DodgeTalk Forum banner
Status
Not open for further replies.

98 ram 1500 poor mpg, rough idle and dies

5K views 19 replies 5 participants last post by  key99 
#1 ·
Issue has been going on for about 2 years and I have yet to figure it out. I have hooked up my scan tools to it and cannot seem to find the problem. If I let the truck idle, it will eventually start to "bog" down, you can hear the IAC sucking air and you can smell gas. Now, I have replaced the following.

map sensor
front o2 sensor
IAC
TPS

and done a full tune up (plus, cap, rotor)

I have yet to find out what the issue is. Does not matter if it is cold or hot. It will bog down to about 300rpm and as low as 184 rpm and sometimes it will go back up to 400 rpm, other times just dies.


and yes, the cat is not clogged. Done checked. Any idea's?
 
#4 ·
Watch ign timing on scanner; does it remain ok when it starts to bog/loose rpm?
 
#5 · (Edited)
Here is a screenshot report of when it was bogged down and smelling gas and such. I have the elm327 adapter, just a matter of finding good software to record the live data.

http://www.farmtalk.org/3.html


Also, with truck running the alternator is putting out about 13.5-13.7 volts at the battery posts.
 
#7 ·
how old is your O2 sensor, when mine was going out it acted like yours, ran good so long as I wasn't cruising or idling. How old is your battery? If your battery is bad the alternator is using up a lot of that to try and charge it instead of feeding all your electronics that run and control your truck.
 
#9 · (Edited)
At first I thought pre-cat O2 sensor. BUT you have replaced it. Possibly check it before going further? I know you can check it "caveman style" with an OHM meter & a torch. Its not a Bosch is it? They have a bad reputation, I can testify for that with a GM :mad :I'm not an expert but isnt the pre-cat O2 sensor supposed to jump around a lot, trying to get to .7ish volts while the rear O2 should be more steady at .7 (since the mixture should be perfect by then)? Your front O2 just hangs around .32-.36. Maybe try unhooking a vacuum hose while scanning to see if it changes the front O2 reading? It should. The lazy numbers just kind of stand out. The rear had a low/high change of 3.9 volts, while the front only had .04. Again, its just a screenshot but you cant disagree with numbers.

Another idea FWIW. This may be another totally different issue unrelated to the O2, its just reading what is there-if it is working.. Say the fuel pressure was just too high, bad regulator or whatever reason. You could get the same symptoms. Have you slapped a fuel pressure gauge on it yet? Dont think too much, you need fuel/air/spark. You can never have enough air & spark, but you can fuel.

I'm using the ELM 327 adapter & the paid version of Torque so the numbers are readable to me, just different format. I havent had much luck downloading the numbers like you have, so I'm liking your version!

(edit)
Looking more at your screenshot. Air intake temp was *150-154* thats high. Its not that hot in Ohio right now for sure! Do you have some kind of cold air intake on the truck? I need to check mine, but that seems way out of spec. The O2 sensors are at the end of the line, reporting the results. The AIT sensor is at the front of the line. Maybe crazy, just an idea-that kind of raised a flag. Its reporting super freakin hot temps outside, so it dumps more fuel in to adjust & wont ever hit perfect, giving you a fat fuel mix. Maybe try unhooking the AIT sensor while scanning, along with inducing a vac leak? Just throwing out ideas.
 
#11 ·
Ok, the sensor is not a bosch brand I do know that much. I did do a fuel pressure reading and had steady 49psi (sometimes 50) even when it would run like a dog. I live in Indiana and when I done that scan it was 54 degrees outside. Not sure where the AIT sensor is even at. Also, it has all the stock housing and stuff.
 
#12 ·
I said it kind of wrong, a hot air intake reading would lean it out-oops. Its late for me & the old brain is sleeping! Either way, its located in the kegger intake. Thinking of this guy (new forum is killing me, heres a link)-

http://shop.advanceautoparts.com/wc...e//756/large/18480652_bwd_wt3023_pri_larg.jpg

Pretty sure it goes here, in the hole in the upper right side of the intake, just left of the waterneck where the open port is-



Others here know tons more than I do for sure & will help. I have a 96 & the fuel pressure seems to be close to what I have measured, maybe a little high but not too bad for your symptoms. I really dont know the pressure offhand without having to look them up. A blown "bellypan" gasket on the intake will kill all power & mileage & toss out a lot of smoke with a loss of oil. Does it smoke? I've been through 2 bellypan replacements so far. Usually it make a "odd" sucking sound when you really nail it. You can check by opening the throttle blades & looking for oil puddles on the bottom of the intake.
 
#13 ·
As said in the previous post, Plenum gasket may be leaking. Are you burning oil?
Issue has been going on for about 2 years and I have yet to figure it out.
When it first started was it immediate or did it slowly get that way?
Did you disconnect the battery to relearn the new parts you put in?
There have been other posts about bad IAC's right out of the box.
 
#14 ·
As said in the previous post, Plenum gasket may be leaking. Are you burning oil?

When it first started was it immediate or did it slowly get that way?
Did you disconnect the battery to relearn the new parts you put in?
There have been other posts about bad IAC's right out of the box.
Yes, it does burn oil, but I have looked down the TB and do not see any oil puddles or anything. To be honest, it just started and did not seem to be gradual. I did notice today while idling at a stop light for about 2 minutes tops, when I went to take off i put my foot on the gas and all the truck would do is go "put put put" like it was not getting fuel,spark, or something. I had the pedal down to half throttle and after about 10 seconds of it doing this, it come right into it and power was back.


and Yes, I always disconnect the battery when I change parts.
 
#15 ·
I'll try to get mine up to closed loop, 200* like yours & compare numbers with you. I'm thinking your kegger is ok, something else is out of whack!

I just did the exhaust on mine & forgot to weld in the bung for the post cat O2 sensor. oops! Right now its just tucked in behind a heat shield (not tossing a code but not correct). My cat is gutted. Hopefully the numbers will help some. I'm over 300K (odometer died at 289K a while ago) so we are close. I flat out eat valve stem seals to the point where I change them yearly to reduce oil burning & smoke. Maybe that is an issue?
 
#16 ·
Did you ever get around to comparing the numbers to mine?
 
#17 ·
Voltage output is low, but probably due to idle speed too low.

... #1 runner where IAC mounts is pretty warm, my IAC also reads 150 ish*f: the battery temp sensor probably reads closer to ambient temp.

... Screenshot shows a DTC ??

... DK if it's the same code, but first line under Monitored Test Results [Mode 06] shows a FAIL
 
#18 ·
Voltage output is low, but probably due to idle speed too low.

... #1 runner where IAC mounts is pretty warm, my IAC also reads 150 ish*f: the battery temp sensor probably reads closer to ambient temp.

... Screenshot shows a DTC ??

... DK if it's the same code, but first line under Monitored Test Results [Mode 06] shows a FAIL
the DTC is for the 02 sensor that is after the converter. and that is a hit or miss for that to throw a check engine light. If I read it correctly on what minimal "support" the software I was using had, the error in mode 6 would be due to the check engine light being on and the dtc being on (check engine light) for the rear 02.
 
#19 ·
JMW, I tried data logging on my Elm 327/Torque Pro stuff & screwed something up :mad: I tried to warm it up to 200* & log stuff to compare with you but it looks like I didnt set what I was trying to log, all I got was locations & screenshots. I was a little frustrated & gave up on it for now. Its "operator error" but its getting to me so I'll try again!

What app are you using with your adapter? Your's looks easier to read. Worst case is I can compare some screen shots when warmed up. I think 186* was the hottest I could get it (180* thermostat that working very good apparently). Sorry for no info so far, I was trying!
 
#20 ·
My bad: in earlier post I should have said "IAT", not IAC; and IIRC, my IAT sensor shows temps of close to 160, using a 195*f stat.
 
Status
Not open for further replies.
You have insufficient privileges to reply here.
Top