erratic running BBC 454

[bad larry]

I have searched w no concreat results, hoping some bowtie gurus will chime in... 1988 TBI 454 in a v30 w 54K, poping through the intake under partial to full load (sometimes) both hot and cold, slight misses at idle, worse when damp out (sometimes), I changed the ff when I first got the truck w 37k on it in late 08, I changed it again 4 months ago when it felt like it was starving for fuel as well as poping and lacking power. This seemed to help up untill maybe a week ago. Now back to poping and hesitating. It sat over the weekend last week and it was raining on sat and sun, I started it on mon and it was missing bad, poping, and hesitating, after it warmed up it got a little better but not great by any means.. I suspected H2o in the fuel so I added some dry gas and fueled up at a different station (one that goes through a lot of fuel) and it seemed to smooth out but the condition came back when I got down to 1/4 tank or so... Its been raining here for weeks floods all over the place.. Yesterday I added some more dry gas and 93 from the same station and it seemed to smooth out again. This AM went out to the truck fired her up, idled smooth, drove down the road good untill maybe 160-170 degrees then poping started again... So narrowing it down from MAF, coolent temp sensor, vacume leak on TB, h20 in gas, another clogged FF (I will inspect today or tomorrow)..... Anyone had this erratic behavior form their 454? Sometimes it runs fine hot or cold... ??? I'm def not afraid to dig in but I thought someone might have some experience..

 

[Stomis]

Heres the basic TBI check list of odd running conditions.

Pull the TB and rebuild it with new gaskets and fuel injectors if the pattern doesnt appear good. This shouldnt cost you more than $35 and maybe $75 with injectors (source them online). Given your situation I would put a new fuel pressure reg in too. Doing this rebuild will eliminate alot of possibilities, low pressure, gunked up TB, bad injectors (which you should be able to see btw), and the O so damn common bad TB base gasket...

New coolant temp sender - $12

Replace all vacuum lines with new hose - $15

A good upgrade is the heated O2 sensor. Comes from any early 90s TBI 4.3 s10 if I remember. Basically you wire the purple wire into your original o2 wire, then theres 1 or 2 grounds and an ign hot.

Fuel filter as you said but I doubt it.



I'm putting my money on the TB base gasket. Have you tried douching the motor with carb cleaner and seeing if the idle changes to find a vacuum leak?

 

[bad larry]

I'm putting my money on the TB base gasket. Have you tried douching the motor with carb cleaner and seeing if the idle changes to find a vacuum leak?

Thank you for the jump start! I havent put the carb cleaner to it yet but I will... I had been looking at the TB rebuild kits and injectors on ebay so yeah I guess its time... You got a source for a vacume line kit, LMC or somethin like that thats pretty comprehensive? Or should I just buy 6-8' of the stuff and cut to match...

 

[Stomis]

Thank you for the jump start! I havent put the carb cleaner to it yet but I will... I had been looking at the TB rebuild kits and injectors on ebay so yeah I guess its time... You got a source for a vacume line kit, LMC or somethin like that thats pretty comprehensive? Or should I just buy 6-8' of the stuff and cut to match...

Yep just get a kit and cut to match. Its honestly just a good idea period every 10 years or so for a vehicle to do that.

 

[bad larry]

Update, I rebuilt the TBI today minus the injectors. NOTE: the rebuild kit had a slightly different FP regulator that the stock one, I assume its just the nature of the rebuild kit.. I bypassed the heater hose to the TBI, installed a new coolant temp sensor, and checked the egr valve, it was free. When I started it it didnt go fast warm up idle like it usually dose and ran rougher than it B4 ... Gaylord Farker!!
WTF! I unplugged the MAP sensor and plugged it back in and it smoothed out a little but it's still not right... Looks like by the exhaust its running a little rich... I took the positive terminal off the battery to reset the ECU and thats where I am currently. Anyone come across these symptoms? The only thing I couldn't hook back up was part of the cruse control vac line that goes to the round dome on the drivers side..
Without searching all over creation, can someone give me some part #'s for cap, rotor, IAC, TPS, and MAP? I know I'm on the verge of goin up in flames here but this is my DD, I'm on call and I live on a pesudo 3rd world island.....

 

[bad larry]

Alright.... I ordered a O2 sensor, a cap, rotor and wire set, a MAP sensor, and a egr last week. Today I installed the cap (old one was pretty corroded) rotor, 02 sensor, MAP sensor, and EGR. Oh I changed the FF too. The truck runs a little better but still is missing and pops occationly through the intake under load. It idles ok but you can still hear a faint miss..It kinda feels like its running on 7... .... It had sat for a while b4 I bought it and wasnt ever a daily driver for the previous owner. I suspect the fuel pump sock may be totally caked. This weekend I will verify the timing, drop the fuel tank and check the pump/sock filter and replace if needed, and replace the plug wires as the ones that came from rock auto were not the correct wires. They were the non strait deep well ends, they were the small 90 degree ends that dont work on BBCs w exhaust shielding... Trouble shooting this TBI gremlin has been total BS...

 

[sweetk30]

most bbc i have seen with poor power or poping up threw the carb or tbi had a bad cam with rounded loabs.

i have a 454 new that i drove home. drove fine till half to full throttle pulled intake and found 4 exaust lobes almost flat. the motor had less than 70k miles

 

[bad larry]

Awww... Man.... Thanks Doc... Sh$!! This thing has 55k and I feed her mobil1 10 30 on a religious basis... How about a second opinion!? I'm hoping, plug wires, fuel pump, injectors... In that order! If that cam is fuct I'm building a MOTOR!!!

 

[Can Can]

Please tell me you replaced your wires before you did anything else........

Popping/bucking on acceleration and hesitation = bad spark plug wire(s).

 

[bad larry]

Can Can Please tell me you replaced your wires before you did anything else........

Popping/bucking on acceleration and hesitation = bad spark plug wire(s).

Dude.... I tried... Rock Auto sent me the wrong wires, and I live on a "we don't have that in stock" island... I reordered, wires tonight....

 

[bad larry]

Alright, I replaced the wires today and the condition got a little better but I'm still down on power and it still has a lingering hesitation... The truck dosent sound quite right kinda like it has a very faint exhaust leak or odd misfire...

 

[marko]

Did you ever check the timing?