Ok. Please help

I'm at my wit's end here....

Rundown on the car:

1987 GTA L98

1.75" shorties, CAI, 1.6rr's, lt4 hotcam, etc.


Here are the parts I replaced today:

TPS (set at 0.54, goes to 4.1 when WOT)
Coil
Cap
Rotor
Wires
Plugs (ac delco, 2 heat ranges colder, gapped at 0.35)

I shot the timing at 6*

When idling, it surges pretty badly from 600-1200 rpms. If I'm in drive, and I hold the brakes, it will start surging and making the car creak forward a little each time.. very noticable surging.

If I give it part throttle, it stutters (feels like if you run out of gas around a corner..) until about 1500 rpms, where it then smoothes out an accelerates fine.

I hear a noticable sound similiar to pinging when it idles, but I'm almost 99% sure it's the timing chain hitting the timing chain cover. Is it possible the timing chain 'thwap' is being picked up as knock and the car is pulling timing because of it? If the chain jumped a tooth, I would assume the car would run even worse than it does, because at WOT over 1500 rpms it pulls fine.. not as strong as it normally is, but still decent.

Or, is there a possible I pulled one of the knock sensor wires when I was doing my header install, and missed the reinstallation of it. Where are the sensors located?

Could it possibly be an ignition module?


MAF?

Or maybe even the fuel system..

I'm running SVO 24# injectors... I dont have my FP gauge hooked up currently, but the last time I checked i was running 51PSI.

Could it be a clogged filter even, or maybe my intank died.. I've ran out of steam, patience, and sunlight to check the fuel system today..


But, if anyone has any pointers, hints, tips, tricks, ANYTHING.... *PLEASE* let me know

 

Hows the IAC look ?

 

hello, i'm a little weary to awnser this so if i'm wrong please correct me, but don't bash!

it seems that your tps voltage is too high!! idle tps voltage should be at .48 & .52 anything higher the computer would think it was off idle, or throttle open, and try to add more fuel, this could be the studder or bog that your reffering to.. also i have a friend that had a 305tpi in his 90 irocz, it kept constantly quitting and stalling out, and when he tried to race forget it!! he had clogged fuel injectors, and the reason i feel the car did what it did, is the computer senced it was running lean and increase fuel open time and richend the other cylenders so bad it made the engine bog, and flood out!! maybe this is the problem, maybe not, but i hope it's a step in the right direction!! hope you get it fixed dude!!

badgta

 

ok i see two things that i would look at first.
1: 51psi for your fuel mite be a little to high. try backing it down 5psi to 46 or so.
2:how long have you had your SVO 24# injectors in for. the surge that you discribed is the same one that i had when i had bad injectors. sometimes it would even stall.

you can set your TPS up to .62 volts before you get a check engine light. but for the most part it should be in the range of .5 to .54 volts. i dont think that is your problem.

 

I've had the injectors for about 2 months...

when i get home, i'm going to install my inline t-rex, fuel filter, and then rest the pressure to 48 or so.

Hopefully this will cure it...

I'll keep you guys posted on what I find... any more suggestions?

 

I know that this might sound a little dumb, but have you looked for a vac leak? If all lines and injector seats work fine (no leaks) then you may have a problem with the injectors. Did the problems start when the new injectors went in? If so try swaping out those with the old ones if they were still in working order. I had a similar problem that happened to my car, and the problem turned out to be a combonation of the injectors and two small vac leaks.

thanx
G

 

Im on the IAC/TPS wagon

Unless its less complicated like vacuum which would explain a NEED for large injectors/Fuel pressure.

 

the injectors have worked flawlessly for about 2 months now.. and then this happens.. I tried unplugging the o2, as thats the only thing has changed and the problem started.. no change in symptoms. I will try a new IAT tomorrow.

Thanks for the help guys.. keep the suggestions comin!

 

You mean IAC? The IAT/MAT wont effect it.

 

meant IAC.

 

sounds to me like you should check your EGR valve, mine was doing the same and i replaced a bunch of **** and finally i had it scanned saying the EGR is bad, it might help.

 

how do you check it, push in from the bottom of it and see if the condition changes any?


it will probably just be easier to replace it... how much are they, $20?

also, how much is the IAC, i'm assuming like $15-20

 

I bought an EGR valve from GM a couple years ago and it was $80, and I think they charge $40-$60 for an IAC. For the EGR go with AC Delco, they are made specifically for your engine/vehicle, the ones from auto parts stores are generic. Don't know about aftermarket IAC's though. For under the hood I try to keep it AC Delco to save hassles.

~M~

 

cool, thanks.

 

I am having pretty much the exact same problems right now.

When the car is cold/ first come out for the day it doesnt want to idle in drive, I have to two foot the damn thing to keep it running. then it warms up and thats ok but the surging at stop lights starts up.

Im going to check the codes on it tonight if I get a chance. other wise it might have to wait till the weekend to get fixed. Let me know what you find out, hopefully one of us will find the problem.

 

i pulled the IAC today and it was pretty gummed up..

Upon inspection, it's f*cked.. time for a new one.

Where do you get one? Discount auto parts and everywhere else said I'd have to order it, and thats 5-7 days....

 

I found the IAC and TPS both at NAPA, they were both around $40 each. And they had them in stock. The dealership had them too but they were like $60 each.

 

scanned the FP today, and it was jumping between 9psi and 32psi at idle, and steady at about 25 psi when wot.

I changed the fuel filter, it didn't help. I then hooked up my inline T-rex fuel pump.. Bam. 46psi idle, 53psi WOT


problem solved


Thx guys..

 

I took off my IAC and found that the entire tip had at least a 1/8" of carbon built up on it, plus the passage ways in the TB for the IAC were all gunked up. After taking it all apart, cleaning it up real good. It works, no more surging.