2.9 Barely running and running rich

Adhawk · May 2, 2011

Hope someone can help me, My 1986 2.9L Ranger is running real rough at idle and running extremely rich. A month or so ago it always fired up on the first turn of the key, and now it struggles to start and stay going. Everything I have done so far has made it continue to downslide and progressively get worse.

I pulled the stored codes, reset the Brain and have replaced the ECT sensor, IAC, new battery cables, new vacuum lines and fuel filters. The codes I got were in reference to the ECT, TPS, and EGR. I have tried to get codes again with my test light, but all I receive is a solid light. The fuel pump runs continuously with the key on. I replaced the frame pump couple years ago (with the noisiest one ever), and it has always just primed the system for a couple seconds with the initial turning of the key. I have disconnected the fuel lines at various pionts in the system to check the flow and and see if both pumps work and flow\pumps seem good. I don't have a pressure tester to verify pressure at the shrader on the rail so thats all I haven't checked Fuel wise. I pulled a few plugs the other day, and all that I pulled were black and sooty. I'm pretty sure the EGR is plugged up, as I pulled it off over a year ago and used a drill to clean out all the built up carbon where it bolts to the intake manifold. I un-bolted it again a week or so ago, and it still looked the same as the day I cleaned out that port so that leads me to believe its not recycling into the intake manifold. I pulled the vacuum line on the FPR (Installed new one about two years ago) and there was no gas in it or coming out. I also replaced the Fuel relay and relay harness at that time (They were packed full of corrosion). Anyways, that sort of sums up what I've replaced and the issue at hand - I hope someone has some insight into what I could do or check from here, I'm not quite ready to call the scrapper yet as it still runs and operates but just not very good.

Thanks for any help guys.

RyanL · May 2, 2011

I kind of get the hint that your truck sat for a while (just like mine did and it ran like complete crap when I tried to make it road worthy again). Wire connections corrode, fuel and vacuum lines crack, seals leak, etc etc. Vehicles tend to not do too well when they sit a lot. If that's the case, I bet your fuel filter is all gummed up (even though it may not have many miles on it). Your injectors might be clogged up or just not functioning. I did a handful of things to get mine running decent again, but the biggest cause turned out to be a flaky ignition module (it seemed like mine was running rich, but I guess it was just missing a lot and I was smelling the unburnt fuel). I'm going to make it a point to at least take it for a spin once a week and not let it just sit there endlessly. As far as your codes or lack thereof, I think that it takes a while (several trips) for codes to pop back up. I wish that I could be of more help, but just look at the last couple of pages in this forum under this section and you'll see lots of other guys with almost the exact same symptoms caused by different problems mostly. The easiest things to check out would be your intake air temp sensor (located in the center of the intake manifold on the passenger side of it) and your 2 wire coolant sensor which can both make your truck run rich as hell if they are out of whack. The MAP sensor and oxygen sensor can be a little more difficult to test out. Good luck.

Adhawk · May 3, 2011

Thanks for the reply, I will look into the air temp sensor and the O2. I did replace the ignition control module and coolant sensor already, as well as have pulled a few plugs on the wiring harness and noticed the corrosion. I don't know what I can really do about corroded plugs\wires cleaning-wise (baking soda and water?) I do kinda question the the injectors being plugged, however it seems weird they would all fault at once as well as the truck was running and driving a month ago. I've had goofy problems with it shutting off on me when driving and then not restarting for 10-15 minutes the past couple years, but after a previous post on here, I replaced the the ignition module on the distributor. I didn't get to drive it enough to take stock if it fixed the problem then because I had foot surgery soon after and it sat until recently. I have a stinking suspicion my problem lies within wiring\sensors\etc, I just don't know where I should look first.

Thanks, anymore ideas appreciated!

holyford86 · May 3, 2011

Check your computer grounds. (There's a ground that's on the back of the passenger side head that's often missed.) and pull codes.

Adhawk · May 8, 2011

So I drove it into the garage last week, where it sat till this evening. I needed to do an oil change in my car and so I tried and tried to get it started but it just doesn't want to. I decided to take the opportunity to pull the computer and check its harness connection. It had a bit of corrosion on each side of the plug, there is a buildup on top of the pins on the brain, still kinda gooey. I can also see it down in the plug holes. I decided to cram some baking soda\water mix down into the plug side and eat away the corrosion, I will do my best to get the excess off the pins on the computer side by hand since water probably isn't a circuit boards best friend. My plan is to dry the plug a few days, cram some dielectric grease onto the pins and holes and button it back up. Could this be causing my issues? I've seen way more corrosion in connections before and it didn't look corroded in a way that would short anything, but I have to wonder. Guess I'll find out in a couple days. As for pulling the codes, still just a solid light before I pulled the brain, undid the battery a few times to clear it with no results. New grounds a few weeks ago.

RyanL · May 8, 2011

I don't know if baking soda and water is the best thing to use around the computer or other harness connections for that matter. A good contact cleaner would be best. Your's is a bit different from mine since it has that whole EGR mess along with 2 fuel pumps which creates more problems. There's also some sort of canister for fuel on yours which also can cause problems. I would start with the basics like spark before trying to troubleshoot your fuel system. Does it seem to have consistent spark? If you have a timing light, you could clip it onto each spark plug wire and have someone turn it over while you check the flashes. You said something about new grounds in your last post; what did you mean by that? There's grounds everywhere in that truck. If the rest of your connections are in such bad shape, I can only imagine what condition all the grounds under the hood are in. Your best bet would be to clean them all up with a wire brush in a drill or something. Are you certain that the test to get the codes is being done right (it's very easy to connect to the wrong pins)? Maybe you should try to get the codes using the check engine light method just to see what you get (connect a jumper wire from the signal return pin to the self test in pin and then turn the ignition switch to the on position - http://www.therangerstation.com/tech_library/OBD_I.html). It might also be worthwhile to check into the ECU relay before jumping to the conclusion that the ECU is toast. It's hard to troubleshoot 20/25 year old vehicles and it's even harder to do over the internet because there is so many things that could be wrong with them. Good luck.

Adhawk · May 15, 2011

So I'm still messing with it, I got a fuel pressure tester and am getting 45psi with KOEO, it drops to 40psi when I start it. I replaced the TPS this week which was a story in itself (found out I have a Bronco II engine and Harness - engines never been swapped). I just tinkered with the Fuel pressure inertia switch, the plunger was up about an 1/8th inch so I put rubber bands on to hold it down and started the truck - it made no difference, pump still runs. Then I disconnected the FPIS, used jumper wire on the plug - no difference, pump still runs. Then I removed jumper wire - no difference, pump still runs. Isn't disconnecting it or the plunger being up supposed to kill the fuel supply? The pump continues to run with the key on no matter what I do to it short of disconnecting it. I kinda don't think my problem is with the pump however as pressure is correct and it just makes pressure in the line, but what would make it run constantly with the key on engine off? Another interesting point is when I get it running and juice the throttle, it backfires within the exhaust up near the cats. I'm heading back out now to check the timing. Cap, Rotor, Wires and plugs are new about a year - 1.5 years ago.

Thanks

Adhawk · May 15, 2011

I forgot to mention I also disconnected the O2 sensor, truck ran just as crappy with it disconnected with no discernible change.

Halffast · May 20, 2011

I have 2.9L in 86 Ranger and HAD same problem

Adhawk,
I had the same problem. It turned out to be the Fuel Pressure regulator on the fuel rail.There is a vacuum hose from rear of regulator to the intake manifold. Engine vacuum is applied to one side of a diaphram that has a strong spring pushing the other way. Mine had a hole in the diaphram which let fuel right into the intake. Pull the hose and check for fuel in it. You should not smell fuel in the hose. If there is a hint of fuel, the diaphram and the regulator is bad. If the hose is free of fuel, then the other item I would suspect is the O2 sensor, when the O2 sensor ages they cause a richer mixture, by telling the ECM there is excess oxygen in the exhaust pipes, (that needs to be used up).

Halffast · May 20, 2011

Adhawk,
Just noticed you ran engine with O2 sensor disconnected, that is not a good test, I am surprised it ran at all. Disconnect some sensors and it won't run and might mess up the ECM. My 2.9L is running bad again after I changed a lot of stuff including the ECM, it ran like new for a few days and now it barely runs again! You can damage an ECM, and maybe I did? (I bought my 86 new and I am sick and tired of the OBD I ECMs they use, they are tough to diagnose.) Good luck with yours.

2.9 Barely running and running rich

Adhawk

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RyanL

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holyford86

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