man o man, im on week 11 of this motor build and am getting close. put the rebuilt motor in last week. got all my little issues worked out like fans, oil and tranny leaks. great. took it for a ride last night for the first time and it has no power. as in wont do a brake burn on cement. the car drives fine, no engine light on, gauges all look good, starts n idles fine. just when i put my foot to the floor it doesnt go like it should and it is in first gear. exhaust smells and looks good not rich. compression is good. spark plugs look fine. its not backfiring. just sorta hesitating when it climbs the tach but not missfiring just not climbing as quick as it should. its like its not getting enough air but im sure it is thru the cai. i want to say its something stupid cause i did all the work myself and am missing something. sorta vague i know but thx for any ideas on where to go from here cause i got none. maybe not enough fuel???!!! not sure how to test that.


93 z lt1 auto.

 

What type of build/rebuild was this? Is everything stock/OEM replacement?
Or is it a performance build?
We need pretty much as much information about your build you can give us.

 

Is this a race only engine, or is it for a street car? Don't go beating on the engine like that until the thing is good and broken in. Unless maybe your plan is to make it not live a long life?

 

k here goes....

nah not a performance build (although our other car is a 69 chevelle ragtop 350ci 400hp h/cm (ihra) 11.20 1/4 mile). spun a bearing on the original motor at the track. traded a steel crank for a block, crank, pistons, cam that only had 20k miles from a 95 or 96 that burnt to the ground. took the block to get the passages cleaned, frost plugs and cam bearings, didnt touch the cyc walls as they were perfect. new bearings n rings. everything clean clean clean. all stock parts. my original heads n intake. new to the build was a elec water pump n splug wires n 160 thermo n cai. dist looked fine/ fairly new. good mid headers but were on from before not new to the build. 11 week old gas but filled it last night no difference. no air pump n pluged the lines/ intake (new to the build). pluged the throttle body water lines too then hooked it back up the original way as i though i had a seperate issue there. probably will plug em agaian once i get the power back. tranny rebuilt the day before i spun the bearing and seems to be great. accel/decel to break in a motor btw. thx and im checking CF every hour cause im really lost here. couldnt find a code reader obd1 this morn but not sure if that would help or not. thx so much. MI

 

well i just recently went threw a problem about exactly like yours. it would run fine and idle, but try to give it gas and it dosnt want to go. i replaced the fuel pump and took the cat out in the process and it ran better then ever.

 

The no engine-light thing makes this very difficult...

Time to think!

 

check the connection on the knock sensor. it will retard your timing and will not set a code.

 

geez craby when i read ur post i thought u were on to something cause i got when i had the two blocks side by side on the floor i compared em and my old block had one knock sensor and the new had two. anyways tried all three and same thing. although when i leave the sensor unpluged the 2 fans kick in. guess that means the wiring is ok. i put some chaulk marks on the crank pulley and put the timming light to her and it seems too advance properly. im still not convinced that it isnt a timming issue though. thats how it acts. just takes longer to get to 3500 rpm than it should and doesnt sputter on its way there.
i need to check the fuel pressure and not sure how. i have a vaccuum gauge but not sure what i should get for readings. a buddy has a shop and is gonna lend me his obd1 scan tool. i never used one. does it show pressure, timming n stuff?
anyways im going to a acdc concert this week so it'll all have to wait till the weekend unless magically i figuare something out today.thx.mi.

 

just an update here...yeah im still lost. bought a fuel pressure gauge, followed the sticky and everything was fine. never droped below 42. rev it a little and it goes up to 49 or so. off it holds steady. about 42.
did the paper clip thing and had half a dozen codes but it was all me upluging things last week. reset it with the batt unhooked and headlights on, took it for a drive, bout 15min and nothing. no codes.

so if i got fuel pressure does that mean im getting enough fuel at acceleration in the way that does the throttle postion sensor tell the pcm to put more fuel as i hit the pedal? cause i still think it needs more fuel even if the gauge says i have pressure. any of that make sence?

getting pretty frustated here and thinking about taking it to GM. any ideas? anyone? damn.

 

got it to throw a code. i drove it a little farther this time. code 63 MAP sensor circuit signal voltage high (low vacuum indicated).