shutters and sputters, ands wants to stall out

[dcmorgan2004]

i have a 1990 ranger 2.3L 2wd auto ( suppossed to be a4ld but not sure due to it not having the original trans), and when i come to a stop at a stop sign/signal it likes to sputter and shutter, and if i dont hit the gas or put it in park soon enough it will stall out.

 

[enjr44]

This a bump.

But, my first guess is if your rpms are dropping when stopped, the IAC valve is not opening to maintain the correct idle speed when stopped. Computer controls idle by opening and closing the IAC for various engine loads when at idle.

 

[dcmorgan2004]

i performed the test prcedure for the iac valve that i found in my chilton service manual. it said that if the ohm reading was not between 7-13 ohms to replce the iac valve. well i had 24.5 ohms, so i will try changing the iac valve and see what happens. thanks for your suggestion enjr44.

 

[enjr44]

I did not know what the IAC's ohms should be.

I do know that if you unplug it with the engine running at idle the rpms should drop a bunch, maybe even stall. If the rpm doesn't drop it is not working or you have a significant vacuum leak.

I also know that if you remove it, and with it plugged in, turning the key from off to run you should see the plunger move from closed to full open each time the key is cycled. If it doesn't it is either dead or you have bad wiring or a bad computer.

That is the only way I know to test the IAC.

 

[dcmorgan2004]

i unplugged the iac valve and the engine stalled. plugged it back in, started it up, and using a mechanics stethoscope, (i hope i spelled that right), i listened to see if the iac was make any type of abnormal noise. it sounded a little spiratic at first but then settled down and sounded smooth, like it was working properly. i dont know if its the iac or not, changing it could fix the problem or it wont. i've been wondering if the problem could be related to the transmission, because from what my dad has told me about the truck, ( i purchased it from him, and he purchased it from where he worked) the original trans was rebuilt, then junked, then the repalcement trans was rebuilt before it was installed, then it got rebuilt again, only they went with a cheaper mechanic, and my dad said that he didnt like the way it felt at all, but it ran, and he didnt have to pay for it. so thats where i'm at, don't know what to do. any suggestions are appreciated.

 

[a2thy]

Wish I could offer you a solution with an adequate degree of certainty, but I'm currently troubleshooting the same problem with my '97 Mazda B2300 5 spd with the same engine as yours. A few years back my truck threw some code related to the EVAP system indicated by a check engine light that remains on to this day. Only recently had I discovered that the EVAP problem could be related to the symptoms both our trucks have. Do you also have a check engine light? and if so, did it throw a similar code? My truck's symptoms are: inconsistent idle (RPMs fluctuate more than they should), inconsistent/erratic voltage (indicated by on-dash volt meter), stalling (particularly just after starting), engine power cutting out randomly resulting in an abrupt shudder/jerking throughout the whole truck (particularly while cruising or accelerating). My fuel filter was recently replaced so I'll rule that out for now. Unless someone offers some new insights, my next steps are: Writing down the exact code my truck has from the CEL, inspecting/replacing all EVAP parts in question, Seafoam the intake as well as the fuel system (to potentially unclog the fuel injectors and any intake/fuel system components that may need it), test my IAC valve, test my voltage regulator, and if all else fails start removing parts and inspecting them in further detail.

 

[a2thy]

Not sure exactly how related our problems are, but check out my past thread if you can find it useful: http://www.therangerstation.com/forums/showthread.php?t=158672

 

[dcmorgan2004]

just a quick update.
changed the iac valve, problem still present but not as bad. idle is better, but will still sputter a bit when I come to a stop sign/signal. trouble shooting maf, and tps, iat, and o2 sensors. may replace all (one at a time of course) just to see if anything fixes the problem. still dumfounded, but optimistic.

 

[enjr44]

Don't know where you got your valve; but, read through this tread before you go changing a bunch of parts.

http://www.therangerstation.com/forums/showthread.php?t=162804

 

[dcmorgan2004]

I got the valve from rockauto.com, its physically the same as the original, except it doesn't have the ford logo on it. 40 bucks altogether, but at least I eliminated it as the major cause. like I said, the issue lessoned, but is still present. any other suggestions will be helpful and appreciated.

 

[enjr44]

Well, I guess you can start replacing stuff; but, a lot of folks have discovered that the after market valves do not perform as well as the OEM valves.

I'd rather get an original valve out of a yard than an aftermarket. I have also been told that the electrics in some the aftermarket valves have a problem giving the ECU proper feedback. Just FYI from experience.

 

[dcmorgan2004]

update:
I decided that before I go putting money into a bunch of parts to at least get a new muffler and tail pipe, (muffler fell off a few weeks ago, and tail pipe missing when purchased), so apparently this seems to have fixed the problem for now. the shuttering started before the old muffler fell off. so at this point I'm considering it fixed. if it starts up again with the same problem I'll try changing the o2 sensor.