1HZ subtle power hiccups

[Gregol]

Hello hello from Switzerland,

I just got this beautiful troopy HZJ75 from 1999 with 200'000km on a 1HZ engine 4.2 D without a turbo.

My problem :

I have this kind of subtle hiccup power loss that becomes very distinct just around the happy cruising rpm zone. The only way to drive is by going above this zone to get rid (to have it less) of the hiccup effect. Forcing me to drive very sportive.

I first realized about it when I was going snail speed up a very steep hill in first gear and I had this distinct drop in power every seconds or so. The engine is not choking, its more like no torque for a millisecond.

What should be my steps to figure out the problem?

PS: I am not a mechanic more of a wood guy, but I want to learn.


Best
Gregory

 

[mohawk]

fuel filter is a good place too start....

 

[roscoFJ73]

Its either air getting into the fuel system or a fuel blockage of some kind.
Is it making any kind of smoke?
Does it start easy hot/cold?
Do you have dual fuel tanks? If it does, do you get the same problem using both tanks?

 

[roscoFJ73]

I had this air problem at idle from a bad fitting. But sometimes they get a bubble of air at higher speeds. When that happens its like you described, a loss of torque but still runs smooth.

 

[Gregol]

Thanks for all the replies.
I am not sure its air bubbles, because the power drop is rhythmic and regular and always at the same rpm for each gear.
It's very visible at night with the edge of light of headlamps on the road.

G

 

[Gregol]

Its either air getting into the fuel system or a fuel blockage of some kind.
Is it making any kind of smoke?
Does it start easy hot/cold?
Do you have dual fuel tanks? If it does, do you get the same problem using both tanks?

No smoke, it starts perfectly hot and cold.
I have dual tanks but they are not in parallel.

 

[AndrewHadji]

I had this air problem at idle from a bad fitting. But sometimes they get a bubble of air at higher speeds. When that happens its like you described, a loss of torque but still runs smooth.

So how did you fix that? What was the cause?

 

[roscoFJ73]

So how did you fix that? What was the cause?

I'm not 100% sure. At first I thought it was the filter head and primer but was most likely a leaky fitting or a split fuel hose.

 

[roscoFJ73]

No smoke, it starts perfectly hot and cold.
I have dual tanks but they are not in parallel.

I can only suggest checking all the fittings on the fuel lines as well as the filter seal. There is a gauze screen in the fuel tank pick up that can get blocked. There is also a mesh screen under the fuel supply line on the injector pump that can be checked.
If that is all ok you may need to remove the fuel injection pump and have it tested.

Is one of your fuel tanks aftermarket?

 

[AndrewHadji]

I can only suggest checking all the fittings on the fuel lines as well as the filter seal. There is a gauze screen in the fuel tank pick up that can get blocked.

Sorry to hijack the thread with my questions, but facing a similar but not as bad issue. Just to confirm that there no other way to access that screen, you gotta drop the tank for it no?

 

[Gregol]

I can only suggest checking all the fittings on the fuel lines as well as the filter seal. There is a gauze screen in the fuel tank pick up that can get blocked. There is also a mesh screen under the fuel supply line on the injector pump that can be checked.
If that is all ok you may need to remove the fuel injection pump and have it tested.

Is one of your fuel tanks aftermarket?

Thanks for those infos, I will pass them on.
I am driving back to the shop that sold me the truck Wednesday from my actual position to have it check. Will update the thread asap.

Yes the secondary fuel tank is aftermarket, but was installed by the previous owner here in Switzerland. I have to activate a pump to fill up the primary tank from the secondary. And I have to keep an eye on it because there is no automatic switch off. A little portable cooking timer does the trick

 

[roscoFJ73]

Yes the secondary fuel tank is aftermarket, but was installed by the previous owner here in Switzerland

The reason I asked is because some tanks fitted by owners cause all sorts of strange things. I don't think its your problem as it seems to be rpm related. But never say never.

 

[roscoFJ73]

Sorry to hijack the thread with my questions, but facing a similar but not as bad issue. Just to confirm that there no other way to access that screen, you gotta drop the tank for it no?

Yes, I think you do have to drop the tank. I have only done the rear tank, it wasn't hard. Borescopes are cheap now, you might be able to undo the tank plug and slide the scope inside to inspect the fuel pick up gauze.

 

[EsbenDenmark]

Did you ever figure out the problem.. mine 75 is doing something really similar. Going down the highway 80km/h then for a few seconds at a time it is not pulling quite as much. Feel like there is suddenly a strong headwind or something.
Not enough to change the speed, but enough the you can feel it.

 

[Gregol]

Did you ever figure out the problem.. mine 75 is doing something really similar. Going down the highway 80km/h then for a few seconds at a time it is not pulling quite as much. Feel like there is suddenly a strong headwind or something.
Not enough to change the speed, but enough the you can feel it.

Yes my problem was that one of the injectors was not working and covered in soot. Had the Catch Can Pro installed to prevent further issues.
All well since!

 

[roscoFJ73]

mine 75 is doing something really similar.

Any post should start by stating the engine type and klms. They came with 3 diesels and 2 petrol engines

 

[roscoFJ73]

Had the Catch Can Pro installed to prevent further issues.

I cant see how a catch can would make any difference. Injectors usually fail and then the soot builds up because the fuel is not being burned efficiently.

 

[Gregol]

I cant see how a catch can would make any difference. Injectors usually fail and then the soot builds up because the fuel is not being burned efficiently.

My great mechanic had the Catch Can installed at the same time he resolved the injector issue so I thought it was related. My mistake I guess.
I personally don't know much about engine's debugging, yet (working on it).