hidden gremlins

[dannormal]

Hello all
Australian owned Jimny. 2002 model with M13A engine. Vehicle broke down. I found that the Catalyctic Covertor had crumbled and was blocking the exhaust. I removed the exhaust and smashed out all the substrate material. Refitted the exhaust. Vehicle ran perfectly. (also no codes for you code people) A week later vehicle starts to play up again. Perfect when cold. Drive for approximately 8 km and it starts to misbehave. Driving at any speed with steady throttle it starts to hold back and lose its power. If you push the throttle further it will not respond and if you persist it will backfire through the exhaust. If you persist it will "really" backfire. Pull over to the side of the road it runs as barely and then stalls. Leave it for 5 minutes it will start and run like new again. Drive back home it may do it again or not. If left to run at home it will not do the problem.
The vehicle has been driven with the exhaust off and the problem is the same so it is not the exhaust. When the problem starts the ECU light now comes on and says "low voltage at map sensor". I replaced the map sensor but it did not fix the problem. I have swapped out the coils, tested 02 sensor, cam angle sensor and crank angle sensor.
Not sure what else to do really. Must be the computer i guess.
Anyone got any clues
Cheers

[Joe Z]

It can be quite a few things but try some free stuff first. start it up at night and see if you see any spark jumping from the distributor cap or wires, pull the distributor cap and see if the brass tab up top the rotor is broken or moved and that the inside of the cap looks good with no moisture in it, spray the inside and outside of the cap with WD-40 as moisture in the cap will cause that. A Clogged fuel filter could be another cause,check the spark at the end of the plug wires to be sure the spark is nice and blue..... not yellow. water in fuel tank which you could add a can of Heet to see what happens...... that's just a few things that are easy fixes and free.
Joe

[dannormal]

Thanks for the quick reply Joe Z. If only it was something as simple as that. Maybe it still is!! The vehicle is Coil on two plug. (No Distibutor). I have tested both ignition coils and the spark plugs are brand new. I have checked the spark is not jumping to earth inside the "tube". The fuel is clean. The fuel pump pressure is sound as is the flow rate and there is no aeration while the pump is operating. Keep the ideas coming, cos I'm all out

[Joe Z]

disconnect the fuel at the carbeurator and half fill a small glass jar and let it sit all night and see if anything collects at the bottom. maybe the timing chain jumped a tooth or timing is too far retard..... I've also seen where the filter in the tank would get all junk on it while running and then when it stalls it clears off. I even had one time myself that had the same symptoms as you was when i had the fuel gauge out of the tank i used clear silicone to form a gasket and what squished inside expanded about five times it size and would clog the screen and then when it stalled would fall of and run good again for a short while.
Also Do a compression check and see what that shows..... If it's low in any cylinder put a few squirts of oil in that cylinder and if it comes up then it's the rings...if it doesn't it's the valves..... and the list goes on. not sure if zuks have accelerator pumps in the carb but if that goes bad it would somewhat do that. Wire the choke open in case it's closing and you don't know it,..... and the list goes on. Hope you find it.
Joe

[hotrodsami]

I am not real familiar with the Jimny but if he is talking about a map sensor, cam angle sensor, and a crank angle sensor not to mention that it is a 2002 I am going to take a guess and say he has fuel injection and not a carb.

Have you looked to see if you have any vacuum leeks? that might make your map sensor throw a code.

[Scudo]

Suzuki m13a has no carb. Efi.

Faulty map will misread air coming in and fuel/air ratio would be out

Back firing = unignited fuel being ignited in the hot exhaust/manifold backfires can happen in the intake too so . In this case more throttle = louder backfire. Definitely no lack of fuel.

A compression test will let you know if cam timing is good. Good compression = good timing (for now). Vehicle at operating temp and cranked with WOT will give correct results.

It runs well when cold and only gives problems under load when warm but not problems sitting at idle all day when warm, correct?

[dannormal]

Thanks again Joe Z but as the other guys are saying, this is a vehicle with no carburettor. I am hearing you concerning those other probs concerning clean fuel and blockages etc.
Map sensor is indeed Manifold Absolute Pressure sensor. It cant be the timing belt, it does not have one. The timing chain faulty should cause the symptoms all the time. What tells me this is that the vehicle drives PERFECTLY until suddenly the fault comes in. This seems to be an electrical prob to me. Heat related definitely. Cold good. Hot bad. Computer maybe? What you said about Map sensor Scudo makes sense so it should not be the map sensor. I think the map sensor codes up because the engine backfires and runs so badly that the map voltages are seen as faulty by the ECU.