"Solved" my engine sputtering/hesitation problem
- Thread starter mr_goat
- Start date
I found my problem , it was my wheel setup and tire size that every so often trigger the traction control. I drove around with the tcs disabled and no stuttering. I hope this helps somebody.
I hate to resurrect an old thread, but I figure it is better than starting a new one?
Similar to the OP and others, I am getting a hesitation around 2500-3500 RPMs. I have a FP gauge installed. My pressure seems to be in spec according to the manual: 46-53psi with the FP regulator hose disconnected and 36-44psi with FP reg hose connected. I have tried bypassing the resistor, no change. I have a new fuel filter. Plugs and coil packs are a couple years old but only have a couple thousand miles on them. What would be the most logical next step? I see Brian K notes that fuel pump failures are not common, and additional fuel can mask other problems. Should I be sending the injectors out for cleaning? Are there other tests I can perform to narrow this down? Would prefer not to drop the gas tank until I rule out other potential causes..
Thanks!
Similar to the OP and others, I am getting a hesitation around 2500-3500 RPMs. I have a FP gauge installed. My pressure seems to be in spec according to the manual: 46-53psi with the FP regulator hose disconnected and 36-44psi with FP reg hose connected. I have tried bypassing the resistor, no change. I have a new fuel filter. Plugs and coil packs are a couple years old but only have a couple thousand miles on them. What would be the most logical next step? I see Brian K notes that fuel pump failures are not common, and additional fuel can mask other problems. Should I be sending the injectors out for cleaning? Are there other tests I can perform to narrow this down? Would prefer not to drop the gas tank until I rule out other potential causes..
Thanks!
Disconnect your tcs at the harness connector behind the bulkhead , your car is stuttering or hesitating because of your wheel setup , you probably can’t see it , because it happens so fast , the tcs , traction control causes this hesitation. You can always just push the tcs button, turn off traction control.
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The fuel pressure test as described in the service manual is really more of a fuel pressure regulator test. It can flag a really bad pump; but, probably not a tired pump. Since the test is done at idle it really does not confirm fuel deliverability. In order to do that you need to measure fuel pressure with the engine under load, something like 110 km/hr and pull out to pass going up a hill. However, the fact that the resistor by-pass makes no difference to the operation of the car suggest that the problem is probably not pump / fuel pressure related.
Have you confirmed that the TCS is not activating? The flashing TCS activation light in the tach would be an indication that you have TCS activity. As a test, you can switch the TCS off which should illuminate the TCS off indicator in the cluster. If you have the TCS off indication and and you are still getting the hesitation then the problem is likely not caused by the TCS. Also, TCS activation would be more vehicle speed related. If you experience the hesitation and shift gears to change engine speed and the hesitation goes away that would not be consistent with a TCS issue.
Rule out the TCS first. If you confirm that the TCS is not the issue, if the injectors have never been serviced and the car is a 1991, sending the injectors out to be cleaned would never be a bad idea and would rule them out as a cause.
Have you confirmed that the TCS is not activating? The flashing TCS activation light in the tach would be an indication that you have TCS activity. As a test, you can switch the TCS off which should illuminate the TCS off indicator in the cluster. If you have the TCS off indication and and you are still getting the hesitation then the problem is likely not caused by the TCS. Also, TCS activation would be more vehicle speed related. If you experience the hesitation and shift gears to change engine speed and the hesitation goes away that would not be consistent with a TCS issue.
Rule out the TCS first. If you confirm that the TCS is not the issue, if the injectors have never been serviced and the car is a 1991, sending the injectors out to be cleaned would never be a bad idea and would rule them out as a cause.
I would try to disconnect the O2 sensors. That will throw a CEL, but if the hesitations disappear you found the problem. Easy to do. Cost nothing. Eliminates one possible cause.
Update: I tried unplugging the TCS computer, no change. I will try unplugging the o2 sensors next. After that I will be looking into getting the injectors cleaned. I will keep you all posted. Thanks for all your help!!
I have mixed thoughts about disconnecting the O2 sensors. They could be causing the problem, particularly if the sensors are resulting in a lean mixture (not the way they normally fail). If you disconnect the O2 sensors I suspect the short term fuel trim goes to zero. However, if the problem has been around for a while the long term fuel trim will have accumulated. The service manual does not indicate whether a sensor failure forces the engine into open loop or it can still operate in closed loop using long term fuel trim. If the engine can run in closed loop using just the long term trim then the hesitation may persist even though the sensors have been disconnected. Erasing the long term trim by doing a reset (pull the clock fuse) would help eliminate this possibility.
Does the hesitation occur when the engine is cold? The ECU does not go into closed loop until the engine comes up to operating temperature. If the hesitation appears after the engine is up to temperature that could be consistent with a closed loop problem caused by faulty O2 sensors.
Does the hesitation occur when the engine is cold? The ECU does not go into closed loop until the engine comes up to operating temperature. If the hesitation appears after the engine is up to temperature that could be consistent with a closed loop problem caused by faulty O2 sensors.
The hesitation only occcurs when the engine is hot, and has been driven for at least 20 minutes at operating temp. The hesitation also ONLY happens at partial throttle, maintaining speed or slightly accelerating, around 2500-3500 rpms. Does not occur any other time or under other conditions.
That might be consistent with an O2 sensor problem causing the engine to run lean once it goes into closed loop operation. However, dirty injectors can be masked by the rich fuel mixture the ECU applies during warm up with the hesitation re appearing after warm up is complete. So, the problem could be dirty injectors or failing O2 sensors. Unfortunately, you don't have an OBD II compliant ECU so monitoring O2 sensor voltages is more difficult. A savvy mechanic with a high impedance voltmeter or a scope can set up to monitor the sensor voltage on a running engine and should be able to tell you whether the sensor has exceeded its best before date. You could also do [MENTION=12617]asylum[/MENTION] 's test (after clearing the ECU memory) to see if that improves things.
Replacing original O2 sensors on a 1991 would probably never be a complete waste of money. However, getting that front sensor out of the OEM cast iron manifold can be a treat. I think there are more than a couple of owners who have managed to snap the sensor off with the tip remaining in the manifold.
Replacing original O2 sensors on a 1991 would probably never be a complete waste of money. However, getting that front sensor out of the OEM cast iron manifold can be a treat. I think there are more than a couple of owners who have managed to snap the sensor off with the tip remaining in the manifold.
So I unplugged my o2 sensors and could not get it to hesitate. So I am cautiously optimistic that I have identified the issue. I do probably have an exhaust leak between the stock boat anchor and the test pipe (one of the bolts snapped, previous owner added to weld on there to “seal” it). Could this small leak be the issue? I wouldn’t think so because it isn’t really close to the o2 sensor. So my next step is replacing the o2s, others have said they may be seized, so maybe now is a good time to slap some headers on there, 2 birds/1 stone type deal.
Update: I replaced my o2 sensors over the weekend, and the hesitation has not reappeared! Thanks all for your help!
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