jdm91integ

When I'm stopped at a red light, sitting there and idling, sometimes I'll feel the motor jerk for a sec. then stop, then jerk again and stop. When it does this it almost feels like someone bumped into the back of the car. The weird thing is there's no rhyme or reason to when it happens. My first thought was the motor mounts, but I checked them and they seem fine. Now I'm thinking it might be something to do with the fuel system. The car gets bad gas mileage and it hesitates to start after it has sat over night. Maybe it's a leaky injector flooding out the motor causing it to jerk around? The car drives just fine when your crusing down the road though. Any thoughts or opinions to what the problem is, is appreciated. Thanks.

P.S. The car is a '93 Accord and it's an automatic.

JimBlake

How old are your spark plugs, wires, distributor cap & rotor? It might be any of these.

jdm91integ

Yeah I should have included a list of things I've changed recently. I've changed all these things in hopes to get better gas mileage, but nothing has worked. Now just recently the motor jerking problem has started.
Things I've changed in the last 1500 miles,
Cap&Rotor
Spark plugs
Spark plug wires
Air filter
Fuel filter
Pcv valve
Coolant flushed and refilled
Motor oil & filter
Transmission fluid

I've done all the basic stuff, that's why I think it something more complicated that's causing the motor to jerk at idle sometimes.

JimBlake

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jdm91integ &raquo;</TD></TR><TR><TD CLASS="quote">... When it does this it almost feels like someone bumped into the back of the car...</TD></TR></TABLE>Does it only do it in gear, when you're holding it with the brakes? Does it act like that in neutral or park?

Since you've done all the normal tune-up stuff, I want to be sure whether it's an engine vs. transmission problem.

Find an empty parking lot, put it in low-1st gear, let the car move with the engine idling. Don't press the gas. Does it jerk or move smoothly?

jdm91integ

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JimBlake &raquo;</TD></TR><TR><TD CLASS="quote">Does it only do it in gear, when you're holding it with the brakes? Does it act like that in neutral or park?

Since you've done all the normal tune-up stuff, I want to be sure whether it's an engine vs. transmission problem.

Find an empty parking lot, put it in low-1st gear, let the car move with the engine idling. Don't press the gas. Does it jerk or move smoothly?
</TD></TR></TABLE>

Since there's no rhyme or reason to when it happens it's hard to test diffrent scenarios. I did already try putting the car in park and seeing if it would jerk. But it didn't. Since it doesn't always jerk I can't be sure that it won't happen in park. All I know is it only jerks when idling in gear and it doesn't always do it. It has jerked a couple of times right as I took my foot of the gas and started accelerating after being stopped. But once I got moving it didn't jerk again. When the car jerks it almost feels like the car is trying to lurch forward. It's kind of hard to explain but the jerking will only last as long as it takes you to count to 1. But it will happen multiple times and not always the same amount.

JimBlake

Maybe your IACV is acting strange. That's supposed to hold your idle steady. When you put the car in gear, it opens up a bit to take up the load of the torque converter. At this new, more open position, maybe it's kinda sticky or unsteady?? I'm not sure of a good way to test that, other than borrow a good one from another car.

But I'm sorta leaning towards transmission trouble. Something like a lock-up clutch trying to lock up when it's not supposed to... If your car jerked while moving, I guess that would disprove this idea. I'm not a real guru of automatic trannys, so maybe some idea occurs to anyone who is?

Maybe one way to tell the difference between these 2 ideas is what the tachometer does. If the tach increases, just as if you had stepped on the gas, that would indicate an engine problem like the IACV. If the tach drops, that would point to a tranny problem.

alb_accord

does it do this once u come out of high speeds(come out out of the high way) if yes u got to start checking ur vavles.
my f22a did that and about 6 months later my exaust vavle on the #1 piston was gone. but this is the worst scene scenario.

jdm91integ

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JimBlake &raquo;</TD></TR><TR><TD CLASS="quote">Maybe your IACV is acting strange. That's supposed to hold your idle steady. When you put the car in gear, it opens up a bit to take up the load of the torque converter. At this new, more open position, maybe it's kinda sticky or unsteady?? I'm not sure of a good way to test that, other than borrow a good one from another car.

But I'm sorta leaning towards transmission trouble. Something like a lock-up clutch trying to lock up when it's not supposed to... If your car jerked while moving, I guess that would disprove this idea. I'm not a real guru of automatic trannys, so maybe some idea occurs to anyone who is?

Maybe one way to tell the difference between these 2 ideas is what the tachometer does. If the tach increases, just as if you had stepped on the gas, that would indicate an engine problem like the IACV. If the tach drops, that would point to a tranny problem.
</TD></TR></TABLE>

Well today when I was driving the car, I made sure to pay close attention to what the car was doing when it would jerk. I kept my eyes on the tach and I didn't see the rpm's change at all while it jerked. One thing I did notice was that once the radiator fan came on the car didn't jerk again. I don't know anything about automatic trannys or very much about Accords. This is my girlfriends car but I'm driving it right now since my Integra is down. Hopefully I can pinpoint what's causing the jerking. Thanks for your help so far.

jdm91integ

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by alb_accord &raquo;</TD></TR><TR><TD CLASS="quote">does it do this once u come out of high speeds(come out out of the high way) if yes u got to start checking ur vavles.
my f22a did that and about 6 months later my exaust vavle on the #1 piston was gone. but this is the worst scene scenario.</TD></TR></TABLE>

The car will jerk when stopped after any speed of driving. Whether I just came off the freeway or I'm stopping at the next red light. But like I said before it doesn't always happen. I hope it's not something internally wrong with the engine.

jdm91integ

Need to figure this out BUMP.

Steed77

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jdm91integ &raquo;</TD></TR><TR><TD CLASS="quote">Need to figure this out BUMP.</TD></TR></TABLE>


Just an Idea..... Turn OFF the air/heat. To me it sounds like the A/C comp. turning on. Leave it off and see if it still continues. I would start there. Good luck

KatyHonda

If the mileage is poor, a problem w/ the fuel delivery/control system seems most likely. You don't mention the CEL being illuminated, so no codes.

My first choice for your problem is a bad O2 sensor causing poor fuel mileage and bad idle. O2 sensor monitoring by ECU might be fooled (slow response) and still cause problems w/o a CEL. If engine runs better cold than hot, this would be more likely since the O2 sensor is not used when engine is cold.

Next thing that might cause your jerking and poor mileage and not set CEL is a bad fuel pressure regulator w/ leaking diaphragm. Pull vacuum line and sniff for fuel smell. If yes, the diaphragm has ruptured. This results in high fuel pressure which causes a rich condition, and also allows fuel to be pulled into engine through the vacuum line.

Good Luck

jdm91integ

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SilverGhost &raquo;</TD></TR><TR><TD CLASS="quote">


Just an Idea..... Turn OFF the air/heat. To me it sounds like the A/C comp. turning on. Leave it off and see if it still continues. I would start there. Good luck</TD></TR></TABLE>

It's definetly not the A/C that's causing the jerking. I know what your saying though. The jerking that I'm experiencing is much harder than when the A/C compressor turns on.

jdm91integ

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by KatyHonda &raquo;</TD></TR><TR><TD CLASS="quote">If the mileage is poor, a problem w/ the fuel delivery/control system seems most likely. You don't mention the CEL being illuminated, so no codes.

My first choice for your problem is a bad O2 sensor causing poor fuel mileage and bad idle. O2 sensor monitoring by ECU might be fooled (slow response) and still cause problems w/o a CEL. If engine runs better cold than hot, this would be more likely since the O2 sensor is not used when engine is cold.

Next thing that might cause your jerking and poor mileage and not set CEL is a bad fuel pressure regulator w/ leaking diaphragm. Pull vacuum line and sniff for fuel smell. If yes, the diaphragm has ruptured. This results in high fuel pressure which causes a rich condition, and also allows fuel to be pulled into engine through the vacuum line.

Good Luck</TD></TR></TABLE>

Yeah there's no CEL or codes. The car has almost 200,000 on it. The 02 sensor is orginal so it's probably mainly to blame for the bad gas mileage. This isn't my car though, it's my girlfriends. So talking her into spending atleast $50 on something that may or may not help her gas mileage is kinda hard. If it was my car I would have already replaced the 02 sensor. I'll definetly check out the FPR. It sounds easy enough. Thanks for your help.

JimBlake

Try something just for grins...

Stop somewhere, leave it in drive, hold the brake with your left foot with the same pressure you usually use at a stoplight. Then tap the gas pedal. How hard must you tap the gas to make it jerk the 'same' amount as what you're talking about? And how high does the tach move when you do this?

If you have to tap the gas much at all, & if the tach moves much, then I think you need to look at transmission problems. Because all the other things don't seem like they can actually jerk the car. Anything related to the engine, has to be acting in the direction of revving it up. And strong enough to act thru the torque converter, & overpower the brakes.

A ruptured FPR floods the engine, it might even stall. A bad O2 sensor doesn't do much to idle, but it makes gas mileage get worse. Even the IACV going full-open for a moment might not be strong enough to jerk the car while you're holding the brakes.

Vpolishchuk

Bump.
Im having the same issue with my 1999 Acura CL 2.3.

Did you figure it out?

merriljw

My 2011 Civic was having this same problem. I could reproduce it reliably when stopped at a light, idling with the A/C on. I thought it feels like the transmission's torque converter momentarily engages since the engine idle speed doesn't change.

I took my car to the dealer. They did a bunch of diagnostics on the engine and transmission, and even had the equipment monitoring when it happened. They couldn't see anything wrong with any engine or transmission codes.

Next, the dealer's service manager begin doing some tests. He could reproduce the problem with both the A/C on or just turning the steering wheel while stopped. These cars have electric powered accessories, and when the alternator kicks on while idling in gear (maybe just idling, they didn't say), this jerking will happen.

I wondered why the car didn't do it when it was newer? They said that my original OEM battery was weak and needed to be replaced. This made sense because an older, weaker battery, would require the alternator to go into a higher charge rate to charge it up.

So, long story short, I had them replace the battery with a new one, and the problem is greatly reduced. It still happens now and then when the alternator kicks in, but it's much better.