MD

Anybody got a guess on why a 99 4.0 OHV would reguarly throw a P0171
code first, then eventually add a P0174? I've cleaned the MAF, checked
for vacuum leaks, etc. I haven't tried replacing the intake manifold
gaskets yet. I haven't had the time. I do have a hookup and the
software to read the OBD info, such as fuel trim if that would help
diagnose it. The 174 code doesn't always show up, and the 171 always
occurs first. Seems to be worse in cold weather.

thanks,
Murray

Jim Warman

You've described the intake gaskets to a T... I'll bet it runs rough when
cold and smooths out when warm....

"MD" <murray.devore@gmail.com> wrote in message
news:1129953854.066606.63000@f14g2000cwb.googlegroups.com...
> Anybody got a guess on why a 99 4.0 OHV would reguarly throw a P0171
> code first, then eventually add a P0174? I've cleaned the MAF, checked
> for vacuum leaks, etc. I haven't tried replacing the intake manifold
> gaskets yet. I haven't had the time. I do have a hookup and the
> software to read the OBD info, such as fuel trim if that would help
> diagnose it. The 174 code doesn't always show up, and the 171 always
> occurs first. Seems to be worse in cold weather.
>
> thanks,
> Murray
>

MD

Yep. It does. How hard are those to change out? I'm pretty handy with
tools.

thanks,
Murray

Bigusdickus

MD wrote:
> Anybody got a guess on why a 99 4.0 OHV would reguarly throw a P0171
> code first, then eventually add a P0174? I've cleaned the MAF, checked
> for vacuum leaks, etc. I haven't tried replacing the intake manifold
> gaskets yet. I haven't had the time. I do have a hookup and the
> software to read the OBD info, such as fuel trim if that would help
> diagnose it. The 174 code doesn't always show up, and the 171 always
> occurs first. Seems to be worse in cold weather.
>
> thanks,
> Murray

Real easy... I did mine in about 4 hours with the help of a haynes'
Make sure you have a long star drive bit to reach down to the top
manifold bolts remove the top cover and you can see the front ones
theres 8 in there somewhere.The bottom manifold has conventional bolts.

Dick

johanb

I think you're talking about the SOHC

He has OHV

"Bigusdickus" <sailingintoth@blueyonder.co.uk> wrote in message
news:1130001207.082907.180990@g14g2000cwa.googlegroups.com...
>
> Real easy... I did mine in about 4 hours with the help of a haynes'
> Make sure you have a long star drive bit to reach down to the top
> manifold bolts remove the top cover and you can see the front ones
> theres 8 in there somewhere.The bottom manifold has conventional bolts.
>
> Dick
>

Bill Rubino

My 98 was part of a recall for bad gaskets...4.0 soch. Might want to check
with FoMoCo
"johanb" <ollieb1oREMOVE@THIScs.com> wrote in message
news:5Tx6f.25$yH.5413@news.uswest.net...
>I think you're talking about the SOHC
>
> He has OHV
>
> "Bigusdickus" <sailingintoth@blueyonder.co.uk> wrote in message
> news:1130001207.082907.180990@g14g2000cwa.googlegroups.com...
>>
>> Real easy... I did mine in about 4 hours with the help of a haynes'
>> Make sure you have a long star drive bit to reach down to the top
>> manifold bolts remove the top cover and you can see the front ones
>> theres 8 in there somewhere.The bottom manifold has conventional bolts.
>>
>> Dick
>>
>
>

MD

New gaskets didn't fix it. Ran for about 1 day then P0171 showed back
up. <insert choice of adjectives here> Anybody have any suggestions
where to look next? O2 sensor? Bad injector(s)? I already checked all
the vacuum lines while I had it apart and they were fine.

Thanks,
Murray

Happy Traveler

Would be nice if you quoted some of the history of this thread - couldn't
find anything...
Have you checked fuel pressure?

"MD" <murray.devore@gmail.com> wrote in message
news:1130950886.857372.25590@g49g2000cwa.googlegroups.com...
> New gaskets didn't fix it. Ran for about 1 day then P0171 showed back
> up. <insert choice of adjectives here> Anybody have any suggestions
> where to look next? O2 sensor? Bad injector(s)? I already checked all
> the vacuum lines while I had it apart and they were fine.
>
> Thanks,
> Murray
>

ross via CarKB.com

MD wrote:
>New gaskets didn't fix it. Ran for about 1 day then P0171 showed back
>up. <insert choice of adjectives here> Anybody have any suggestions
>where to look next? O2 sensor? Bad injector(s)? I already checked all
>the vacuum lines while I had it apart and they were fine.
>
>Thanks,
>Murray

I have heard of a FEW people that ran some good fuel injector cleaner thru
the tank and got this code to clear. Try NAPA and see if you can find bg44k -
about 25.00 a can but it works well. Techron is also effective, but the
bg44k works better. Might as well do your fuel filter if you have not
chenged it recently.

Other UNusual stuff that causes p0171

1. Dipstick tube sucking air - bad seal
2. PCV hoses sucking air.
3. Cracked air intake tube between MAF and throttle body - pull it and check
it carefully for cracks.
4. EGR valve loose, or leaking.
5. Tube from exhaust manifold to EGR valve cracked, or loose
6. Hose from fuel vapor recirc system (evap solenoid) to intake manifold
cracked or leaking.
7. Loose throttle body bolts
8. Exhaust system leak before O2 sensors (since you are setting p0174 that
would require TWO leaks)

If you check all this stuff, do the cleaner and fuel filter, I think you have
good chance of finding your issue.

If you feel like it, post your LT and ST fuel trims at idle, 1500 rpm, and
2500 rpm., and whether you set the code at idle or while driving.


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