M90 rebuild (rudy)

[2000StreetRod]

For many of the DTCs a CEL is not set until the fault occurs multiple times. That's to prevent excessive trips to the dealer for an occasional fault.

There's a table in the tune that the PCM uses when it determines that the MAF sensor has failed. The PCM needs the airflow measurement to accurately calculate engine load. As I recall the PCM uses the TPS value and the engine RPM to estimate airflow when the MAF sensor has failed.

I forgot that someone did your tune in person instead of remotely. I guess that you only have an AFR meter and a DTC reader which limits your instrumentation for troubleshooting. Did you upgrade your PCM to OBD II/EEC V? If so, I think there are some inexpensive OBD II monitors available with limited but useful datalogging capabilities.

Have you reduced the fuel pressure since your tune was done because of the high flow pump? If so, that will lean the AFR which has a significant effect when the engine is idling after the cold start phase is complete.

 

[jd4242]

For many of the DTCs a CEL is not set until the fault occurs multiple times. That's to prevent excessive trips to the dealer for an occasional fault.

There's a table in the tune that the PCM uses when it determines that the MAF sensor has failed. The PCM needs the airflow measurement to accurately calculate engine load. As I recall the PCM uses the TPS value and the engine RPM to estimate airflow when the MAF sensor has failed.

I forgot that someone did your tune in person instead of remotely. I guess that you only have an AFR meter and a DTC reader which limits your instrumentation for troubleshooting. Did you upgrade your PCM to OBD II/EEC V? If so, I think there are some inexpensive OBD II monitors available with limited but useful datalogging capabilities.

Have you reduced the fuel pressure since your tune was done because of the high flow pump? If so, that will lean the AFR which has a significant effect when the engine is idling after the cold start phase is complete.

Yea im still ond1..

The fuel pressure was greater with the new pump but i adjusted it back down to where it was before..everything ran fine for 5 days then started acting up,no changes were made in those 5 days

 

[2000StreetRod]

Check Fuse 18 (15 amps) in the fuse panel. Maybe it is blown and there is no power to your O2 sensors. According to my Haynes wiring diagram you only have 2 sensors - one pre-cat for both banks and one post-cat for both banks.

You can try disconnecting the IAC valve electrical connector to see if that makes a difference. Maybe the IAC valve is faulty. On my Sport the PCM sets a corresponding DTC for the disconnection.

Does your AFR meter only monitor one bank? If so, is there a bung for it on the other bank that you could switch to? If not, you might try listening to the injectors on the unmonitored bank to determine if they are all pulsing.

Another possibility is the PCM "thinks" the engine is warm when it still is cold after engine start. Check the electrical connection to the engine coolant temperature (ECT) sensor. According to my Haynes 1992/93 wiring diagrams the LT GRN/RED wire connects the ECT sensor to the PCM and the GRY/RED wire is the common return for most of the sensors.

 

[jd4242]

Check Fuse 18 (15 amps) in the fuse panel. Maybe it is blown and there is no power to your O2 sensors. According to my Haynes wiring diagram you only have 2 sensors - one pre-cat for both banks and one post-cat for both banks.

You can try disconnecting the IAC valve electrical connector to see if that makes a difference. Maybe the IAC valve is faulty. On my Sport the PCM sets a corresponding DTC for the disconnection.

Does your AFR meter only monitor one bank? If so, is there a bung for it on the other bank that you could switch to? If not, you might try listening to the injectors on the unmonitored bank to determine if they are all pulsing.

Another possibility is the PCM "thinks" the engine is warm when it still is cold after engine start. Check the electrical connection to the engine coolant temperature (ECT) sensor. According to my Haynes 1992/93 wiring diagrams the LT GRN/RED wire connects the ECT sensor to the PCM and the GRY/RED wire is the common return for most of the sensors.

I actually have checked that fuse,i have not checked for voltage at the o2s though. .

it does only have 2 o2 and both where pre cat originally. And yea my wideband does only monitor one bank,the driverside..i can only get to the passengers side injectors,the supercharger blocks the driveside..also blocks my IAT sensor

Unplugging the iac kills the motor..

Coolant temp is only thing i havent replaced or checked..ill check tonight. .

Thanks for the help also,its got to be something im just over looking

 

[jd4242]

Wellllllll i found the issue. ...also something else is smacking when cold start up..i thought it was the supercharger coupler but the supercharger feels tight and not making noise with belt off..it sounds like piston smack or timing chain smack...

But the issue i have is where the lower manifold was ported and came through the runner walls...i used ""high temp liquid metal"" basically jb weld made for broilers,to patch the runner..this was originally done by my machinist and went back over it polishing the runners...

Well the patch has cracked and air is blowing straight out it...i went to spin the supercharger to test the coupler and felt air....so supercharger has to come off and question is do i repatch it and let her rip again or throw a stock lower manifold on it...it has lasted like 5 years...

Also next concern is did pieces fall down into the cylinder damaging my piston or wall and thays what the smacking sound is on cold start up.....

Unfortunately this sounds like a tear down...at least the charger,ic,lower manifold and probably passenger head needs to come off..might try to scope through the plug hole to view the piston and wall...

Mannn i cant catch a break!!!!

 

[CDW6212R]

Ouch, I hate that but you know more now. Try the scope and see what is visible before pulling the head etc, apart. Hopefully it's just that intake to fix. Take a break, relax knowing you've tracked it down, and go at it again tomorrow.

 

[jd4242]

Ouch, I hate that but you know more now. Try the scope and see what is visible before pulling the head etc, apart. Hopefully it's just that intake to fix. Take a break, relax knowing you've tracked it down, and go at it again tomorrow.

Yep..ill definitely know when i pull the manifold off if any went down into it...

I honestly dont thonk any did because there was very very minimal inside the runner,and what was is paper thin..i think just the last couple pulls i made where i went FULL boost after new pump,blew the patch off ..

The slap is got to be piston smack..i did some research and JE,especially the asymmetrical forged pistons are known for it..it stop after about 10 seconds or so..this motor was made loose for boost and juice also so till things warm up,im told its not uncommon to get piston smack..

I just dont know if im going to try to patch this intake or get my spare and try to port the crap outa it WITHOUT coming through the side..my machinist took ALOT out and i went back over it polishing it and cleaning it up some more...

Im also going to go ahead and replace my feed line with a -8an wile its off..i might weld the silencer holes up in the sc also...i want this thing to scare people a mile away!!! Its LOUD now!!

 

[CDW6212R]

Forged pistons typically will make a little noise when cold. It's common, just keep great oil in it, and don't run it hard until the oil warms up each time.

Porting isn't as important, or effective, in boosted conditions. All porting or better airflow does help of course, but don't go too far knowing the boost forces flow through a lot of restriction. I'd want the intake ported a little, but I would avoid going full tilt there.

The stock 302 intakes(GT40) are very common on blown engines, and there isn't a big trend to convert to a bigger intake(and there are bunches of them). When I have to fabricate blower plenums, I'll start with the best intake I could get(TFS R), but only because I have the choice. I'm glad I do have the choice, but it won't gain a ton of power(maybe 30hp) in my combo.

 

[2000StreetRod]

I'm glad you found the problem but sorry it was bad news.

 

[Dono]

JD,
I'm going to say get another intake and straighten out the runners as best you can while leaving lots of meat. Too bad there are zero aftermarket intake options for your motor.

The pic looks like it blew out, and not in, so I'm really hoping it was under boost when it blew and all pieces went out, and not in.

Why do we do this to ourselves?

 

[4pointslow]

Boost Leak!!!! Crap, glad you found the problem.
I second the information on forged pistons, they seem to be made with more clearance between the cylinder wall on purpose for expansion.
That fact that that intake hole repair lasted 5 years is amazing.
I have found no repair myself that works when using glue's, epoxy's, or liquid metals on engine parts.
There is too much expansion and contraction from heat cycling.
Heck, I cant believe that the automotive goop is still holding on the bottom of my washer fluid bottle for the water methanol fitting.

Put that stock intake on, do light porting if you have to wait for parts or something.

 

[jd4242]

So been doing some research on fuel line sizes and it appears fuel pump size is more important than line..

This was response from DW
"""Jeremy, thank you for contacting Deatschwerks Technical Support. We have found 3/8 fuel line is more than sufficient to easily support 1000whp on gasoline as our own shop vehicle is making 800whp on ethanol on factory 5/16 lines and see no fuel flow loss thru that system. EFI cars aren’t as sensitive to fuel line size as carbureted cars were... You may only see a few psi drop in fuel flow going from a -8 down to a -6 vs a carb car you may see 20 - 30 % drop.

Andy Stewart
Technical Products Specialist,
DeatschWerks Fuel Systems
(405) 217-0129 |
astewart@deatschwerks.com
""

And a link to further support it...so im not going to change my lines out right now,i did price everything just to change my feed out and came to $251 pefore shipping, i just dont have that right now...

Fuel Line Sizing — What Size Do I Need?

AN Fuel Line Sizes | Fuelab

 

[4pointslow]

That's good info right there!

 

[jd4242]

Well thats no good...thats as big as the hole is..if i was real good at tig,id try to weld it..may take it to my guy and see how he feels about it.

 

[CDW6212R]

That does look possible to fix, if the surrounding area is thick enough to weld to. I hope your guy thinks that way too.

 

[Dono]

Be awesome if that area could be built up. I'm guessing that cast manifold will be extremely difficult to weld with the impurities in it. Everything seems to be one big experiment and we keep learning.

 

[vroomzoomboom]

im going to be the guy that says scrap it, start new. it might be too thin in surrounding areas to weld. that and that was also on a lower hp motor, that probably made less boost, and heat. is it worth your new motor, if it happens again, you dont catch it, and throw alumn. down in the one of pistons?

 

[jd4242]

Yeaaaa dont think he's fixn this...The whole runner is paper thin...

 

[jd4242]

im going to be the guy that says scrap it, start new. it might be too thin in surrounding areas to weld. that and that was also on a lower hp motor, that probably made less boost, and heat. is it worth your new motor, if it happens again, you dont catch it, and throw alumn. down in the one of pistons?

Of all the people to be the voice of reasoning. .....only reason i call you a friend is because you do just as stupid stuff as me.. figured you tell me to duct tape it and send it!!! Haha

 

[CDW6212R]

Yes, it's time to replace that. I couldn't tell it was the injector next to the outside clearly before. To fix that would have to place metal outward into the injector. That's a good test piece, but move to the next intake.