CEL and mild hesitation at 40 - 60 mph
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rover3l
- Posts: 514
- Joined: Sat Oct 11, 2003 3:22 am
- Car: 1998 Q45, 2000Q45 Anniversary, 1965 Rover 3L,
CEL and mild hesitation at 40 - 60 mph
I had a CEL appear intermitantly over the last week and took it to the autoshop for a diagnosis. The codes showed it to be a leaking injector and a KS.
However, about 2 weeks ago we replaced an under plenum vacuum hose, the cause of my emission failure and the automechanic thought the codes may be residual from this. We decided then as a first strategy to reset the codes and to carry out a fuel rail flush and decarb. He used some computerized device made by Snap On and a fluid known in the trade as "soap". The process is multi step and isolates the fuel rail at one point. It is also designed to clean the plenum and throttle body etc. He ran the process twice over and apparently got a ton of carbon out. One of the final parts of the process is that the device does some sort of pressure check on the injectors and the result showed there was no pressure loss. He thought that was a good sign and that just maybe we will get away with this procedure.
The result so far is that the codes are clear and the CEL has stayed off. The main effect though is it is like driving a new car as the acceleration from rest is amazing, much stronger and smoother. We will see how it goes over the next week or so and whether my codes reappear in which case it looks like the plenum will have to come off for at least the KS's and maybe one or more injectors.
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Q45tech
- Moderator
- Posts: 14296
- Joined: Tue Apr 30, 2002 3:19 am
- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
Re: (Q451990)
The ignition advance number [in 0.1 degree increments] is the SUM of a dozen parameters:
Coolant temperature, rpm, tps voltage, speed, gear selected, MAF flow rate, knock sensor accumulated knocks, time/rpm rise rate, time rate of throttle openingtps rate of change, battery voltage, AC on/off/, and ambient temperature.
Each parameter creates a + or - offset from a preprogrammed rpm and load value.
Having the perfect ignition advance at each rpm increment is critical to ride the fine line betwen knock and loss of potential power and efficiency.
1 more degree can allow knock to start , but it takes a 4-5 degree reduction to stop knocking once it has begun!
To create peak torque the ignition advance must be such that the bulk [~~~~66-70% +-] of the fuel has burned by 15-17 degrees after top dead center. So the combustion time varies from -40 +17=57 degrees at light cruise to -22 +17=37 degrees at WOT 4,000 rpm.............and -15 + 17=32 degrees at idle. A -15 to a -40 total advance [BTDC].
Factory settings are usually 3-5 degrees less than optimum advance.To protect against bad gasoline and computer slow response time in calculating a closer to ideal number. Bad sluggish sensors.
In 90-95 a separate WOT map [look up table] is provided for each gear to take some of the guess work out of calculating an ignition advance number!
Still many sensor modify the end result! 1st gear acceleration depends more on the MAP while 2nd has more time to think about what the correct number is.
750 rpms to 6500 rpms in less than 4.5 seconds in 1st vs. 7.5 seconds in 2nd gear. The computer makes a full cycle calculation every 1/10 of a second so 450 cycles [chance to change ignition advance] in 1st vs 750 cycles in 2nd gear.
Modern 96 and later calculate 10 times faster and 2002 are 20 times faster.8 bit vs 16 bit vs 2 -16 bit cpu. The computers are always behind guessing the correct value then applying a correction value based on knock counts per 1/10 of second.........part of adaptive learn system.
Without the feedback from KS they just give up and retard the number to what was safe when the engine was new.........whether that is fully safe on a old abused ngine is unknown [safe number plus 3 more for age?].
The is no parameter for ecu to know how many miles are on the engine.
The KS are really the ONLY feedback the ecu has, other than rate of change rpm............WOT switch vs gear vs rpm rise per second but you could be in mountains not on level road so -------pretty useless.
The KS are CRITICAL to safe engine operation.>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Just one of those $300-400 +500 = $900[plenum removal] repairs necessary every 100-200k........when you change plenum hoses you always replace BOTH KS plus harness [$400] to save on duplicative labor.Same with valve cover reseal and all hoses ..........what $1700 to keep things right for the next 100,000 miles compared to the $15,000 [15 cents per mile] in total maintenance and repairs per 100,000 miles......100k>200k.
Remember Honda Civics cost 6 cents per mile and older Q cost 15 cents just $7,000/6-7 years ~~$1,000 more per year plus fuel and incidentals.
People don't spend from day one over and above warranty repairs so by 100k they end up owing the car $5,000.............the 15 cents per mile assumes you have already spent the $5,000.Which is not usually true why we say every new to a used buyer needs to ASSUME the car needs significant work to bring back close to standard.
Buy a used Q do $5,000 in repairs then start spending the 15 cents per mile ........it gets worse if you don't drive 20,000 miles per year [spend $3,000 per year on M&R].........the M&R cost per mile........it always average $3,000 per year!
Used Lux cars cost about $8,000 per year to drive assuming payments/interest....... [about the same as a new Taurus]. Compared to $5-6,000 for new econo boxes/basic 4 cylinder manual pickup trucks or $10,000-$12,000 for brand new luxo cars [Q45/Ls400/BMW 540].
The guy with $250 payments, $250 M&R, $100 insurance, $200 gasoline,.......spends $800 per month to drive a used Q..............you can see that he skips M&R or significantly reduces it. Nothing left in budget! For repairs or maintenance!
Always think that a USED car can cost you just as much as the payments per month to keep running.
Money Smart people buy 2-3 year old econo box/pickups Japanese/Korean even domestics and save the $2-3,000 per year . Altima, Corolla, Honda.
Another example of my 2:1 posts.
You pay one way or the other......there is no free lunch in automotive ownership.
Coolant temperature, rpm, tps voltage, speed, gear selected, MAF flow rate, knock sensor accumulated knocks, time/rpm rise rate, time rate of throttle openingtps rate of change, battery voltage, AC on/off/, and ambient temperature.
Each parameter creates a + or - offset from a preprogrammed rpm and load value.
Having the perfect ignition advance at each rpm increment is critical to ride the fine line betwen knock and loss of potential power and efficiency.
1 more degree can allow knock to start , but it takes a 4-5 degree reduction to stop knocking once it has begun!
To create peak torque the ignition advance must be such that the bulk [~~~~66-70% +-] of the fuel has burned by 15-17 degrees after top dead center. So the combustion time varies from -40 +17=57 degrees at light cruise to -22 +17=37 degrees at WOT 4,000 rpm.............and -15 + 17=32 degrees at idle. A -15 to a -40 total advance [BTDC].
Factory settings are usually 3-5 degrees less than optimum advance.To protect against bad gasoline and computer slow response time in calculating a closer to ideal number. Bad sluggish sensors.
In 90-95 a separate WOT map [look up table] is provided for each gear to take some of the guess work out of calculating an ignition advance number!
Still many sensor modify the end result! 1st gear acceleration depends more on the MAP while 2nd has more time to think about what the correct number is.
750 rpms to 6500 rpms in less than 4.5 seconds in 1st vs. 7.5 seconds in 2nd gear. The computer makes a full cycle calculation every 1/10 of a second so 450 cycles [chance to change ignition advance] in 1st vs 750 cycles in 2nd gear.
Modern 96 and later calculate 10 times faster and 2002 are 20 times faster.8 bit vs 16 bit vs 2 -16 bit cpu. The computers are always behind guessing the correct value then applying a correction value based on knock counts per 1/10 of second.........part of adaptive learn system.
Without the feedback from KS they just give up and retard the number to what was safe when the engine was new.........whether that is fully safe on a old abused ngine is unknown [safe number plus 3 more for age?].
The is no parameter for ecu to know how many miles are on the engine.
The KS are really the ONLY feedback the ecu has, other than rate of change rpm............WOT switch vs gear vs rpm rise per second but you could be in mountains not on level road so -------pretty useless.
The KS are CRITICAL to safe engine operation.>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Just one of those $300-400 +500 = $900[plenum removal] repairs necessary every 100-200k........when you change plenum hoses you always replace BOTH KS plus harness [$400] to save on duplicative labor.Same with valve cover reseal and all hoses ..........what $1700 to keep things right for the next 100,000 miles compared to the $15,000 [15 cents per mile] in total maintenance and repairs per 100,000 miles......100k>200k.
Remember Honda Civics cost 6 cents per mile and older Q cost 15 cents just $7,000/6-7 years ~~$1,000 more per year plus fuel and incidentals.
People don't spend from day one over and above warranty repairs so by 100k they end up owing the car $5,000.............the 15 cents per mile assumes you have already spent the $5,000.Which is not usually true why we say every new to a used buyer needs to ASSUME the car needs significant work to bring back close to standard.
Buy a used Q do $5,000 in repairs then start spending the 15 cents per mile ........it gets worse if you don't drive 20,000 miles per year [spend $3,000 per year on M&R].........the M&R cost per mile........it always average $3,000 per year!
Used Lux cars cost about $8,000 per year to drive assuming payments/interest....... [about the same as a new Taurus]. Compared to $5-6,000 for new econo boxes/basic 4 cylinder manual pickup trucks or $10,000-$12,000 for brand new luxo cars [Q45/Ls400/BMW 540].
The guy with $250 payments, $250 M&R, $100 insurance, $200 gasoline,.......spends $800 per month to drive a used Q..............you can see that he skips M&R or significantly reduces it. Nothing left in budget! For repairs or maintenance!
Always think that a USED car can cost you just as much as the payments per month to keep running.
Money Smart people buy 2-3 year old econo box/pickups Japanese/Korean even domestics and save the $2-3,000 per year . Altima, Corolla, Honda.
Another example of my 2:1 posts.
You pay one way or the other......there is no free lunch in automotive ownership.
-
rover3l
- Posts: 514
- Joined: Sat Oct 11, 2003 3:22 am
- Car: 1998 Q45, 2000Q45 Anniversary, 1965 Rover 3L,
i couldn't agree more. i have set out to maintain my Q to a high standard. For example I have just changed out all 9 active accumulators and most suspension rubber plus upper links and tension rods. What a difference.
Regarding the knock sensors and harness I will do this and a plenum job if need be but now that I have had the injectors and iuntake system cleaned there are no codes. Could the KS's still be bade even though no codes are showing and how would I know?
Regarding the knock sensors and harness I will do this and a plenum job if need be but now that I have had the injectors and iuntake system cleaned there are no codes. Could the KS's still be bade even though no codes are showing and how would I know?