92 Firebird, 305 E, TBI. Complete rebuild with mild comp cam (XR258H). Stock heads, stock TBI, no air pump, gutted converter. Has the stumble on idle as in other threads, but only when warm. No engine codes with the stumble, but getting worse and sometimes dies in gear. Pulling 17 in Hg from front of TBI at base. Have had trouble with the timing due to idling problems. Car starts easily hot and cold. High RPM performance not there. Put new fuel pump in tank (Airtek) but am questioning quality of pump.

Eventually threw codes 15, 32, and 34. Since the rebuild (about 600 miles), I have replaced the coolant sensor, EGR valve, MAP sensor, new distributor, new MSD wires, new MSD coil, new distributor cap, new IAC, new non-adjustable TPS, new TBI gaskets (fuel inj are several years old)in addition to all the new internal parts (even down to new camshaft bearings).

My question is what to check next? I am pulling out what little hair I have left.

 

Sorry - forgot I replaced the O2 sensor as well.

 

What part #?

 

08-500-8

 

ur problem might be on the cam i guess, the stock tune might not be happy with the aftermarket cam on it.

 

480/488 lift, 112 lsa 206/212 duration.

Tha's a nice cam I have that in my 360 tbi.

Stock heads do not allow that much lift, a set of TFS 175, more fuel and EBL flash to tune it should turn that 305 in to a wery fun engine.

 

The Competition Cams Tech said that I wouldn't have to change the computer program. Now I am concerned. BTW - what is EBL, LSA, and TFS? I am old school on rebuilds (mid 70's engines). My son and I just finished this and it is his car.

 

The EBL is a replacement ECM develop by a member here, its the best thing to tune for TBI , its faster for datalogs and easier to use all around, u dont have to burn chips or anything , just plug your laptop to it while its in teh car and tune away, here its their website http://www.dynamicefi.com/.

LSA i think its Lobe Separation for the cams, im no expert on that but thats what i think it means or close to that.

TFS i think he means aftermarket heads that come already with small combustion chambers so they are like direct bolt ons for 305s.

 

Fuel pressure is 13 lbs at the filter. Has anyone ever set the valve lash on these roller cams when it is running? I used to do it all the time in the old days - feeler gauge under the rocker...........(Comp Cams said to just set the lash when cold).

 

Only andjusted the rockers with the engine off, as described in the GM service manual. Works wery well.

What did you do about the lift of the new cam on the stock heads?

This is the best to tune and run a modded TBI engine http://dynamicefi.com/

 

Went with new springs that had more force, got rid of rotators, made sure installed height was in spec