I have A problem with my 87z28 surging and i had athread with alot of great ideas and ive sort of isolated the problem.I disable my EST wire at the ECM due to hanes manual sayin it waz @ b4 instead of d4 so i thought what the hell an changed em. Well problem was solved no surging at idle my comp cam 236@50 510I 520e was sounding sweet.But I lost power in other words I disabled my timing advance and the car idles great but lacks the power it had.Well I confirmed Haynes had a misprint on there wiring dia. for the ECM I hooked it back the right way and my surge returned with it.Ive went thru ECMs control modules and ESC modules with no luck.No shorts checked all wiring.I broke down and bought a scan tool when I disable the EST i get a code 42 when i enable it it surges till it eventually dies. Local GM says to many mods for them to do anything with it and none of the manufacts like motorvation accel etc. have a clue.One thing that was weird was the superscanner from actron wouldnt acess the ECM as an 87 efi350 0r 305 but did as a 2.8l but gave false codes so I tried 86 efi 305 and got correct info. Ah Actron didnt have a clue why.But what I was wandering is if anyone could hook me up with a ecm mapping site so I can interp some of the info I know quite a bit like TPS and O2 sen And TCC lock up but i dont know squat about IAC counts or MAF values and i think if I had some of the values i might be able to finally figure thi thing out. Im not beyond breakin down and learnin chip burning but i feel this is something simple im missin because ive got 2 stock chips and one custom and it does the same thing with all of them.Any help or comment would be greatly appreciated thx. :hail: :hail: :hail:

 

Sounds like a IAC problem. When my car surged at idle, I took it to GM. They showed me that my IAC was compressed and full of carbon. After replacing it, the car idles correctly.

Sorry, don't know any ecm mapping sites.

Hope this helps.

 

Thx for the reply I put an IAC in when I first built the engine via the instructions that came with it.That was the first thing chev told me to do also plus its a new 58mm TB. Ive got the superscanner but nothing to reference it with to tell waz up. I hope I could get some of the values from some of th chip burners or a web site were I can get um. But any ideas that are given I promise Ill try.Ive been hasslin with this thing so much Ive done to much to list but I could have missed something so any input will be beneficial thx agian:hail: :hail: :hail:

 

I had a problem with this in my '85 TPI Vette. After changing the M.A.F., IAC,and ECM all to no avail.. you'll never guess what the problem was.

Recently before this started happening, I had a new A/C compressor installed. Had the dryer and all plumbing swapped out as well. I then took it to a local A/C guy (lots of them here in AZ) who proceeded in doing all the prep and charging of the system. After this was all finished, I was quite disappointed with my new A/C. It wasn't very cold at all and the blower seemed to only blow at one speed. Then the surging started.

After changing all mentioned above, another buddy of mine came over and we started talking about it. He checked the system and noticed that it was WAY over charged. after taking it down a bit, the surging stopped! The A/C was ICE cold and the blower blew at all different speeds again.

I know this isn't a thread for A/C.. but still if you've got the setup and it's functional, check the pressure in the A/C system... if it's a bit high, bring it down. IT just may do the trick.

I almost forgot.. this was accomplished with the ORIGINAL M.A.F., IAC,and ECM back in the car.

Hope this helps some.

 

It really sounds very timing related if it idles smooth with only base timing. Have you tried leaving the ESC hooked up like it is now (surging) and then unhooking the knock sensor for a while?

 

Hey thx for the replys. Gents im runnin so many mods i took that AC and the cooler in front of the radiator and stuck it back till I got the engine tweeked dont get me wrong Im not turnin 500hp but enough to were im takin it a little at a time. The knock sensor i did try with no change i even replaced it for sh_ts and giggles no change. I tested contunity on every da_n wire on that ESC all the way to the ECM with no shorts. I would just burn it but its my wifes and I probably wouldnt get dinner for a while she loves that DAM_ TPI Im an old carb lover myself first TPI ive fooled with but when its just runnin WOT its a neck breaker but when you stop for a light it will suge till it dies.I have learnd alot and plan on spendin the whole weekend on it any more ideas throw em at me hell ill try anything if I get it fixed ill post waz up with it. :lala: :lala: :hail:

 

I don't think the ESC stuff is on the chip. Have you tried a different calpack or ECM with a stock chip?

Have you tried swapping distributors with someone to eliminate the electronics inside that?

 

Waz up just replaced and cleaned IAC no change. Rechecked timing.Checked MAF and other sensors with probe everything ok other than MAF with low voltage @ KOEOff . Probe instructions say it shouldnt do that?Other than that it had good viltage changes when engine waz reved.I had stock distributor in it Replaced with Accel billet dist have swapped 3 different chips in ECM 2 stock one mtorvation no change. After recent test drive I keep gettin code 42 and 43. Ive got 3 control modules and 3 ESC so I dont think anythings wrong with them gonna drink another cold one and try some more sh_t. THX for the input 305SBC you have any more ideas let me here it ill Try anything. :hail: :hail:

 

It seems from a LOT of posts that 'surging' is a very HOT TOPIC!! I have a 406 in my Monte SS with a 7730 ECM, Speed Density. T56 and a TPI off of a 5.7 1989 IROC... and I have had surging since I built it! Mine doesn't happen at idle tho, it is when it's cold and accelerating, it stumbles so bad that I am forced back into the seat then a milisecond later I am flying into the windshield!!
I have replaced all sensors checked EVERYTHING dozens of times to no avail!!
I did program the ECM for 30 lb/hr injectors and I am using 24 lb (new ones will be here on Montag).. but, I don't think that is the problem.. at first I thought it might be my VSS signal from the T56, it's a high-count AC signal and I am running a Dakota Digital box for my VDO Speedometer and running the 7730 ECM off of the 4000 PPM output.. now I am wondering if I should send the 40K PPM VSS AC directly to the ECM? I don't think this is the problem tho as the main problems with screwed up VSS signals is speedometer, EGR, and canister-purge solenoids so I don't think that is my problem..
Well, if the 30 lb injectors does the trick I post it here.

 

I initally had 30lb inj. from accel on mine and swithed to 24 no help for mine. Im on my way to Lowes to get a propane tank to check for vacum leaks cause the new IAC is @ 0 counts @ idle and I heard that could mean vac. leak ill let yall know how it goes. If 30lb works for you let me know hell ill switch back thx for the input. :hail: :hail:

 

When it surges up to the high idle unplug the IAC connector and see what happens. If it still surges then that eliminates the IAC.

You could also check your air ducting between the MAF and the TB for leaks or lack of seal. Then you have to check all vacuum lines & PCV. One easy way is to cap off all of those lines including the one to the power brake booster and to the fuel pressure regulator.
If it still surges then you know a great many things that it cannot be at that point.

 

Hey THX knowing to cap all those off will help out alot going to try that tommorrow evening. The reason I think I had to have missed the vacum leak is because an article I read said if the IAC is @ 0 at idle then theres air coming from somewhere beyond it so my inital check i might have missed something if the IAC is blocked the air off. Ill keep postin results and checkin for new ideas. :hail:

 

Update.. I put in the Accell 30 lb'ers today and the surging is GONE!! Yeaaaah!!!
At first I was thinking that it shouldn't make 'that' much of a difference but it sure did! It now pulls from idle through 5500 without skipping a beat!!! It is actually fun to drive now.
Let me know how your problem is coming when you get time.

 

Thx for the input Krag im still havin the same problem no vacum leaks ive checked everywhere from the MAF back. I did however discover a puddle of oil under my car were it had idled so long and found the rear of the oil pan had a pretty major leak. A mechanic at a shop told me im probably havin some vacum problems through the pcv durin the leak.The car only pulls 12 inckes of vacum at idle. Sounds crazy to me but according to folks around here he kmows his stuff. ??? but i do have to fix the leak and i beleive the rear seal housing is cracked. That cost me 50 dollars at cheverolet. i havent give up and I might try a set of 30 lb injectors I had a set before and it did the same thing. But like I said Ill try anything. The car is still given code 42 I replaced control module and checked wiring agian. I took it for a test drive after doin some adjustin and noticed it waz cuttin out when at a steady rpm but if i accelerate or smoke the tires no hesitation no cuttin out but when you stop to turn or at a light it dies and sets code 42 at which time it only puts out .35 volts or so to the est wire which when it dosent set code it is about1.80 to1.90 volts at idle and increaces with engine speed sounds about right so I still havent figured it out but i havent give up yet either.

 

Bummer... did you try blocking off the PVC vacuum hose (riight at the plenum) so the motor has no "built-in" leaks?) you would lose your power brakes but maybe it would show if you do have a PVC leak? Also, did you check to make sure the power brake vacuum booster isn't leaking?
I'm sure it's not the problem but I sure looked long and hard at my VSS signal as I read that if it's not working it can cause a surging during acceleration only (don't really know if it can, but something to check..)
I checked everything except my injectors so I ended up with a lot of 'surging' experience so let me know how yer doin' and I'll try to help.

 

Hey i need all the help i can get this surge stuff is new for me. Iplugged everything and checked for vac. leaks still surged with everythin plugged brakes PCV etc. Waz up with the VSS and surging? Im gonna be back on it hot and heavy this weekend so any ideas lets here im. Ill keep you posted. checked my timing advance at idle it was 30 deg at idle and whenever it would try to drop the rpm and thus or timing it would stumble and almost die. I read an article that stated that est was controlled by rpm and engine temp according to my ECM its code 42 EST but how many diff Friggin things control RPM from vac leaks to injectors to IAC MAF makes you a little crazy well folks i thought I would just whine a little. Please any ideas or input is greatly appreciated and thx alot krag for all your useful info. lay the surge ideas on me and ill try it. :hail:

 

12" of vacuum at idle? You have a leak, no question. It may be leaking around an injector, under the manifold at the lifter valley, cannister purge hoses, power brake hose/booster, etc. You should be pulling quite a bit more vacuum than you are and about the only explaination is a leak.

 

Deik, if you want to check for a vacuum leak first (remember timing, EGR or clogged catalytic converter will cause improper vacuum) a "normal" motor will run 16 to 22 inches vacuum at idle.
The important thing to keep in mind about vacuum leaks is that they have the most noticeable effect at idle. At part and full throttle, there’s so much air entering the engine that a little extra air from a vacuum leak has a negligible effect.
I found the best way to find a leak is to take a propane torch, unscrew the 'head' (torch nozzle) and slip a rubber hose on it, turn on the valve so a little is coming out (enough so you can hear it and enough so the radiator fand won't blow it away) then with the motor idling and the IAC motor unplugged (the computer will try to adjust the idle so we have to prevent that) move the open end around everywhere there may be a leak like injectors (these has o-rings that can dry out and leak) throttle body and shaft, the EGR, etc. if you find a vacuum leak the the motor will increase RPM and smooth out. You can also use a can of carb cleaner to do it but it's easier to poke the propane hose around (and safer due to flammability!).
Did you check the fuel filter and the fuel pressure?
Once all that is done, I will go over the VSS (Vehicle Speed Sensor) and what I found can affect the TPI.
Good luck, I'll check back with you this evening.

 

Waz up Krag. i did that very thing about a week ago went over everything 3 times and a tank of propane. At idle with the bypass pulled idle @ 800 rpm it only pulls 10 to 12in of vac. at a steady idle with the esc engaged it varys with idle. I did a compression check as well any where from 150 to 170psi on every cylinder. Ive checked every wire involved with the timing for contunuity all is ok. Ive replaced MAF, ESC ,ECM,and the control module and installed a new accel dist. letme give you the lo down on the engine 87 TPI 350 .40 bore .10 crank vortec stock heads comp cam 234 236@50- 510 520 lift with springs lifters chain the whole kit adjustible fuel pressure reg @48psi per BBK instruct. hooker comp headers, 3in flowmaster exhaust no cat.,motorvation chip and 2 other stock chips no change.accel dist. istalled with hopes of fixin surge no change. Tranny 700r4 with 2400 BMstall holeshot and shift kit. This engine was stock before and I never had any problems I dropped a valve and had excuse for overhaul . It never offered to surge before but I never had VSS hooked up till now cause cable was broke and I never got around to fixin till overhaul. Oh yeah 3.73 posi gear. Well i hope that gives you a little more insight into why Im not to sure about the inital vac and what it should be Ive built many engines with big cams and alot less vac. but not with TPI or ESC. I did install a vac. booster from summit cause i did expect brake prob. but i checked it for leaks and it had none. This is a sweet ride and is one of three third gen. I own and would appreciate any assist gettin this one a goin The other two i chunked the ECM and went carb Id really like to keep the TPI cause it does have killer throttle responce. Thx for the help. :hail:

 

Morley sorry just noticed your post it didnt tellme i had two replys. When i checked for leaks I plugged all vac hookups and checked manifold, injectors, throttle body, runners, egr, anything that had a gasket and vac. on it. Cranked it up and it still surged and that shocked me but at any rate i hooked up one thing at a time fuel reg. canister egr etc. and checked all components 3 times with propane tank and hose and i mean i cranked the propane up the last check nothin! blows my mind its a mid size cam but i have used smaller like summit 234 234 @50 488 488 lift that only pulls 8-10 in of vac @ idle but its a sceamin 305 but its carbed do you think that could effect the idle due to it being an EST system Idles rough with esc by passed but no surge and its not that big a cam comp cam said the cam was made to be used with ECM controlled cars but who knows im sure they make mistakes but i did dial the cam in and all specs were on the money.

 

Even with that size cam you should have more vacuum, that cam doesn't really give a loping idle.
If you did plug everything up and couldn't find any leaks with the propane, then the last place to look is the intake to lifter valley seal. Check your plugs and see if one of them has more of an oily look to it than the others. If it is sucking air from the crankcase it will also be pulling in a lot of oil vapor and that should leave a residue on the plug for that cylinder.
I'd also check my ignition wires, if one is leaking it will cause a surge or miss at idle (more noticable at idle anyway)

 

Waz up gents i know several have been followin the ongoing saga of m very expensive surge problem well i got it I had put 3 different control modules in the car one was an accel and the other 2 were autozone specials that I had them check before I even left the store. They all did the same thing surgin but each one change just a little bit like one my car just cranked once and died and that module waz shot one of the autozones then i used the other one and it would idle good when cold but when it warmed up it would surge then i bought theaccel billet dist. and the car didnt want to idle at no less than 1000rpm or better you could put it in drive and it would almost die and then you would have to push the brake as hard as you could and it would still spin the tire just sittin there. So i kept gettin the code 42 which meant problem in the control module - EST circuit so I went to cheverolet and bought a new module not remanufactured and the car has been runnin great ever since. Im not sayin this fixes all surges because theres a hundred different things i ve found that make one surge but it sure as hell fixed mine and i told everyone Id post my fix so there it is thx for all the help from everyone. :hail: :lala:

 

That's great! I know from experience how that surging can make a car a pain to drive! And as you said, there are so many different things that can cause surging.
Yours would get worse when it warmed up and mine when it was cold!
But, it is cool when we have problems and we post it and get different input from people that has had simular problems... it allows us all to usually check something that we didn't think of...
Have fun with a smooth acceleration!!

 

Never, Never buy an ignition module from a parts store. ALWAYS get genuine AC Delco, quality control on those aftermarket ones is just crap.

 

By Genuine AC Delco I hope you mean Genuine Wells components (Autozone Specials)

 

Nope, sorry. GM only for ignition modules.

 

well what i was saying is that Wells (the company who makes Ignition modules for autozone) also makes Ignition Modules for ACDelco. as well as pretty much ever other electrical component for ACDelco...

 

Well IF they do then their quality control for their own branded stuff sucks big time.

 

i will admit to that.. (I work in the Automotive Parts Industry).
when i learned that Wells supplies parts for Motorcraft, ACDelco and one other company who i can't remember right now. and they have been since 1908. (Wells even made components for some of the "smart" bombs in WWII) Now im not sure if another company also makes parts for the ACDelco name, (other then wells) or did in the past. Buy pretty much wells has gotten a bad rep. in the past but in reality their parts aren't bad. its just mixing new and old components together that starts to sometimes causes problems. and in many cases i see that its something else causing the ignition modules (and other eletrical components) to go bad such as wiring etc that people dont realize until after their third replacement or so... And sometimes its just bad luck.
You always hear about the problems people have with "aftermarket" products, as when people have issues about a problem with something they create post like ("new ignition module burned up" etc.) . but when they get somethign that works correctly, they don't start a post titled ("got a part and it worked correctly") so unless your in the buisness and see a very low return rate you don't realize how many of these parts are sold without problems..

oh and ACdelco used to only make spart plugs, but as of about a year ago or so they stoped doing that. ACDelco is now just a marketing company, a VERY sucessful marketing company..

 

Wells Oil pressure sending unit, Tango Uniform in 1 week.

Wells Dist cap & Rotor, 2 months later the terminals were loose in the cap causing an erratic idle.

Wells water Temp sensor, T/U in 3 weeks

The list goes on and on. Every single Wells electrical component I have ever bought has failed in less than 6 months, not a good track record. I will only buy AC Delco electrical parts now and Accel caps & rotors, Never had a single one fail on me in the short term.

They may well make the parts for Delco, but Delco has higher standards the vendors have to meet to wear that name on their parts.