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post #1 of 24 Old 03-21-2020, 07:20 PM Thread Starter
Andrew090202
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Gas mileage

I have a 2003 Jeep Grand Cherokee Laredo with straight 6. I recently replaced the fuel injectors with aftermarket bosh 12-hole fuel injectors. Now the engine idles perfectly fine, but when I shift it in to reverse or drive the rpm’s drop to around 500 and the vehicle starts shaking. I went from around 15mpg to 7.2mpg. I have a check engine code on that says system to lean bank 1. The code is P0171. The fuel trim level are also high. Any advice on what’s wrong. I know I shouldn’t be driving it like this and I have to get to and from work.

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post #2 of 24 Old 03-21-2020, 07:41 PM
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why did you switch injectors? Any other codes, other work - Always want the big picture.

As for the P0171, what are the fuel trims ?
Look at the MAP.

In theory when lean is the PCM will correct by adding fuel, A SWAG look for a vacuum leak, maybe the inj orings...

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #3 of 24 Old 03-21-2020, 07:48 PM
Livewire9
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If you disconnected the battery??? ..Drive it 4 a bit I got 22 + out of my 00 4.0 stock 180k untill it died wrist pin..
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post #4 of 24 Old 03-21-2020, 08:31 PM Thread Starter
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Originally Posted by jtec View Post
why did you switch injectors? Any other codes, other work - Always want the big picture.

As for the P0171, what are the fuel trims ?
Look at the MAP.

In theory when lean is the PCM will correct by adding fuel, A SWAG look for a vacuum leak, maybe the inj orings...
I switched injectors because the Jeep has over 200,000 miles with the stock injectors. I was getting 15 mpg on the highway with cruise control. Also if I was doing higher speeds, between 40 and 50, and I gave it gas it hesitated. I have a P0141 which is for an o2 sensor, but I had that code before I switched injectors, so I don’t think that would cause it to run rough. That’s a downstream o2 sensor. For other work I have replaced a vacuum line to get the ac vents to work and I have replaced the throttle position sensor, because it was broken.

I’ll have to tell you the fuel trims tomorrow because it’s late and I don’t remember them.

I’ve done some testing with the fuel trims, and I don’t think it’s a vacuum leak.
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post #5 of 24 Old 03-21-2020, 08:33 PM Thread Starter
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Originally Posted by Livewire9 View Post
If you disconnected the battery??? ..Drive it 4 a bit I got 22 + out of my 00 4.0 stock 180k untill it died wrist pin..
I did disconnect the battery, but it’s been days.It still runs rough when in drive or reverse, but it idles fine in park or neutral.
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post #6 of 24 Old 03-22-2020, 12:08 AM
jtec
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ideas,
could you post ALL the codes.
might want to check fuel pressure with a gauge, post PSI.
Is engine reaching correct ECT @ 210deg F ?
Is AIRBAG light on?

The low RPM under load has me thinking a IAC issue, and I suspect a code.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #7 of 24 Old 03-22-2020, 07:57 AM Thread Starter
Andrew090202
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ideas,
could you post ALL the codes.
might want to check fuel pressure with a gauge, post PSI.
Is engine reaching correct ECT @ 210deg F ?
Is AIRBAG light on?

The low RPM under load has me thinking a IAC issue, and I suspect a code.
So the codes are P0141, P0442, P0171, and P0455. Two of them are evap that have been there since I got the vehicle. It’s not quite reaching 210, it’s around 201-205. The airbag light is not on.

Fuel trims:
Shrtft1-19.5%
Longft1-32.9%
Shrtft2- -2.4%
Longft2- -3.8%
These fuel trims are from a freeze frame at 34 miles per hour at a coolant temp of 201.
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post #8 of 24 Old 03-22-2020, 08:19 AM
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did you have those fuel trims before injectors?

something is confusing P0171 and - 32.9% that is a minus not a dash?
IDK if its a minus 32.9 thats dumping fuel - do you have a fuel pressure gauge AND a easy attach point on fuel rail - a schraider valve?

the plugs must be wet and black.

201 - 205 you should be in closed loop.

those codes we know p0171 is lean, the p0141 is B1S2 check for a wiring issue in sensor pigtail pinched rubbed thru.

those EVAP codes, p0442 and p0455 for now pinch closed the purge valve vacuum line from eng. Familiar with that?

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #9 of 24 Old 03-22-2020, 09:56 AM Thread Starter
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Originally Posted by jtec View Post
did you have those fuel trims before injectors?

something is confusing P0171 and - 32.9% that is a minus not a dash?
IDK if its a minus 32.9 thats dumping fuel - do you have a fuel pressure gauge AND a easy attach point on fuel rail - a schraider valve?

the plugs must be wet and black.

201 - 205 you should be in closed loop.

those codes we know p0171 is lean, the p0141 is B1S2 check for a wiring issue in sensor pigtail pinched rubbed thru.

those EVAP codes, p0442 and p0455 for now pinch closed the purge valve vacuum line from eng. Familiar with that?
Here are the fuel trims revised.
Fuel trims:
Shrtft:19.5%
Longft1: 32.9%
Shrtft2: -2.4%
Longft2: -3.8%
These fuel trims are from a freeze frame at 34 miles per hour at a coolant temp of 201.
I don’t have a fuel pressure gauge. It is in a closed loop. I haven’t checked the spark plugs yet because they aren’t that old and kind of hard to get to. I have the o2 sensor to replace it but I can’t get it to break loose and it’s almost touching the oil pan. I can probably find the vacuum hoses to pinch off because I have a vacuum diagram.
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post #10 of 24 Old 03-22-2020, 10:33 AM
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Ok you cleared up that confusion, its ADDING 32.9% that is indicative of a vacuum leak and makes sense with the p0171. That - dash was confusing the issue for me just needed to check on it.
Could be bad fuel pressure, before we look for a gauge is there a schraider valve on the fuel rail?

that Purge valve is on the driver fender by master cylinder. The code suggests a LARGE leak
P0455.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #11 of 24 Old 03-22-2020, 11:41 AM Thread Starter
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Ok you cleared up that confusion, its ADDING 32.9% that is indicative of a vacuum leak and makes sense with the p0171. That - dash was confusing the issue for me just needed to check on it.
Could be bad fuel pressure, before we look for a gauge is there a schraider valve on the fuel rail?

that Purge valve is on the driver fender by master cylinder. The code suggests a LARGE leak
P0455.
Yes, there is a schrader valve on it.
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post #12 of 24 Old 03-22-2020, 01:05 PM
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the fuel pressure gauge is an inexpensive tool.
First ask at part stores if they do loaners or rentals.
Ask your posse of friends, might be one of them has one.

Did you check vac line to PURGE.?
Can you try the carb spray trick to check for vac leaks?

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #13 of 24 Old 03-22-2020, 04:50 PM Thread Starter
Andrew090202
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Quote:
Originally Posted by jtec View Post
the fuel pressure gauge is an inexpensive tool.
First ask at part stores if they do loaners or rentals.
Ask your posse of friends, might be one of them has one.

Did you check vac line to PURGE.?
Can you try the carb spray trick to check for vac leaks?
The vacuum line seemed fine from feeling it and looking at it. The vacuum line is a hard plastic. The purge is ticking if you put your hand on it. Is that normal.
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post #14 of 24 Old 03-22-2020, 11:53 PM
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yes it ticks thats normal...

we want to be sure the valve is closing not letting vac pass thru or a vac leak manifold to valve.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #15 of 24 Old 03-23-2020, 11:12 AM
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Quote:
Originally Posted by Andrew090202 View Post
Here are the fuel trims revised.
Fuel trims:
Shrtft:19.5%
Longft1: 32.9%
Shrtft2: -2.4%
Longft2: -3.8%
These fuel trims are from a freeze frame at 34 miles per hour at a coolant temp of 201.
I donít have a fuel pressure gauge. It is in a closed loop. I havenít checked the spark plugs yet because they arenít that old and kind of hard to get to. I have the o2 sensor to replace it but I canít get it to break loose and itís almost touching the oil pan. I can probably find the vacuum hoses to pinch off because I have a vacuum diagram.

looks a bit strange
Bank1 shows lean and bank2 is OK
The late model straight 6 had 2 banks but not all Is it 2003 with dual pre cats and 4 oxygen sensors? Or Cali emisions?


Anyway, bank 1 are first 3 cylinders counted from the radiator.When you swapped the injectors didnt you mistakenly swap the plugs between 1st and 2nd injector?
These are close to each other and it happens sometimes. Easy check is to look at wire color. All injectors have a common dark/light green wire. The other one is specific for each injector
1 - white/dark blue
2- tan
3- yellow/white



Also check the O2 sensor wiring. The bank 1 upstream sensor wires go from the fuel injector rail down in front of the intake manifold behind the PS pump

current 2x XJ, 2x JK-U, SJ, M38A1, WJ
gone XJ, TJ, XK, ZJ
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