low end power disappeared?

Topic: low end power disappeared? (Read 21092 times) previous topic - next topic

low end power disappeared?

December 22, 2014, 05:04:46 PM

Well I finally finished my SO to HO conversion. Explorer intake, TW heads, HO cam, 19# injectors and a DA1 (in a pear tree). The engine runs and has much more power at high rpms but it's very soggy at low rpms. Even hesitates a little bit. I can't spin the tires from a stop.

Too much air or too little? I still have the SO fuel pump but I would think that fuel starvation wouldn't happen at low rpms. One interesting thing is that prior to my conversion, I ran with the IAC disconnected because it would throw itself into a high idle at random times even when warm. Without the IAC it worked perfectly (except when cold, I had to keep it going). Now it surges a little at idle and if I unplug the IAC, it dies immediately.

Any ideas? Thanks in advance.

low end power disappeared?

Reply #1 – December 22, 2014, 05:25:02 PM

Look for a vacuum leak. Swap in a 155 LPH pump. Do a KOEO, KOER, and CM check.

low end power disappeared?

Reply #2 – December 22, 2014, 05:55:09 PM

Did you do a base idle reset?

http://sbftech.com/index.php/topic,1031.0.html

Darren

low end power disappeared?

Reply #3 – December 22, 2014, 06:59:00 PM

Nope, but I will now :-) I'll let you know if that improves things. Thanks!

low end power disappeared?

Reply #4 – December 22, 2014, 10:01:13 PM

Sounds like a timing issue.

low end power disappeared?

Reply #5 – December 23, 2014, 12:59:57 PM

Haystack,
Can you elaborate more on the timing issue? My first guess would be you are referring to the cam and timing chain but wanted to make sure that is what you meant.

Darren

low end power disappeared?

Reply #6 – December 23, 2014, 01:06:08 PM

A couple free things to check:
1) run codes
2) see if the EEC is advancing the timing by using a timing light and revving up the engine
3) check your fuel pressure at idle with the vacuum hose connected and disconnected
4) look for vacuum leaks as previously mentioned

From there I would suspect your can timing as Haystack pointed out. Did you degree the cam?

Darren

low end power disappeared?

Reply #7 – December 23, 2014, 01:25:38 PM

Did you remove the distributor when doing the swap?

low end power disappeared?

Reply #8 – December 23, 2014, 02:34:33 PM

Quote from: Aerocoupe;441891

A couple free things to check:
1) run codes
2) see if the EEC is advancing the timing by using a timing light and revving up the engine
3) check your fuel pressure at idle with the vacuum hose connected and disconnected
4) look for vacuum leaks as previously mentioned

From there I would suspect your can timing as Haystack pointed out. Did you degree the cam?

Darren

FYI-
Spark Timing Check
KOER test locks the timing at the base plus 20° (±3°) during the test, plus for two minutes after the last code is outputted.

low end power disappeared?

Reply #9 – December 23, 2014, 04:10:41 PM

I did remove the distributor, replace the timing gear with a double and of course changed the cam to an HO cam. Is there a write up on how to do the KOER test? thank you for all of the suggestions.

low end power disappeared?

Reply #10 – December 23, 2014, 04:11:11 PM

Quote from: V8Demon;441868

Look for a vacuum leak. Swap in a 155 LPH pump. Do a KOEO, KOER, and CM check.

+1 and check base timing.

If you don't have a timing light get one or borrow one.

low end power disappeared?

Reply #11 – December 23, 2014, 06:32:22 PM

Quote from: marianadeeps;441898

I did remove the distributor, replace the timing gear with a double and of course changed the cam to an HO cam. Is there a write up on how to do the KOER test? thank you for all of the suggestions.

You DID reroute the ignition wires to the H.O. firing order, correct?

As far as checking for any codes: http://sbftech.com/index.php/topic,2471.0.html

low end power disappeared?

Reply #12 – December 24, 2014, 10:10:46 AM

Quote from: V8Demon;441904

You DID reroute the ignition wires to the H.O. firing order, correct?

Yes I did. I've now done the TPS/idle adjustment and it no longer surges, and the IAC is working properly. Now I'm thinking that I just don't have the low end torque I used to have. My power band is way up in the 3000 rpm and above. Should I advance the timing? Trade in my x-pipe for an h-pipe? Install a higher stall torque converter? I'm hoping to find a relatively inexpensive solution. Has any had this issue with their engine upgrade?

low end power disappeared?

Reply #13 – December 24, 2014, 11:17:45 AM

I'd say you need to whip out the timing light..

low end power disappeared?

Reply #14 – December 24, 2014, 01:01:14 PM

Did you degree the cam when you installed it? If not did you at least follow the timing chain manufacturer's instructions and install the cam straight up? We need to know this to help you with any further mechanical advise. Any further mechanical advise would also be pending you pulling any codes both KOEO and KOER.

Darren