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Discussion Starter · #1 ·
Hello all, I'd like to start of by saying this site is amazing and thanks to all those that help. I've read hundreds of pages of info on my problem and I can't find anyone with exactly the same issue I'm having. Thus this post.

I have a 1995 Sidekick JLX, 1.6 liter 16 Valve Automatic Tranny and have been fighting this problem for months. At my wits end. The Kick starts and idles great, will accelerate with little to no issue. Maybe a little reduction in power. My problem is, when in Park or Neutral I Idle great 800rpm on the nose. If I give it throttle it revs no problem but misfires horribly. It will however continue to rev up just as fast as a kick that has no issues. At highway speeds 75 mph its very noticeable if I'm just maintaining a speed. If I accelerate, I dont feel any hesitation/bucking. If I let off the gas, same thing. But maintaining speed it bucks and misfires With cruise control on it's unbearable. I've paperclip jumped the clip out by the battery. My CEC does work and I get a code 34. MAF Voltage low.

Now here's the problem. If I unplug the MAF I have zero hesitation, zero misfire. It runs like a top. I know its not a good idea to drive around like that and I dont.

My father has a perfectly running 94 kick and I pulled the MAF off his to check. It runs exactly the same with his MAF or mine.

I've back probed the maf sensor clip and I get Power on Engine off "blue/black wire same as battery voltage 12.5 volts. It rises accordingly when the vehicle is started.

Black Wire is reading .09 volts

Grey/Black Power on Engine off 1.3 volts
Started 1.9 volts
Tires blocked, Ebrake on. In drive full throttle raises to 3.17 volts at I'd guess 3k rpm'ish

I've pulled the ECU down. Unplugged it "very carefully" Opened the case. C103 capacitor is not a Rubycon C101 is however there are no acid leaks on the board and no bulges in the capacitors. I've also checked pin B8 and it matches MAF. I have not check B6 which I just read about tonight for the TPS. I will check that tomorrow.

I don't understand why I'm getting a DTC 34 if all my voltages are checking out well within tolerance. What am I missing? Why does it idle fine but buck and hesitate under throttle?

I thought maybe spark plugs, wires, cap, rotor, fuel injectors but like I said. It runs perfect with the MAF unplugged and the system in LIMP.

Timing Belt was done about 10k miles ago. Timing is set perfect at 8degrees just as my sticker says. Fuel Mileage is about 20mpg mostly city with about 700lbs of stuff inside including myself.

I did notice earlier today that my G103 ground to top of starter is on the back side of the top bolt "tranny side" instead of the engine side. Could that make any difference? The tranny housing is Aluminum I believe.

I'm grasping at straws at this point. I hope I covered all the necessary info, if not, I'm happy to provide anything I can.

Thanks in advance for your time.
 

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First, reset the ECU by removing the dome light fuse for a minute and then replacing - this resets the ECU memory, so that the code 34 will be cleared - if it comes back now, it is in real time.
When you pull the MAF you are forcing the ECU to run on a predetermined table of values, so that it is not using the signal from the sensors to run the car. The car will seem to run 'better' but actually run quite rich, horrible gas mileage, etc.
It would seem that your wiring test on the MAF is within factory spec. Have you also tested these wires at the ECU as well?? Particularly the grey/black wire which is the output signal back to the ECU.
 

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Discussion Starter · #3 ·
Thanks for the reply,

Ok, I pulled the dome light fuse and reset the ECU. I verified this by using the CEL with the key on, engine off and getting only a code 12.

I read about the MAF and understood what you were saying it does when unplugged. I was just stating that unplugging it shouldn't magically make a faulty set of plugs, wires, cap, rotor, injectors start working flawlessly. IE... no more misfiring...right? You are also correct in that she runs very very rich with the maf unplugged.

Yes, I also checked the gray/black wire at the ECU, that was what I meant when I said I checked pin B8. All the values at the ECU on the gray/black wire match the values while back probing the gray/black wire on the MAF.

After restarting the vehicle, and revving lightly my DTC 34 came back again. This time it brought a friend DTC 44 "Idle Circuit Switch". If I'm not mistaken I've pulled the dome fuse before to clear codes and had this code pop up. It disappeared on it's own though. I suspect it may throw the code because of the rev to 2500 and all the misfiring?

I did also check this morning Pin B6 which is the pin for the TPS. The value on it was 5.02, just fyi.

What's next?

Thanks in advance for your time.
 

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Any testing or diagnostics done on the sensors presumes that the mechanical timing of the car is correct - that your valve timing is correct (compression test will show this) and that your ignition timing is correct as well.
The TPS and MAF are somewhat related - the TPS advising the position of your throttle pedal so that the ECU knows how to regulate fuel delivery, and the MAF advising the ECU of the airflow which increases as you go faster, so that the ECU also knows how to regulate. Your MAF is showing a low air flow at higher engine speeds - I think that this can also be set if the airflow is lower than spec, at idle, as well. This can be caused by a bad ground (although your ground seems to be ok) as well as any 'illegal' air - which would be ay air entering the system that does not come through the MAF (vacuum leak on a hose gasket, cracked manifold, etc). It is somewhat easy to check for vacuum leaks by pinching the vacuum hoses with a pliers, and seeing if any of the pinched hoses cause a change in idle - your ISC should cause a drop in idle (air hose from the air pipe at the air filter to the ISC), but none of the others should.
 
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