Alright everyone, it gets to the point where I go through red lights because I hate having to sit at redlights with this car thus its also making this car not fun to drive at all anymore. Like the title states, the car surges like crazy. In park the RPMs jump a litte bit but not as much, underload its a whole diffrent story. Sitting at redlight the car surges so bad it almost wants to stall its self, but it seems like somthing in the ECM picks it up then it idles fine again for mabye 30 seconds if I'm lucky and then it will repeat the same thing. The car is not stock and its a stock ECM so I think it may be that I need to burn a new prom BUT the cam isnt really big enough to throw it off any how heres whats done to it....Holley Stealth Ram, 24lb. fuel injectors, comp cams 268H, ported L98 Iron heads, hyperutic pistons 9.5:1 compression and of course headers back exaust, 373's blah blah but none of that really matters. I have replaced the IAC valve in the past so its probably not that but u never know could have gone bad, BTW no codes are being throw at all. any suggestions?

Typical stuff.

Check for vacuum leaks, clean the TB and IAC, set up the TPS and timing correctly, and verify a solid ignition system.

Does this happen on cold starts, or only after warming up?

well here's the update...

worked on it for a bit tonight, fooled around with the TPS mostly, no vaccum leaks, IAC is clean....but i came to somthing very interesting....adjusted the TPS (without a voltmeter) just fooled around with it a bit and testing it by sound and how it idled. Once I got the idle dead on, drove it around a bit and it seemed fine, idled great didnt surge, stopped at lights and no surging. Well probably 10-15 minutes later of driving, I came to another stop light and then it started to surge again. So i went back to my house, re-adjusted it (thinking mabye it got bumped back because i didnt tighten the torx screws tight enough) went back out fine. Pulled into a honey farms shut it off went in gota drink, came back out drove off came to another stop light and started surging again.

To me it sounds like the TPS may be bad. Could that be it?

Could be. Get a volt meter and set the TPS, if it doesn't surge drive it until it does and check the TPS voltage again, if it isn't the same as when you set it, throw that bugger in the trash and get another.

yeah im gona try and bum a volt meter off a friend cause mine stopped working but i was setting it without it cause i could tel jus by the engine rpms and idle till it felt right, but im jus gonna spend the 30 or so bucks and jus throw one in, worth a shot.

well i had to order one new, 40 bucks, like I said its worth a shot, I tried adjusting the TPS again today, got it dead on then seemed fine for the first 20 minutes of driving, stop at lights it was fine then it started surging again after driving it for a bit. Like i said it seems like its re adjusting it self and it has a mind of its own.

alright another update, just had to go fill it up with gas.....so....it seems like after i adjust it drive around for a bit shut it off, it resets its self back to where it was when i start it back up......does it seem to be a bad tps if it doesnt hold its proper voltage?

You really need to adjust the TPS with a voltmeter. The ECM may be reacting to your adjustments, then trying to rewrite tables through the integrator based on the new (but erroneous) TPS voltages, and finally arriving at poor fuel control settings based on the poor TPS adjustment.

While you're in there, make sure the TPS is getting the 5VDC reference voltage from the ECM.

I'm curious to see what the solution to this problem is. I am having the same problem, but I'm basically stock from top to bottom.
Get it good and hot and the thing starts surging. Sometimes worse than others. My situation seems to be worse on hot humid days.

bought a volt meter today, threw the new TPS in. Set it up till I got .54 volts.....at WOT im getting 4.7.....car is still surging tho and it seems like it doesnt it only when its warmed up.

I never got a chance to set the IAC which may be my problem. I coudnt find the torx screw on the side of the throttle body that ur suppose to set the minumum air speed with....said its on the side but couldnt find it...????

i read somthing on this subject in my manual not 2 long ago. the TPS will cause surging but also the EGR will. if u have a manual 4 the car go 2 the emission section and read on how 2 check the EGR. 1 more thing, maybe u have intake leaks.

there is no EGR provision cause i have the HSR ram on it, but it thorws no codes or nothing plus it actually did it before i put the HSR on it when i jus had regular tpi, its jus been getting worse and worse before i could tolerate it.

ya, im also interested to see wat the outcome of ur problem is, my TA also surges at idle onece warm, its a bone stock 350 tpi

hmmm still cant find the torx screw that u use to adjust the air speed, it was a getting a littel dark so it hard to see plus i was running out of patience...which side is it drivers, passengers?
its probably right in front of me, im jus blind

Driver side on the throttle body near the top

Are you guys having temp problems associated with the surging?
The last time I took the Z out, the temp kept creeping higher, which seemed to increase with the surge problem.
All the fans are working, the water pump is only four years old, the thermostat is older, but the cooling system is working. I can see the temp fall and stay within range when I'm driving.
After the car had sat for about 90 minutes, things had cooled off and at the first stop light I had a nice smooth idle. No surge. Then as the car warmed up, the surge was there, but very minimal. So this must be an electronic/vacuum situation.

Are you guys having temp problems associated with the surging?
The last time I took the Z out, the temp kept creeping higher, which seemed to increase with the surge problem.
All the fans are working, the water pump is only four years old, the thermostat is older, but the cooling system is working. I can see the temp fall and stay within range when I'm driving.
After the car had sat for about 90 minutes, things had cooled off and at the first stop light I had a nice smooth idle. No surge. Then as the car warmed up, the surge was there, but very minimal. So this must be an electronic/vacuum situation.

yes, I'm having the same problem as well, even when the car is hot, I can turn it off and restart it, and I have nice, smooth idle for a miute or so, then I think it goes into closed loop and starts to run rough.

I need to know the outcome of this too.

Okay, I've been doing some digging this morning and this is what I've run across.
This is from the Chilton's 82-92 Camaro book. I'm not saying this is the solution, but a suggestion.

Incorrect EGR Operation

"Too much EGR flow at idle, cruise or during cold operation may result in the engine stalling after cold start, the engine stalling at idle after deceleration, VEHICLE SURGE DURING CRUISE AND ROUGH IDLE.
If the EGR valve is always open the vehicle may not idle.
Too little, or no EGR flow allows combustion temperatures to get too high, which could result in spark knock, engine overheating, and or emmission test failure."

I know our Z has had a problem with stalling after cold starts for a couple of years now. It's just recently we've begun to encounter the overheating, which increases the surging and just plain sounds nasty when revving in park.

This may not be the solution, but it may be something to look at.
Good luck to all.

How much is an egr selling for these days?

If they are not too much I may try it.

$50-$70

okay i went to set my idle speed today..followed the tech article and where it says disconnet the plug for the iac which i did, and the car doesnt start! how am I supose to set the idle speed if the car doesnt start when its disconnected?

ok well i guess this is just another one to add to the surging/heating problem. i seem to be ok on temp as far as how high it goes but it heats up quick. i got a code 32 the other night and my idle surges pretty bad. i am guessing its my EGR since the code said so, but havent had a chance to check it out since i have barely any tools cuz im poor as hell, lol. i have stalled a total of maybe 20 times in the past 20 days driving to work. it happens when im at a stop light, decelerating, and trying to park. also, when i accelerate and get to about 50 my car stumbles BAD, i mean the whole car jerks. Now the problems have all gotten worse and its hard to accelerate to even 30 when im warmed up all the way. everything seems worse when warmed up. well i hope someone has any clues?

see my car doesnt stall....but the thing that gets me is i know its a problem with my IAC...the IAC valve is new, all it needs it to be set. But it says to disconnect the plug into the IAC and start the motor to you can set it properly, well I did and then the car doesnt start..so how the heck am I suppose to set it properly?!? Well I tried starting it with out dicconecting it and tried to adjust it, raise the RPMS up a bit and then shut the car off then start it back off, doesn't surge anymore....however when I start it the RPMs skyrocket at idle to about 1200 rpms! so I turn it back down, shiut it off fire it back up again then it idles at around 750-800 but the surging begins again....why is is so difficult to properly set this? and i know THATS my problem, i just can't set it the way your supposed to.

Bad,
Did you also put a jumper between ports A & B on the diagnostic connector? I use a paperclip bent straight and then back to jump them when I want to check codes and such.
If you did this, then which wire are you disconnecting? It should be tan with a black stripe.

loose plug?

Also replace your maf burnoff relay (hi bob! IZ WOO WOO)

IROC, I'm glad you've at least got the problem figured out. Now it's just a matter of dinking with it until things start sitting right.
As for me, I'm not stalling, yet. I'm getting to temp and watching the rpms bounce between 500 and nearly nothing as I'm surging along at every light. However, the bonus is people seem to give me a lot of room at the lights. They must think the thing's going to die at any second.
While I'm at it, can I show some love to the designer who buried the EGR system beneath the air plenum? Ya can't even get a finger under there to see if the valve is functioning correctly. I'm waiting for the next paycheck to go and get the system tested.
On my 91 305, there is an EGR valve and an EGR selenoid that is controlled by the electronic system. So the problem could be either the EGR valve is not holding vacuum, or the selenoid is nearly shot and not cycling correctly.
If anyone pulls off the great EGR swap, please let us know the result.

diagnostic connector is on the driverside below the dash below where the SES light is correct? becuase i have a MAC tools code card snanner and connected it to the two ports and then it reads the engine codes...is that hte same thing?


and which ones are ports A and B?

also, i disconnected the plug connected to the end of the IAC

ttt, i have narrowed it down to that, so i need some help and guidence on how to set the idle speed properly...like i said jus need guidence...

The diagnostic connector where you plug in the scanner is correct. They are the 2 right, upper ports that are A & B. Connect them together, disconnect IAC, and then set idle to 450-500rpm. Then plug everything back in, and let us know if/how it works now.

okay it seems like the car doesn't start because i have the paper clip connected to the A&B ports, when I dont have it in and t he IAC is off it will start with jus the IAC off not...why is it my car isnt starting when i put the paper clip in? and yes the computer is running the trouble codes when I go to start it.

now im thinking could this be prom ECU related now?

also could it be timing/fuel pressure is off? I know im running rich becuase everytime my car is running all I can smell around me is fuel.
thanks for all the help guys. :hail:

Are you taking the paper clip out before you start the engine?

u arent supposed to leave the A and B ports connected when starting the car. when u have the A and B ports jumped the ECM is put into diagnostic mode which will tell u trouble codes blah blah. take the jumper OUT and then start the car with the IAC disconnected, set the idle, shut off car, reconnect IAC start car and see how it went! im pretty sure thats right, if not someone correct me please! good luck man!

ahhh its all making sense now, none of the tech articles had that detail unless i misread. ill try that out tomorrow and let u guys know how it works
= me

Damitt, I knew I forgot something..Thanks for correcting my lack of instruction

step #1 jumper A&B in the aldl and turn on key

step #2 unplug IAC

step #3 pull out jumper from aldl

step #4 start car, set idle to 450 or so by adjusting stop screw in top of throtle body

* note you may have to hold throtle open or adjust screw out to get car to start, after car is running set BASE idle with adjusting screw

step #5 after idle screw is set you HAVE to reset your TPS sensor because you moved the throtle plate. .54 seems to be the voltage everybody is running

step #6 plug in IAC and start car and idle should be set correctly.

step #7 ENJOY

ok i followed ur instructions exactly. ran the diagnostic with the paper clip waited 30 or so seconds, unplugged the IAC took the paper clip out and started it...problem is the car wont stay running! i tried to hold the throttle down to keep it running and let off and let the ECM catch itself but it would just die!

im wondering mabye my IAC is bad?? it shouldnt be cause its not throwing a code even when its unpluged.

HELP! been trying to figure this out for over 2 weeks now and if its still surging even after i figure out how to do this im driving it into the dirtiest swap i can find!!!

You are probaly going to have to screw your throttle stop out some more to keep it running.

your IAC can't work when its unpluged.

I just did my car, you need to hold the throttle open and let it down very slowly until it idles. you may want to turn out the screw until it idles at 600 or so and slowly adjust it down from there.

i shoulda known im gonna go try it right now...

Don't you have to have the car at normal operating temp also?

well i tried, the idle speed is set dead on along with the TPS a .54 volts...car still surges.

Hmmm well seeing as the car is running at hotter temps now that you said it, it reaches over 200 now even today over here its reached 95 degrees....would a high temp cause that? I also have a small coolant leak buyt its really not enough for it to run extreamly hot, ive had coolant leaks like you'd read about and the temps woudnt even budge as long as I kept coolant in it....

i have a hypertech fan switch in my garage (somewhere) that i got end of last year but never got a chance to put it on becuase i didnt drive the car much last year


thinking it may be temp related it doesnt do it when the car is cold....could this be it?

ok i adjusted everything but the car wasn't really fully warmed up, i probably came home from work and adjusted it a half hour later, so evendently i screwed it up again....so when i adjust the idle speed and TPS when the car isn't fully warmed up it doesnt really matter or it just doesnt help the cause?

WOW i know what you all are going through. My 91 Formula350 is being a dog and running like crap. we changed the EGR Valve last week and it is still running like crap. So i found online and in my service manual that it could be the EGR Solinoid. so i dont know what the heck to do i kind of think it is the ECM. If anyone figures this thing out i would love to know what to do.

Greg

Coolant temp sensor and or manifold air temp sensor....been down that road.

Here is something that really solved my problems like this..

Just like you I had been down the IAC, TPS, EGR vaccum, hair pull out and ready to kill car stages.

Have you thought of cleaning out your throttlebody and pennelum with some throttlebody cleaner? Mine was horridly disgusting. Also try cleaning the IAC and the chambers around it.

Another thought as well is if your car does not see many long trips and has a good amount of miles or Kms on it, have you thought of using some STP injector cleaner in your next fill up?

This solved my idle issues until my wrecking yard TPS gave up on me LOL.

Just a different angle on things you might appreciate.

well im narrowing down some more possible solutions to this problem.....

trying to figure out if its doing it only when the car is warmed up and at operating temperature or it its doing it becuase its running a little bit to hot.......

or


if its cause i set the IAC without letting the car fully warm up??......

hmmmm

My car surges to the point that it kills itself while in gear and idling.


282* .465" cam w/ 1800 stall = teh lose

see my cam isnt that big enough to throw the idle off that bad, but im still gonna throw in the "it needs a custom prom" theory in the bin of suggestions as well

Yup, mine does a little bit of surging, but it's not that drastic. I'm hoping that when I can finally get the 350 prom for the car, that it will work it's way out of there. Kind of hard to tell for me if the car was doing it before I swapped the motor, because when I bought it, I knew the 305 had a rod-knock, so I didn't really want to have it running, ya know...but ever since I changed to the 350TBI, it has had a slight surge.