

It is an automatic, the previous owner had it rebuilt *i thought* I'll have to check into that, it would really suck if it was the trans....I may consider a manual swap then, a trans rebuild is ugly, and this car needs all the help it can get off the line. :x

 

Anyways, thanks for the ideas, I'll just hope its not the worst....

[RareGMFan]

It almost sounds like you're hitting the fuel cut-off (the Jeff M chip will do that stuttering/vibrating type thing when you hit too much boost), but why at 7 psi, and why only in 2nd gear, I can't say. Mine's vibrating horribly right now anytime I push it beyond half throttle. Sometimes worse then others, but it's been doing it all the time for the best 3 weeks, or so. But of course, I have a number of SES codes on. I don't know if it's really a tranny issue, considering the idling issues, and poor gas mileage you're getting. No trouble codes?

[FastSE2DR]

boost leak...

[z284pwr]

boost leak...

 

Why only in 2nd gear? It should get worse with more load right....oh and we have a pressure tester to....which shows no boost leaks?

 

It almost sounds like you're hitting the fuel cut-off (the Jeff M chip will do that stuttering/vibrating type thing when you hit too much boost), but why at 7 psi, and why only in 2nd gear, I can't say. Mine's vibrating horribly right now anytime I push it beyond half throttle. Sometimes worse then others, but it's been doing it all the time for the best 3 weeks, or so. But of course, I have a number of SES codes on. I don't know if it's really a tranny issue, considering the idling issues, and poor gas mileage you're getting. No trouble codes?

 

This one, possible, I can throw the stock chip in and see if its chip related. No SES codes, idle is "better" than it used to be, but if you hit the throttle just right, it stumbles very bad, and yeah, its faster off idle at 1/4 throttle than at WOT throttle

[Garrett Powered]

when my tranny band broke in my automatic, it was in first gear and it would shutter like that. and it would still drive around, just strip out easy like a 12 point socket. Dont know if you broke your 2nd gear band or what? Hope not.

I could tell you if I drove it. Does 2nd have a band like 1st gear?

[z284pwr]

Well is what I don't if it is the trans, how come it would only do it at the beginning of 2nd gear? After about 4300 or so it goes away and it normal? I forget what the trans shifts at but it is only in the shuddering range for a little bit of 2nd gear, but once it gets into 4000+ or so RPM it just goes away and it fine? I dunno, I'm not an automatic expert so I wouldn't know if that would be a sign of it or not.

 

The boost leak idea, I dunno, I put the pressure tester on it and it seems fine, how long should it be able to sustain the pressure? After a bit it slowly bleeds it off maybe that is a boost leak? Then the next question is, tracking down where it would be since all the vacuum sources come from the same spot right by the TB which would be the only place its possibly leaking

 

Oops, here is an edit....This may not be related, but it does a real good job at puffing out black smoke on start up, and accelerating on the freeway/highway it leaves some killer black smoke.....*rich as hell*

[FastSE2DR]

it should be able to sustain it as long as you hold it...

[TurboGTU]

I"ve read somewhere that different O2 sensors read differently for differen setups...I think it was radioshack engine book???? I'll search my docs..

 

But anyway..differnt O2s read differenly at different temps and pressures. Some get distroyed by pressure or too much heat. So if you don't have a OE TGP O2..you might be asking for it. I know mopar guys switch back to OE after they used aftermaket (Bosch)...replacement O2s. Like the ECM doesn't like it.

THis could be related to too rich of a mix.

Low lowend power and rich mix can also be your cam if its a aftermaket cam made for a carb setup. EFI cams have little overlap and lots of lobe seperation. If you have a weak idle vacume..the ECM will think its stalling and add more fuel and open the IAC up, mess with timming to bring the RPMS to scale. Jeffs Chip was tune for OE setups. SO ..your a whole other ball game...you need a one off if extensive porting work had been done and different cam has been used.

 

Also..the ECM doen't seem to like aftermarket injectors with the stock code/Jeff code. I think Jeff said 19lbs or 21lbs accels would be close to 22lbs TGP injectors. TDC (3.4 DOHC) injectors were the same I think.

 

Also..if it only does it on 2nd..and not in third or 1st..its not boost leak. If you had boost leak...it would show its ugly face badly in 3rd going WOT. It would sound like and feel like overly retarted timming (spark retard).

 

SO it looks like the trans is slipping to me. Whats the fluid smell/look like? Any particles on the dipstic? Thise trans should only use Dex II. Maybe III. BUt no V. ..as it slips too much with V.

If you do go the route of fixing it..Raybestos and Alto are your only clutch sources for GOOD clutches. Sonnax for hard parts. No cheap made in Japan crap here. If Jeff has some parts..that would be WAY better. As far as 5spds go..only the TDC trans..the regular 282 is a weak suck at best. I've seen a fiero using a NSX trans$$. Or WestCoastFiero trans$$.

Personally..im going to have mine rebuilt with "salt bath" or "nitrogen rich oven" induced hard parts with reds /with regular steels. This is my goal.

 

OH NO!.. :shock:

[TGPilot]

I remember when my TGP started to shutter in 2nd....I think it was about 1-2 weeks later and I was looking for a donor car for a 5-speed swap! :shock: 8)

[Garrett Powered]

After a bit it slowly bleeds it off maybe that is a boost leak? Then the next question is, tracking down where it would be since all the vacuum sources come from the same spot right by the TB which would be the only place its possibly leaking

 

Oops, here is an edit....This may not be related, but it does a real good job at puffing out black smoke on start up, and accelerating on the freeway/highway it leaves some killer black smoke.....*rich as hell*

 

Sounds like when it leaks out of the FPR if its not the tranny. my mechanic would always say that "thats your tranny slippin."

 

Vacu-tite! tee on the FPR. It leaks out in lower rpm s in 2nd gear under boost. between like 45-55mph.

[z284pwr]

I"ve read somewhere that different O2 sensors read differently for differen setups...I think it was radioshack engine book???? I'll search my docs..

 

But anyway..differnt O2s read differenly at different temps and pressures. Some get distroyed by pressure or too much heat. So if you don't have a OE TGP O2..you might be asking for it. I know mopar guys switch back to OE after they used aftermaket (Bosch)...replacement O2s. Like the ECM doesn't like it.

THis could be related to too rich of a mix.

Low lowend power and rich mix can also be your cam if its a aftermaket cam made for a carb setup. EFI cams have little overlap and lots of lobe seperation. If you have a weak idle vacume..the ECM will think its stalling and add more fuel and open the IAC up, mess with timming to bring the RPMS to scale. Jeffs Chip was tune for OE setups. SO ..your a whole other ball game...you need a one off if extensive porting work had been done and different cam has been used.

 

Also..the ECM doen't seem to like aftermarket injectors with the stock code/Jeff code. I think Jeff said 19lbs or 21lbs accels would be close to 22lbs TGP injectors. TDC (3.4 DOHC) injectors were the same I think.

 

Also..if it only does it on 2nd..and not in third or 1st..its not boost leak. If you had boost leak...it would show its ugly face badly in 3rd going WOT. It would sound like and feel like overly retarted timming (spark retard).

 

SO it looks like the trans is slipping to me. Whats the fluid smell/look like? Any particles on the dipstic? Thise trans should only use Dex II. Maybe III. BUt no V. ..as it slips too much with V.

If you do go the route of fixing it..Raybestos and Alto are your only clutch sources for GOOD clutches. Sonnax for hard parts. No cheap made in Japan crap here. If Jeff has some parts..that would be WAY better. As far as 5spds go..only the TDC trans..the regular 282 is a weak suck at best. I've seen a fiero using a NSX trans$$. Or WestCoastFiero trans$$.

Personally..im going to have mine rebuilt with "salt bath" or "nitrogen rich oven" induced hard parts with reds /with regular steels. This is my goal.

 

OH NO!.. :shock:

 

The O2 Sensor is an OE TGP sensor, we made sure of that when we ordered it, we do have another we that I can swap out that isn't one, just to test funciontality of the unit

 

On the engine part, the cam isn't a carb setup cam, it was a custom grind turbo spec cam with plenty of seperation.... *....http://home.earthlink.net/~z284pwr/beretta/cam_small.jpg* yeah I know its not perfect, the desktop dyno showed no loss in low end power, just gains on top end, which it definitely has. But yeah, I don't say this isn't causing bottom end power loss, or richness on bottom end, I'm sure it could have something to do with it, would you have any ideas on what timming *should* be, I do have the ability to datalog it like i said to check for that, I never saw anything out of wack on that part datalogging it. Idle vacuum is pretty good actually, its not much lower if any lower than stock. Porting isn't huge extensive, the heads were ported, lower intake, and the logs were port matched as well, but nothing crazy. Yeah I do probably need a one off tune, the expertise to do that myself aren't quite there yet and yeah, until I find what to do there, its kinda a JeffM chip or nothing.....

 

The injectors are GM spec injectors actually, the place said they were the same, I searched the part number on them and verified they were GM injectors, the size I couldn't figure out, the place said they were newer part number replacements, but who knows what they look up. If you say 3.4 DOHC injectors were possibly the same, I could always find some of those to try from the JY, just to see if they work.

 

And yeah, its very possible there is a boost leak, which we have always suspected, a small one, with how crappy that upper intake pipe connects with that flimsy coupler, its a pain to get it exact

 

Trans slipping, yes possible, it was "overhauled" in '96 from the previous owner, the fluid needs a change that was just verified yes, but no particles on the dipstick at all, its totally clean in that department. So we plan on a fluid change here shortly.

 

We'll see what we come up with, for now it doesn't get driven much at all and with winter rollin around, if there is snow, it doesn't get driven anyways, so we have time to decide what to do. If we did the 5spd swap, oh I would really be tempted to steal the Fidanza out of the GT to put in it, but we'll see, thanks again as always for all the info, :kiss: ..... no no, just playin, haha, i was bored, thanks though, much appreciated everyone

[TurboGTU]

Yea..my cam seems good at idle and low end...but it pulls hard after that. I also did run rich for my liking when I still had the TGP setup. But I would still check the basics of checking for cracks or leaks around the map sensor hoses and all vacume hoses.