infrequent lagging throttle response
Thread Starter
Racer
Joined: Dec 2012
Posts: 277
Likes: 9
From: Clark County Nevada
infrequent lagging throttle response
'94 coupe, 45K miles. I notice infrequently when I step on the throttle the car lags and kind of sputters, for a few moments and then it's fine. It seems to only happen right after car has been started and first driven. Work so far that has been done in the last year includes:
-New vented opispark
-New plugs, wires
-New injectors
-New radiator
-New themostat
-New coolant temperature sensor
-New hoses where needed
I also did a block/headgasket test, with the test kit rented from autozone, that tests for exhaust gasses in the coolant and results were negative.
Other than that small, occasional issue the car runs great.
Any ideas?
-New vented opispark
-New plugs, wires
-New injectors
-New radiator
-New themostat
-New coolant temperature sensor
-New hoses where needed
I also did a block/headgasket test, with the test kit rented from autozone, that tests for exhaust gasses in the coolant and results were negative.
Other than that small, occasional issue the car runs great.
Any ideas?
Race Director
Joined: Mar 2015
Posts: 15,926
Likes: 579
'94 coupe, 45K miles. I notice infrequently when I step on the throttle the car lags and kind of sputters, for a few moments and then it's fine. It seems to only happen right after car has been started and first driven. Work so far that has been done in the last year includes:
-New vented opispark
-New plugs, wires
-New injectors
-New radiator
-New themostat
-New coolant temperature sensor
-New hoses where needed
I also did a block/headgasket test, with the test kit rented from autozone, that tests for exhaust gasses in the coolant and results were negative.
Other than that small, occasional issue the car runs great.
Any ideas?
-New vented opispark
-New plugs, wires
-New injectors
-New radiator
-New themostat
-New coolant temperature sensor
-New hoses where needed
I also did a block/headgasket test, with the test kit rented from autozone, that tests for exhaust gasses in the coolant and results were negative.
Other than that small, occasional issue the car runs great.
Any ideas?
I changed the knock sensors at the same time to do a proper flush
Last edited by antfarmer2; Jun 19, 2015 at 04:01 PM.
Instructor
Joined: Jun 2011
Posts: 205
Likes: 3
From: Great Mills Maryland
My 94' did the same thing before my rebuild. I replaced all sensors, switches, opti, O2, coil, everything during my rebuild. Complete engine rebuild and was I surprised when it still sputtered and lagged behind, not as bad but still there. Before I could floor the pedal and the car would buck, sputter, and I could feel and hear popping under the car. Now I've been focused on the TPS because the voltage is low during readouts, changed two and still low. Now its looking at all the wires. My car has 108K on it and before I would let it warm up longer, mine did it after start up also. Yours is low miles but looks like you had to change out some parts already. I'd check Throttle position sensor, MAP sensor, and fuel pressure. The only thing on mine I didn't change is the fuel pump, had it out but didn't change it. Good luck.
Thread Starter
Racer
Joined: Dec 2012
Posts: 277
Likes: 9
From: Clark County Nevada
If it is the TPS wouldn't it be happening all the time? Why only at start up?
I was also thinking it could be a bad or clogged or failing fuel pump, but then why only after startup?
I was also thinking it could be a bad or clogged or failing fuel pump, but then why only after startup?
Last edited by Barchetta; Jun 20, 2015 at 10:42 AM.
Thread Starter
Racer
Joined: Dec 2012
Posts: 277
Likes: 9
From: Clark County Nevada
...btw ... the lagging throttle response, sputtering and poping (like a backfire) was hapening really bad and more frequently before the injectors, plugs, wires were relaced. Since then it is very infrequent and only right after starting up and only happens once and then it runs fine. To me it seems like it would be more fuel related like a sensor or component that delivers, regulates or measures air and/or fuel, rather than an electrical issue. All the wiring appears to be in good condition. However, I could be wong as it's only an assumption.
Last edited by Barchetta; Jun 20, 2015 at 10:40 AM.
Race Director
Joined: Mar 2015
Posts: 15,926
Likes: 579
...btw ... the lagging throttle response, sputtering and poping (like a backfire) was hapening really bad and more frequently before the injectors, plugs, wires were relaced. Since then it is very infrequent and only right after starting up and only happens once and then it runs fine. To me it seems like it would be more fuel related like a sensor or component that delivers, regulates or measures air and/or fuel, rather than an electrical issue. All the wiring appears to be in good condition. However, I could be wong as it's only an assumption.
that's what o2's do I used bosch are you going to do it?
Melting Slicks
Joined: Jun 1999
Posts: 2,931
Likes: 127
From: Ashland Alabama
Not really. TPS can either die outright, have dead zones all the time or act up based on temperature. The last one I changed in mine worked fine cold but went nuts the warmer the car got. Even to the point before it went out of having nothing from 1/2 pedals worth onward when the motor was warmed up.
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Thread Starter
Racer
Joined: Dec 2012
Posts: 277
Likes: 9
From: Clark County Nevada
It could't hurt. the parts aren't that expensive. I'm assuming if the O2's are failing it could happen just at startup untill the system compensates? I was reading up on symptoms and it was suggested that O2's should be looked at as maintenance items replaced at 50k miles.
Are the Bosch to OE specs?
Are the Bosch to OE specs?
Race Director
Joined: Mar 2015
Posts: 15,926
Likes: 579
It could't hurt. the parts aren't that expensive. I'm assuming if the O2's are failing it could happen just at startup untill the system compensates? I was reading up on symptoms and it was suggested that O2's should be looked at as maintenance items replaced at 50k miles.
Are the Bosch to OE specs?
Are the Bosch to OE specs?
Thread Starter
Racer
Joined: Dec 2012
Posts: 277
Likes: 9
From: Clark County Nevada
Not really. TPS can either die outright, have dead zones all the time or act up based on temperature. The last one I changed in mine worked fine cold but went nuts the warmer the car got. Even to the point before it went out of having nothing from 1/2 pedals worth onward when the motor was warmed up.
Mine being an auto I notice when in last gear, usually at cruising speed, throttle response and acelleration is slow unless I downshift into D or step on throttle hard, but I understand that is just normal torque converter operation.
Last edited by Barchetta; Jun 20, 2015 at 12:15 PM.
Melting Slicks
Joined: Jun 1999
Posts: 2,931
Likes: 127
From: Ashland Alabama
When this last one went it was at cruising speed.
But it sounds more like your car needs a tuneup than anything else to be honest. I was just pointing out that the tps can be erratic and not a dead completely thing.
Id start with airfilter (my 86 would do exactly where your referring to when it got dirty), plugs, and o2 sensors. To me that's a tune up.
But it sounds more like your car needs a tuneup than anything else to be honest. I was just pointing out that the tps can be erratic and not a dead completely thing.
Id start with airfilter (my 86 would do exactly where your referring to when it got dirty), plugs, and o2 sensors. To me that's a tune up.
Thread Starter
Racer
Joined: Dec 2012
Posts: 277
Likes: 9
From: Clark County Nevada
Btw... I usually let the car warm up to about 100df before I drive. It happens shortly after that. Also after it has been driven and sitting off for a while, and engine still warm, then I start up again and drive it hapens (as mentioned before) once then it is fine. I'm almost sure it's in closed loop when it happens.
Last edited by Barchetta; Jun 20, 2015 at 01:21 PM.
Instructor
Joined: Jun 2011
Posts: 205
Likes: 3
From: Great Mills Maryland
Don't know if you have a manual or not. Scan 1 bottom right para and scan2 left side, Describes fuel metering a little. Scan 3 trouble shooting steps. Just a guide, for me I have to know how a system works first. Check for any codes you may have.