Hesitation off idle
Registered User
Joined: Jul 1999
Posts: 3,647
From: Winnipeg, Manitoba, Canada
Has anyone tried a friend's fuel rail complete with injectors and regulator yet?
If your fuel psi is normal, that is not an indicator that your fuel injectors are ok.
[This message has been edited by Gripenfelter (edited July 16, 2002).]
If your fuel psi is normal, that is not an indicator that your fuel injectors are ok.
[This message has been edited by Gripenfelter (edited July 16, 2002).]
Registered User
Joined: May 2002
Posts: 87
From: ARNOLD MO USA
so what if it arcs to the block its ok or not? you would think it would arc to it for sure! since the car does start and drive...
ANOTHER THING MY CAR WILL NOT CUT OUT UNLESS ITS DRIVING UNDER SOME TYPE OF A LOAD (WOT) IN NUETRAL AND PARK IT IS JUST FINE//??????? PLEASE HELP MY CAR HAS LOST ITS >>MOJO<< :-)
ANOTHER THING MY CAR WILL NOT CUT OUT UNLESS ITS DRIVING UNDER SOME TYPE OF A LOAD (WOT) IN NUETRAL AND PARK IT IS JUST FINE//??????? PLEASE HELP MY CAR HAS LOST ITS >>MOJO<< :-)
Registered User
Joined: Nov 2001
Posts: 3,515
From: Kansas
i am wondering how many of you guys are getting knock retard when you mash on the throttle. what that could cause is a jolt that is picked up by your knock sensor which then proceeds to pull out timing causing an obvious lack of power or hesitation.
many of you need to scan your cars before you start to make conclusions about anything. case in point, when i got my scanmaster, i noticed my MAF was bad(never got a code) and never would have known otherwise nor did i suspect it. so check for anything out of the ordinary and read up on Freds scanmaster page so youll understand normal opporating conditions.
------------------
Brad
1997 Z28 M6
T-tops, chrome rims, all options, SLP Dual/Dual, cutout, !CAGS, FIPK, LT4 KM, Air Foil, TB bypass, pro 5.0, OBD1, !EGR, !AIR, CSI waterpump, 160* thermostat, 1LE intake elbow, PCM tuning by, www.PCMFORLESS.com , taylors, singe-cat SLP shorties minus the cat!
many of you need to scan your cars before you start to make conclusions about anything. case in point, when i got my scanmaster, i noticed my MAF was bad(never got a code) and never would have known otherwise nor did i suspect it. so check for anything out of the ordinary and read up on Freds scanmaster page so youll understand normal opporating conditions.
------------------
Brad
1997 Z28 M6
T-tops, chrome rims, all options, SLP Dual/Dual, cutout, !CAGS, FIPK, LT4 KM, Air Foil, TB bypass, pro 5.0, OBD1, !EGR, !AIR, CSI waterpump, 160* thermostat, 1LE intake elbow, PCM tuning by, www.PCMFORLESS.com , taylors, singe-cat SLP shorties minus the cat!
Registered User
Joined: Oct 2000
Posts: 2,402
From: Toronto, ON Canada
I'm trying to summarize results for the most common problem:
Normal conditions: floor the car in 1st gear at about 1100 RPMs and it spins /chirps wheels and runs strong. Instant accelerator response.
Hesitation: floor the car around 1000 - 1200 RPMs and there is no reaction for about 1 second, then the engine feels like it's dying, or short on air/fuel and barely starts pulling. You can hear popping sound sometimes (engine popping, not muffler). As RPMs hit 1900 - 2000, the engine kicks in and the car takes off.
1. Problem occurs when in closed loop (after the car warms up). It will not occur when the entine is cold.
2. Problem is much worse when temperature is really high.
3. Disconnecting the MAF completely will eliminate the problem.
4. Does not depend on descreened/ported or completely stock MAF.
5. 93 cars (which don't have MAF) also have it.
6. Problem worsens when turning on A/C, as it robs the engine of some power.
My thoughts on this:
1. Do LT1Brutus's suggestion. This may be a very good solution.
2. Does not seem to be injectors / wires / plugs / coil, since the problem occurs only in closed loop.
2.5 Does not seem to be mechanical fuel delivery (fuel pump, fuel filter, fuel rails). This means that even if during hesitation the fuel pressure drops, it is computer- and sensor-related. Don't waste $$$ on replacing those components.
3. Since the problem occurs almost at idle, have the car relearn idle. Every time the PCM loses its battery connection, it has to relearn idle. To do this for manual transmission (I will post later about how to do this for automatic transmission when I get home):
a) when the car is turned off, disconnect and reconnect the battery.
b) start up the car and turn on air conditioner.
c) let it run with air conditioner for 10 minutes.
d) turn off air conditioner and let it run for 10 minutes.
e) turn off the car for about 30 seconds
4. Something else (on which I don't have much hope) is TB bypass. Does anyone who has done this mod experience the problem? Coolant going through TB will heat up the air to higher temperature than it's at as it passes MAF. So MAF reads one temperature of the air, and TB heats it up by a few degrees. The end result is incorrect air/fuel mixture. We all know the air flows faster with higher RPMs and it flows slower at low RPMs. Slow flow through TB may be just what is necessary to heat up the air and cause this problem. Again, just a thought.
Edit: Something else. Since the problem occurs in closed loop vs. open loop, how about finding out from what sensors the PCM reads data when it goes into closed loop (vs. open loop) and going through them one by one?
I am doing #2,3,4 shortly, and will report the results.
[This message has been edited by muckz (edited July 16, 2002).]
Normal conditions: floor the car in 1st gear at about 1100 RPMs and it spins /chirps wheels and runs strong. Instant accelerator response.
Hesitation: floor the car around 1000 - 1200 RPMs and there is no reaction for about 1 second, then the engine feels like it's dying, or short on air/fuel and barely starts pulling. You can hear popping sound sometimes (engine popping, not muffler). As RPMs hit 1900 - 2000, the engine kicks in and the car takes off.
1. Problem occurs when in closed loop (after the car warms up). It will not occur when the entine is cold.
2. Problem is much worse when temperature is really high.
3. Disconnecting the MAF completely will eliminate the problem.
4. Does not depend on descreened/ported or completely stock MAF.
5. 93 cars (which don't have MAF) also have it.
6. Problem worsens when turning on A/C, as it robs the engine of some power.
My thoughts on this:
1. Do LT1Brutus's suggestion. This may be a very good solution.
2. Does not seem to be injectors / wires / plugs / coil, since the problem occurs only in closed loop.
2.5 Does not seem to be mechanical fuel delivery (fuel pump, fuel filter, fuel rails). This means that even if during hesitation the fuel pressure drops, it is computer- and sensor-related. Don't waste $$$ on replacing those components.
3. Since the problem occurs almost at idle, have the car relearn idle. Every time the PCM loses its battery connection, it has to relearn idle. To do this for manual transmission (I will post later about how to do this for automatic transmission when I get home):
a) when the car is turned off, disconnect and reconnect the battery.
b) start up the car and turn on air conditioner.
c) let it run with air conditioner for 10 minutes.
d) turn off air conditioner and let it run for 10 minutes.
e) turn off the car for about 30 seconds
4. Something else (on which I don't have much hope) is TB bypass. Does anyone who has done this mod experience the problem? Coolant going through TB will heat up the air to higher temperature than it's at as it passes MAF. So MAF reads one temperature of the air, and TB heats it up by a few degrees. The end result is incorrect air/fuel mixture. We all know the air flows faster with higher RPMs and it flows slower at low RPMs. Slow flow through TB may be just what is necessary to heat up the air and cause this problem. Again, just a thought.
Edit: Something else. Since the problem occurs in closed loop vs. open loop, how about finding out from what sensors the PCM reads data when it goes into closed loop (vs. open loop) and going through them one by one?
I am doing #2,3,4 shortly, and will report the results.
[This message has been edited by muckz (edited July 16, 2002).]
Registered User
Joined: Jul 1999
Posts: 3,647
From: Winnipeg, Manitoba, Canada
Its obvious that all of you have different problems. I've been reading along and I think everyone should go do the following and report back...
(This ONLY applies to people that are having the hesitation off idle as soon as the car is started up)
1) Change Fuel Filter.
2) Dump a bottle of Heavy Duty Fuel System cleaner into the tank and run the entire tank.
3) Swap in a friend's MAF (if you are 94+).
4) Swap complete throttlebodies with someone else. (That will clear up any questions about the IAC and TPS)
5) Swap fuel rails with someone else.
------------------
'93 Camaro Z28 Automatic with a ZL1 hood.
No bottle.
No blower.
383 cubic inch serving of horsepower...hold the rice please.
Thats all you need to know.
ICQ: 23984221
Gripenfelter's Homepage
Disclaimer: The opinions expressed by me are not necessarily supported or indicative of the Government of Canada or any other Federal Employee.
[This message has been edited by Gripenfelter (edited July 17, 2002).]
(This ONLY applies to people that are having the hesitation off idle as soon as the car is started up)
1) Change Fuel Filter.
2) Dump a bottle of Heavy Duty Fuel System cleaner into the tank and run the entire tank.
3) Swap in a friend's MAF (if you are 94+).
4) Swap complete throttlebodies with someone else. (That will clear up any questions about the IAC and TPS)
5) Swap fuel rails with someone else.
------------------
'93 Camaro Z28 Automatic with a ZL1 hood.
No bottle.
No blower.
383 cubic inch serving of horsepower...hold the rice please.
Thats all you need to know.
ICQ: 23984221
Gripenfelter's Homepage
Disclaimer: The opinions expressed by me are not necessarily supported or indicative of the Government of Canada or any other Federal Employee.
[This message has been edited by Gripenfelter (edited July 17, 2002).]
Registered User
Joined: Nov 2001
Posts: 40
From: Oakland, CA, USA
This description matches my problem EXACTLY as far as symptoms goes, dead on. As far as solutions goes, I have a couple things to try still, egr, air, check for fireworks under hood etc, just havent had much time for car.
Anyone have any success with anything?
------------------
1997 30th Anniversary Z28
Exterior: Arctic White with Hugger Orange Stripes
Interior: Arctic White Leather with Embroidered 30th Anv Emblem.
17x9.5 17x11 ZR1's
LS1 Aluminum Driveshaft,
BMR Adjustable PHB, Moroso CAI,
CSI Electric Water Pump, 1LE Intake Bellows
http://filonic.fbody.com
Anyone have any success with anything?
<font face="Verdana, Arial" size="2">Originally posted by muckz:
I'm trying to summarize results for the most common problem:
Normal conditions: floor the car in 1st gear at about 1100 RPMs and it spins /chirps wheels and runs strong. Instant accelerator response.
Hesitation: floor the car around 1000 - 1200 RPMs and there is no reaction for about 1 second, then the engine feels like it's dying, or short on air/fuel and barely starts pulling. You can hear popping sound sometimes (engine popping, not muffler). As RPMs hit 1900 - 2000, the engine kicks in and the car takes off.
1. Problem occurs when in closed loop (after the car warms up). It will not occur when the entine is cold.
2. Problem is much worse when temperature is really high.
3. Disconnecting the MAF completely will eliminate the problem.
4. Does not depend on descreened/ported or completely stock MAF.
5. 93 cars (which don't have MAF) also have it.
6. Problem worsens when turning on A/C, as it robs the engine of some power.
My thoughts on this:
1. Do LT1Brutus's suggestion. This may be a very good solution.
2. Does not seem to be injectors / wires / plugs / coil, since the problem occurs only in closed loop.
2.5 Does not seem to be mechanical fuel delivery (fuel pump, fuel filter, fuel rails). This means that even if during hesitation the fuel pressure drops, it is computer- and sensor-related. Don't waste $$$ on replacing those components.
3. Since the problem occurs almost at idle, have the car relearn idle. Every time the PCM loses its battery connection, it has to relearn idle. To do this for manual transmission (I will post later about how to do this for automatic transmission when I get home):
a) when the car is turned off, disconnect and reconnect the battery.
b) start up the car and turn on air conditioner.
c) let it run with air conditioner for 10 minutes.
d) turn off air conditioner and let it run for 10 minutes.
e) turn off the car for about 30 seconds
4. Something else (on which I don't have much hope) is TB bypass. Does anyone who has done this mod experience the problem? Coolant going through TB will heat up the air to higher temperature than it's at as it passes MAF. So MAF reads one temperature of the air, and TB heats it up by a few degrees. The end result is incorrect air/fuel mixture. We all know the air flows faster with higher RPMs and it flows slower at low RPMs. Slow flow through TB may be just what is necessary to heat up the air and cause this problem. Again, just a thought.
Edit: Something else. Since the problem occurs in closed loop vs. open loop, how about finding out from what sensors the PCM reads data when it goes into closed loop (vs. open loop) and going through them one by one?
I am doing #2,3,4 shortly, and will report the results.
[This message has been edited by muckz (edited July 16, 2002).]</font>
I'm trying to summarize results for the most common problem:
Normal conditions: floor the car in 1st gear at about 1100 RPMs and it spins /chirps wheels and runs strong. Instant accelerator response.
Hesitation: floor the car around 1000 - 1200 RPMs and there is no reaction for about 1 second, then the engine feels like it's dying, or short on air/fuel and barely starts pulling. You can hear popping sound sometimes (engine popping, not muffler). As RPMs hit 1900 - 2000, the engine kicks in and the car takes off.
1. Problem occurs when in closed loop (after the car warms up). It will not occur when the entine is cold.
2. Problem is much worse when temperature is really high.
3. Disconnecting the MAF completely will eliminate the problem.
4. Does not depend on descreened/ported or completely stock MAF.
5. 93 cars (which don't have MAF) also have it.
6. Problem worsens when turning on A/C, as it robs the engine of some power.
My thoughts on this:
1. Do LT1Brutus's suggestion. This may be a very good solution.
2. Does not seem to be injectors / wires / plugs / coil, since the problem occurs only in closed loop.
2.5 Does not seem to be mechanical fuel delivery (fuel pump, fuel filter, fuel rails). This means that even if during hesitation the fuel pressure drops, it is computer- and sensor-related. Don't waste $$$ on replacing those components.
3. Since the problem occurs almost at idle, have the car relearn idle. Every time the PCM loses its battery connection, it has to relearn idle. To do this for manual transmission (I will post later about how to do this for automatic transmission when I get home):
a) when the car is turned off, disconnect and reconnect the battery.
b) start up the car and turn on air conditioner.
c) let it run with air conditioner for 10 minutes.
d) turn off air conditioner and let it run for 10 minutes.
e) turn off the car for about 30 seconds
4. Something else (on which I don't have much hope) is TB bypass. Does anyone who has done this mod experience the problem? Coolant going through TB will heat up the air to higher temperature than it's at as it passes MAF. So MAF reads one temperature of the air, and TB heats it up by a few degrees. The end result is incorrect air/fuel mixture. We all know the air flows faster with higher RPMs and it flows slower at low RPMs. Slow flow through TB may be just what is necessary to heat up the air and cause this problem. Again, just a thought.
Edit: Something else. Since the problem occurs in closed loop vs. open loop, how about finding out from what sensors the PCM reads data when it goes into closed loop (vs. open loop) and going through them one by one?
I am doing #2,3,4 shortly, and will report the results.
[This message has been edited by muckz (edited July 16, 2002).]</font>
------------------
1997 30th Anniversary Z28
Exterior: Arctic White with Hugger Orange Stripes
Interior: Arctic White Leather with Embroidered 30th Anv Emblem.
17x9.5 17x11 ZR1's
LS1 Aluminum Driveshaft,
BMR Adjustable PHB, Moroso CAI,
CSI Electric Water Pump, 1LE Intake Bellows
http://filonic.fbody.com
Registered User
Joined: Apr 2001
Posts: 369
From: Toronto, Ontario, Canada
The more I read the more I start to thing, ICM.
We're all experiencing this. We've all got different mileage and routing of our wires, new or old optis, different fuel pumps etc...
We ALSO all have different plugs.
It looks more and more like we all have one thing in common. Stock placement of the ICM. Its a simple processor, and you know what your PC does when it overheats, it crashes. This ICM gets incredibly hot, regardless of engine temp.
Last night I dynotuned with a 393 SC LT1 with a crane (****) box, and fireball coil. You should have seen how smooth this curve was.
I will be relocating my coil, and ICM shortly, and trying out moving it back from the head to start.
I'm more confident than ever, this is our issue. It does SO much at 5000 RPM, to be sitting on the head of the engine like that.
Cam.
DR.ZED
We're all experiencing this. We've all got different mileage and routing of our wires, new or old optis, different fuel pumps etc...
We ALSO all have different plugs.
It looks more and more like we all have one thing in common. Stock placement of the ICM. Its a simple processor, and you know what your PC does when it overheats, it crashes. This ICM gets incredibly hot, regardless of engine temp.
Last night I dynotuned with a 393 SC LT1 with a crane (****) box, and fireball coil. You should have seen how smooth this curve was.
I will be relocating my coil, and ICM shortly, and trying out moving it back from the head to start.
I'm more confident than ever, this is our issue. It does SO much at 5000 RPM, to be sitting on the head of the engine like that.
Cam.
DR.ZED
Registered User
Joined: May 2001
Posts: 279
From: Overlandpark, Ks
Well has any one tried anything? what is the verdict? I too am disapointed with my cars hesitation. I put on long tubes and CAI with gmmg exhaust and still am getting beat by a stock 96 ws6. i though i would at least be even with him. he didn't beat me by much before the headers? What ever this heistation/loss of power is i want to fix it. Lets figure this out guys! I descreened and ported my MAF. I will borrow a stock one from a friend and try that.
------------------
1995 Silver Z-28
* Black Leather, T-Tops, Bose Audio, A4 w/2.73's.
*MODS*
Ported MAF, !CAT, fan switch, !TB Coolant bypass, Hooker Longtubes, GMMG Chambered exhaust, 4" homemade CAI w/ram air scoop
* 1/4 mile- 14.372@ 98.09mph w/ 2.391 60' time (stock)
*New times to come soon!!
------------------
1995 Silver Z-28
* Black Leather, T-Tops, Bose Audio, A4 w/2.73's.
*MODS*
Ported MAF, !CAT, fan switch, !TB Coolant bypass, Hooker Longtubes, GMMG Chambered exhaust, 4" homemade CAI w/ram air scoop
* 1/4 mile- 14.372@ 98.09mph w/ 2.391 60' time (stock)
*New times to come soon!!