Ok its me again same problem 2nd mechanic still no results, my car has been in 2 shops for 3 months no body can find the problem and these are good mechanics, 1985 vette headers, cat back, and gutted cat, now the problem is that when the car starts it will idle for a minute mabey then the motor stats to sputter or surge and if you try to give it some gas it will shut down, but if you tickle the peddle and get the RPM above 1800 it will run fine but if RPM falls below 1800 it starts to surge again, when you pull the codes off it has like 13 different ones like to rich to lean things that can't happen at once, i replaced the computor twice new air sensor ESC idle sensor new distributor if it comes off its been replaced, every thing checks out good when you test them and every thing is set to spec.we did notice that the computor seems to be getting hot,before i put it out off its misery mabey one off you fellows can come up with a fix.HELP

 

Can you list out the codes that it is throwing? Maybe there are one or two that are major contributors to this problem.

 

Was the fuel system checked? Pressure under load?

 

3 months? what have these shops been doing in 3 months?

 

How old is the battery? Is it maintaining correct voltage while under load? A low/bad battery will raise hell with the ECM.

 

I had a defective egr valve in my 87 that gave a similar problem. It would surge with gradually increasing rpm and lower rpm.. then die. !#@$# in traffic to get it home. Hard to start also,, nothing $750 at my local dealer didn't cure.

It doesn't have to be your egr, but I would look at it and all the plumbing to it. A broken vac line to the egr will cause it to malfunction.

99 Nassau Blue

 

Start at the beginning. When it dies, what goes away? Is it air, fuel, spark, or compression? Once that has been determined, THEN, clear all the codes. Start the engine, and when it dies, check what codes have been set during that brief run. One step at a time will get you there.

RACE ON!!!

 

I have a new battery in also smoke tested for vac leaks nothing as for the codes all codes were rechecked over and over again every thing that was thrown out was either replaced or checked out fine with futher testing....as for the time at the shops after 1 week of checking the car out and not finding anything they would look at it when they could so i wouldn't have to morgage my house..

 

Does that mean the car is no longer setting codes?

I have to repeat my previous question:RACE ON!!!

 

They're few possible causes, but it's a good bet it's the 02 sensor or the 02 sensor circuit.

When the engine is first started, the ECM ignores 02 feedback until the 02 reaches about 600 degrees F. During that time, the engine will run off pre-programmed maps in the PROM. Usually the engine will run relatively well in that open loop mode.

Once the 02 reaches 600 F, and the systemgoes closed loop, the ECM begins to accept feedback from the 02 sensor and uses that feedback to determine injector duty cycle (on-time).

Other possible causes are: leaking intake manifold/runner/plenum gasket, leaking vacuum hose(s), malfunctioning or incorrectly set TPS, MAF and/or Coolant Temp sensor.

If you had a scanner that can read the data real-time as the engine is idling, like Diacom, you can monitor the activity of the sensors and zero in on the one operating out of range.

The sensors to be particularly concerned with are MAF, TPS, Coolant Temp, IAC and 02.

Just my thoughts.

Jake

 

Hi Jake i was hoping you would join in, The maf was replaced also the coolant temp. and 02sensor, the tps is set at .54 And they did a smoke leak down test everythink is ok, the only thing we haven't changed is the prom, parts man at apple chev said it wouldn't make a differance, i have the 4+3 tranny and he said that there were 2 different 4+3 trannys and he would have to know which 1 i had but the numbers are rubbed off the tag and we can't read it, mine has the OD on the top of the shifter if it comes into play,i'm copying every thing you guys say and takeing it to the mechanic and so far its all been done, Every body is looking for the hard end and i think its probably something real stupid that you can't see because of the forest, if you know what i mean Thanks Ron.....

 

Another thought I had: Our systems are VERY sensitive to vacuum and exhaust leaks.

I once had a hairline crack in the #3 header, upstream of the 02 sensor and it caused all sorts of idling, surging and Lean Exhaust Present SES codes. You'll need to very carefully check all exhaust pipes and gaskets for a crack or leak, especially upstream of the 02.

Since you've already spent so much time and $$ trying to track down this problem, here's what I'd do next:

I'd next cap off all the vacuum ports to the engine: those that feed the brake booster, fuel pressure regulator, cruise, hose barb located under TB, gas tank vent system, etc. to eliminate them as a possible source.

If the problem doesn't go away, I'd then check for vacuum leaks using some fluid - I simply use water from a garden hose - and flood all the areas where two parts mate. Intake to head, runners to intake, runners to plenum, EGR, injectors to intake, TB to plenum, MAF bellows/accordian, PCV hose to intake, brake booster vacuum hose/connections, etc. I once had a vacuum leak caused by one injector "O" ring that almost drove me up the wall to locate. My garden hose found it!

If the engine stumbles, and/or white smoke comes out the tail pipe(s), you've found a leak. Remember, it only takes a tiny leak to cause a problem.

If nothing shows in those checks, I'd get a real time data logger, like Diacom or a ScanTool and monitor the sensor activity as the engine idles. A data logger should show which sensor is operating out of range, but the sensor, itself, may not be bad. Instead it could be the connection to that sensor.

My approach is to check the simple/basic stuff first - simple/basic as in spend NO $$$.

Hope this helps.

Jake

 

Hope this helps the mechanic said that when he disconnects the wire from the computor to the dist. that makes it advance the motor smooths right out,But off course it doesn't run right but it doesn't surge or shut off,untill battery is disconnected and then the wire reconnected then the trouble is back.And its not throwing out any codes now, Thanks Ron.....

 

Take out the module in the dist and have it tested at your local discount parts store.

 

You can also try checking the ignition timing with a timing light to see if the ECM is taking over control of the ignition timing after the engine has run for a short period. Timing should advance at idle to the low 20 degree BTDC range once the ECM takes control.

Back near day one, I found my ECM wasn't doing that, so I swapped in a borrowed ECM (used my PROM) and the engine smoothed out. Bought a replacement ECM for $100 and haven't had that problem since.

Many 'F' body cars (Camaros, FireBirds, Trans Ams) use the same ECM as ours; they have a different PROM programming though.

Jake

 

OK the timeing is not advanceing when warm, it stays at 6 deg.Now like i said we replaced my ECM with a new 1 and still same problem so we borrowed 1 from another shop and same thing, so i don't see how it could be the ECM, would the prom make it act this way? i can't buy a prom from the chev. dealer they no longer make them alternative is to buy a performance chip or have some one burn me 1. any thoughts...Thanks Ron.........

 

Re-read my previous reply.

 

Try the easiest\least expensive things first. Having the distributor module tested at one of the larger auto parts stores is free. If it checks 'bad", I suggest having it tested at a second DIFFERENT auto parts store; say AutoZone then Pep Boys/O'Reilly's/etc.and/or have a new one off the shelf tested.

I suggest this because of a personal experience I had when O'Reilly's had a defective tester and my module and two NEW ONES OFF THE SHELF, tested bad. AutoZone then tested mine again and it tested GOOD; problem turned out to be the coil.

If several ECMs give the same no-timing advance result, I'd suspect the wiring/connections.

Are you sure the EST wire has a good connection? Tan wire with black stripe in a weatherpak connector located near the power brake booster.

Jake

 

Jake, thank you. You echo'd my thoughts. I was too lazy to type it all out. I have seen this many times and the module was often the problem. I never believe in swapping out parts. Free test makes sense to me.

 

Get your car out of there first of all. Get a manual, a multimeter and listen to the guys here. JAKE, PeteK,vader 86,CFI, 65Z01, SunCR all know what they are talking about. This forum is the best "shop" in town.