hesitation, rough idle, half the mpg

[wonderer]

I just got done replacing the feul pump on my 92.

Since then, I get a CEL after warm up, hesitation from even the lightest movement of the gas pedal, (this was there somewhat, before I replaced the pump), and NASTY gas milage... Use to be able to get 220 miles around town, now about 110 per tank on the highway, Grr...

I thought I heard something about the evaporating system failing after replace pump, but lost the thread here...

Checking codes real soon,(will post), maybe today. Old fuel pump made noise ,, wonder if it isn't the regulator that's been the prob the whole time.

Also, I just changed the oil hoping that would make it run better (not), it was the right amount of oil , but smelt real strong of gas... I could be imagining that, because you can usually smell some gas order in the oil..

Any help on this would be gladly be welcome.

Tanks...

 

[MrShorty]

Definitely pull the codes. Then resolve any KOEO codes. Once it passes the KOEO test, then move on to any KOER codes. Once it passes the KOER test, clear the memory codes, and resolve any that come back.

It doesn't seem like to much of a stretch to think that a weak FPR could suddenly be overwhelmed by a new pump, which causes it's weaknesses to go to complete failure. A bad FPR may not show up in the computer codes (computer doesn't monitor fuel pressure) except as an O2 sensor code. If you've smelled gas in the oil, I would check the FPR. First, pull the vacuum line to the regulator and see if there is gas ini it. If there's gas in the vacuum line, the FPR is bad. If not, get a fuel pressure gauge and see what the fuel pressure is.

 

[wonderer]

Thanks, gonna start with regulator, throttle position sensor and mass air flow sensor cleaning, soon as I get time.. Guy with meter forgot to bring to work, maybe tomorrow?

 

[wonderer]

still looking...

Got mem code 173 too rich..

Noticed , (while it's stalling), a little buzz when I push the gas pedal, and as soon as engine catches and revs, the buzz disappears as it sincronizes with engine noise.. Also seems to be a very faint knocking sound, 1 knock per rev, sounds like a double knock like a bad wrist pin on a piston but sure that aint the prob,, wasn't there before.. Injector? Seafoam???

There was a fella here who just raplaced his fuel pump and then got a cel... Wish I could find that thread lol. May save me some serious effort..

Pulled vac line from regulator , no gas,, but gas smell... Almost had my hands on a pressure guage grr, next week..

Gonna try to find specs on sensors to measure them and see if bad...

Have 2 seperate issues here, stalling, wich started before the pump change, and now the cel with bad gas milage.

 

[MrShorty]

Did you get an equivalent KOER code, or did it pass the KOER test? This gives and indication of whether the problem is intermittent or consistent.

 

[Rhett]

A rich CEL code could mean a bad FPR. Why did you replace the fuel pump in the first place? It may not have been the problem. Bad O2 sensors can also cause the rich code, though in my experience they tend to cause a lean code more often.

It's good to get to the bottom of the codes, and whether they appear in key-off engine running or key off engine off, as MrShorty is doing. That way you don't replace things that are working fine.

At this point, without knowing more specifics, I would advise you replace the O2 (I think your truck has one O2 sensor) and also replace the FPR.

 

[simonda]

Looks like we are fighting very similar problems. See link to my thread.

http://www.explorerforum.com/forums/showthread.php?p=1086901#post1086901

I have replaced my O2 sensor and that did not help-still code 173. I looked at the vacum line on my FPR but no gas in the hose. I plan to get someone to measure fuel pressure next week unless I decide to just buy a new FPR over the weekend to see if that helps.

 

[wonderer]

Let's see,,,

Cleaned maf with tuner cleaner.

Checked iac valve, moves quite well with 9 volt battery.

Checked tps, it goes through the range without jumping.

Found the Ho2 sensor leads:
measured 3.8 ohms on the heater, (30 degrees at the time)
and swings from .1 to .9 volts on the sensing wires when
you fire it up and let it run for a minute or two.
It’s supposed to swing from .1 to 1.1 volts, quickly, when you start the engine.

I have to wonder about the exhaust, not in the best shape, not real loud , but it leaks. So thinking about putting on exhaust from the rear cat back.

Exhaust pressure has something to do with the O2 sensors and gas mileage/performance.

Brothers S10 lost a muffler and then got 5 mpg instead of 20 something.

Still stuck on : code 173 O2 sensor not switching or too rich

Tomorrow, hopefully I can get the fuel pressure measured.

 

[MrShorty]

measured 3.8 ohms on the heater, (30 degrees at the time) and swings from .1 to .9 volts on the sensing wires when you fire it up and let it run for a minute or two. It’s supposed to swing from .1 to 1.1 volts, quickly, when you start the engine.

So it looks like the O2 sensor can function normally. But you indicate that the CEL is on essentially on all the time. I wonder what KOER code you would get with the O2 sensor unplugged. Unplugged you should get a 172 instead of a 173.

 

[wonderer]

The cel is on only after warm up , about 5 minutes after a cold start.

Couple more things to add:

Exhaust smells like it's burning oil, could have been doing this all along and as the exhaust leak got worse (into the pass compartment), I'm starting to smell it more, plus been working on it in my garage ,(cough). I just changed the oil and it seems to have gotten a little over full on me, (it holds 5 quarts don't it???),maybe I should attempt to drain some out...

Also: there is a cycling of the rpms after warm up, about 1/2 second up, then about 1/2 second down, (purge soleniod?)...

This is not the same idle problem when it first comes up cold...

That starts about 10 seconds into running and continues to about 3-5 minutes, acompanied by the hesitation and wierd buzz noise when starting to move the gas pedal down. Then it runs fairly well except for the idle cycling..

There is another test for the sensor that I wasn't aware of till now, think its a lean test, create serious vac leack and see if sesnor volts drop back down from 1.1 to .4.

Still need to test fuel pressure at the rail, wish I had all the equiptment needed to work on these things...

 

[wonderer]

I think my problem is solved...

We measured the fuel pressure at the rail yesterday. It read 45psi w/engine off, but when I started it up , it went to 85psi!

That also explains the nasty oil burning smell,,, gas in crank case...

I'll post again to verify what symtoms were cured , but I'll bet most, if not all will be.

 

[wonderer]

Problem solved !

I replaced the fuel pressure regulator yesterday, at she runs like a top!

All of those symptoms cured ..
Rough idle ,
Stalling ,
Hesitation , even with extremely light gas pedal pressure
Horrible gas mileage ,
Light buzzing noise when stepping on throttle , (while it's hesitating)
Horrible oil-burning smell from exhaust ,
( caused by gas getting into crank and diluting the oil ! )
And of course, a check engine light with code 173 to rich .

Sorry about all the spaces between commas and periods , but I want this information to be 100% searchable so others can learn from this .

Now , if you do replace that regulator and it does fix your problem, then change your oil immediately!!! I found quarts of extra fluid in there! Yes, thin , gassy smelling , oil!

Hmm, that makes 2 oil changes in a week lol.

Remember , I originally thought that this was a fuel pump problem , because the pump started making all kinds of noises , different sound every time you turn the key...

Maybe it was going bad also, because of the 145000 miles on it, but what I found when replacing it was worth the job even if the pump was good!

The lines on the pump assembly where on the verge of leaking / cracking do to rust, I barely touched the one line and it snapped like a pretzel! The rest of the line are stain steel and appear to be in perfect shape, don't let this fool you into thinking your lines are good, if you got a 150k miles on it , maybe you should drop that tank and take a look at those lines???

!!! I would hate to have waited until the fuel , ( at 45 psi, the average household water pressure), started spraying all over my underside and all over that hot , leaky , exhaust of mine !!!

Thanks for all the help , this is a great sight for the experienced/inexperienced!

I have to say though, it's time for me to move on, I needed a vehicle that could haul stuff so I bought a ford econoline van , an E-350! It's an old work van, we used it to haul kegs, pallets of stuff, the like, very tough truck the rear axle has a place to attach duels! In the proccess, I need to sell my ex now, because I cant have that many vehicles sitting around. Darn , lol. By ALL!