metalhead8711

Hi everyone. As the title suggests I have an 89 camaro with a rebuilt 305 and a tbi Vin code e. One day I ran the vehicle and it gave me the best drive it ever had and now it has a crazy surge again. The first time it surged it was a bad battery ground cable. Now I added more grounds and it still surges. I replaced the egr valve which did look carboned up and a vacuum test confirmed it won't hold vacuum. The other day I noticed that the top of the injector pods looked really moist and stained where the injector harness connects too. I made the observation that looked like too much fuel is pooling up on the primaries but I am not really sure if this is normal since I haven't really verified a good working tbi unit to tell the difference. It's also worth mentioning that the car has always idled really high for an automatic. Around 1000 rpm. I have also included a on YouTube. This pooling is really visible on the 1:40 mark of the video.

So far I've noticed that the car starts and idles nice at first but after a few minutes it starts to surge really bad at idle whether its in park or gear and during driving as well. During driving I'll literally jam the pedal but would get no response until a second later the car launches forward. It feels like I'm driving a mechanical bull.

roadthrills

On the GM TBI stuff a common surging and/or rough idle issue is the temp sensor on the front of the intake. They will go bad and not throw the cel. Another thing I've seen several times through the years is a broken fpr spring but that will be issues all the time and not just intermittently.

Tom 400 CFI

It sounded pretty normal to me. High idle when cold...slowed down to a normal sounding idle...I thought. Have you looked for vacuum leaks? Checked fuel pressure?

The "puddling" on the throttle plates looks normal to me.

Schurkey

Verify fuel pressure at prime, and with the engine under load.

Assure all the tune-up items are in good shape.

Connect a scan tool, verify ALL sensors and computer outputs. Look at the fuel trims when it's acting-up.

metalhead8711

Hi everyone. So here is an update. So far I have replaced all of my vacuum lines, I have replaced the coolant temperature sensor, the fuel filter amd I have completely rebuilt the tbi with a new iac valve and new injectors. The problem persists. The engine has a completely new fuel tank with pump and sending unit replaced as well as strainer back in 2020. I am completely stumped. Vacuum gage indicates healthy vacuum when it's not surging but I cannot find any mechanics that service these cars anymore. They won't touch rhem and I can't really drive the car behaving like that more than a mile. The only thing I can't really verify is the fuel pressure but it pumps great and the parts are new and haven't given me issues in the last four years till this month. I have lifetime warranty on those so I can in theory swap them out but the labor is starting ti hit my wallet.

ShiftyCapone

iTrader: (7)

Did you check where the base timing is with the EST unplugged? Should be 0 to 2 deg. You said it has a new pump, but are you sure it has enough pressure?

Tom 400 CFI

Did anyone else see the actual problem in his video? If the video is intended to share the symptom with us, I'd say that he doesn't have a problem. (?)

metalhead8711

it's been years since I have checked the timing. I know it idles really high but I can't seem to adjust the idle with the surge present. I haven't checked fuel pressure yet. I don't have the tool to do so but I will investigate. It gave me the surge before but a new ground cable solved it for maybe a month and now the surge is back but worse. By odds the chances of a new pump failing should be pretty low but not zero. I've managed to locate a Mechanic that still services obd1 cars. I'm gonna call it and take it in today. I'll keep yall posted on his diagnosis.

Buccaneer

I don't know what your issue is with this? It would appear that it is running OK, to me. I never heard ANY surging. The idle goes up on cold start and drops down, what's the issue? Seems to run smoothly. Aside from that TB is dirty, I see no issues with surging or fuel on top of throttle plates.

metalhead8711

hey dude. I just drove it to the mechanics shop. The idle was surging again and dr8ving the car felt like i was riding a mechanical bull. It was bucking back and forth like if you didn't shift right on an stick shift. But the car is an automatic.

Buccaneer

Well, I'm just saying is that the vid you posted if that is your issue sounds just fine to me and others. I would definitely look at the fuel pressure to see where it is set. GL Have your mechanic check that.

Schurkey

You haven't tried to "adjust" the idle speed...did you?

The idle speed is computer-controlled. The only "adjustment" is done at the factory, using the base-idle screw which is then helpfully sealed behind a tamper-evident plug so that folks don't screw it up.

The other "adjustment", if you can call it that, is programmed-into the software run by the computer.

Once someone dicks with the base idle screw, all bets are off. Until it's returned to the proper idle speed, problems with the idle are likely.

AGAIN: Have you tested fuel pressure, have you assured that all the normal "Tune-up" items are acceptable, and have you connected a scan tool to verify ALL the sensors, ALL the computer outputs, the fuel trims, etc.

roadthrills

I feel like it's a faulty temp sensor in the front of the intake.......maybe you got a new bad one, it happens a lot more than it should these days.

Schurkey

All he has to do is connect a scan tool and find out if the sensors are providing faulty data. An ohmmeter could be used, but that's an enormous pain in the asp.

Diagnosing a computer-controlled vehicle with no way to communicate with the computer is two steps away from hopeless.