Stumbling Problem in Great Detail
11-17-2003, 03:33 PM
#16
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Join Date: Sep 1999
Location: NASHVILLE, TN
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I don't think the fuel pressure sounds right "48-50psi when it stumbles" (unless a '93 is different). Mine will be 38 at idle and go up to 43'ish when I get on it. It never spikes up to 50psi. Might check that again.. especially if that is when it is running rich/stumbling. Did you program for the larger injectors?
11-18-2003, 02:44 AM
#17
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Join Date: Jun 1999
Location: The Haven, Fl
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Yeah it could be a coil. Brand new 300 Accel I bought w/ the coil lasting 6 days or so. Put the old one back in and bam back up and running. Still need a new coil though since it stumbles from time to time. THat coil is 7 yrs old. Gonna get a a crane coil this time around and see how it does since it's got the most volts 53K.
11-18-2003, 07:43 PM
#18
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Location: Waynesboro, PA
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The car's got pretty extensive tuning, and yes, it's been corrected for the larger injectors.
The fuel pressure was taking a jump up due to the throttle being wide open. It's acting normal, just like my service manual specifies.
I got stuck on the road for another day, so maybe tomorrow I'll be home and able to get back to wrenching on it. Going to try the coil swap and see what happens. If that doesn't work, I'll swap the ICM from my other 93 onto it and see how things work then......
It's a love hate relationship isn't it??
The fuel pressure was taking a jump up due to the throttle being wide open. It's acting normal, just like my service manual specifies.
I got stuck on the road for another day, so maybe tomorrow I'll be home and able to get back to wrenching on it. Going to try the coil swap and see what happens. If that doesn't work, I'll swap the ICM from my other 93 onto it and see how things work then......
It's a love hate relationship isn't it??
11-18-2003, 09:22 PM
#20
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Join Date: Aug 2000
Location: Dallas, TX
Posts: 60
I've yet to see if anyone suggest a vaccum leak - From your list of things checked, it's difficult to tell if you've been taken off anything recently that would cause it....
What about Intake elbow leaks/tears (especially underneath, where you cannot see)...or a intake manifold gasket going south..?
Have you used vaccum gauge on it...?
The PCM is compensating for something it 'sees'....a lean condition from too much unregulated air or a similar cause....is making it dump fuel into the system. The rest is up to you, Neo..
Just my .02....
What about Intake elbow leaks/tears (especially underneath, where you cannot see)...or a intake manifold gasket going south..?
Have you used vaccum gauge on it...?
The PCM is compensating for something it 'sees'....a lean condition from too much unregulated air or a similar cause....is making it dump fuel into the system. The rest is up to you, Neo..
Just my .02....
11-18-2003, 11:22 PM
#22
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No Vaccuum leaks, the intake manifold is fine. It's just really stumping, especially since there's so many things that could be the culprit, and there's really no way to just single out which one it is except through trial and error.
My course of action over the next few days will be swapping my coil first, then the ICM from my other 93. Next will probably be the EGR since I was throwing a code for that before the head/cam package went on. After that, I'm going to be at a complete loss.
My course of action over the next few days will be swapping my coil first, then the ICM from my other 93. Next will probably be the EGR since I was throwing a code for that before the head/cam package went on. After that, I'm going to be at a complete loss.
11-19-2003, 08:02 PM
#23
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Well, after swapping in a new battery (old one died for some reason - 1 month old Red Top at that) I swapped the coil first, then the ICM. Same issues. I'm noticing that it's only after the car has been running for about a minute that the problem starts to appear. The longer it runs, the worse it gets. When it's first started cold, there's not a single issue that I can tell. Unfortunately, I can't really do a cold test drive to check for the hesitation.
I'm thinking possibly Oxygen sensors, but the problem appears before the system goes into closed loop.
I was watching the scanner, and the MAP voltage at idle is hovering around 2.1X. When I step on it, it goes up into the upper 3 to mid 4 range, then backs off down to the 1 range. Is this right?? The MAP sensor is brand new. Harness possibly. Could this even be the problem. It's still running so rich at idle after a while that it burns my eyes.
I'm thinking possibly Oxygen sensors, but the problem appears before the system goes into closed loop.
I was watching the scanner, and the MAP voltage at idle is hovering around 2.1X. When I step on it, it goes up into the upper 3 to mid 4 range, then backs off down to the 1 range. Is this right?? The MAP sensor is brand new. Harness possibly. Could this even be the problem. It's still running so rich at idle after a while that it burns my eyes.
11-21-2003, 06:48 PM
#25
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Updated........
Here's a couple pics of one thing my cars doing:
Running Rich
Again
I have done the swap of the TB from the other car, still same problem. MAP is good, can't be the O2's since it happens well before closed loop comes around. If it was the fuel filter, then I wouldn't be running so rich and stumbling because of the richness causing a misfire (assumption only). Fuel Pressure Regulator checked out. As did the Fuel Injectors. Pressure was fine. EGR only causes about a 100 RPM drop when the diaphram is depressed at idle, indicating a blockage of the exhaust passages, but I'm hearing that won't cause my problem. Tune should be fine, but I'm going to get another one done starting all over again. Coolant temperature sensor (water pump) checks out as it's giving good readings. ditto with the one in the head. Computer is good, as I've run with the same results on three different PCM's. ICM was swapped, and checked out good, as did the coil. Wires are good, plugs are a little fouled (carbon deposits) due to the running rich. Brand new opti too. That's about it.
I'm at my limit. If I can't figure something out this weekend, I'm probably going to be dropping the car off at the (shudder) dealership either next week or the first week of december. >:
Does anyone have any other ideas??
Running Rich
Again
I have done the swap of the TB from the other car, still same problem. MAP is good, can't be the O2's since it happens well before closed loop comes around. If it was the fuel filter, then I wouldn't be running so rich and stumbling because of the richness causing a misfire (assumption only). Fuel Pressure Regulator checked out. As did the Fuel Injectors. Pressure was fine. EGR only causes about a 100 RPM drop when the diaphram is depressed at idle, indicating a blockage of the exhaust passages, but I'm hearing that won't cause my problem. Tune should be fine, but I'm going to get another one done starting all over again. Coolant temperature sensor (water pump) checks out as it's giving good readings. ditto with the one in the head. Computer is good, as I've run with the same results on three different PCM's. ICM was swapped, and checked out good, as did the coil. Wires are good, plugs are a little fouled (carbon deposits) due to the running rich. Brand new opti too. That's about it.
I'm at my limit. If I can't figure something out this weekend, I'm probably going to be dropping the car off at the (shudder) dealership either next week or the first week of december. >:
Does anyone have any other ideas??
Last edited by Fastbird93; 11-21-2003 at 06:50 PM.
11-21-2003, 09:23 PM
#26
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Location: Glen Burnie, Md
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MAP should go to BARO at WOT 98-103 kPa depending on barometer. I dont know how that translates into voltage
Could it just be idling so rich its fouling the plugs out and loading up? Possibly they are drying out when it sits (cold starts) then gets worse? When a motor starts runnign rich (real rich) for some reason alot of times it takes out the O2 sensors as well. Put some new ones in and find the problem, straighten it out and then the old ones sometimes can burn off and run right, but fouled O2s have made a viscous circle for me before, fix one proble, then o2s have been fouled, which in turn fouls the plugs again or etc.
Could it just be idling so rich its fouling the plugs out and loading up? Possibly they are drying out when it sits (cold starts) then gets worse? When a motor starts runnign rich (real rich) for some reason alot of times it takes out the O2 sensors as well. Put some new ones in and find the problem, straighten it out and then the old ones sometimes can burn off and run right, but fouled O2s have made a viscous circle for me before, fix one proble, then o2s have been fouled, which in turn fouls the plugs again or etc.
11-21-2003, 11:58 PM
#28
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Join Date: Jul 2003
Posts: 82
everyone says not to do the opti cause it ain't it I had that exact same problem in my 94' z28, i replaced IAT Sensor, O2's, Coil, Spark Plug Wires, I invested 500 $ into my car then my last thing I was gonna do before sell it was the Opti, I did it, and guess what it made my car run so good, just like it did when I first got it.
We hooked it up on the computer when it was cold, and it didn't throw an OPTI code i warmed her up to where she was surging at idle and stumbling, and it threw an Opti Code.
Change the Opti or get it checked, I had identical symptoms.
We hooked it up on the computer when it was cold, and it didn't throw an OPTI code i warmed her up to where she was surging at idle and stumbling, and it threw an Opti Code.
Change the Opti or get it checked, I had identical symptoms.
11-22-2003, 10:03 AM
#29
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Originally posted by mechmsb
everyone says not to do the opti cause it ain't it I had that exact same problem in my 94' z28, i replaced IAT Sensor, O2's, Coil, Spark Plug Wires, I invested 500 $ into my car then my last thing I was gonna do before sell it was the Opti, I did it, and guess what it made my car run so good, just like it did when I first got it.
We hooked it up on the computer when it was cold, and it didn't throw an OPTI code i warmed her up to where she was surging at idle and stumbling, and it threw an Opti Code.
Change the Opti or get it checked, I had identical symptoms.
everyone says not to do the opti cause it ain't it I had that exact same problem in my 94' z28, i replaced IAT Sensor, O2's, Coil, Spark Plug Wires, I invested 500 $ into my car then my last thing I was gonna do before sell it was the Opti, I did it, and guess what it made my car run so good, just like it did when I first got it.
We hooked it up on the computer when it was cold, and it didn't throw an OPTI code i warmed her up to where she was surging at idle and stumbling, and it threw an Opti Code.
Change the Opti or get it checked, I had identical symptoms.
11-23-2003, 12:23 AM
#30
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Join Date: Jan 2001
Location: New Phila, OH
Posts: 357
I have had a similar problem with my car for over a year now. The car constantly stumbles and runs poorly. When the car finally goes into closed loop ~350 seconds the car will sputter and die immediately. I have replaced everything just like you did. Opti 2 times, plugs, wires, coil, ICM, MAP, 3 different computers, 5 Alvin chips, 1 new stock chip, new intake gaskets, IAC, No EGR, 3 sets of O2's, wiring harness, plus many other things. I am beginning to think it may be the tuning on the car. I have had no other reasonable answers other than this. I have tried everything to fix this car. Have you ever tried another tuner? I have had a few small problems with Alvin in the past, but he has always tried to fix me up. I am going to try Madwolf when I get some more datamaster logs. Let me know how it turns out for you.