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4.9 hesitation under light acceleration by wanobi
Started on: 06-04-2008 02:30 PM
Replies: 17
Last post by: wanobi on 07-01-2008 12:40 PM
wanobi
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Report this Post06-04-2008 02:30 PM Click Here to See the Profile for wanobiSend a Private Message to wanobiDirect Link to This Post
As the subject says, I have a slight hesitation under light acceleration, if I give just a little more gas it smooths right out.

Example, set cc at any speed as i start going up a hill you can feel the hesitation and if i give a little more gas it is fine.

Only does this after it has reached normal operating temp.
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stickpony
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Report this Post06-05-2008 02:05 AM Click Here to See the Profile for stickponyClick Here to visit stickpony's HomePageSend a Private Message to stickponyDirect Link to This Post
 
quote
Originally posted by wanobi:

As the subject says, I have a slight hesitation under light acceleration, if I give just a little more gas it smooths right out.

Example, set cc at any speed as i start going up a hill you can feel the hesitation and if i give a little more gas it is fine.

Only does this after it has reached normal operating temp.


bad tps, or bad iat, or bad coolant temp sensor, or bad o2 sensor(s), test them one at a time..
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stickpony
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Report this Post06-05-2008 02:19 AM Click Here to See the Profile for stickponyClick Here to visit stickpony's HomePageSend a Private Message to stickponyDirect Link to This Post
 
quote
Originally posted by wanobi:

As the subject says, I have a slight hesitation under light acceleration, if I give just a little more gas it smooths right out.

Example, set cc at any speed as i start going up a hill you can feel the hesitation and if i give a little more gas it is fine.

Only does this after it has reached normal operating temp.


any engine codes?
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wanobi
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Report this Post06-05-2008 09:59 AM Click Here to See the Profile for wanobiSend a Private Message to wanobiDirect Link to This Post
no codes. I'm pretty sure my TPS is out of range. I had to replace it because it had gone bad. i've got some time today, so I'm going to set it by the manual and see how it goes. Good news is I don't have the "sail on" condition no more, just this slight hesitation.


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J Gunsett
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Report this Post06-05-2008 01:21 PM Click Here to See the Profile for J GunsettClick Here to visit J Gunsett's HomePageClick Here to Email J GunsettSend a Private Message to J GunsettDirect Link to This Post
I have the same problem. Ran fine last year, took it out of storage this spring and now I have the hesitation. Is yours stick or auto? Does it idle OK? What about WOT? Mine seems to not have as much hesitation when I first start it up and the block is cold (but that only lasts for a few mins), does yours act the same?

Jack

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wanobi
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Report this Post06-06-2008 02:10 AM Click Here to See the Profile for wanobiSend a Private Message to wanobiDirect Link to This Post
mine is an auto. idle is good, cold engine runs fine. warms up and hesitation. the problem has got to be between the tps and the isc motor. I will work on it more this weekend and figure it out.
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jstricker
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Report this Post06-06-2008 08:35 AM Click Here to See the Profile for jstrickerClick Here to Email jstrickerSend a Private Message to jstrickerDirect Link to This Post
The injectors on the 4.9L are terrible about clogging when the car has been sitting. Their design leaves them to where they really can't do much else other than gum up if sitting long enough. You can try some Techron (or similar) in the tank or rig something up to run the engine on some type of injector cleaner, short of that, the only way to unplug them is take them out. It's not as bad if it's running well enough that you can drive it so you can work something through it with the gas, much more of a PITA if it won't run.

Of course, this assumes that everything else (MAP, TPS, O2 Sensors, etc.) are in good working order.

John Stricker
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J Gunsett
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Report this Post06-06-2008 08:00 PM Click Here to See the Profile for J GunsettClick Here to visit J Gunsett's HomePageClick Here to Email J GunsettSend a Private Message to J GunsettDirect Link to This Post
wanobi, how does yours run at WOT? Sounds like we may have the same problem. I am going to try swapping in another PSM and see if that changes anything. Keep me posted if you find the problem.

Jack

[This message has been edited by J Gunsett (edited 06-06-2008).]

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ka4nkf
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Report this Post06-06-2008 08:49 PM Click Here to See the Profile for ka4nkfClick Here to Email ka4nkfSend a Private Message to ka4nkfDirect Link to This Post
 
quote
Originally posted by J Gunsett:

wanobi, how does yours run at WOT? Sounds like we may have the same problem. I am going to try swapping in another PSM and see if that changes anything. Keep me posted if you find the problem.

Jack



Sounds like a egr problem. Plug the egr valve and run it to see if that is it.
The egr valve gives a little problem when you are runnung light throtle { like 45 mph"}
Don

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arte444
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Report this Post06-06-2008 09:06 PM Click Here to See the Profile for arte444Click Here to Email arte444Send a Private Message to arte444Direct Link to This Post
Not to hijack but, is there a way to clean/fix the egr valve?
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stickpony
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Report this Post06-07-2008 06:51 PM Click Here to See the Profile for stickponyClick Here to visit stickpony's HomePageSend a Private Message to stickponyDirect Link to This Post
 
quote
Originally posted by wanobi:

no codes. I'm pretty sure my TPS is out of range. I had to replace it because it had gone bad. i've got some time today, so I'm going to set it by the manual and see how it goes. Good news is I don't have the "sail on" condition no more, just this slight hesitation.



its also possible the cam gear skipped a tooth.. how many miles on the current timing chain? eliminate the tps and isc first, then look to the distributor to see if there is any play
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wanobi
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Report this Post06-08-2008 02:06 AM Click Here to See the Profile for wanobiSend a Private Message to wanobiDirect Link to This Post
 
quote
Originally posted by J Gunsett:

wanobi, how does yours run at WOT? Sounds like we may have the same problem. I am going to try swapping in another PSM and see if that changes anything. Keep me posted if you find the problem.

Jack



it runs great at WOT. But I have to come clean, it was running fine until I adjusted the min idle screw, tps and isc plunger. I'm in the process of putting everything back like it was. My tps was bad and I have replaced it . The new one is set within factory specs now. we'll see what happens after i put the min idle screw back to its starting position and the isc plunger back also. I have a feeling it will probably clear up my problem, if not, I'm replacing the gas filter next and running some injector cleaner through the system.
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J Gunsett
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Report this Post06-08-2008 09:28 PM Click Here to See the Profile for J GunsettClick Here to visit J Gunsett's HomePageClick Here to Email J GunsettSend a Private Message to J GunsettDirect Link to This Post
Well I removed the EGR valve and checked it out. The 4.9 EGR valve does not work like other EGR valves, you can not use a vacuum pump to test them. So I cleaned it, checked it for leaks (none) and re-installed it with a new gasket. Still have the hesitation. Will try the other PCM I have next.

Jack
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wanobi
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Report this Post06-10-2008 02:04 AM Click Here to See the Profile for wanobiSend a Private Message to wanobiDirect Link to This Post
ok, I got my tps, isc and min idle screw back to the settings they last were at when I didn't have my hesitation. with car warm, I pushed up on the egr valve and it caused it to stumble. My next step is to get some injector cleaner and a new gas filter. I'll be going with Lucas injector cleaner.
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wanobi
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Report this Post06-11-2008 12:46 PM Click Here to See the Profile for wanobiSend a Private Message to wanobiDirect Link to This Post
I found a couple bad vacuum lines dealing with the cruise control. Replaced those and added the lucas fuel injector cleaner.

Tomorrow I will replace the fuel filter and drive the tank of gas out and see what we have at the end.
If it still has the hesitation, I guess I will have to break down and take it to a shop to have them put it on their scope to find what is wrong.
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wanobi
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Report this Post06-25-2008 12:59 PM Click Here to See the Profile for wanobiSend a Private Message to wanobiDirect Link to This Post
Took me awhile to get back to this, but here is what I now know.

I have codes:

52 ECM memory reset

65 Cruise Servo Position Signal Problem

71 Intermittent MAP


can anyone help?

If any other data is needed I have it so let me know. I really would like to get back to driving my car. It's drivable know but the hesitation is very annoying. Plus it's affecting my MPG's
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wanobi
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Report this Post06-26-2008 02:18 PM Click Here to See the Profile for wanobiSend a Private Message to wanobiDirect Link to This Post
ok, I fixed the intermittent map signal. cleaned the egr tubes in the TB again.

hooked up my data reader and went for a drive and now I have 2 questions.

1. egr duty % it goes from 100 to 0....its either one or the other is this what it is suppose to do?

2. my injector pulse time usually is the same on both banks, but when its starts the hesitation or stumble..one bank will read lower than the other. This sounds like where my problem lies. What controls my injector pulse times?

Can someone point me in the right direction?
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wanobi
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Report this Post07-01-2008 12:40 PM Click Here to See the Profile for wanobiSend a Private Message to wanobiDirect Link to This Post
I believe I have good news.. I ohm'd out the injectors cold. They all read 17 ohms. checked all the connectors on the injectors themselves. They all seemed good. I keep leaning towards the EGR system, so I replaced the EGR solonoid. Performed the idle relearn procedure and when the ISC adjusted itself the car was idling smoothly. Went for my test drive. No hesitation or stumble. I will drive it to work tonight and will know for sure then.
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