I've tried everything. Engine runs terrible after full rebuild. please help me - Third Generation F-Body Message Boards

roguecoxnet · 03-22-2009, 10:49 PM

I don't really know where to start. I have a 87 350 TPI fully rebuilt, all new sensors except MAF. The thing runs terrible. When I ground the dia. terminal to get a base timing it won't even run at 6*btdc. seems I have to have the timing mark on the harmonic balancer at 12 oclock to get it to run decent. heres the stuff I added on the engine and maybe someone can point me in the right direction where I'm wrong

9.72:1 forged pistons
ZZ4 camshaft
2.02/1.60 aftermarket 64cc heads with high lift springs
1.5 Roller rockers
double timing chain kit installed at TDC (not atdc or Btdc setting)
BBK adjustable fuel pressure regulator set to 45psi
24lb ford racing injectors
shorty headers

I tried pulling a code but all it does when I ground the dia. terminal it blinks 1 than 2. (code 12 right?) means everything is good but when I pull out the jumper wire the light stays on. I've set the TPS to .55 volts and the IAC I can't even get an idle to set. It seems to run really rich with back fires. I don't have the ecm programed for the larger injectors yet but it shouldn't be causing this much problems.

The timing is whats throwing me off. I'm a dencent mechanic and I checked to be sure TDC on the compression stroke was right and the timing tab I got from oreillys say TDC when its TDC. took the cap off the distributer at TDC and its pointing right at #1 cylinder but it won't hardly run like that. I know its long but I honestly spent days researching with dead end after dead end. please if anyone can take a few minutes to help me it would save me so much time, stress and sleep. thanks guys.

I check this about every 30 minutes so if you have any questions please post and I will get back asap.

This ad is not displayed to registered members.
Register your free account today and become a member on ThirdGen!

Chevy8588 · 03-22-2009, 11:18 PM

there is a single wire that must be disconnected on the distributor for set timing mode for you base time 1987-90 all models W/distributor, disconnect timing connector, single wire connector in engine harness between distributor and ECM.

bonesbrakr · 03-22-2009, 11:24 PM

I dont know if its the same but on my 89 with a 350 you dont ground the diag terminal to set the timing but unplug a wire under the hood located by the AC components. I am also guessing you got the aftermarket timing tab cause you bought a different timing cover. Make sure the timing tab is in the same location as on the stock cover. With those many mods you are going to have to do more tuning then just adjust the injector size.

roguecoxnet · 03-23-2009, 12:19 AM

Quote:

Originally Posted by Chevy8588

there is a single wire that must be disconnected on the distributor for set timing mode for you base time 1987-90 all models W/distributor, disconnect timing connector, single wire connector in engine harness between distributor and ECM.

ya I have stock harness that I cleaned up and removed alot of the random plugs. I cut that one out like an idiot. can I just unplug it from the distibuter? there is two plugs that go into it.

roguecoxnet · 03-23-2009, 12:21 AM

Quote:

Originally Posted by bonesbrakr

I dont know if its the same but on my 89 with a 350 you dont ground the diag terminal to set the timing but unplug a wire under the hood located by the AC components. I am also guessing you got the aftermarket timing tab cause you bought a different timing cover. Make sure the timing tab is in the same location as on the stock cover. With those many mods you are going to have to do more tuning then just adjust the injector size.

That tab I bought from oreillys says all SBC 350 up to 1990 something with 8" balancer. it mounts on the drivers side of the timing cover and TDC on the tab is about 3 o'clock on the harmonic balancer.

FlamedChevy · 03-25-2009, 09:43 PM

I have the same problem. I have a complete rebuilt engine. With the ESC disconnected the timing must be set at 10-12 BTC in order for it to run, and it runs real rough. With the ESC connected it still runs rough like it is to lean. All sensors are new. We pulled this engine from a 1986 Z-28. I have a aftermarket harness from Larrys Electric. I know I am over looking something. THanks

FlamedChevy · 03-30-2009, 10:57 AM

bump

FUNIROC · 03-30-2009, 12:16 PM

Can you give more info on what has been done? Like you have checked plug wires are they new do they all check good, did you make sure you put the rotor button on properly? Are you sure you don't have wires plug wires crossed? Is the cam installed correctly, how did you install it? Have you reset the ECU?

What all has been done (mods)? What all have you tried? We have to start from scratch without more input.

Mathius · 03-30-2009, 04:17 PM

Did you do a compression check?

Other thing I thought of... when the rebuild was done, did you get a new balancer? Make sure it's the right one?

I had a timing issue on my '76 Chevy Malibu that I spent years trying to figure out. I put a new timing chain in, a new camshaft, and it seemed like the thing just wouldn't run unless I put the rotor 2 teeth off. I would go to time the thing and the timing mark would be on the other side of the engine! I couldn't figure out how the thing even ran.

When I did the cam swap I bought a new balancer just because I had to take the old one off, I figured I'd just replace it. I had beadblasted my pulleys and intake and wanted the balancer to look good as well.

Turns out the new balancer had the mark in a totally different spot. The balancer that was on the car (from the factory as near as I can tell) was the wrong one. I had no problems timing it after that and everything made sense.

Mathius

FlamedChevy · 03-31-2009, 08:52 AM

Thanks for the reply. This engine came from a 1986 Z-28.I have installed it in a 1937 chevy. I had the engine rebuilt by a guy with 40 years of building. He used stock parts no mods. New cam, lifters, bearings,30 over pistons and rings. New tining chain and Felpro gaskets. Complete head work to stock spec. I have a wiring harness form Larrys Electric he has double checked and says it is good. I replaced all sensors with stock parts execpt the module in the distributer. I plan on getting the module checked. I will start from the top on checking everything from TDC to plug wires.

FlamedChevy · 03-31-2009, 08:54 AM

I also show no codes. To clear the ECM I disconnected to power to it for 30 Seconds. The timing chain cover is the original and so is the damper. I am starting at square one....

roguecoxnet · 03-31-2009, 07:54 PM

Quote:

Originally Posted by FlamedChevy

I also show no codes. To clear the ECM I disconnected to power to it for 30 Seconds. The timing chain cover is the original and so is the damper. I am starting at square one....

I'm about to sell this thing. bought a autoprom and adapters, burnt proper chip, installed and still have the same problem. I have spark but the injectors are not firing. the cold start injector seems to be the only injector firing or just leaking. any Ideas. after I burnt the chip it did the same thing so I took everything out and put the memcal back in and its the same. injectors don't fire. funny thing is a few weeks ago when we fired it up for the first time it ran great just went down hill. please if anyone can take a second to help it would be awesome.

FlamedChevy · 03-31-2009, 07:58 PM

Today I swapped the IAC with the old one and the idle settled down, not as rough as before, not as rich. Guess the new one is bad. Took ign module to local parts store and it checked good 3 times. As for the timing it is still 10 BTC in order to run with brown wire disconnected.

Will check TDC tomorrow.

Chevy8588 · 04-01-2009, 02:56 PM

test the injectors, if one is screwed they wont fire, also do you pressure at the rail?

FlamedChevy · 04-13-2009, 03:31 PM

Did a fuel pressure test 10 lbs and falls fast to zero. Next capped off return. Same result. Next pulled fuel pump. Leaking fitting on fuel pump letting fuel bypass and no build pressure.The fuel tank was custom made and has been sitting empty for 3 years. Repaired fitting and replaced return hose. 45 lbs pressure. Engine runs great.... A good friend told me to check fuel pressure..Man was he right.