Low(er) power when cold

[Rngr94]

Hey all,

I am new here, but have been a long time viewer.

I have a problem with my 94 3.0 Ranger. When the engine is cold it has low(er) power when I first take off. I start it and when I get on it (give it gas) it bogs down and even sputters at times. What is strange is that it seems to idle ok. Once it warms up a little it is much better -- no more sputtering (when i gas it) and the power increases. I have 106K miles on it. I have changed the spark plugs and have motorcraft plugs it it. Fuel filter was changed about 1 year ago.

I know there are lot of experts on here so your help it greatly appreciated.

PS: I said Low(er) power because I do know that these 3.0 are not beasts to begin with!

Thanks!

 

[Wicked_Sludge]

one should expect power to be lower on a cold engine. the PCM has retarded the timing and leaned the fuel mixture in an attempt to keep the truck from stalling.

aside from basic tune-up items, there are hundreds of things that can cause these symptoms. you should have your base timing checked and set, see if there are any stored trouble codes in the PCM, and maybe have your dealership hook up to it and do datalogging to see exactly what the PCM is seeing.

 

[djm3452004]

Hey all,

I am new here, but have been a long time viewer.

I have a problem with my 94 3.0 Ranger. When the engine is cold it has low(er) power when I first take off. I start it and when I get on it (give it gas) it bogs down and even sputters at times. What is strange is that it seems to idle ok. Once it warms up a little it is much better -- no more sputtering (when i gas it) and the power increases. I have 106K miles on it. I have changed the spark plugs and have motorcraft plugs it it. Fuel filter was changed about 1 year ago.

I know there are lot of experts on here so your help it greatly appreciated.

PS: I said Low(er) power because I do know that these 3.0 are not beasts to begin with!

Thanks!

My '94 extended cab 4x4 is doing the exact same thing. I've only owned it a little while, but it performs the same way, particularly as I go through 2nd and 3rd gears (manual). It's like it has low power with sporadic short "surges" until I finally get to speed and the truck warms up. My idle is similarly ok. The codes the dealer gave when I had it scanned were memory codes only, and dealt with the voltages from the MAF sensor. The truck has no current trouble codes. Logic says it may be the MAF sensor, but I hate replacing parts blindly, so I figured I'd resurrect this post.

Please let me know if anyone has any ideas other than the above.

Thanks!
Dave

 

[Tedybear]

Keep in mind these ol' beasts are running in "OPEN LOOP" for a preset amount of time and/or the temp sensors. Preset amount of time is mentioned because you do not need a lot of "OPEN LOOP" time to warm up sensors to temp--when they are already pre-warmed up from driving. From a 'stone cold' point of view, it will take much longer to get into "Closed Loop" where the computer looks at all the sensors and does the fuel/air mapping that way. (eg: If the coolant is well below 'normal'? The computer senses that and leaves it in OPEN LOOP mode until it's warmed up)

OPEN LOOP: Working off a known set of variables to ensure the engine runs fair, and won't stall--normally uses more fuel due to the computer keeping the mixture rich.

CLOSED LOOP: Works off all the sensors and the internal fuel/air maps stored. Maintains optimum air/fuel mixture for good performance and mileage.

LIMP MODE: Mentioned to complete the set. Used when a key sensor craps out, and the computer can't control the air/fuel mixture correctly. CEL will be 'on'..and it'll get bad mileage and crappy performance. It's meant to get the truck/car to a shop to be repaired. Extended driving in this mode is NOT recommended!!

In the case of the mass air flow sensor, this one on an OBD II setup..like most systems with the ability to report "live information" to the scan tool is a safe bet. Mass Airflow Sensor: Just measures the air flow into the engine. If that's not reporting correctly? That would most likely create problems when in closed loop. Open loop (engine not warmed up yet) It would rely more on the TPS sensor.

(not saying it couldn't be the issue...but if the scan tool does 'live data feed" from the sensor? Pretty simple to figure out if it's bad or not)

S-

 

[djm3452004]

I had a Ford dealer scan the codes because it was an OBD-1 system, and there is no way I'm going back to let him scam me out of another $80. Evidently it's something temperature-related, but as I mentioned in another post, the truck has never had the power I assumed it would, even when completely warm. I can live with that, but the spotty performance when cold is definitely more of an irritation. The dealer also checked fuel pressure as well, and said it was "within specs." I have recently tuned it up with new cap, rotor, good-quality wires and platinum plugs.

The thought suggested by someone else is that the truck was designed to have less power when cold (which would naturally be true to a point)but not to the level of having the truck "lurching" or "surging"when throttle is applied in gear while cold.

I guess the question remains: What sensor(s) could cause poor running and power when the truck is cold? It strikes me that it has to be a lean mixture condition, just not bad enough to trip a CEL. But why does it idle well?

My thoughts would be:

Throttle position sensor (as suggested above): Though this could cause spotty performance when throttle is applied while allowing a nice, smooth idle, it does not explain why it would only do it when it was cold, or why it wouldn't trip the CEL if it was not performing properly.

Coolant temperature sensor: faulting out, making the truck think it's always running warm, and leaning out the mixture causing poor cold running

MAF sensor: Does this detect intake air temperature? If not, is there an intake air temperature sensor? A fault there may also make the truck think it's always warm outside, causing a lean mixture.

Faulty Oxygen sensor: If one of these failed or was giving bad readings, would I get a CEL or just crappy performance?


Anyway, please review and let me know what you all think--

Thanks!
Dave

 

[fastpakr]

So you've checked recently and there are no current KOEO or KOER codes, and nothing stored in memory either?

Throttle position sensor is easy to check with a basic volt meter. I believe the resistance readings for the coolant and air temp sensors are available online as well - typically you measure them with the sensor in ambient temp air as well as after being immersed in boiling water.

O2 sensor output can be measured with a meter - you're looking for the voltage to exceed 1v at certain times. I can look that info up in a book I've got... somewhere around here. O2 is unlikely the culprit on a cold engine, as its output is ignored for a few minutes during the warmup cycle.

Start with verifying the codes. If you haven't done it before, I can link you to the info that explains how to do it with just a paperclip. For that matter, if you're coming near Roanoke sometime soon I can show you how to do it.

 

[djm3452004]

Thanks for your thoughts, Fastpakr.

I decided to opt to replace the TPS since it was a cheap start ($30 at Advance). Unfortunately, it did not have an effect and the truck still has low power and the "surging" in gear when cold. I will really have to delve in deeper as the other mess of sensors would add up to quite an expense.

The codes that the Ford dealer found were 111-10-157 and 111-10-158 which both deal with the MAF sensor power, but it was my understanding that since the first number was 111, the system was "ok" at the time of their test, and the 157 and 158 were memory codes. Since the truck experiences this loss of power every time it's cold, it seems odd that a MAF sensor fault wouldn't kick a CEL every time it screws up. This may have something to do with the open vs. closed loop system, though.

I guess to me, again, since this appears to be a temperature related issue, I need to take a look at the temperature-checking sensors. Advance lists both air and coolant temperature sensors at about $20 a piece. It does make me wonder, though, whether the input of any of these sensors are taken into account by the ECM during the open loop phase when cold.

I guess we're working through it here. If anyone has any other thoughts please let me know--

Thanks!
Dave

 

[fastpakr]

The dealer charged you $80 to give you those codes? Go back and DEMAND your money back. Your truck would have spit out 3 digit codes only, so your results were provided by somebody incompetent.

Take a look at the articles on the tech page about doing the EEC-IV/OBD I diagnostics. You can do them with a paperclip in just a few minutes. Like I said, I'm in Roanoke and if you're ever out this way I can demonstrate the process.