I need sugestions because I'm clueless at this point. I've checked the IAC and the TPS, both work fine. The injectors are also new. The alternator is going bad, volts drop to 13 if below 700rpm, then idle surges up and volts go back to 14.3. Battery is a new red top. Engins is the new 330hp vortec 350. The torque converter has about 3000 miles on it at most, same with trans rebuild.
The car is running really crappy down low. It can chug along at steady throttle and low speeds (<40mph) but if I try to accelorate it backfires BAD and takes a few seconds to catch up. This is the first time it started, I haven't changed anything since my previous problems. Before it had a slight throttle delay and I had to push the pedal down slowely or it would miss. It doesn't like to run at anything less than 900rpm or when I put it in gear and foot on brake it stalls. I was getting 23-27mpg on the highway (540mile drive from NJ to Ohio) I drove over 1000 miles in one week. The problems just kept on getting worse. It also is getting really hard to start sometimes. I checked the fuel pressure and it looks fine, everything looks like it's working right but under load the thing just craps out. I'm not getting any SES light but I think my MAP sensor might be the problem but wouldn't it through a code? All these problems are making it VERY difficult for me to program my own eproms. The only thing I've done so far is diable EGR and the speed limiter. If anybody could come up with the reason why the car is crapping out I'd be your friend for life. Oh yeah, and the fuel pressure seems to be very high. I have a 160 thermo but am swapping in a 180 when I get new hoses this week. The car doesn't overheat EVER, I just can't figure this thing out (pulling hair from head right now).

------------------
, Jon (350 TBI!)
91 Red My website

 

Sounds like possibly some type of sensor failure. Vacuum leaks can also cause surging and stalling at low rpms. Have you replaced all of the vacuum lines? How about the o2 sensor? Hopefully its just a really small problem, if you haven't replaced all those hoses, check them. I had such a bitch of a time with a vacuum leak once...

What happens when it is hard to start? Does it die really quick after you get it cranking?

Josh

 

I second the Vaccum leak.



------------------
60 Ranchero - Project ( Money Hole )
85 Sport Coupe LG4 - Daily Driver
Reader's ride -&gt; My Ride

Just another Hot Rod kid, or thats what they all tell me.
Livin' the Stereotype

 

I have all new vac lines. I did have to tap into the rear vac fitting on the intake for the power brakes because the RPM intake doesn't have a fitting in the front like the stock unit. I'm using hose clamps on everything. One thing I don't have plugged up is the heater to heater core "switch". I'll try plugging that up. I'll check for vac leak but can anybody tell me where to look specifically. I'll check my console and around the engine but is there something I might overlook? I'm also going to go to a mechanic tomorrow and have them plug up a scanner. I want to see if my map sensor is working.
When it's hard to start it just feels like it doesn't have enough power to turn it over. But it always does after a noticable delay. That only happens like once out of 4 start ups so I'm thinking it's a loose wire on the starter solinoid. I hope my starter isn't going bad.

------------------
, Jon (350 TBI!)
91 Red My website

 

Sounds like you have two fun problems to fix! A real nice place to get a vacuum leak is under the throttle body, there are like three vacuum lines going there. Try between the TB and charcoal canister. Unplug the lines while the car is running and seal them off with your finger, see if it runs better. Check out that O2 sensor also, thats always good to replace.

I hate starting problems, the starter on our cars is a bitch to take out sometimes. Again, there are tons of problems that could go wrong there, just fix it when you feel like it(when it wont start anymore

Good luck.

 

Well, Im not entirely familiar with TBI, but common places for Vac leaks are around the TB, around the intake ports, and at the PCV.

the brake Booster should take a pretty large hose, Im sorta confused about how you rigged that up ?

On TBI, where does it go stock? Does it go into the back of the TB like on a carb ?




------------------
60 Ranchero - Project ( Money Hole )
85 Sport Coupe LG4 - Daily Driver
Reader's ride -&gt; My Ride

Just another Hot Rod kid, or thats what they all tell me.
Livin' the Stereotype

 

Vacuum leak from the intake ports into the lifter valley are??? Can't see them or easily test for them, unfortunately... Pull ALL of your plugs and look for an oil-wetted one or several. On your NEW crate motor, you should have no oil on the plugs (fresh rings/valve seals) and you could probably bet that the intake gasket has leaked into the valley area, picking up oil from just under the plenum area, wetting the plugs...

let us know. Plus, pulling the plugs can diagnose things further, as well...

EDIT: hard/long starting procedures can be distributor ignition module and/or the pickup coil... and of course, our friend, the fuel pump relay or fuse..



[This message has been edited by FastBroker (edited May 14, 2001).]

 

Hmmm, vacuum leak could be it, I'm sure you'll find it if it is the case, Jon. But, the symptoms you described reminded me of how old guys used to describe their cars in the sixties, after they'd put the fourth carb atop a small block. Brutal hesitation (almost stalling), then neck snapping acceleration for a second. You said that the fuel pressure seems to be high. Are you using the holley/454 TBI? I hate to point at something so obvious, but check the plugs.
If you still think its a vacuum leak, I've heard about spraying carb cleaner over each section of vacuum line to look for breaches. When (if) the engine stumbles like as if you'd sprayed the cleaner in the TB, that's where your leak is. Good for cleaning off the rubber hoses, too.

------------------
No guts, no glory.

 

I think it's a vac problem because I remember trying to use the vent and no air came from the upper vents.
The power brake vac line is tapped into the rear fitting (runner) because the RPM intake doesn't have the extra fitting I needed. Vac is vac so it doesn't really matter where it comes from, just as long as it's there. I'm thinking I'll just unplug the vac lines and see how it runs, if it runs the same I'll know i have a vac leak right?

------------------
, Jon (350 TBI!)
91 Red My website

 

I've never heard of anyone drawing power brake vacuum off an intake runner. I'd try plugging this one and see how it runs. I think there is ported and non-ported vacuum, and coming from the runner is non-ported, which is used for PCV most of the time. Like I said, I'm not at all sure on this. Could be a vacuum leak in the brake booster.

 

Disconnect all vac lines (except for MAP) and see how it runs in the driveway BUT DO NOT DRIVE IT! See if that helps diag.

Did you pull all the plugs, yet??? Oil wetted, I bet...

 

You know, I had this same problem with my 305 TBI car. The fuse for the ECM had blown and I think the injectors were just dumping fuel out. I don't even know how the car ran, but it fouled out my plugs and just chugged unless I stomped it. I replaced the fuse and changed the plugs and it runs fantastic now. I would really like to know how the car ran with out the ECM working....

Chris

 

If the plugs look OK and you can't find a vacuum leak, I would troubleshoot the fuel system. You stated your fuel pressure is OK, but the symptoms you describe could be caused by a faulty fuel pressure regulator, filter, or other fuel system component.

 

ROFLMAO...
TBI = SD
SD IAC = vacuum leak
vacuum leak = high idle

sorry, thanks for playing, but a vacuum leak WILL NOT cause a driveability problem on a SD car (unless it is only affecting one cylinder, like a leak at the gasket as FB mentioned.) SD doesn't care where the air enters the engine. If you don't believe me you can prove it to yourself real easy. Disconnect your power brake line and notice how your idle goes up, then your IAC will extend and it may even go back to normal or get as close as it can, then it may throw an IAC related code cuz it can't get to it's desired idle.

What would i check? Pablo was having a helluva time diagnosing all kinds of weird problems with his TBI that boiled down to bad injectors. Other than that, anything could be off in your calibration. Or anything could be broken in the ignition. The problem could be getting worse due to any of the stuff i just mentioned letting your car foul the plugs, making it run worse. And you could always have a bad sensor too.
What all have you done so far to the PROM besides disabing EGR and the SL? You are running a bigger engine with completely different vacuum/airflow characteristics than your old 305. The throttle delay is (or started as) most likely a problem in your pump shot tables. Like i said before, if you haven't been checking your plugs, the rest could be caused by yuour off calibration fouling things up.
...ed

------------------
Ed Maher - Moderator @ The Carb Board
92 Z28 Convertible - Quasar blue / Tan top
LB9 4L60 GU2 G80 - stock, soon to be sleeper
-=ICON Motorsports=-

- Definitely prototypes, high powered mutants of some kind. Too weird to live, too cool to die

 

Question for you Ed: If there is a vacuum leak then stuff that depends on vacuum isn't going to work right? There would be a lack of vacuum to the MAP sensor. Wouldn't that cause problems?

------------------
, Jon (350 TBI!)
91 Red My website

 

An IAC is a controled vacuum leak. When you set minimum idle you are stting the amounbt of vacuum leak past the throttle plates such that the IAC can control the idle speed within a certain range. If you introduce another vacuum leak to the system, the IAC simply closes up that much more.
The concept of vacuum leaks as evil is from carbs and MAF EFI, where air leaks past the idle circuits or metering device are bad because they have not been measured, thus the car runs leans, which can cause all sorts of weird driveability problems.
As i previously stated SD EFI doesn't care where the air comes from. All it knows is pressure in the manifold, temp rpm and TPS (basically) and injects fuel based on that. not how much air is passing a certain point in the intake tract.
...ed

------------------
Ed Maher - Moderator @ The Carb Board
92 Z28 Convertible - Quasar blue / Tan top
LB9 4L60 GU2 G80 - stock, soon to be sleeper
-=ICON Motorsports=-

- Definitely prototypes, high powered mutants of some kind. Too weird to live, too cool to die