Popping on acceleration

[dgreene]

one of my cars has developed a weird pop on acceleration. It happens when you punch it from a stand still around 3000 to 3500 and around 8-10 PSI of boost. I would have some better data on it but my laptop just took a dump in the middle of recording it with DS. Sometimes it will do it when you punch it while going, but almost never does it when you ease into it. Am currently running a max of 15 PSI. When it pops I only get a small amount of knock, around 3 or so but that is really bad since I like none at all, and the boost will jump momentarily at that point.

Stuff I've tried since it started:
Replaced coil pack(should have a new GM module Thurs.)
New Plugs and Wires(plugs gapped at 35, then to 33)
Different chips and computers
Running with DS not installed
Reseting TPS and IAC
Fuel Preasure verified at 42 PSI vacuum line off and around 58 PSI at 15 PSI boost
New fuel filter
Checked grounds and Positive Bat cable
Checked CAM sensor setting
Traded MAF's with a known good one.

At idle everything looks good:
TPS=.42 MAF=7 BLM Cell 0=126 IAC=15 Temp.=161 O2 very active.

WOT as far as I can remember:
TPS=4.69 MAF=254 BLM Cell 15=134 Temp 163 O2's 790-820
Boost =15

Car= 87, TA-49, Big neck IC, 50# injectors, Lubrant street chip, Adj. reg, KN cone filter, Walbro 307 and hot wire kit, cat back Hooker exhaust w/test pipe, RJC powerplate.

Anyone have anymore suggestions? I should have a new notebook by the weekend to record some data and probably wont try it but once when I get the coil pack on Thurs to see if that clears it up before I get another notebook to keep tabs on everything.

TIA

 

[jastrckl]

I chased a problem like this for ages. turned out to be my CCCI (the module under the coilpack). You may want to look into that, sorry, they're expensive. Good luck.
-Josh

 

[dgreene]

Thanks for the reply Josh. I should have a new one on Thursday. Hopefully that will be it.

Just as a thought, could weak valve springs cause this as well? My baby is due for a changeing soon, and it might get it this weekend......

 

[blackbuick87]

Probably not weak valve springs, that happens at high rpm when the valve bounces off the head

I had the same problem, turned out to be the module also, only after I replaced everything else
But now I have spares

Another possibility is a flat cam lobe, but a module sounds more likely

 

[forzfed]

I had the same problem, but it turned out to be my DS connection. Car ran fine and then one day it started popping. I know you said you ran it with out DS. Did you have the ribbon cable disconnected from the ECM? That is what I had to do. I also grounded the ecm and also shielded the ribbon cable. Don't know if you have that done already. Just some input, let us know what you find? I ran my car popping a little too long and it K.O.'d the ECM. So you might want to try the ECM from your other car. Good Luck!

 

[dgreene]

Thanks for the replies!!

I will try another computer, although I've tried one spare that doesn't even have the mod to run DS. I have spare everything(almost), but don't have anymore spare modules. I can't wait to get another module to try, I'm betting that it will be the prob. We will see thursday.


Thanks!

 

[dgreene]

Got my new CCCI module from GN today. I also opted to get a new coil pack too. I will put them on when I get home from work. I will let everyone know if that did the trick or not.

 

[turbo buicks]

please let us know. i seem to be chasing the same problem w/my car.

 

[dgreene]

Turbo Buicks, your car and my Moonroof car are almost the same combo.

I will let you know tonight.....

 

[Michael McCoy]

Donnie it sounds like your problem is this: your car wants you to drive it down to Baker's this Sunday for the Carolina's chapter meeting!! Thanks as always for all your help with the business buddy.

 

[FromaBuick6]

This may sound funny

But make sure your plug wires aren't arking onto anything close. I troubleshot a similar problem with my T+ and it was a plug wire too close to the T+ spark wire. - T

 

[turbo buicks]

thanks, ill check that

 

[dgreene]

You know Mike, I'm actually thinking about seeing if someone could look at this SOB to see if they can help me out, and that chapter meeting would be a good place to start.(not to mention that I need to get into some stuff and be more social AND find some parts for my '70 GS 455 car)

Anyways, the new GM Coil pack and CCCI module didn't do jack for me. There went another 160(I know someone at the dealership) for nothing. I also tried a different cam sensor cap and it do it either. I was going to change the whole sensor out, but it didn't have any play so I just changed the cap. Checked all the plug wires by hand with it running. Nada.

I do have a semi good run from DS using a borrowed laptop if anyone would like to look it over for me. Just send me an email and I will send it to you. donnie@creativebigprint.com

Thanks everyone!!

 

[blackbuick87]

Doesnt look like you have changed the O2, those are only 25 bucks.

Try to describe again exactly what it does. Now you need to look into the possibility of a broken valve spring or maybe a flat cam lobe

 

[dgreene]

I have a new O2 to try, just haven't yet since this one has only 678 miles on it......I'll try it anyway, it can't hurt.

I'm going to change the springs this weekend, which will also give me a chance to look for a worn down lobe.

Thanks for the help!!

 

[6=8]

Hi There,

I chased this problem for a few years, and it turned out to be a combination of several different items. I will list them for you in the order I went, but I hope that if you try any of these that you do the cheap items first!

Each time I "Repaired" an item; the popping was reduced or unchanged. Each item involved replacing the factory stock OEM item (Except the headers/Chip). My GN was very close to being stock, and my popping was at about 10-12 PSI/anytime I went passed 1/2 throttle, similar to your issue.

Since it was/is my daily-driver car, popping like it was, just kept my foot out of it for about a year or so until it really started falling off it's performance mark. Then I got busy:

1. TypeII ign upgrade (w/wires/plugs @ 130,000 mi (No help)
2. Timing chain @ 138K miles (Big Help- Missing teeth, sloppy, but was still in phase)
3. Valve Springs @ 140K (Big Help- Popping during cold start/cranking over in the morning eliminated!)
4. Boost falling off due to cracked PS ATR header... Popping almost gone, and so is any performance.
5. Postons Headers @ 148K (Boost/spool great... Popping returned... More severe KNR reading 20+! Oops)
6. 93 Octane chip installed, KNR better, but still too high
7. Real Boost Gauge installed... Factoy Boost Gauge was pretty close but falls off at 15psi... Not always lighting the last red LED. Actual boost is closer to 18-20PSI!
8. Found smaller vacuum "Y" fitting orifice: www.johnsperformance.com and installed. Can go almost full throttle before POP! but KNR still too high. Boost 14PSI
9. 100 octane fill up- WOW! Popping gone/ KNR max 2 WOT

So, your plan to change valve springs is a great one, and also may explain that when you experience a POP, your boost increases momentarily (If an intake valve is not seating/partially open and the fuel ignites in that cyl, backpressure in the intake/PSI will increase with the "Backfire.")

Make sure you are not over boosting, too! And at 70K miles, you may want to replace or at least inspect the timing chain. Try filling up with REAL 100 octane fuel just to see if that makes a difference.

One trick I learned is to run some CD-12 or other "Free up sticky valves" in the oil as an experiment. If the popping goes away, the springs are probably weak and not closing the valves all the way, which is where my money is at this point.

HTH and good luck to ya!

 

[turbo buicks]

i used to have a random pop out the exhaust at idle until i replaced my valve springs the other day. pops gone and idles much better. i think my problem is the spark plug wire i had to fight with to get off. probably cant keep up w/the RPMs. also a friend had thesame problem w/his TTA, turned out to be the cam sensor.

 

[dgreene]

OK, here's the stuff changed so far.

Coil Pack(new)
Module(new)
Cam Sensor
ECM(new)
MAF
Plugs(new)
Chips


O2 and Wires have less than 16months on them and only 500 or so miles. The timing chain is only about 6 months old and less than 250 miles on it.

Will be changing the Springs and Crank Sensor this weekend and for the hell of it the wires and 02 if the springs and cs don't fix it.

Wish me luck!!

 

[dgreene]

Ok guys, the valve springs did it. I should have my ass kicked for not changing them sooner. There were a few of them that I could pull down with the tool with my pinky finger. Talk about weak. Pulls like mad, idles better, runs smoother all around.

Now if I only had the 300 I spent on the other stuff back I could buy some more stuff for my car. Now I can get back to tuning instead of hunting trouble!! I would like to thank everyone who took the time to write and help me out with this situation.

 

[turbo buicks]

glad to see you got it fixed ironically my car did what your car was doing, but after valve springs. i think its a plug wire though b/c it took me 10 mins to get it off with gloves on.