LS1 Throttle Response issue
 

Hi Everyone,

Please excuse my way of explaining this I am a novice.

Also - apologies in advance to Ford boys.

I am going for engineering Mon 8th Dec and have done a little bit of "testing" and find I have a fairly decent flat spot with regards to throttle response.

Essentially when you increase the throttle gradually its not that bad, but increasing medium to fast causes it to cough and splutter a bit. Cruising is ok.
i.e. Down on power a fair bit when you accelerate (i.e. coughs a fair bit).

Note: My engine is a Ls1 5.7L with Cable Accelerator (EURO II Emission) and stock tune from sideshow

I have double checked all electrical connections etc - not that its still not one of them.

I double checked Fuel pressure during idle and acceleration and its a constant 60psi. (I thought it might be a fuel delivery/volume issue rather than pressure).

I was (and am still) a bit suspect of my spark plug leads as they have been on and off a few times during the build and one of them physically looks a bit suspect.


I decided to remove one injector plug at a time, and I found one of the spark plug leads was not on the plug properly. This improved things a little but the flat spot is still there.

(One thing I did notice was that unplugging some leads had more effect than others - although only slightly)

I double checked the other plug leads and they “seemed” to be on ok.

I am still suspect on the plug leads and am going to get a new set tomorrow – not a bad thing to do when you are building a new car anyway I’d say.


I double checked that the MAP sensor plug is plugged in properly, I haven’t checked its operation with a Voltmeter yet though. That might be my next step if the plug leads dont fix it. i.e. 5V at engine off - 1 to 1.5 during idle and about 4.x when accelerate (I'm told).

I have also double chekced that I have blocked off both the Brake Booster vacuum inlet and dash instrument vacuum inlets - any others I have forgotten - I cant see any.


Any suggestions? (other than getting a tuner to hook up and see what/if any codes are coming up)?

Thanks

rgds

Gregg

If you are going through engineering soon perhaps you have "bunged up" the exhaust too much. I had to De-tune mine to not cough and splutter under acceleration, due to the amount of "bunging up" I did....

Alternately, how old is the fuel in it??? What are the plugs Like??? I know Gav's machine was idling rough then wouldn't even start due to ****ty plugs....

Thanks Plums.

My exhaust is a 4 into 1 collector and then Cat, Muffler and then hot dog resonator at the back (I have a dual underbody system). I dont have any restrictor plate on it yet so "I think" it might be ok. But you never know.

Fuel is new.

Plugs are what came with the engine which is a second hand 50,000klms VY Series 2 Commodore engine - so history is relatively unknown.

I will do the leads today and then if that fails then the plugs. New plugs is probably a good idea anyway regardless of how its running.

Thanks for the tips I'll kepp "plugging" away.

Rgds

Gregg

P.S. Any Melbourne Cobra owners know a good "mobile" LS1 tuner I could pay to come and have look if I get stuck?.

I would change the plugs, as Bobby said, my engine misfired then died all together.
I can only assume that the plugs where old (40,000k's), had sat for ages and then was started and stopped and not really run for any lenght of time.
If you are ready to go through reg and are beggining to drive, you are mad to not change them and rid yourself of a potential problem.

Gav

Yeah I think I will change the plugs.

New leads didnt improve things.

I also checked the MAP sensor and that seems to be working.

Rgds

Gregg

If plugs dont help, I know a few guys have had injector issues after the engine has been sitting a while?

I think I was lucky, I had no issue that was not induced by me.

Injectors are my next option after plugs.

I have induced a few errors myself as well.

Boxhead, do you have any instructions on Inspecting/cleaning the injectors?

Rgds

Gregg

Now this is a great op for us ford guys
ANY TAKERS ?

I'll come back later to add on

Greg, I work For Holden, I have a few questions and hopefully will be able to help you.

What ECM are you using, factory or aftermarket?

If it's factory are you using the AFM or has it got a mafless tune?

While searching for a misfire/flatspot etc, you should not disconnect the sparkplugs with the engine running.
What happens is the other three on that bank will go richer to compensate for the high oxygen content emitted from the cylinder you cause the misfire on. Although unburnt fuel comes out the exhaust port, it's the oxygen we haven't used that causes the others to go rich.

Have you put TECH 2 on yet to see what codes (if any) are stored.

Lean bank DTCs P0170, P0171 are common and PCV ventilation hose or loose intake gaskets are common.

If you can drive through the flat spot and it makes good power, then you can count the fuel system and the igntion system out. I'd say you might have a fuel trim issue, look at data display STFT and LTFT.

Thanks Gary for the suggestions.

I am running a stock ECU and tune with MAF.

No I havent put a TECH 2 on to see what the ECU thinks. I dont have access to one or know someone who has one at present.

I will double check the PCV hose and intake gaskets.

I wouldnt say it is making good power at the moment (say medium power at present), you can increase revs at a medium pace but when you give it a bit it struggles.

I am still suspect on the ignition system. Am changing the plugs tomorrow to rule them out.

Was thinking if that doesnt resolve it to double check the coils are ok somehow.

Then trying to find someone with TECH 2 to see what codes are being stored etc.

Last resort was a compression check?

Rgds

Gregg

Greg, I've got the gear to give your injectors an ultrasonic clean. I've got a heavy duty ultrasonic bath that I've done a few sets in now. Seems to work real well. I'm back in Aus so bring them over if you like.

Cheers

Mike, thanks for the offer.

I am hoping that replacing the spark plugs will do the job - but down the track cleaning the injectors would be a good idea yo ensure all is performing as it should.

I am planning on going to the Melb Club meeting tonight - hope to catch up with you there if you're going.

Rgds

Gregg

See Peter, all you Ford guys are speachless, you have never heard of one of these having trouble, so you dont know what to say.

Go the mighty beer can :)

i think ill pass, ive already stirred up a hornets nest. tomcat.

Nah, it is all in fun Tom, just take it all with a grain of salt these boat anchor V's beer can debates.

hey greg i sent u email so reply to it or on here

did we do mafless tune or just use yr std tune and turn off security

if u want maybe send ecu back and ill recheck tune

i looked over the tune but i need to know jwhat we did to compare it

thnaks

jim

ohhh come on Boxey 95% of the crap in these forums is all about these ls's with problems
Get with it son
There's nothing in here about any Ford issues
Don't know about beeing speechless, I think nobody knows were to Start :LOL::LOL::LOL:

By the way GAz64 is on the money
Leads, coils, plugs cause miss fires if they are faulty especially under load, lack of power is in the tune and fuel trim, timing etc

WINDSOR WONT BLOODY FIT THREAD - That would be the thread just below this one :LOL::LOL::LOL:

I love the LS ford debate. My favourite is when you fellas go on about it being correct for the car - when half of you are happy to have a body that looks like it was moulded out of plasticine by a blind kid who once heard a cobra, or a hood scoop that could fit about 7 LS1's under it, or a single full width roll bar barely 6 inces off the rear deck, or a set of chrome sidepipes what look like they came off a Kenworth....so purist, and then you go and get all fussy about the badge on the engine. Cracks me up every time. :)

I'm with you Tenrocca, and you forgot the intake manifold wot looks like it was stolen from a church organ. :rolleyes: :LOL:

Thats what I like about this forum - very helpful advice plus some healthy Chev/Ford debates without people taking offence.

Thanks for the suggestions so far.

I am gradually working through the problem by proecess of elimination.
(Fuel pressure ok, plugs changed, plug leads changed, coils seem ok).

I think its driveable enough (for my Engineering on Monday 8th).

I just hope the emissions are still ok with (what I think) is the tune being off.

I might be getting a loan ECU to try beforehand which might solve my problem as my original ECU might have had a dodgey Tune in it. We only just removed the VATS and adjusted the HS FAN temps.

Will let you know how I go.

Any further suggestions (other than a swap to a ford engine :) ) are welcome.

Rgds

Gregg