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4.0L OHV & SOHC V6 Tech General discussion of 4.0L OHV and SOHC V6 Ford Ranger engines.

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Old 10-15-2011
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rough idle, gas smell, lurching at stops

Hi, guys,

This is my first post, but I have been lurking for a little while. I am extremely new to doing any work on a vehicle, so I apologize for my naivety. You all seem really helpful though, and I'm hoping someone can lead me in the right direction.

I recently bought my 91 Ranger, and, when I idle, it lurches forward pretty significantly. It also sometimes cuts out completely or almost all the way. Twice on a longer trip it actually smoked, and when it is behaving badly, it smells really strongly of gas. Thanks to previous advice on these forums, I figured it might be the MAF. i took it out and my truck runs GREAT. i cleaned it (using MAF cleaner), put it back in, and it sucked again. upon further inspection, i discovered there was NO air filter. I put one in, and it ran even worse. I unplugged the MAF and drove to work today and back with no problems, except an occasional hesitant acceleration from a stop.

I went to the auto yard and pulled another MAF, went home, cleaned IT, and put it in. Ran poorly again after about 5 minutes.
Each time this happens, if I shut off the truck and restart, it usually stops- at least for a little while.
Because my truck runs so much better with the MAF disconnected, does this mean it's almost certainly the issue? I wonder if perhaps I pulled another bad one at the junk yard? I can exchange it, so I will try that, but can anyone tell me if this could be related to something else? The actual wiring to the MAF looks pretty old. Could that be the problem?

Sorry such a long first post! Hope it's not too repetitive of a question. Thanks so much for your help!
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Old 10-15-2011
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i forgot to say my truck is a '91 ford ranger, 4.0, v6.
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  #3  
Old 10-15-2011
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id replace the MAF with a brand new one...and with the truck running a lot better with the maf unplugged then im willing to bet the MAF was bad
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Old 10-15-2011
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I'm with DJ, Your MAF is probably bad. but you also may want to look into cleaning your Idle Air Control Valve.
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Old 10-15-2011
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ok, cool. that's what i'm thinking. a little more info that may or may not matter, but has me concerned- after replacing it with a different maf from the junkyard, it's run BETTER, but still has the same problems, just less amplified. before, once it started lurching at stops, it wouldn't stop. every stop, it seemed to get worse, until i would shut it off and restart. now, it's just mellow lurching, and it stops occasionally and it more intermittent. you think this still fits the bill of bad MAF?

thank you SO much for your help.
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Old 10-15-2011
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oh! and re: iac valve- i should probably clean it anyway, so that's what i'll do (and btw- which cleaner is best for that? i get mixed replies from searching online), but it seems like that may not be the big issue, if i'm reading my truck's responses correctly. i unplugged the iac and ran the truck and it seems ok but just really weak. is it ok to drive around a little with it unplugged for a few minutes to test it further? i unplugged it while the motor was running also, and the motor just shut off, but i'm guessing this is normal?

i apologize again for being so clueless, and i SO appreciate your guys' help on all this. guess i have to start somewhere!
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Old 10-15-2011
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Quote:
Originally Posted by kristen View Post
oh! and re: iac valve- i should probably clean it anyway, so that's what i'll do (and btw- which cleaner is best for that? i get mixed replies from searching online), but it seems like that may not be the big issue, if i'm reading my truck's responses correctly. i unplugged the iac and ran the truck and it seems ok but just really weak. is it ok to drive around a little with it unplugged for a few minutes to test it further? i unplugged it while the motor was running also, and the motor just shut off, but i'm guessing this is normal?

i apologize again for being so clueless, and i SO appreciate your guys' help on all this. guess i have to start somewhere!
Just parts and brake cleaner will work, pull your IAC off, its two bolts, i think like 10mm. then just spray your brake and parts cleaner in the two holes leading to the inside of the valve. shake it around a bit, dump it out. Repeat process until there isn't any dirt coming out anymore.
I wouldn't really drive with it off, just clean it up real quick, only takes like 10 -15 minutes.
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Old 10-15-2011
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had/have the same problem, few things ive noticed that really knock it down.

1. look for vacuum leaks. my EGR valve had a vacuum leak, fixed it and that took away half the lurching and stalling problem.

2. cleaned MAF, ended up getting a new one with lifetime replacement for 50

3. clean IAC + throttle body. Easy to get off and back on. I just used a little rag, air intake cleaner from CRC (super cheap, wont hurt teflon coating) and a toothbrush and maybe 20 minutes. scrubbed the dirt out and it truly helped.

4. (and this sucks) let the truck kinda heat up first before you roll anywhere. I give it 2-3 minutes in warmer months, 6-8 in colder. it seems to drive better all around
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Old 10-16-2011
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ok, so, i guess i need to look for vacuum leaks, but that's something i've never done before, so i'll hafta figure that out. the latest update is that i exchanged the maf that didn't work with another. i also cleaned the hell out of the iac. it's weird. before, the cel would come on every once in a while for a second. now, the car's running better, BUT there's still the occasional lurch/rough idle (it's the same kind, but much mellower), and the cel comes on at some point and never goes off. ugh, i'm so confused! it also still smells like gas, although it's much less.

could it have fixed most of the issues but still need spark plugs? or something else? guess i need to really try to figure out the code reading and/or check the vacuums and hoses!
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Old 10-16-2011
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You can take it to somewhere like auto zone, and they should be able to read the codes for you.
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Old 10-16-2011
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Quote:
Originally Posted by kristen View Post
Hi, guys,

This is my first post, but I have been lurking for a little while. I am extremely new to doing any work on a vehicle, so I apologize for my naivety. You all seem really helpful though, and I'm hoping someone can lead me in the right direction.

I recently bought my 91 Ranger, and, when I idle, it lurches forward pretty significantly. It also sometimes cuts out completely or almost all the way. Twice on a longer trip it actually smoked, and when it is behaving badly, it smells really strongly of gas. Thanks to previous advice on these forums, I figured it might be the MAF. i took it out and my truck runs GREAT. i cleaned it (using MAF cleaner), put it back in, and it sucked again. upon further inspection, i discovered there was NO air filter. I put one in, and it ran even worse. I unplugged the MAF and drove to work today and back with no problems, except an occasional hesitant acceleration from a stop.

I went to the auto yard and pulled another MAF, went home, cleaned IT, and put it in. Ran poorly again after about 5 minutes.
Each time this happens, if I shut off the truck and restart, it usually stops- at least for a little while.
Because my truck runs so much better with the MAF disconnected, does this mean it's almost certainly the issue? I wonder if perhaps I pulled another bad one at the junk yard? I can exchange it, so I will try that, but can anyone tell me if this could be related to something else? The actual wiring to the MAF looks pretty old. Could that be the problem?

Sorry such a long first post! Hope it's not too repetitive of a question. Thanks so much for your help!
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Nope, disconnecting it and getting the desired result absolutely does not prove it's bad.

The reason you are having problems fixing the problem is because you aren't following a systematic diagnostic process, instead, guessing and throwing parts/labor at it. The hit-and-miss method usually results in wasted time, wasted money, and frustration.

With that said, begin by doing a real good visual under the hood, looking for obvious problems like disconnected/frayed/etc wiring and vac hoses/connectors/fittings. Repair the obvious damage/problems. Next, pull the code(s), making note of the number(s) and if it's CM, KOEO, and/or KOER. Now look in a real service manual, like the factory one or an Alldata on CD, and follow the simple diagnostic flowchart to solve the problem. Never buy any sensor/component until it's proven to be bad. And always remember, just because something is NIB doesn't assure with 100% certainty that it's good.

*Assuming this smoke you get is black, I'm cautiously suspecting you *might* have a problem with the FPR (failed part, easy to diagnose, pull the vac hose and sniff for gas/visually inspect for presence and there should be none) or the evap emission system. Based on what I've read in this thread and a few assumptions, I suspect it's running rich, but that's what the diagnosis is to prove or otherwise. Of course, what I just said is like putting the cart before the horse and just a guess, based on the symptoms you describe and history.

On Edit: With your MAF disconnected, you are forcing it to kick up a code (ie, DTC). Make sure the MAF and anything else is connected and past codes are cleared, then drive and kick up a "real" DTC. Not doing this is inviting a failed diagnosis, wasted time, etc etc.
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Old 10-16-2011
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Originally Posted by CowboyBilly9Mile View Post
Nope, disconnecting it and getting the desired result absolutely does not prove it's bad.

The reason you are having problems fixing the problem is because you aren't following a systematic diagnostic process, instead, guessing and throwing parts/labor at it. The hit-and-miss method usually results in wasted time, wasted money, and frustration.

With that said, begin by doing a real good visual under the hood, looking for obvious problems like disconnected/frayed/etc wiring and vac hoses/connectors/fittings. Repair the obvious damage/problems. Next, pull the code(s), making note of the number(s) and if it's CM, KOEO, and/or KOER. Now look in a real service manual, like the factory one or an Alldata on CD, and follow the simple diagnostic flowchart to solve the problem. Never buy any sensor/component until it's proven to be bad. And always remember, just because something is NIB doesn't assure with 100% certainty that it's good.

*Assuming this smoke you get is black, I'm cautiously suspecting you *might* have a problem with the FPR (failed part, easy to diagnose, pull the vac hose and sniff for gas/visually inspect for presence and there should be none) or the evap emission system. Based on what I've read in this thread and a few assumptions, I suspect it's running rich, but that's what the diagnosis is to prove or otherwise. Of course, what I just said is like putting the cart before the horse and just a guess, based on the symptoms you describe and history.

On Edit: With your MAF disconnected, you are forcing it to kick up a code (ie, DTC). Make sure the MAF and anything else is connected and past codes are cleared, then drive and kick up a "real" DTC. Not doing this is inviting a failed diagnosis, wasted time, etc etc.
I agree with this, sort of. You can google almost any code and find the answer to it. So just make sure you know what code it is. I'm willing to bet is a MAF code since you ran the truck with it unplugged.
To clear any codes, just take off your negative battery cable for 15 minutes or so and then reconnect.
How is your gas mileage been? If your running rich or lean, Gas mileage is going to go to hell.
Is there anything significant you can remember about the Lurch? is it after you've been doing like 55mph for a bit? anything like that sometimes does help. I know when my IAC gets dirty (same engine as you) that my truck likes to die on startup when its warm.
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Old 10-16-2011
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Originally Posted by StxDangerRanger View Post
I agree with this, sort of. You can google almost any code and find the answer to it. So just make sure you know what code it is. I'm willing to bet is a MAF code since you ran the truck with it unplugged.
To clear any codes, just take off your negative battery cable for 15 minutes or so and then reconnect.


Yup, that's why I did that edit, to make sure he pulls a real code and does a proper diagnosis rather than drag out the repair process any longer. Thanks for telling him how to clear DTC's, I overlooked that. Personally, I wouldn't waste one second more guessing/replacing/preying at this point. Careful on "the answer" to DTC's found by googling; some explanations are good others are not. It's pretty hard to go wrong if a guy just uses the proper diagnostic flow chart for the DTC(s) (like the dealer techs or a good mechanic would) to systematically isolate and pinpoint the cause(s) of the code(s), then repair. Do it like a pro, get results like a pro, solve problems like a pro. One final note, people often seem to quickly conclude that a CEL and a code, or a driveability issue always mean a new sensor is the fix. Often, that isn't the case. But hey, it keeps parts houses busy selling parts and making money.

How is your gas mileage been? If your running rich or lean, Gas mileage is going to go to hell.

I held back on saying that, hoping he'd volunteer the info. Reason is, sometimes I like to hear people describe things in their own words rather than potentially influence them. Sometimes, this give me more to work with. No real biggie in this case.

Is there anything significant you can remember about the Lurch? is it after you've been doing like 55mph for a bit? anything like that sometimes does help.

I'll await the outcome of his diagnosis process, up to the point he has valid DTC(s) in hand. Life for him could be much easier if it kicks up a valid DTC(s).

I know when my IAC gets dirty (same engine as you) that my truck likes to die on startup when its warm.

If you remove the tube between the TB and the AF box, you will notice an idle speed adjustment screw. This is the default in the event that an IAC solenoid fails. To check yours to make sure it's adjusted correctly, pull the wire off the IAC solenoid at idle and make sure it idles @600RPM. If it doesn't, adjust that screw until it does. Oh, the engine should be fully warm to do this adjustment correctly. Also, it's possible that you have a very small leak in your FPR, making warm starts a brief rich mixture start. Very easy to diagnose this and rule the FPR out.
*The message you have entered is too short. Please lengthen your message to at least 1 characters. There, problem of my insertion of comments in a post solved. :D
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Old 10-16-2011
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Google is usually right, but if i question it, i plug it into my scanner at work. (i've got a Snap-on Soulus) and it'll tell me. I've had a few members PM me with some codes before to help them out.
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Old 10-23-2011
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thanks, you guys, for all your help! i'm FINALLY having time to work on things today. i do know that it is not the maf. i actually had someone do a tuneup for me (and check things out on a basic level) so that i wasn't the only one working on my truck (since i'm a complete newbie) and he told me to get a new maf and try it and i did. it didn't solve the problem. so now i am going to attempt to decipher the cel, although i'm nervous about doing it right for some reason! stxdangerranger- if i can't figure it out, i may pm you! thank you for all your help, and if you have any more tips, feel free!

kristen
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Old 10-23-2011
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ok. so. after all this worry, i took off the negative battery cable to reset the cel. there was some corrosion (not a ton, but enough), so i cleaned it off too. about 20 min later, i reconnected the negative cable and checked the positive cable. i was actually able to crank that bolt a couple times around, so i think it was pretty loose.

i went for a drive to re-activate the cel with the correct code (since i'd been driving with my maf disconnected prior to that), and it ran SO SMOOTHLY. usually, it starts acting up no more than 5 minutes into it, and it's got a slightly noticeable inconsistent idle from minute one. this time, i drove for 20+ minutes and not a single shudder.

could this seriously have been the issue?
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Old 10-23-2011
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Originally Posted by kristen View Post
ok. so. after all this worry, i took off the negative battery cable to reset the cel. there was some corrosion (not a ton, but enough), so i cleaned it off too. about 20 min later, i reconnected the negative cable and checked the positive cable. i was actually able to crank that bolt a couple times around, so i think it was pretty loose.

i went for a drive to re-activate the cel with the correct code (since i'd been driving with my maf disconnected prior to that), and it ran SO SMOOTHLY. usually, it starts acting up no more than 5 minutes into it, and it's got a slightly noticeable inconsistent idle from minute one. this time, i drove for 20+ minutes and not a single shudder.

could this seriously have been the issue?
Theoretically, no since all you did was clear any DTC's from the ECM. I don't know what version of engine management system you have, but if it's EEC-IV, that ECM will actually "learn" idle over a short period of time, this is invoked when the batt is disconnected. I would expect the issue to return. You did the right thing by clearing what was porbably a MAF code. Be aware that whatever code was in there may have not directly pointed to the MAF since some of the systems work together. Next time it throws a CEL, pull the code, making note of it being KOEO, KOER, or CM. The latter is every bit as important as the code itself, as you use this info to determine which code to fix first (start by fixing KOEO and the lowest # code first, reset ECM, drive, then work your way up if that's what it takes, and failure to follow the correct sequence of code repair has the potential to increase your time spent, bogus parts purchase, and frustration). The EEC-IV ECM will store all DTC's for 50 duty cycles, after that they will self-clear. Your emission sticker on the radiator core support should tell you what version of engine management system you have.

*If you have a code now, pull it and post it.
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Old 10-23-2011
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could have been in lean mode. I'm not sure if a MAF code will throw it that way thorough.
I'd just go ahead and keep driving it. If it throws a code then pull it. if not just consider it a fluke.
As for learning the idle, your normal idle should hang around 700 rpm. if its not that, then there still may be an issue.
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  #19  
Old 01-05-2012
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What is a MAF?? I am having problems 2.3L idle when stopping.
Thanks
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