Need help after rebuild

[Owlpond1]

Just got my '85 back after a rebuild (Phil Bassage, did a great job) but the engine is not running properly. Trying to sort it out on my own without going back to him. Engine barely idles/stumbles at idle and at about 4500 rpm completely cuts out (seems running rich) and has no power. Has great power from a rolling stop and at top end but really stumbles and blows black smoke in the mid-range. I have no scan tool. Here's what I've done (and assume everything that went back on the motor was good).

Installed new TPS (Holley) and have it set to .43 volts at idle and 4.9v at WOT.

Have tried with MAF disconnected and connected but no difference.

Has an '87 coil pack but otherwise all stock.

Next move is to upgrade ECM so I can connect a scan tool and get to the bottom of it.

Thoughts?

 

[BRAD_PADGETT]

Next move is to upgrade ECM so I can connect a scan tool and get to the bottom of it.

Do this first before you throw parts and $ at it.

 

[hotairgnx548]

Just got my '85 back after a rebuild (Phil Bassage, did a great job) but the engine is not running properly. Trying to sort it out on my own without going back to him. Engine barely idles/stumbles at idle and at about 4500 rpm completely cuts out (seems running rich) and has no power. Has great power from a rolling stop and at top end but really stumbles and blows black smoke in the mid-range. I have no scan tool. Here's what I've done (and assume everything that went back on the motor was good).

Installed new TPS (Holley) and have it set to .43 volts at idle and 4.9v at WOT.

Have tried with MAF disconnected and connected but no difference.

Has an '87 coil pack but otherwise all stock.

Next move is to upgrade ECM so I can connect a scan tool and get to the bottom of it.

Thoughts?

I think that you need to keep your foot out of it until you solve your problem with the idle/stumble etc. John

 

[standupjskiguy]

""Have tried with MAF disconnected and connected but no difference.""
I'd guess that is where the problem is.
Have you tried cleaning it with the special cleaner available at the auto parts store?
If it looks dirty, that could be the problem.
I still have the original MAF in our 85 with 140K miles on it.

 

[jiho2]

Installed new TPS (Holley)

What TPS does Holley sell that works with a stock Hot Air motor? Or any Buick turbo, for that matter ....

 

[Owlpond1]

What TPS does Holley sell that works with a stock Hot Air motor? Or any Buick turbo, for that matter ....

It's a holley PN 543-29. It works fine I have it set to .42 at idle and get 4.9V at WOT. Just ordered a new ECM, Maf/translator and TT chip, hoping this helps with my issues (oh and a Scanmaster).

 

[v6turbo87]

What is your fuel pressure at idle with the vacuum hose Off?

 

[jiho2]

It's a holley PN 543-29. It works fine I have it set to .42 at idle and get 4.9V at WOT.

So .... it's for the Chevy V8 TBI units. Only difference from Hot Air is, the connector sticks out perpendicular instead of straight up. And Holley's is cheaper than aftermarket for GM TBI.

Now I'm curious how the TPS for the '85-'86 4.3L Chevy V6 would work. It looks identical to the original Hot Air TPS. (The later 4.3L has holes instead of slots so you can't adjust the voltage, for some reason.) (EDIT: I should say, for some reason it took GM a while to figure out that the ECM can auto-zero at startup....)

Thanks for the info. Sorry to barge into your thread when you're trying to solve a problem.

 

[Owlpond1]

What is your fuel pressure at idle with the vacuum hose Off?

I'll have to get a new gauge mine doesn't work. I'll check and report back.

 

[Owlpond1]

Update:

Installed 87 ECM and TT chip, Maf translator and ls1 maf, also new IAC and TPS (as noted above). Scanmaster readings as follows:

(At WOT in parenthesis)
O2 238 (this jumps all over when driving down to 042 up to 850)
AF: 6 (255 at WOT generally 12-119 while driving)
INT: 128 (135)
BLM: 119 (128)
TPS .42-(4.35-4.8 two diff passes)
IAC: 25 (119 at WOT)
CC 226 (118-125 at WOT)

Getting a code 34 as well.

Have checked for vacuum leaks and don't find any with the carb spray method.

Still a rough idle and a terrible stumble/bog at about 3,000 RPM under load but with pedal mashed it goes like hell with 13 PSI boost and no knock.

Any suggestions?

 

[hotairgnx548]

Update:

Installed 87 ECM and TT chip, Maf translator and ls1 maf, also new IAC and TPS (as noted above). Scanmaster readings as follows:

(At WOT in parenthesis)
O2 238 (this jumps all over when driving down to 042 up to 850)
AF: 6 (255 at WOT generally 12-119 while driving)
INT: 128 (135)
BLM: 119 (128)
TPS .42-(4.35-4.8 two diff passes)
IAC: 25 (119 at WOT)
CC 226 (118-125 at WOT)

Getting a code 34 as well.

Have checked for vacuum leaks and don't find any with the carb spray method.

Still a rough idle and a terrible stumble/bog at about 3,000 RPM under load but with pedal mashed it goes like hell with 13 PSI boost and no knock.

Any suggestions?

About the code 34 do you have the accordian stock pipe to the throttle body still? CHECK IT FOR CRACKS AND LEAKS COULD BE THE CODE 34 John