LOW RPM STUMBLE! FOR ALL THAT HAVE SOLVED OR HAVE FACTS INSIDE PLEASE! ?'s
04-21-2004, 02:48 PM
#16
Registered User
Join Date: Jul 2003
Location: Los Angeles (west)
Posts: 83
I know that folks love to jump all over the opti for these issues. I have searched these forums over the last few weeks (yes WEEKS) and read literally hundreds of posts on this issue, and here is my assessment from the problems and solutions I've read about (BTW, not enough of you post your solutions when you find them):
1. Opti is usually NOT the problem (in a very small number of cases it has rectified all, but usually only some of the problem)
2. Coil and module is usually as above.
3. Plugs and wires: Some have had good luck with replacing these.
4. O2 sensors: almost never the problem
5. Header/exhaust leaks: A few have eliminated the stumble by finding these.
6. Bad grounds: Several members have eliminated the problem by removing and cleaning all grounds to the chassis.
7. MAF sensor: one or two members have had luck by cleaning the MAF.
8. IAT: some have reported that replacing this, even when the original one 'appeared' to be operating correctly corrected the problem completely.
9. Bad compression: At least one member, after years of troubleshooting found that 2 cylinders on one bank had terrible compression, causing the problem.
10. Knock sensor: At least a couple of guys found that they were getting terrible retard from knock...bad sensor.
So, it appears that there is no ONE solution, which is why this problem is SO DAMN PREVALENT!!!
MY suggestion: Don't change the Opti right off the bat, it appears very unlikely that it's the problem.
BTW: In my efforts to elimate my stumble (which is the same symptom as all of yours), I have done the following (to no avail):
Opti (and water pump while I was there)
New O2 sensors
New coil
New module
New plugs (champion)gapped to FSM specs.
New MSD 8.5 MM wires, incl. coil wire
I'm running headers (this is in a Datsun 240Z) and my wires are routed over the valve covers and ARE NOT touching anything at all....
Checked Fuel pressure and it's in spec.
All EGR equip. is removed and blocked off and editted out of PCM (TunerCat)
No air pump or evap. purge
I have installed another (powdercoated) intake with all new gaskets. No vaccum leaks detected anywhere!
I am still hunting for a solution. I will be installing Accel 30lb injectors and a new Walbro 255lph pump.
The saga continues.......
Tim
1. Opti is usually NOT the problem (in a very small number of cases it has rectified all, but usually only some of the problem)
2. Coil and module is usually as above.
3. Plugs and wires: Some have had good luck with replacing these.
4. O2 sensors: almost never the problem
5. Header/exhaust leaks: A few have eliminated the stumble by finding these.
6. Bad grounds: Several members have eliminated the problem by removing and cleaning all grounds to the chassis.
7. MAF sensor: one or two members have had luck by cleaning the MAF.
8. IAT: some have reported that replacing this, even when the original one 'appeared' to be operating correctly corrected the problem completely.
9. Bad compression: At least one member, after years of troubleshooting found that 2 cylinders on one bank had terrible compression, causing the problem.
10. Knock sensor: At least a couple of guys found that they were getting terrible retard from knock...bad sensor.
So, it appears that there is no ONE solution, which is why this problem is SO DAMN PREVALENT!!!
MY suggestion: Don't change the Opti right off the bat, it appears very unlikely that it's the problem.
BTW: In my efforts to elimate my stumble (which is the same symptom as all of yours), I have done the following (to no avail):
Opti (and water pump while I was there)
New O2 sensors
New coil
New module
New plugs (champion)gapped to FSM specs.
New MSD 8.5 MM wires, incl. coil wire
I'm running headers (this is in a Datsun 240Z) and my wires are routed over the valve covers and ARE NOT touching anything at all....
Checked Fuel pressure and it's in spec.
All EGR equip. is removed and blocked off and editted out of PCM (TunerCat)
No air pump or evap. purge
I have installed another (powdercoated) intake with all new gaskets. No vaccum leaks detected anywhere!
I am still hunting for a solution. I will be installing Accel 30lb injectors and a new Walbro 255lph pump.
The saga continues.......
Tim
Last edited by Tim240z; 04-21-2004 at 02:50 PM.
04-21-2004, 04:41 PM
#17
Registered User
Thread Starter
Join Date: Oct 1999
Location: Atlantic City, New Jersey (south jersey)
Posts: 418
JESUS CHRIST I POSTED THIS ALMOST 2 YEARS AGO! LOL LOL! FUNNY THING IS IT WAS GONE ON THE Z I HAD BACK THEN BUT NOW I HAVE A 95 Z M6 AND THIS CAR HAS IT ALSO! LOL
04-22-2004, 05:52 PM
#18
Registered User
Join Date: May 2003
Location: Regina,Sask,Canada
Posts: 724
I have some of this on my 96z.Not all the time ,sometimes seems the car runs very hard and sometimes kind of dogs it and that can be on back to back runs.
I put in a new tps today.Seems to be better.Tps is very easy to change out in our lt1s..took maybe ten minutes and its not that expensive.The tps sensors can wear out and get flat spots and cause funny bogs.
I am not sure my problem is 100% cured.Have to do a bit more driving.I still plan on some other steps too.blocking off egr sounds like a good one.Can't you just block off line on intake that controlls the egr valve to open.Might be easier than putting the plate in there.
Other ideas for some of you guys are cleaning the maf can sometimes do this for sure ,especially if you an oil type k and n like many people run.
And fuel filter should be changed out every 10000miles I think its pretty simple and easy to do .I usually pay like ten bucks US to have local quick change guys do it.
Also some good injector cleaner like redline can't hurt full bottle at beginning of year and some maintenance treatment after that.
Personally I have zero interest is swapping out the crappy opti even once.I will be going with a deltec system if it needs fixing.
Also I wonder if the dreaded intake manifold leak can cause some of these problems from vacuum leak.I did have it on my old 97 ta but forget now if it caused some bogging or not.
I put in a new tps today.Seems to be better.Tps is very easy to change out in our lt1s..took maybe ten minutes and its not that expensive.The tps sensors can wear out and get flat spots and cause funny bogs.
I am not sure my problem is 100% cured.Have to do a bit more driving.I still plan on some other steps too.blocking off egr sounds like a good one.Can't you just block off line on intake that controlls the egr valve to open.Might be easier than putting the plate in there.
Other ideas for some of you guys are cleaning the maf can sometimes do this for sure ,especially if you an oil type k and n like many people run.
And fuel filter should be changed out every 10000miles I think its pretty simple and easy to do .I usually pay like ten bucks US to have local quick change guys do it.
Also some good injector cleaner like redline can't hurt full bottle at beginning of year and some maintenance treatment after that.
Personally I have zero interest is swapping out the crappy opti even once.I will be going with a deltec system if it needs fixing.
Also I wonder if the dreaded intake manifold leak can cause some of these problems from vacuum leak.I did have it on my old 97 ta but forget now if it caused some bogging or not.
04-22-2004, 06:54 PM
#19
Registered User
Join Date: Apr 2004
Location: INDIANA
Posts: 1
Re: LOW RPM STUMBLE! FOR ALL THAT HAVE SOLVED OR HAVE FACTS INSIDE PLEASE! ?'s
Originally posted by CJ Black LS1 Z28 M6
Okay... I have a 94 Z28. Right now it has Bosch Platinum Plugs and Taylor wires brand new Borg Warner Coil and GM wire. Anywhere from 1000-2500 RPM's it will stumble and hesitate badly.
FACTS
It DOESN'T stumble or hesitate during WIDE OPEN THROTTLE
IT DOESN'T stumble or hesitate until the about/past 180 degrees
IT ISN'T THE MAF because I unplugged it and it did the same thing
I Checked the wires in the pitch black and didn't see any arching
The wires are away from the headers with wire ties (I know they still can be damaged inside)
QUESTIONS
If it was the Opti wouldn't it do it all the time and not at certain temperatures?
If it were the O2 sensors wouldn't the car stumble during high RPM's when the car is floored?
If it were the fuel pump wouldn't it do it when the car is 1st starting to move?
Could it be a plug or plug wire even though there is no miss when i rev the car?
Could it be plug or plug wire even though it takes the car until 180 degrees or above to start stumbling?
Sorry to ramble on guys but I have some other repairs I want to do to the car and I don't want to spend ALOT of money replacing everything just trying to replace things that don't need to be replaced yet. This is killing me everytime I drive my Z I miss my 99 Z28 M6 1000x more
please help
Okay... I have a 94 Z28. Right now it has Bosch Platinum Plugs and Taylor wires brand new Borg Warner Coil and GM wire. Anywhere from 1000-2500 RPM's it will stumble and hesitate badly.
FACTS
It DOESN'T stumble or hesitate during WIDE OPEN THROTTLE
IT DOESN'T stumble or hesitate until the about/past 180 degrees
IT ISN'T THE MAF because I unplugged it and it did the same thing
I Checked the wires in the pitch black and didn't see any arching
The wires are away from the headers with wire ties (I know they still can be damaged inside)
QUESTIONS
If it was the Opti wouldn't it do it all the time and not at certain temperatures?
If it were the O2 sensors wouldn't the car stumble during high RPM's when the car is floored?
If it were the fuel pump wouldn't it do it when the car is 1st starting to move?
Could it be a plug or plug wire even though there is no miss when i rev the car?
Could it be plug or plug wire even though it takes the car until 180 degrees or above to start stumbling?
Sorry to ramble on guys but I have some other repairs I want to do to the car and I don't want to spend ALOT of money replacing everything just trying to replace things that don't need to be replaced yet. This is killing me everytime I drive my Z I miss my 99 Z28 M6 1000x more
please help
IT COULD BE THE AIR PUMP
04-22-2004, 09:57 PM
#21
Registered User
Join Date: Jun 2001
Location: Grants Pass, OR, USA
Posts: 29
Stumble Mumble
Had low speed stumble, changed opti, changed coil, changed wires, changed plugs, changed TPS, changed temp sensor (one in water pump),relocated coil and ignition module, checked knock sensor, replaced O2 sensors, tested IAT, checked fuel pressure, replaced injectors, tried a few other thing I dont remember, tested everything I or anybody else could think of.
Still had low speed stumble. When in closed loop 1800 rpm and below, warmer it gets the worse the stumble was.
Read about IAT's that test ok but give faulty signals at some temperatures. Replaced IAT, stumble gone below 170 degrees. Already had 160 degree thermostat, added manual fan switch, life is good.
93Z, Red, M6, TBB, OffRoad Pipe, B&M Shifter, 60K
Still had low speed stumble. When in closed loop 1800 rpm and below, warmer it gets the worse the stumble was.
Read about IAT's that test ok but give faulty signals at some temperatures. Replaced IAT, stumble gone below 170 degrees. Already had 160 degree thermostat, added manual fan switch, life is good.
93Z, Red, M6, TBB, OffRoad Pipe, B&M Shifter, 60K
04-22-2004, 10:01 PM
#22
Registered User
Join Date: Sep 2002
Location: middleboro, MA
Posts: 175
I think you can pretty much rule out Tunes. I have spent the last week throwing a good 20 tunes at it and i have about 50 logs. The constants seem to be that when it hesitates (immediately on entering closed loop) it shows a value for the EGR DC, and has at least some spark retard that is not knock related. Also my car seems to run very rich. I have logs i can email if anyone is interested. I tuned everything i could think of, upping and downing spark advance, i played with the EGR spark advance correction vs vacuum vs RPM table, i even played with the traction control tables and nothing seemed to make any difference.....If anyone has any more ideas on what i might try i am willing to play with it more, i am just plain out of ideas i have throw a few parts at it but i think i just might throw a new set of O2's at it next...
04-24-2004, 12:49 PM
#23
Registered User
Join Date: Aug 2002
Location: BC
Posts: 2,325
I posted some information the other day about the coolant hose being too close to the IAT sensor, not too many replies but it would make perfect sense. Just look at the intake sensor and see if one of the coolant hoses is right beside it, touching or almost touching. If it is zip strap it down to a nearby hose so it isnt beside the temperature sensor.
It was throwing off my sensor BIG time and giving it some way wrong readings. I think it may have also damaged the original one because even after I moved it, the temps were no longer skyrocketing in traffic, but were about 5 degrees C higher than they should be.
So just check the sensor for nearby hoses, it doesnt hurt and its free.
It was throwing off my sensor BIG time and giving it some way wrong readings. I think it may have also damaged the original one because even after I moved it, the temps were no longer skyrocketing in traffic, but were about 5 degrees C higher than they should be.
So just check the sensor for nearby hoses, it doesnt hurt and its free.
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