ahhhhh power loss issues - I just don't know enough

N

Nathan Wallace

New Member
Hi guys,
2003 Mitsubishi Lancer CH, with 253xxx on the clock (120xxx on 4G94 engine), F4A42 auto trans.

Ok so here is the skinny, brief as possible:

August 2016 - October 2017 - Random loss of power issues while driving, happened about 6 times total in this period, and only while my wife was driving, never to me.
August 2017 - October 2017 - Different loss of power symptom, engine loaded up, belt squeal and a little smoke out the bonnet. Happened once while I was driving, assumed failing AC compressor.
October 2017 - Engine spun a bearing in cylinder 4 (oil starvation), second hand engine put in by yours truly early Nov 2017.

Everything has been perfect for 1700kms, till yesterday.

Jan 24th 2018 - Slight loss of power cough on family trip to the beach. On way back, power loss issue has become permanent. If you mash the go pedal, revs sits around 2K, and total loss of power, car starts slowing.
Can still drive, but must accelerate slowly and keep power output low. You can still get to 100kph, just takes longer to get there than desired.
Also, when you come off the pedal, power resumes when the revs drop, and you feel a little jerk (sometimes, not all the time) as the power comes back.
Power loss point and power return points are very predictable.

Done so far:
LiquidMoly throttle, intake and engine upper cleaner
Injectors cleaned with FlashLube injector cleaner in fresh 98 octane petrol
Checked spark plugs. They have only done 1700kms, and in great nick
Removed air filter and run
Tried some old coil packs from the last engine, that have new leads
New fuel filter
New fuel pump

I tried disconnecting the O2 sensor in the tunnel near drivers foot (can only find one under the car, pre cat), to make the car go into some sort of limp mode and try to use more fuel, and check if CEL comes on.......no change at all, no CEL at all. Theory is that if the problem gets worse, then fuel pump was not keeping up, or if got better, then O2 sensor was playing up. Now that I have no CEL when O2 sensor is gone, maybe that's the culprit?


What else should I be looking at?
 
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Oh yeh suppose I better mention, I kept my foot down, doing a test drive after the family came home. I had the CEL light come on then, and when I backed off and power came back the CEL went off. So it does work, and comes on during ignition for a sec.
 
Sounds like a tps sensor ?? I had a similar problem, no fault code showing up on my reader, checked at son in laws workshop as well, still no code shown, replaced tps sensor now all good.
 
Oh yes, forgot to ask but I assumed that when you replaced engine you are referring to a bare engine replacement using previous engines bolt ons, and problem continued with this new replacement engine? Hence my suggestion of tps sensor.
If it wasn't and you replaced it with a complete long motor than that would indicate problem other than engine related, so did you use bare motor or complete long motor with all bolt-on from donor car.
If not as frosty7 and I suggest, best check air flow meter and tps sensor to start with?
 
wouldnt tps lead to a bit of a jumpy idle, as youre parked up the needle will be bouncing from say 600-1200 .
 
Yeh the engine was pretty long. I had the intake manifold, exhaust manifold, power steering pump and idler pulley. They cut the wiring harness, so I had all the coil packs, sensors etc. Used as much as I could from the newer engine. That's what made me think fuel pump/filter, as those are old. There is no jumpy idle. When you start it, it sounds totally normal, until you try to go with any decent acceleration. Never heard of the TPS. I will have to look at that. How can you test the TPS or the MAF sensor for failure? Looks like I need to get it scanned. Will any mechanic scan it for me?
 
I just switched out the TPS for the old one I had on the previous intake manifold/T-Body. No change in power loss.
It does it in every gear, park and neutral.

MAF next I take it?
 
Thanks interesting, i would have bet it was that, ok well next try the MAF as frosty7 suggested, if no luck take it to auto electrician see if it throws a code up, otherwise you will have to look at other options like fuel pump/clogged fuel filter etc like you said.
Don't think it would be oxygen sensor, that's more of a starting/hard to start issue, and if you have changed the complete engine that rules out camshaft position sensor as well, not too much left, check out and see if it throws any codes, then go from there.
 
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I would suggest replacing the O2 sensor. I had done everything you have listed aswell, cheap way to check is get a o2 sensor at the wreckers. that's what ive done after replacing multiple maf sensors, coils, coil leads, 3 sets of spark plugs, clutch, and more! I was very close to replacing the transmission until someone suggested its all a fuel/air problem. which in my case was correct.


**edit, didn't see / really read wagonmasters reply. I thought the exact same thing. but from what ive learned, the o2 sensor continually monitors the air/fuel ratio and compensates for it. my car was fine in all aspects until it carries the load in all the gears. you mash it up then lag.. lag..lag.. then jerk then it goes okay. **
 
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Found out the culprit!! It is the MAF sensor. I tested the sensor for the Hz readings coming out under acceleration, and it seems that the Hz readings are just either to high, or too low, for every other example I have read (200Hz to 700Hz under full WOT).
I unplugged it, and the engine runs smooth as ever.
 
I have a multimeter that measures frequency of ac and dc circuits. I need it for my work (refrigeration and air con sales, service, repair, install)
 
I don't remember reading that you used the old maf sensor, must have assumed wrong as i thought you used old throttle body as well, oh well at least you found what was wrong.

Are you going to try to clean it first before you replace it, or have you already done that?

What is the make of that meter you are using, is it a Fluke meter or another specific meter for you job?
 
LOL yeh I have a Field Piece multi-meter. Just need it for capacitance, volts (AC and DC), amps, temp, and Hz.

Yeh I use the new throttle body, but the new parts ended there.
I had to fit the old MAF to T body air duct. Everything from the forward to the air intake was old gear.
Good to know though.
Getting a second handy tomorrow, fingers crossed they have one still in the car they have on site.
 
Cool, just had a quick look at their website, I gather it's a port bench style field piece meters, I see some reasonably priced lt16a and 17a meters, I could use a new meter, will grab one of these that does the 10hz to 40khz freq functions as well as normal functions.
I have an oscilloscope here, but not really practical as a portable device, could test waveform I guess with it but your portable meter looks way better idea.
 
Nice bit of diag! Should be able to pick one up cheaply - if its playing up badly best just to replace. Could be anything from a bit of carbon build up to a loose solder join. Maybe worthwhile to repair and then sell or keep as a spare for later, but wouldnt waste my time chasing it while I need the car for daily duties.
 
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