5.7 efi low WOT continued

[Macrae99]

Hi,
I posted about the problems I was having last year but thought I'd start a new thread so nobody gets confused.
So the problem I had before was the ignition control module and it was showing code 42. I replaced that and finally managed to clear the code but didn't make much difference.

I am still not able to get over 3900 revs. It's a 98 5.7 efi with delco est, S/n 0L317164.
So far it's had new cap, rotor, ignition control module, plugs, leads.
Compressions are 160-180, fuel pressure is good, fuel and filters are good. Tried spraying more fuel in throttle when going but it just bogged so it's not a lack of fuel.
The thing I'm wondering is the timing, when it's set to 12* BTDC it runs better than at 8*. I've checked the timing whilst going and i don't understand it. When accelerating and throttle is 100% the timing goes to 26*. When pulling back the timing advances even more to approx 36-38*. These are all readings from the scan tool but I have confirmed it against a timing light.
I know it's only supposed to be 32* BTDC when base timing is set to 8* and timing should be full in by approx 3200 revs according to what I have read, but I can't actually find a timing curve for the 5.7 with delco est, unless it's the same curve as the thunderbolt?

Does anyone have any more ideas why I'm not getting full WOT, 4600 RPM?

Cheers
Callum

 

[hivoltg]

Re: 5.7 efi low WOT continued

Has the boat ever been able to get into that rpm range in the past? I just wonder if you have too high of prop pitch and motors getting overloaded, the ecu would retard timing to prevent knocking.

 

[Tail_Gunner]

Re: 5.7 efi low WOT continued

Post the engine yr and model number.....describe the method you use to time the engine. The ecu or main body computer advances the timing according to preset curves at various rpm levels. It sound's like you have a short going on somewhere that is the ecu is misreading the rpm levels

 

[Macrae99]

Re: 5.7 efi low WOT continued

I do remember it once getting 4200 just after it had the bottom cleaned. But it hasn't been above this for a while now, the boat has just been out the water last month getting cleaned and a service so it's not cause of any growth.
We have tried a 19" 3 blade and a 17" 4 blade stainless prop but no major change in rpm between them.
Ye it's as if something is making the timing do weird things, I checked all the sensors last year when trying to diagnose the bad IC module but maybe need to check everything again. We have even had a local boat mechanic down having a look but he plugged his computer in and said everything was fine even though it doesn't get full rpm.

 

[Macrae99]

Re: 5.7 efi low WOT continued

Hey gunner, it's a 98 S/n 0L317164.
Plugged in the mercruiser scan tool, set rpm to 1600, entered base timing mode and set timing using timing gun and marks on the crank. Can't do it using scan tool only as it doesn't read ignition advance correctly in base mode, which I think is correct?

 

[Tail_Gunner]

Re: 5.7 efi low WOT continued

So you did not use a shunt.

And the EFI timing tool...The shunt connects to the dist and the timing tool connects to the ecm or data link

I am assuming this is mefi 2 or 3. there should be numbers on your ecu

 

[Macrae99]

Re: 5.7 efi low WOT continued

I haven't used a shunt cable, I have a scan tool so I use that instead of the timing tool to put it in to base mode. It's got a mefi 1

 

[Tail_Gunner]

Re: 5.7 efi low WOT continued

Did you advance the rpm manually to 1800 prior to setting the base timing

 

[Macrae99]

Re: 5.7 efi low WOT continued

Ye I set it to approx 1800 rpm, enter base mode and the rpm drops to around 1000-1200rpm.

 

[Fun Times]

Re: 5.7 efi low WOT continued

The thing I'm wondering is the timing, when it's set to 12* BTDC it runs better than at 8*. I've checked the timing whilst going and i don't understand it. When accelerating and throttle is 100% the timing goes to 26*. When pulling back the timing advances even more to approx 36-38*. These are all readings from the scan tool but I have confirmed it against a timing light.
I know it's only supposed to be 32* BTDC when base timing is set to 8* and timing should be full in by approx 3200 revs according to what I have read, but I can't actually find a timing curve for the 5.7 with delco est, unless it's the same curve as the thunderbolt?

Hi there, Do you by chance have a copy of the OEM Mercruiser service manual number 24? If so, take a look at "Distributor Module Mode" on page 5D-21, it talks about the total advance being 27 degrees. Also I believe you would be interested in reading pages 5D-20 through 5D-26.

http://www.maxumownersclub.com/forum/site_files/manuals/mercruiser/24.pdf

 

[fishngolf]

Did you ever resolve your issue? Experiencing the same on a 94 mercruiser 350 mefi 1.