won't rev past 4000 rpms

jamesbondsc300 · 07-08-2010, 08:04 PM

I have a 1993 SC300 na-t. I'm new to the turbo game...I bought the car with a blown headgasket. I replaced the HG with a 3mm commetic. Now it won't rev past 4000 rpms...sometimes a little more but it stumbles badly. I assumed I had a boost leak so I removed all the IC piping to check for loose clamps or holes(i found none). The car has a to4e turbo and an external wastegate tuned with an AFC NEO(which i also know hardly anything about) my question is....whats left to check? Could it be the wastegate? The past owner said the boost "spiked" and blew the HG...I ordered a boost controller already to remedy this, but I really need some help on this! Thanks in advance

qbnorly · 07-27-2010, 11:30 PM

Quote:

Originally Posted by jamesbondsc300

I have a 1993 SC300 na-t. I'm new to the turbo game...I bought the car with a blown headgasket. I replaced the HG with a 3mm commetic. Now it won't rev past 4000 rpms...sometimes a little more but it stumbles badly. I assumed I had a boost leak so I removed all the IC piping to check for loose clamps or holes(i found none). The car has a to4e turbo and an external wastegate tuned with an AFC NEO(which i also know hardly anything about) my question is....whats left to check? Could it be the wastegate? The past owner said the boost "spiked" and blew the HG...I ordered a boost controller already to remedy this, but I really need some help on this! Thanks in advance

I see no one has any input on this so let me start by asking if you have resolved this?

jamesbondsc300 · 07-29-2010, 06:32 PM

well, I have it kinda figured out.....did a "smoke leak teast'' and found #6 intake runner leaking where it bolts to the head. I'll be installing new lower intake gaskets in about 30 mins so we'll see. The reason I say "kinda" is because I've thought it was fixed after the last 4 IC hoses I
replaced and countless vaccum hoses. Something else keeps popping up

When this is resolved I'll still need to retune with the innovate lm-1 (changed HG from 1.3 to a 3mm) I ordered eariler this week(looking forward to that haha...I'm just gonna have to learn as i go since nobody around mississippi knows anything or is willing to help) Funny thing is that next week I'm moving to florida(where there are tons of shops that do this sort of stuff) Thanks for asking I'll post the results

qbnorly · 07-29-2010, 11:14 PM

Quote:

Originally Posted by jamesbondsc300

well, I have it kinda figured out.....did a "smoke leak teast'' and found #6 intake runner leaking where it bolts to the head. I'll be installing new lower intake gaskets in about 30 mins so we'll see. The reason I say "kinda" is because I've thought it was fixed after the last 4 IC hoses I
replaced and countless vaccum hoses. Something else keeps popping up

When this is resolved I'll still need to retune with the innovate lm-1 (changed HG from 1.3 to a 3mm) I ordered eariler this week(looking forward to that haha...I'm just gonna have to learn as i go since nobody around mississippi knows anything or is willing to help) Funny thing is that next week I'm moving to florida(where there are tons of shops that do this sort of stuff) Thanks for asking I'll post the results

Ok well its good that you found that but from the way its acting I'd say that you have something more electrical going on. When I say that I mean something like a crank sensor or to that effect.
If you think about it a leaking #6 can lose compression but that can only make a miss but not a cut off at 4k. Let me know if you have some questions I don't mind helping out if I can.
Orlando

jamesbondsc300 · 07-30-2010, 12:33 PM

UPDATE: got the new intake gaskets on last night but overtightened the oil feed on the turbo (broke off in my hand! STUPID!) trying to source one local today so i can start and test out. I was thinking crank angle sensor a few weeks ago too, but i got no CEL lights or codes when I checked. I dismissed that conclusion because its no longer stopping @ 4000....after i fixed 3 or 4 boost leaks in the IC piping it started to miss between 3500rpm and up(don't know how high it would rev, i'd get out of it by 4500rpm just in case so not to damage the engine if my A/F is off) I suspect a boost leak because it smells way rich(bit of black smoke too) so I'm still thinking metered air isn't making its way into the combustion chamber. Guess I'll find out when I get a new oil feed and line....

Thanks for the support

qbnorly · 07-30-2010, 10:21 PM

Quote:

Originally Posted by jamesbondsc300

UPDATE: got the new intake gaskets on last night but overtightened the oil feed on the turbo (broke off in my hand! STUPID!) trying to source one local today so i can start and test out. I was thinking crank angle sensor a few weeks ago too, but i got no CEL lights or codes when I checked. I dismissed that conclusion because its no longer stopping @ 4000....after i fixed 3 or 4 boost leaks in the IC piping it started to miss between 3500rpm and up(don't know how high it would rev, i'd get out of it by 4500rpm just in case so not to damage the engine if my A/F is off) I suspect a boost leak because it smells way rich(bit of black smoke too) so I'm still thinking metered air isn't making its way into the combustion chamber. Guess I'll find out when I get a new oil feed and line....

Thanks for the support

Oh ok well if you are getting the car to go past 4k then that tells me that it is not electrical. Sorry I was thinking that it was more like a rev limit at 4k. Well the Black smoke is an indication of running rich but yeah you should have a wideband so that you know whats going on in the motor at all times. Get an easy out and take that broken piece out and let me know whats up from there.

**airpowr** · 07-31-2010, 12:07 PM

Sounds like a big time leak, electrical should throw a CEL. Might have been more wrong with the motor other than a head gasket. Not sure if you did but do a compression test and another leak test, if everything is good then it might be the AFC Neo.

qbnorly · 07-31-2010, 01:24 PM

Quote:

Originally Posted by airpowr

Sounds like a big time leak, electrical should throw a CEL. Might have been more wrong with the motor other than a head gasket. Not sure if you did but do a compression test and another leak test, if everything is good then it might be the AFC Neo.

That was my next thing something going on with the AFC.

jamesbondsc300 · 07-31-2010, 04:02 PM

nothing is wrong with the engine (i tore the top end off myself and was thinking maybe a bent valve myself) head has been rebuild, no impact marks on any of the valves. Also passed the compression test i did with flying colors(nearly equal across all cylinders). The lower intake gasket replacement has prolly fixed it, but i won't know until my oil feed kit gets here monday morning. It also has a small leak coming from the butterfly shaft in the throttle body (i can make it stop by moving the shaft side to side) i'm looking for a replacement now. Haven't checked the wiring on the NEO yet, but it is working from the little I've played with it.(ie. I can make it way richer and leaner with the adjustments on the LO map) It's just acting as if I have a hugh metered air leak (can't tune around that haha)

jamesbondsc300 · 08-03-2010, 06:48 PM

Got the oil feed kit in today....its still doing the same thing. I hooked up the LM-1 wideband. When i rev the engine it starts to "miss" around 3k and up. AFR is about 9.9 when it starts acting up confirming that I must still have a metered air leak. I believe its the throttle body shaft(can't find one within a 4 hour drive). I'm also having another problem...when i try to pin the te1 and e1 terminals out to set the timing it won't let me set it below 5 degrees...i'm confused. I thought maybe I had the cams set a mark off but all the marks line up @TDC...WTF? I'm seriously running out of time and sanity here!