hesitation off idle and under load when hot
Thread Starter
Registered User
Joined: Jan 2003
Posts: 63
From: Lake Mary,FL
Re: opti
Originally posted by dan 94 Z
I vote for the opti. My 94 ran great until it reached operating temp. Then it started missing (mostly under load, no matter the gear- A4) My tach needle was bouncing erratically as well.
Mine kept getting worse and worse, and finally it got to the point where it would not start all the time.
Seemed like the optical portion of the opti would get weak after it was warm.
Perhaps it is just coincidental that when you disconnect the batteryDan
I vote for the opti. My 94 ran great until it reached operating temp. Then it started missing (mostly under load, no matter the gear- A4) My tach needle was bouncing erratically as well.
Mine kept getting worse and worse, and finally it got to the point where it would not start all the time.
Seemed like the optical portion of the opti would get weak after it was warm.
Perhaps it is just coincidental that when you disconnect the batteryDan
Last edited by chamealeondroptopZ; Jun 4, 2003 at 03:59 PM.
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Joined: Sep 2000
Posts: 432
From: KCMO
My car has recently developed the same problem, I have changed the opti and it ran better but still hesitates at warm temps under a load. After the car sits and cools it runs ok. I believe it to be a sensor problem of some sort because, it happens when the car warms up. I believe it switches from open to closed or whatever at starts to utilize the sensor info and not preset parameters. This is my thoery I hope I find the problem, right now I am leaning toward a possible map sensor as was suggested to me by a guy who knows more than I.
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Joined: Feb 2000
Posts: 2,026
From: Japan
Originally posted by guywithaZ
My car has recently developed the same problem, I have changed the opti and it ran better but still hesitates at warm temps under a load. After the car sits and cools it runs ok. I believe it to be a sensor problem of some sort because, it happens when the car warms up. I believe it switches from open to closed or whatever at starts to utilize the sensor info and not preset parameters. This is my thoery I hope I find the problem, right now I am leaning toward a possible map sensor as was suggested to me by a guy who knows more than I.
My car has recently developed the same problem, I have changed the opti and it ran better but still hesitates at warm temps under a load. After the car sits and cools it runs ok. I believe it to be a sensor problem of some sort because, it happens when the car warms up. I believe it switches from open to closed or whatever at starts to utilize the sensor info and not preset parameters. This is my thoery I hope I find the problem, right now I am leaning toward a possible map sensor as was suggested to me by a guy who knows more than I.
I would seriously check the ground stud for the PCM. You have to take the stud out of the body and clean it VERY well. Mine was so bad that I changed the bolt completely.
After I did this fix on mine it helped a lot. I gained a bunch of low end power from it.
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Joined: Feb 2003
Posts: 26
I would seriously check the ground stud for the PCM. You have to take the stud out of the body and clean it VERY well. Mine was so bad that I changed the bolt completely.
Last edited by nos4rot2; Jun 4, 2003 at 11:53 PM.
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Joined: Jun 2000
Posts: 98
From: Maryville, MO/Seward, NE
You guys and you're damn opti votes. 
Optis are not as bad as people make them out to be. I didn't get to read all of you're posts in between all the opti bs, but did you by chance scan the car while it's missing and running rough? If you did could you please post some o2 readings, maf sensor readings, knock retard, IAC, and any others that you might have?
If not, might want to think about it monitored. You'll be throwing on parts, hoping it's correct, but in all likelyhood most won't fix your problem.
I'm going to quote something I posted on another board, its about as accurate as I could describe how the engine runs in closed loop.
Optis are not as bad as people make them out to be. I didn't get to read all of you're posts in between all the opti bs, but did you by chance scan the car while it's missing and running rough? If you did could you please post some o2 readings, maf sensor readings, knock retard, IAC, and any others that you might have?
If not, might want to think about it monitored. You'll be throwing on parts, hoping it's correct, but in all likelyhood most won't fix your problem.
I'm going to quote something I posted on another board, its about as accurate as I could describe how the engine runs in closed loop.
I'll try and explain it then a little bit. When you first start your car and until it warms up it runs in open loop. During this cold idle (open loop) it's running off the stored PCM idle readings and making sure it's idling off the PCM stored values and not of the values of the sensors. When your coolent gets to a certain level, this is where your sensors will come into play. The sensors will pick up there data and send it back to the PCM where this will adjust the a/f ratio according to the values of the sensors. Also the a/c compressor has to be off (I believe it's off) in order for to go off the values of the sensors, and in manual transmissions in neutral, or automatics in drive.
Also, something I heard about is a the minimum idle air speed, which is set with a stop screw in the throttle body. This allows certain amount of air to enter the engine reguardless of the IAC position. This is unregistered air entering into your engine if its set too far out and won't allow the blades to close to their desired level that the PCM determines.
The main three sensors that could and will hurt idle (and A/F ratio in general when under 2/3 throttle or less) is the MAF, o2s and the IAC. The IAC meters the amount of air coming in through the throttle body and adjusts air flow into the engine by opening the blades up slightly. The o2 sensors will sensor your o2 reading through the exhaust and will cause the PCM to add or subtract fuel/air from the mixture to get it to read the 14.7:1 air/fuel ratio.
However, even though the PCM might believe the A/F is at 14.7:1, it might be running rich or lean due to faulty sensors, exhaust leak, ect.
The o2 sensor will pick up a lean condition, causing the PCM to add more fuel, making it run rough even though its running ok at the 14.7:1 A/F ratio.
The case with my idle problems and missing at idle and low RPMs under partial throttle was a combonation of the two. I had a faulty o2 sensor causing it to add more fuel under slight load, but under idle it wasn't adding any fuel. However, my IAC was clogged and wasn't picking up the air coming in, so the PCM opened the throttle body blades a little farther causes it to run too lean.
Best thing is to get a monitoring device, and driving around town and watch the o2 sensor readings, and the IAC counts, other sensor reading. A IAC count of 0 is the blades are fully closed, where a 140 count is fully open. I believe normal is around the 60-80 count mark. This can be monitored by a scan tool.
The mass air flow (MAF) sensor is something else to watch for. This measures the amount of air passing through it. In return the PCM adjusts the fuel delivery depending on the operating condition of the engine. A large quantity of air indicated accerlation (adds fuel), and low quantity determines idle of decleratio (subtracts fuel)
Keep in mind all sensors on board play a huge part in the a/f ratio at idle and if one is back you'll get a irratic or bad idle. Best thing to do is to monitor the sensors if you can, so you don't just replace parts that are good and waste money.
Also, something I heard about is a the minimum idle air speed, which is set with a stop screw in the throttle body. This allows certain amount of air to enter the engine reguardless of the IAC position. This is unregistered air entering into your engine if its set too far out and won't allow the blades to close to their desired level that the PCM determines.
The main three sensors that could and will hurt idle (and A/F ratio in general when under 2/3 throttle or less) is the MAF, o2s and the IAC. The IAC meters the amount of air coming in through the throttle body and adjusts air flow into the engine by opening the blades up slightly. The o2 sensors will sensor your o2 reading through the exhaust and will cause the PCM to add or subtract fuel/air from the mixture to get it to read the 14.7:1 air/fuel ratio.
However, even though the PCM might believe the A/F is at 14.7:1, it might be running rich or lean due to faulty sensors, exhaust leak, ect.
The o2 sensor will pick up a lean condition, causing the PCM to add more fuel, making it run rough even though its running ok at the 14.7:1 A/F ratio.
The case with my idle problems and missing at idle and low RPMs under partial throttle was a combonation of the two. I had a faulty o2 sensor causing it to add more fuel under slight load, but under idle it wasn't adding any fuel. However, my IAC was clogged and wasn't picking up the air coming in, so the PCM opened the throttle body blades a little farther causes it to run too lean.
Best thing is to get a monitoring device, and driving around town and watch the o2 sensor readings, and the IAC counts, other sensor reading. A IAC count of 0 is the blades are fully closed, where a 140 count is fully open. I believe normal is around the 60-80 count mark. This can be monitored by a scan tool.
The mass air flow (MAF) sensor is something else to watch for. This measures the amount of air passing through it. In return the PCM adjusts the fuel delivery depending on the operating condition of the engine. A large quantity of air indicated accerlation (adds fuel), and low quantity determines idle of decleratio (subtracts fuel)
Keep in mind all sensors on board play a huge part in the a/f ratio at idle and if one is back you'll get a irratic or bad idle. Best thing to do is to monitor the sensors if you can, so you don't just replace parts that are good and waste money.
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Joined: Jun 2000
Posts: 98
From: Maryville, MO/Seward, NE
Just to add, why I think its running good for a while is because everytime you pull that battery wire you're resetting the PCM. With doing this its resetting all sensor reading back to the original factory readings. While the car is in open loop its not going off the sensors, but after it starts going off the sensors, it's picking up something faulty. with this you're getting you're problems.
It could be one of a dozen possiblities, it's impossible to diagonose these types of problems over the internet without seeing/testing the car and getting some readings.
It could be one of a dozen possiblities, it's impossible to diagonose these types of problems over the internet without seeing/testing the car and getting some readings.
Thread Starter
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Joined: Jan 2003
Posts: 63
From: Lake Mary,FL
Yup,disconnected red battery cable last night,drove perfect this morning till temp got up to about 190(past CAGS) or about 5 miles.The reply from csabatka 1 makes sense,its pretty much what I've thought all along,a sensor getting hot but why is my SES light not on,and my idle is perfect,also my O2's are brand new AC's that I had on a month before this problem.As far as the ground stud,are you talking about that screw right under the pcm?I already cleaned it from the top(looked fine)but if it was dirty,why would disconnecting the battery clean it?Because,I dont have any diagnostic equipment I'll probably be taking it to a shop,thanks for the replys and if anyone else has any more ideas,dont hesitate(no pun intended
to reply.
to reply.
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Joined: Feb 2000
Posts: 2,026
From: Japan
The stud is located just above the red positive junction box.
The stud will look just fine until you take it out of the fender and look at it.
Mine was super corroded, and I am beginning to think that it being that way for so long caused something in the PCM to get hurt like an injector driver or something else.
The stud will look just fine until you take it out of the fender and look at it.
Mine was super corroded, and I am beginning to think that it being that way for so long caused something in the PCM to get hurt like an injector driver or something else.
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Joined: May 2003
Posts: 11
Anyone got a pic of this, I am new to Fbodys, is this right by the battery???? Thanks
Originally posted by 95 Z-28 LT1
The stud is located just above the red positive junction box.
The stud will look just fine until you take it out of the fender and look at it.
Mine was super corroded, and I am beginning to think that it being that way for so long caused something in the PCM to get hurt like an injector driver or something else.
The stud is located just above the red positive junction box.
The stud will look just fine until you take it out of the fender and look at it.
Mine was super corroded, and I am beginning to think that it being that way for so long caused something in the PCM to get hurt like an injector driver or something else.
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Joined: Feb 2000
Posts: 2,026
From: Japan
Originally posted by 1red94z28
Anyone got a pic of this, I am new to Fbodys, is this right by the battery???? Thanks
Anyone got a pic of this, I am new to Fbodys, is this right by the battery???? Thanks
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Joined: Jan 2003
Posts: 382
From: Cypress, Orange County CA.
Originally posted by Fatdog
I would replace the coil with a GM one.Might change the coil wire as well(did you save the old Coil?).Might do the cheap stuff first.(My opticrap was saturated when I totally lost my water pump,and it survived.Clocked at 105,000mi now.Still books to the limiter even in this 97 degree heat today.Hope this helps.
I would replace the coil with a GM one.Might change the coil wire as well(did you save the old Coil?).Might do the cheap stuff first.(My opticrap was saturated when I totally lost my water pump,and it survived.Clocked at 105,000mi now.Still books to the limiter even in this 97 degree heat today.Hope this helps.
Now the car runs beautiful. Go figure.
Thread Starter
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Joined: Jan 2003
Posts: 63
From: Lake Mary,FL
well,I finally took my car to the dealer to get checked after an hour and $82 later the tech said my opti wasn't "putting out enough"(like my ex girl and my pcm wasn't "communicating"with the scanner.They quoted me $486 for opti $227 for PCM and $660 labor.A few days before,I started it up one morning,and all of a sudden the exhaust seemed louder,and the engine felt rougher.Disconnecting the battery still gets rid of the knock and hesitation under 2000rpm for about 5 miles of driving but the roughness and loudnes does not not go away.I took the car to a muffler shop to check for any exhaust leaks-none,the mechanic said its running rich and the bad mixure is making it louder and rougher.Could the knock and hesitation have been my PCM all along,somhow made the opti go bad,and now the roughness is my opti?I am going to order a new opti from Jason Cromer($190) and a new PCM from www.pcmforless.com($99+125 core)and install the opti hopefully over the weekend,save about $1100 and hope these problems go away.
and my pcm wasn't "communicating"with the scanner.They quoted me $486 for opti $227 for PCM and $660 labor.A few days before,I started it up one morning,and all of a sudden the exhaust seemed louder,and the engine felt rougher.Disconnecting the battery still gets rid of the knock and hesitation under 2000rpm for about 5 miles of driving but the roughness and loudnes does not not go away.I took the car to a muffler shop to check for any exhaust leaks-none,the mechanic said its running rich and the bad mixure is making it louder and rougher.Could the knock and hesitation have been my PCM all along,somhow made the opti go bad,and now the roughness is my opti?I am going to order a new opti from Jason Cromer($190) and a new PCM from www.pcmforless.com($99+125 core)and install the opti hopefully over the weekend,save about $1100 and hope these problems go away.
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Joined: Jan 2003
Posts: 83
From: Greenville, SC
I'm in on this same, exact problem. Started a couple of weeks ago when we changed the plug wires, cap and rotor, and front O2 sensors. Now it bogs and stutters at low RPMs once it gets warm. I'm watching to see if anybody else can figure this out.
Could it be a bad batch of Delco O2 sensors?
Marcus
Could it be a bad batch of Delco O2 sensors?
Marcus
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Joined: Apr 2003
Posts: 30
From: Utah
HELP!!!!!!!!!!!!!!!!!!!!!!!!
ALRIGHT GUYS, IM in the SAME EXACT boat and IM SICK OF IT!!!!
my car has had this problem for a good year now, and now that im in the hottest point of the summer, my car is running like *** 15 minutes after I start it up............PLEASE EMAIL ME as much information you can give me to help me out........
I WOULD REALLY appericate it!!
Ok My car, does the following, when it heats up, it will do a few things, hesitate, the tach will bounce all over the place.......and IF I floor it, and get it up to higher RPMs the car will REALLY hesitate, and even make poping sounds from the exhaust........and even once in a while at the top of the rpm range... it will squill/????
and when the car is drive or reverse and my foot is on the brake....the car will sit there and have a spuratic idol......like the tach will just sit there and rev up a little and the car sounds like it wants to cut out........well yesterday for the first time, it DID!!! the car just up and died while i was siting there in my driveway, at that point I said SOB!!!!!!!!!!!!!!!!! I am SICK of this problem, my car looks FREAKING perfict, All i want is for it to run that way.........
Here is what I have done to the car to fix it....................................
Replaced Plugs, Wires, "Cap repair Kit"??? (from dealer),BRAND NEW WATER PUMP, Gutted the Cat, a new MSD Coil (even spaced it away from the engine, so it didn't heat up as much), I have done a TB bypass, and of COURSE i have replaced the Fuel Filter......................
IS THERE ANYTHING ELSE I can do???
Is a new "Cap repair Kit" the same as getting a new OPTI??? whats the difference???
PLEASE HELP ME!!!!!!
The next time i get my car worked on, I WANT IT TO actually run better when I get it back!
I have heard people tell me that me FUEL PUMP is "going out" is that possible, could a Fuel pump go out for over a year, and still run the same???? I would think the fuel pump has nothing to do with the temp of the car.... my car runs FREAKING sweet when u start it up and it's cold, like this fall, my car will run PERFICT ALL DAY LONG, because it's colder, but now that it's 90* every damn day, my car will run like *** after driving it for 20 minutes, please help me!
I am DESPERATE!! I DO NOT WANT TO SELL THIS CAR!!!!!!
my car has had this problem for a good year now, and now that im in the hottest point of the summer, my car is running like *** 15 minutes after I start it up............PLEASE EMAIL ME as much information you can give me to help me out........
I WOULD REALLY appericate it!! Ok My car, does the following, when it heats up, it will do a few things, hesitate, the tach will bounce all over the place.......and IF I floor it, and get it up to higher RPMs the car will REALLY hesitate, and even make poping sounds from the exhaust........and even once in a while at the top of the rpm range... it will squill/????
and when the car is drive or reverse and my foot is on the brake....the car will sit there and have a spuratic idol......like the tach will just sit there and rev up a little and the car sounds like it wants to cut out........well yesterday for the first time, it DID!!! the car just up and died while i was siting there in my driveway, at that point I said SOB!!!!!!!!!!!!!!!!! I am SICK of this problem, my car looks FREAKING perfict, All i want is for it to run that way.........
Here is what I have done to the car to fix it....................................
Replaced Plugs, Wires, "Cap repair Kit"??? (from dealer),BRAND NEW WATER PUMP, Gutted the Cat, a new MSD Coil (even spaced it away from the engine, so it didn't heat up as much), I have done a TB bypass, and of COURSE i have replaced the Fuel Filter......................
IS THERE ANYTHING ELSE I can do???
Is a new "Cap repair Kit" the same as getting a new OPTI??? whats the difference???
PLEASE HELP ME!!!!!!
The next time i get my car worked on, I WANT IT TO actually run better when I get it back!
I have heard people tell me that me FUEL PUMP is "going out" is that possible, could a Fuel pump go out for over a year, and still run the same???? I would think the fuel pump has nothing to do with the temp of the car.... my car runs FREAKING sweet when u start it up and it's cold, like this fall, my car will run PERFICT ALL DAY LONG, because it's colder, but now that it's 90* every damn day, my car will run like *** after driving it for 20 minutes, please help me!
I am DESPERATE!! I DO NOT WANT TO SELL THIS CAR!!!!!!