Man, this is really funky...

Just rebuilt my engine, and I'm having this very serious stumbling problem.. I checked my TPS it was outta wack (.44) so i set it at .54 and at WOT it's 4.34..

I figure that's within spec? At idle the car runs 'so-so'.. it still stumbles when i tap the gas but if i ***** -foot it, it'll run OK..

at over 1/4 throttle it starts to run horrible, and i have to let off the gas or it'll want to cut out on me..

is that how the car owuld act if the MAF is bad? How would i test that? I'm getting codes 36, 42, 44.. My car has all new sensors, including EGR and O2...

ideas? it's an '86 IROC with a 305TPI.. thanks

Colin

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Webmaster: www.IROC-Z.org

 

I have a hard time on start up when its cold it'll put put when i tap the gas but idle ok and it'll run like $hit when i hit the gas but anything over 2000 its ok. I slapped in a new MAF today and wham problem gone and i wasnt even getting any codes.

 

damn, i'm having the exact reverse problem, lol..

i have another MAF, maybe i'll throw that on and see what gives

 

i set my TPS..

.54 at idle... when i moved the throttle blades it would go .54 - .63 - .74 - .86 - .94 - 1.12

you get the idea.. is that normal or should it spool like .54 - .55 - .56?

 

you have it right the first time. Floored it should read in the ballpark of 4.40

 

k good.. it was set at .44 before i started mucking iwth it..

it idles a bit better but still has that horrible throttle past 1/4 throttle...

IAC? i cleaned the passages but didn't reset the motor.. would the IAC affect throttle response past idle?

 

It shouldn't effect THAT much. Does the TPS go to over 4volts at WOT? If it doesn't than that's your problem.

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, Jon (350 TBI!)
91 Red My website

 

4.30 volts at WOT..

this is unbelievable.. i can't figure out why the car will run like this, and then when i start the car a few minutes later it floods???

it's so flooded right now that it's kicked fuel mixture out the throttle body...

i keep getting codes 36, 42, 44... when i just tried to start it now the tach would drop when the revs went up... wtf???

man, i can't wait until this is fixed so this car can be sold... sheesh, my big block HAS to be easier than this

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Webmaster: www.IROC-Z.org

 

have you checked the o2 sensor? that could be the prob or the maf relay?

 

code 44 is running lean. Run a can of carb cleaner over the engine and check for a vacume leaks.

 

brand new O2 sensor, changed it cuz it's such a hassle to change with the motor in..

reason i think the MAF might be bad is the motor broke a piston and oil was literally puddled in the sensor.. i sprayed it off with sensor-safe electrical spray but i'm not sure if that would affect it's operation or not..

i'll let the motor sit for a bit and try to start it with the MAF disconnected..

thanks for the replies guys, i might actually get this figured out tonight

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Webmaster: www.IROC-Z.org

 

any more ideas?

any chance this O2 sensor is bad? it runs horrible, has to be more going on than just the O2 sensor..

i replaced the original with a stock Bosche, non-heated

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Webmaster: www.IROC-Z.org

 

Ahhh... the dreaded "combo codes". First I would make sure that the MAF power, MAF burnoff, and the fuel pump relays are replaced. About 10 bucks each. Then make sure your fuel filter is new. Assuming your MAF is good this takes you to code 44. Vacuum leak. Since your 02 sensor is good, make sure the ground wire to it is good and not melted shorting out. Next take a torks bit and check the manifold bolts. I spent 10 months looking for a 44 and it was the center bolts to my manifold were very loose. With that done check all vacuum lines, the MAF airbox, and TB bellows rubber for good fit. There are other more remote reasons for a 44 if it's not solved by now.
Air divertor valve malfunction.
Plugged Cat.
Plugged Muffler.
Dirty injectors.
Leaking around injectors and/or cold start valve.

As for the flooding down you make have fuel injectors "leaking down" in which case you should have Rich at Cruzin Performance.

http://www.cruzinperformance.com/

rebuild and flowmatch them for you. Be sure to include your cold start valve if you have one.

 

PS.... many 86's had a bad PROM that would send out false codes also. You should check to see if you have the updated PROM. Put a post out for Vader to assist you with this. I replaced the PROM in my 86 T/A and it made worlds of difference.