hesitation
09-24-06, 03:29 AM
#76
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I know this is quite an old thread, but it has helped me tremendously.
My SC400 has been having every symptom listed (significant hesitation when taking off from a stop, hesitation/surging under light throttle, same at around 40-45mph, etc.) Convinced the problem wasn't spark related, I decided to unplug my MAF. Car runs absolutely PERFECT now! Sure, the CEL and TRAC lights are on, but who cares. Tomorrow I'm going to buy some plastic-friendly electrical cleaner and shoot the MAF....see tomorrow if that's the cause!
My SC400 has been having every symptom listed (significant hesitation when taking off from a stop, hesitation/surging under light throttle, same at around 40-45mph, etc.) Convinced the problem wasn't spark related, I decided to unplug my MAF. Car runs absolutely PERFECT now! Sure, the CEL and TRAC lights are on, but who cares. Tomorrow I'm going to buy some plastic-friendly electrical cleaner and shoot the MAF....see tomorrow if that's the cause!
09-24-06, 08:26 AM
#77
I tried cleaning the MAF with no positive results. My SC4 still hesitates under normal acceleration from a dead stop. Actually, it seems more like the trans shifts too soon. It pauses again at the next up shift when continuing to accelerate. It is worse from the AC on, perhaps because of the power drain of the compressor, or I've wondered if it had anything to do with the circuit that increases idle speed when the AC is on.
Oddly enough, sometimes adding a bottle of Techron to the tank helps a little.
Maybe another symptom, but it seems like the power is down. At highway speeds, it downshifts way too often when climbing a small hill or even under slight acceleration.
If it was an older car that didn't have all of the computerized engine controls, I would say that it runs just like a car with ignition timing retarded.
Oddly enough, sometimes adding a bottle of Techron to the tank helps a little.
Maybe another symptom, but it seems like the power is down. At highway speeds, it downshifts way too often when climbing a small hill or even under slight acceleration.
If it was an older car that didn't have all of the computerized engine controls, I would say that it runs just like a car with ignition timing retarded.
09-24-06, 12:06 PM
#78
Banned - could not follow forum rules
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Clean the throttle body and change your air filter...That doesn't work check the TPS sensor to see if it working corectly....That doesn't work change the fuel filter and try and clean your fuel system...If all that still doesn't work check your electical system, then change your ground cable, change the plugs, wires, caps and rotors.....Do all that and you should be good..
10-24-06, 09:35 AM
#79
What is the TPS sensor and where is it?
I took it to an independent shop for a computer analysis yesterday. They weren't real sure of the cause or causes, but suggested that the Oxygen Sensors were 'a little slow' (whatever that means) and that the Idle Control Air Motor was 'very abrupt' and perhaps sticking. They thought that the latter was the primary cause.
The shop was not sure and also quite expensive so I didn't have them replace any of the parts.
I'm going to disassemble the Idle Control Motor to see if cleaning it will help. Or maybe just replace it myself.
Add to the symptoms, an intermittent surge at a constant speed of around 40mph, only noticeable on a smooth quiet road.
(95 SC400, 104k miles)
I took it to an independent shop for a computer analysis yesterday. They weren't real sure of the cause or causes, but suggested that the Oxygen Sensors were 'a little slow' (whatever that means) and that the Idle Control Air Motor was 'very abrupt' and perhaps sticking. They thought that the latter was the primary cause.
The shop was not sure and also quite expensive so I didn't have them replace any of the parts.
I'm going to disassemble the Idle Control Motor to see if cleaning it will help. Or maybe just replace it myself.
Add to the symptoms, an intermittent surge at a constant speed of around 40mph, only noticeable on a smooth quiet road.
(95 SC400, 104k miles)
10-26-06, 07:11 PM
#80
Success...
After reading all the threads on hesitation that I could find on this and another forum I noticed one thing that was mentioned several times. It was the same thing that I had first posted almost a year ago: Adding a bottle of Techron almost cleared it up for a while. I was buying them by the four-pack at CostCo for $9-something (a great deal compared to the auto parts store or Chevron dealer). By itself, that pointed to a fuel delivery problem.
So I changed the fuel filter today and the hesitation is gone.
It is SOOOOOOO much nicer to drive now.
I hope others have the same results.
===================================
So I changed the fuel filter today and the hesitation is gone.
It is SOOOOOOO much nicer to drive now.
I hope others have the same results.
===================================
What is the TPS sensor and where is it?
I took it to an independent shop for a computer analysis yesterday. They weren't real sure of the cause or causes, but suggested that the Oxygen Sensors were 'a little slow' (whatever that means) and that the Idle Control Air Motor was 'very abrupt' and perhaps sticking. They thought that the latter was the primary cause.
The shop was not sure and also quite expensive so I didn't have them replace any of the parts.
I'm going to disassemble the Idle Control Motor to see if cleaning it will help. Or maybe just replace it myself.
Add to the symptoms, an intermittent surge at a constant speed of around 40mph, only noticeable on a smooth quiet road.
(95 SC400, 104k miles)
I took it to an independent shop for a computer analysis yesterday. They weren't real sure of the cause or causes, but suggested that the Oxygen Sensors were 'a little slow' (whatever that means) and that the Idle Control Air Motor was 'very abrupt' and perhaps sticking. They thought that the latter was the primary cause.
The shop was not sure and also quite expensive so I didn't have them replace any of the parts.
I'm going to disassemble the Idle Control Motor to see if cleaning it will help. Or maybe just replace it myself.
Add to the symptoms, an intermittent surge at a constant speed of around 40mph, only noticeable on a smooth quiet road.
(95 SC400, 104k miles)
11-09-06, 03:35 PM
#81
After reading all the threads on hesitation that I could find on this and another forum I noticed one thing that was mentioned several times. It was the same thing that I had first posted almost a year ago: Adding a bottle of Techron almost cleared it up for a while. I was buying them by the four-pack at CostCo for $9-something (a great deal compared to the auto parts store or Chevron dealer). By itself, that pointed to a fuel delivery problem.
So I changed the fuel filter today and the hesitation is gone.
It is SOOOOOOO much nicer to drive now.
I hope others have the same results.
===================================
So I changed the fuel filter today and the hesitation is gone.
It is SOOOOOOO much nicer to drive now.
I hope others have the same results.
===================================
I stopped by the new (read expensive looking) Lex Dlr in Newport Beach, CA. Recognized the shop foreman from his prior job at another dealership. He really knows these cars. He was doubtful of my fuel filter fix (yes, it really is MUCH better) and told me that:
1) The hesitation issue was very typical of 95 SC4s.
2) Cleaning the Throttle Body usually helps.
So I removed and dissassembled the throttle body and carefully cleaned it using a solvent labeled for that purpose. Got it at Pep Boys. The body was quite dirty inside, but no apparent plugged vent holes or anything out of the ordinary. Put it all back together (new gasket) and:
1) Starts and idles fine.
2) Check engine warning light on.
3) Bucks and surges at light to medium acceleration, any speed.
4) Feels good at medium to hard acceleration and the check engine light goes out, but immediately comes back on when foot taken off the throttle and then it starts bucking again.
I was getting mighty nervous thinking that this could be very expensive. I tried cleaning the air flow sensor. Nope.
It seemed to run very slightly better, but still bucked under light acceleration and the warning light was on as above. Removed battery cable for a while to let the computer reset.
Driving around jerking and bucking and cursing at myself for messing with it, I got on a long freeway on-ramp and I nailed it, and, as before, the warning light went out as it ran up strong and smooth through the gears. I kept on it through several max throttle upshifts to about 90-100 or so.
Slowed down as I caught up with traffic and the light didn't come back on. Hmmmm.
Got off the freeway and still no warning light. Smooth motor.
Drove around for a while and it's running great. No bucking or surging. Warning light off. No hesitation.
It's been a week now and it is running better than it ever did. I love it again.
Whew!
Seems like I saw somewhere on this forum that the computer needs to recalibrate if anything in the circuits is changed. Hard acceleration is one of the settings that needs to be reset. Perhaps by cleaning, it got far enough out of whack that it needed to be recalibrated.
Whatever.
I'm gonna leave it alone now.
JC 1995 SC4 105k
http://www.meetingsandmixers.com/
Last edited by john_sc400; 11-09-06 at 03:40 PM.
05-02-07, 02:06 PM
#83
(this is in the category of "If it ain't broke, don't fix it.")
I stopped by the new (read expensive looking) Lex Dlr in Newport Beach, CA. Recognized the shop foreman from his prior job at another dealership. He really knows these cars. He was doubtful of my fuel filter fix (yes, it really is MUCH better) and told me that:
1) The hesitation issue was very typical of 95 SC4s.
2) Cleaning the Throttle Body usually helps.
<snip>
Drove around for a while and it's running great. No bucking or surging. Warning light off. No hesitation.
It's been a week now and it is running better than it ever did. I love it again.
<snip>
JC 1995 SC4 105k
http://www.meetingsandmixers.com/
I stopped by the new (read expensive looking) Lex Dlr in Newport Beach, CA. Recognized the shop foreman from his prior job at another dealership. He really knows these cars. He was doubtful of my fuel filter fix (yes, it really is MUCH better) and told me that:
1) The hesitation issue was very typical of 95 SC4s.
2) Cleaning the Throttle Body usually helps.
<snip>
Drove around for a while and it's running great. No bucking or surging. Warning light off. No hesitation.
It's been a week now and it is running better than it ever did. I love it again.
<snip>
JC 1995 SC4 105k
http://www.meetingsandmixers.com/
The respite was brief. The hesitation returned. Tried another visit to the expensive dealer where I was told that most 95s hesitated as well as bucked at around 40mph both because the engine was detuned for that year (and the early 96s) as well as issues with the TPS which are related to the drive-by-wire system.
Haven't tried to do anything about either yet. But I have noticed that if I add a bottle of Techron when it gets really bad, it helps--not cures it, but helps. I also noticed that if I do anything in the form of maintenance to it: tighten vacuum lines, clean MAF, add Techron, changed the fuel filter, changed spark plugs, whatever, it goes away for a while and then comes back. Tried changing gasoline brands (ALWAYS using premium).
Read something somewhere about setting the TPS using an ohmmeter and a feeler gauge, but did not find the specs or details about how to do so (anyone?)
Most annoying. I buy four-packs of Techron at CostCo and add it when necessary to make most of it go away. Wish I could find a real fix without randomly changing parts until I hit on it.
John
http://www.meetingsandmixers.com/
05-08-07, 01:06 PM
#84
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Revisiting this topic...
The respite was brief. The hesitation returned. Tried another visit to the expensive dealer where I was told that most 95s hesitated as well as bucked at around 40mph both because the engine was detuned for that year (and the early 96s) as well as issues with the TPS which are related to the drive-by-wire system.
John
http://www.meetingsandmixers.com/
The respite was brief. The hesitation returned. Tried another visit to the expensive dealer where I was told that most 95s hesitated as well as bucked at around 40mph both because the engine was detuned for that year (and the early 96s) as well as issues with the TPS which are related to the drive-by-wire system.
John
http://www.meetingsandmixers.com/
Its definately a common problem for the 92-94 SC300s and 400s also. ( My 93 SC300 included.) Wich utilize the Karmen Vortex MAF as opposed to the DBW. Wich may or may be relavant?
I know that the described hesitation occured on my SC when my precat had a cracked weld right by the exhaust mani . Causing the car to run way rich, Thus charing my O2 sensors , as well as ultimately killing my ignition coil as well (theres only 1 coil in the SC300s btw.) My precat had also melted inside, It was like a block of cement inside .
Since i knew i was going na-t shortly, i tried temp fixes (g-rigged) to get by . IE: exhaust wrap .
An interesting thing is, although it would last only 1 week at a time. The hesitation was all but eliminated by stopping the ex leak. the minute the leak would reopen. It would hesitate again. I would rewrap it, and it was gone again.
Prior to that, I had the same hesitation when my solonoid valve #2 was bad . (code 63)..... But perhaps the exhaust leak, ignition coil, O2 sensors, etc may have already been causing it?
I believe that whats difficult about the hesitation issues is, Its theres no single cause. It seems like just about any sensor malfunction will trigger the same/similar hesitation?
06-16-07, 07:14 PM
#85
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i have the same problem, but it will occur then be ok
the engine light will go on and it started to hesitate a little bitat low to mid rpm's, then the light went off and it happened but only like once then the light would go back on and hesitate but not too much, now it's runnin' right, but we'll see how this **** goes. i have a new dragon torque converter(about 8,000 miles on it), just replaced my plugs, wires, and distributer caps, and new fuel filter,
i'm gonna try cleaning my MAF sens. then i'll let ya'll know, we gotta get this **** right,
-Knowledge
i'm gonna try cleaning my MAF sens. then i'll let ya'll know, we gotta get this **** right,
-Knowledge
06-18-07, 03:19 PM
#86
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Hah, maybe i found the prob.
when i read the ecu codes it drew a 13 and 31 which is air sensor and rpm sensor.
when i looked under the hood i found that the wire leading to the sensor(u have one on each cam that is located at the bottom area of each distributor) was being chaffed by the serpentine and grounded the two wires. i fixed that problem and been drivin it for about a day and runs smooth, that took care of the rpm sensor problem, but hopefully the hesitation will not return,
i have not thrown a code yet, but it has to throw it two times in one trip for it to register and also the speed has a factor, you have to have reached 50mph.
i'll let yall know,
-Knowledge
when i looked under the hood i found that the wire leading to the sensor(u have one on each cam that is located at the bottom area of each distributor) was being chaffed by the serpentine and grounded the two wires. i fixed that problem and been drivin it for about a day and runs smooth, that took care of the rpm sensor problem, but hopefully the hesitation will not return,
i have not thrown a code yet, but it has to throw it two times in one trip for it to register and also the speed has a factor, you have to have reached 50mph.
i'll let yall know,
-Knowledge
07-02-07, 04:52 PM
#89
If you ever get the intake off, like changing the starter, have your injectors flowed, then cleaned, and reflowed. Also im going to put a h.d. ground kit on to see if it will fix my slight hesitation.
08-02-07, 10:37 PM
#90
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for the hesitation or bucking under acceleration, with a warm engine try taking the spark plug wires out to see if there is oil around the spark plugs. If so, put the plug wires back in or just leave it overnight to let the engine cool down. In the morning, check to make sure all the oil is gone from around the spark plugs then tighten the valve covers.