34 replies to this topic

[MR77LX]

Hey Guys, 

I have an injected 304 and i have a check engine light fitted. 

Is it possible to connect an OBD port so i can actually plug a scanner in? 

[Bigfella237]

What ECU are you using?

 

And what wiring loom?

[Rockoz]

A 304 wont likely work with OBD11

You will probably need to go for ALDL instead.
Search the net for PCMHammer.

There was a thread here on it a while back, but would be easier searching for the PCMHammer site directly.

Lots of info there for OBD11 and ALDL

 

Cheers

 

Rob

[MR77LX]

Wiring loom  is from a VR commodore V8. 

Haltech GM ECU  

[Rockoz]

From memory, an OBD scanner isnt going to be any help to you.

You will need the proprietary Haltech software and probably an interface lead from them as well.

I think Heath might be the one to check with for more details.

Pretty sure he fitted Haltech to his car.

But I would search their site for what you need.

Should be easy to find out what you need.

 

But you are going to have to find someone who is familiar with Haltech programming.

You could do it yourself, but it is a steep learning curve, and if you get it wrong you can easily destroy an engine.

 

Cheers

 

Rob

[MR77LX]

Thanks mate, i will see how i go. 

The only reason i asked is because my engine has a bit of of a hesitation. 

I strongly feel that its from the tune, but the tuner rekns its from the leads or plugs, 

So I changed all the leads, plugs, dizzy and spark module and the hesitation is still there. 

I cant get my head around it. Its been too so many tuners and they can find it. 

The last tuner suggested to get rid of my AC delco and go with haltech, i did that. Its runs alright and has got some good hp on the dyno. 

However it still has a hesitation/surging on low rpm when driving. But not on idle when revving. 

[Dr Terry]

If it's having this hesitation issue with both computers & you've changed virtually every thing in the ignition system, there isn't much left.

 

Assuming your ignition & cam timing is all good then, fuel pressure  or injectors might be a problem. Is the camshaft stock ? Is it worse when the engine is cold ?

 

Dr Terry

[MR77LX]

The tune guy looked at the fuel pressure when he Dyno it and said its not your fuel. Other wise it would of showed in the dyno. 

Injectors are brand new. (LS2 injectors) 

The motor is a 304 stroked to a 383 come racing engine with aluminium heads and twin throttle body. 

The camshaft is come racing. Just off the shelf part number 755. Its called a street cam. Its not very big. 

It does get a bit better i guess after like 1 hour of driving. 

I just dont understand why when i rev it, its perfect but when i drive it, it starts to hesitate. 

[RallyRed]

May be totally irrelevant,but 2016/17 GM LS injectors are known to be ocassionally dodgey. Just in case that's what you have...although those ones lso normally idle rough too.

Edited by RallyRed, 16 April 2022 - 09:10 PM.

[MR77LX]

Before them I had the blue top injectors fitted.
The tune guy suggested bigger injectors.

[MR77LX]

I wonder if it can be the fuel dampener. Is it possible to have it on back to front?
These are the symptoms of a faulty dampener according to google.
When this happens, the damper's diaphragm re- stricts fuel flow, causing a severe lean condition during acceleration. When the driver punches the gas pedal, the engine falls on its face with a severe hesitation (sometimes almost stalling), bucking, chugging or surging.

[EunUCh]

It could be the damper , could be wrong but i thought the damper had a vacuum diaphragm that was connected to full manifold vacuum

so that at idle conditions pressure was regulated  but when you give it some lack of manifold vac. upped the anti on the pressure to compensate for more air going to engine , (as well as longer injector pulse).

Usually when a "larger" cam is installed generally MAP drops off and can cause the MAP sensor to send wrong info. to the brains of the operation , if it  gets better to a point when up to operating temp it sounds like it might be a tad on lean side in that just off idle area which should be able to be tweaked with numbers in computer in that area of the fuel map.

The reason it will "free rev" ok  in that area is because the engine has no load .(does it smell over fueled or a cleanish burnt smell from exhaust when free revved ?)

Usually when engines are put on dyno the dyno does not allow for driving the car on the road but there could be a way to find fault while on dyno with o2 sensor in the stumble area ?

As already mentioned , be careful with fuel numbers , o2 sensor should show which way it needs to go.

[Rockoz]

Can you get a data recorder hooked up to the ecu?

If you can, you can get useful data from normal driving conditions.

A lot of 'dyno tunes' are done solely on wot conditions.

 

 

Cheers

 

Rob

[MR77LX]

The feed line is connected to the dampener and on the other end, it connects up to the fuel rail. 

The exhaust does smell over fueled but I thought that was normal. 

The fuel map on the ECU apparently is fine, well thats what the tuner said when he had it on the dyno. 

I have also replaced the map sensor as well. 

Im pretty sure we can get data from the ECU if I take it back. But I don't wana go back to the tuner. He is too busy and I feel he has no time for me. 

[rexy]

Have you pulled a spark plug?

A simple AFR meter should be enough to sort out if its a fuel issue or not.

[MR77LX]

On my old Ecu spark plugs were fowled up hard. 

The new tune with the new haltech, plugs are fine. 

I dont have an AFR meter. 

The tuner was adornment that it wasnt fuel.  

I might disconnect my fuel dampener and take it for a drive. 

[Rockoz]

AFR meter would be a good idea to see what is happening.

They arent that expensive from what I have seen.

One for each bank if you can.

Going bigger injectors without changing the tune just wont work.

 

Have a read through PCMHammer and you will likely find your problem already dealt with by someone else. With a solution.

 

Cheers

 

Rob

[MR77LX]

No i went bigger injectors with new ECU and tune. 

I will look into buying an AFR Meter. 

Do you have a link to PCMHammer?

[Dr Terry]

What you guys are calling the fuel 'damper' is actually the fuel pressure regulator, it's function can be seen clearly by monitoring a fuel pressure while the fault is happening.

 

Given the mods to your engine, a 'flat spot' is purely a function of incorrect ignition &/or fuel mapping. This is assuming your fuel pressure & spark strength is good at the time of the symptoms.

 

I would be getting a 2nd opinion from another dyno shop.

 

Dr Terry

[MR77LX]

Hey Dr Terry
So the fuel damper is it a regulator? So I have 2 regs? Because I have another regulator on the rail.
Also I have just disconnected my dampener or regulator and deleted it and the car won’t start.
I’m a bit confused because they said the dampener is only good for stock engines.
So now I have removed it and it won’t start.

[76lxhatch]

The damper and regulator are two different things, not all vehicles use a damper (its there to even out the pulses from the pump).

 

I'd say you're right about the tuner not having any time for you as obviously the tune is no good. As others have said, either get set up with the software and a wideband oxygen sensor so you can make changes yourself, or find someone else who will do a proper tune (and point out any mechanical issues such as vacuum leaks which need to be fixed first).

[MR77LX]

I’m just trying to understand why my car won’t start now after I removed it?
It should start without it. Where is it suppose to fit?
I had it fitted on my feed line going into the the fuel rail. Is that right?

I think I will take your advice and try and find another tuner.

[EunUCh]

I would  get back to where it will start and as suggested download the software and have go yourself , it will be a bit of a learning curve if you have not done it before but is interesting and fun once you get your head around it , have not played with Haltech but had a bit of  a look at some on line tutorials and it looks fairly similar to Motech , just don't forget to save the map you have now just in case you need to go back to it , and you can datalog with the system.

As mentioned the damper and reg. are 2 different animals , damper just dampens injector pulses and regulator controls pressure/flow and

reg. is vacuum dependent and it usually lives on the fuel rail return line to tank.

The other thing is that just like a carbed. engine , when a different cam is installed it usually affects (drops)the manifold vacuum at and just off idle until the cam starts working which would possibly upset the regulator a  bit but being efi ...if it is a fuel problem it should be fixable by tweaking some numbers in the relevant areas.

If the ign. timing is ecu controlled you change that if need be and is probly not a bad idea to get the timing set up to some reasonable point before having a go at fuel curves.

 

[Rockoz]

search for pcmhacking.net

 

Cheers

 

Rob

[76lxhatch]

I’m just trying to understand why my car won’t start now after I removed it?
It should start without it. Where is it suppose to fit?
I had it fitted on my feed line going into the the fuel rail. Is that right?

If we're talking about the damper, yes it should operate without it. It can be located anywhere on the high pressure side of the regulator, position of the factory ones varied (some were at the back right after to the pump). Make sure everything is clean and you haven't accidentally introduced anything that might block injectors.

 

If you removed the regulator then no, you won't have enough fuel pressure for it to run.