I have an 89 ranger 2.9 5spd manul with 231k on it and I have exuasted all my skills and favores to solve the problem. Here is my problem. I have a stumble hiccup and or stall and it is only under load until tonight. The problem started about a month ago. When I take off it felt like i was hit from behind and over time it has gotten worse. My truck bucks horribly under load (mostly starting from a stop). now when I floor it (in 1st 2nd or 3rd) it might stumble once or twice and then take off like a bat out of hell. When I am crusing in 4th or 5th and floor it my truck only stumbles moderitly. As of tonight when I tried to check the TFI Module (ICM) on my distributor wich i was unsuccesful cuase i didn't want to remove my plunum to get at it. My problem also started to hapen with out a load (under idle and reving it). Found this out when I was using a timing light to check my timing and also checking to see if i had a miss. With pip plug remove timing is spot on at 10deg. This has me utterly baffelled!
this is what i have done to date:
New cap and rotor
new plugs (nothing wrong with old plugs)
2 (used) but working spare coils
Checked IAT sensore and to spec
Checked ECT sensore for eec-iv and to spec
TP sensore (one morning i touched the plug on the tp sensore and truck died. so replace tp sensore and tp senore plug cuase plug had broken tang)
Back probed O2 sensore and as far as i can tell checs out. (when i cuased vaccume leak (lean state) voltage went up to about .5 or .6 and when i disconected fule regulator (rich state) voltage when't to around .2 volts (I could be backwards on direction of voltage for this test as it is from memmory) At idle voltage hung out around .3 volts. so from research i did this seems to be normal with a normal digital volt meter.
Fule presure good and does not change one bit during hiccup. (had gauge in cab with me for a test drive and also for high speed test)
High speed test as far as i can tell checked out ( fuel regulator test(fuel regulator disconected from vaccume))
New fuel filter
Injectors ohm out at about with in .2 ohms of each other and where to spec. think it was right at 15 ohms but know i was right in the middle of what my book said.
Third set of injectors in truck and this set is about 2 to 3 years old
fule pump primes like it should.
fule pump is only about 5 to 6 years old but doesn't rule it out.
Oh and with an analog volt meter and koer or koeo test the eec-iv gives pass code 11 with no stored error codes exept for the tp sensor i messed with that one morning.
I think that about covers it. I have owned this truck for about 7 years and put 112k of the 231k miles on it and have been pretty good with upkeep and repairing problems. I found injectore problems with it in the past and fixed it. This truck still gets around 19 to 20 MPG wich is great for 231k miles. I can not afford to take it in to th shop right now to have it checked. please help!
distributor didn't do it. Also changed O2 sensor, IAT, ECT, ECM and did a compresion test and still no luck. I guess I am on for IAC and MAP next and then I would have exausted every emission sensor on my truck. :(
Not that I think this is the case, but I cracked tow heads on my 4.0 91 explorer and it acted exactly like you are describing. I will say if you have 231K miles I would not spend too much fixing this, that is impressive out of a 2.9. It might be time to replace it.
Ya replacing it has crossed my mind but money is the problem right now. It still runs great in lower gears and higher rpm and besides the hiccups when under load. Still has lots of power though and get 19-21 mpg depending how i drive it. just wish i could figure out what is wrong. I am going to dive into the injectors next allthough I don't think they are the cuase either. Thanks for your input.