inconsistent power

[CaseyVR6]

1987 Ranger 2.9L 4x4 5sp

The engine runs perfectly most of the time, but once in a while it almost acts like it's being choked. It's especially noticeable while driving down open road or climbing hills. The engine loses power over a few seconds until it acts like it's going to stall then, very suddenly, it remembers how it's supposed to be running and runs great again. It bogs down and down and down then suddenly runs like it's brand new again. This happens every few minutes while driving and sometimes pumping the gas will help get it back to normal (haven't ruled out coincidental timing). Any suggestions??

 

[puty72]

check your fuel pressure. may be a bad regulator or pump

 

[jhammel85]

Any codes present? Hows the timing, plugs, wires, rotor? How old is the 02 Sensor?

 

[hidesertrat]

When was the last time you changed your fuel filter?

 

[CaseyVR6]

Any codes present?

Maybe you missed the part about it being a 1987... so no.

The 02 is old, but from what I've read the 87 didn't really lean to much on the 02 so I could clip the wires altogether and maybe lost a little fuel economy.

Fuel filter is actually arriving today as a precaution but I'd expect more consistent lagging and less sudden a recovery if the filter was plugged. It may fluctuate and sputter but not the way that it does.

Right now I'm leaning toward idle air, map sensor, or even tps. I was hoping someone would have already experienced this and let me know what they found. Thanks for the help so far. I've covered the really obvious stuff long before I sat down to post (o2, injectors, filter). If nothing else I'll work through the list of what it could be and post what I find.

 

[jhammel85]

No, I saw that it's an 87.

Here's how to check for codes:

http://fordfuelinjection.com/?p=13

 

[CaseyVR6]

No, I saw that it's an 87.

Here's how to check for codes:

http://fordfuelinjection.com/?p=13

I am humbled. I truly had no idea this was possible, leaning too much on OBDII I guess. I'll be back in an hour or so to post the codes.

 

[jhammel85]

It doesn't say much, sometimes nothing at all BUT..its always worth trying! Hopefully it points you in the right direction.

Be glad you can...Previous owner of mine chopped both plugs off

 

[CaseyVR6]

For a blinking light, that was way more confusing than I anticipated...

Here's what I think I have, but I'm going to double check my numbers in a few minutes. (numerical order)

KOEO -
31: PFE or EVP below min. voltage
67: Neutral safety circuit failure

CM -
18: IDM circuit failure or SPOUT circuit grounded
41: HEGO system lean (right side)
31: PFE or EVP fail
29: Insufficient input from vehicle speed sensor

I'm not sure of what any of those are...

 

[jhammel85]

The HEGO system is the O2. I would say that most likely, That is caused by the other codes. The ECT is the engine coolant Temp sensor. An easy and cheap fix that causes alot of issues regarding how lean or rich the system runs....Just like the TPS.

If I were you, I would install the new parts that you've already purchased, Clear the codes (unhooking battery) and seeing what comes back in the following days.

 

[CaseyVR6]

I just replaced both coolant sensors (1 wire and 2 wire), but will install the new parts and go from there. I was going to replace the o2 as well but can't get the old one out (I actually used a breaker bar and an o2 sensor wrench and rounded it off). I'm going to see if I can get the y-pipe out without trashing it or any of the bolts to hammer a socket on the sensor.

 

[jhammel85]

Oh no...I feel for you on the O2 Sensor..

I went down that same road. Did you use a 12 point socket? That'll round it off quick.

Here's my thread on it.

http://www.therangerstation.com/forums/showthread.php?t=72150

I cut the bung out, cleaned it up and rewelded. Its tricky but it can be done.
Don't put yourself through it until you know it has failed.

Also, so you know (you may already), the two wire coolant sensor is for the ECU and the one wire is for the gauge in the truck. The two wire is the ECT...Have you checked it's wiring? Look for bare spots where it's possibly gounding out.

 

[CaseyVR6]

No, I used a 6 point oxygen sensor wrench and a big helping of elbow grease.

I checked the wire for the temp sensor and all looks well, could be from before I changed it. I've only owned the truck for about 4 months and, although garage kept and low miles, it appears whoever the previous owner(s) were they only knew to change the oil and check the fluids. It's needed a lot of small-scale TLC but for the shape it's in (and my love of the older Rangers) it's worth it for me.

 

[jhammel85]

I started with one of those wrenches too. Still don't know why I thought a 12 was such a good idea...

Anyway, Yeah it's always worth it to get it running great again. I bought mine for 1200 bucks, same shape as yours...Decent overall but plenty of TLC and little bugs to work out.

Good luck to ya. Hope those new parts help...Keep us posted!

 

[CaseyVR6]

Test Results: unable to reject null hypothesis

Idle Air Control Valve, Throttle Position Sensor, EGR valve replaced with same symptoms. Next is the fuel filter, then cut out the o2 and weld in a new bung. I'm almost thinking I'll move around the pipe and slightly to the side of the original o2 and leave it in.