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1989 camaro 305 tbi massive engine surge idle and driving.
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.
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.
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.
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.
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?
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?
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. (?)
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?
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.
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.
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.
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.
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.
I can't seem to adjust the idle with the surge present.
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.
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.
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.
high yall. Mechanic just called me back. Still cannot find out why the vehicle is still surging. But he did notify me that the fuel pressure is at 20 psi. I have no idea why it's that high. It's the stock regulator and a new fuel pump from oteillys called precision that's marketed at 12 psi. I'm baffled. Either the pump is working more than it should it it might be clogged?
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.
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?
hi. I'm not sure what the base timing it was set at back in 2020. But it has ran without issue the last four years. Mechanic just notified me that rhe fuel psi is at 20. But the pump is rated at 12 psi. Strange.
the fuel pressure is at 20 psi. I have no idea why it's that high. It's the stock regulator and a new fuel pump from oteillys called precision that's marketed at 12 psi. I'm baffled. Either the pump is working more than it should it it might be clogged?
1. Faulty fuel pressure gauge. Have you verified that the gauge is accurate?
2. Restriction in the fuel return plumbing. Pinched hose, crimped tube, cockroach got inside the fuel pressure regulator and jammed it shut...something like that.
Originally Posted by metalhead8711
I gotta invest in a good multimeter AND scan tool.
FIFY.
Every man with a desire to D-I-Y should have a multimeter. Every man with a computer-controlled vehicle and the desire to D-I-Y should have a scan tool.
A scan tool will do most everything a multimeter will do as far as diagnostics of the computer, sensors, and outputs. The scan tool can verify ALL the sensors AND the associated wire harness in about the time it takes to set-up a multimeter to test one or two sensors without testing the wire harness; and it's enormously better at diagnosing computer outputs. There is just no substitute for a decent scan tool.
Pretty strange! What are you going to do now? What's your mechanic going to do? Does that person know? B/c if *I* were you mechanic, I'd already know why it has 20 lbs...if it really does.
Typically the stock pump will not make more than 18 psi. Everyone seems to think more is better and install a TPI pump that can produce pressures >43 psi. It's the FPR that regulates the fuel pressure as it name implies. Perhaps you have the wrong spring in the FPR or maybe a restriction along the return side. The 20 psi will create a rich/over fueling condition...but I'm not sure if that would create the symptoms that you're describing. Click image
Pretty strange! What are you going to do now? What's your mechanic going to do? Does that person know? B/c if *I* were you mechanic, I'd already know why it has 20 lbs...if it really does.
Good luck!
I would really love your input as too why. My mechanic is gonna tear down the tbi and check if it's the fuel pressure regulator. Maybe I did it wrong? And then check the lines and pump
On my 91 TBI pickup when it was surging as you describe the dealer replaced the throttle position sensor and the idle air control valve. Was still under warranty at the time. Did turn on the check engine light and set a code. Been fine ever since.
Did you ever get a resolution from your mechanic on this?
my mechanic more or less has found a "fix". I call it a compromise. He found an issue with the new fuel injectors that I got from rock auto. We replaced them again. And he ended up replacing the ecm. The car runs better at the time I got it back which was around late summer of 2024. The car still misbehaves at times. Car will run good. Drive good. But at soon as I put it in park to pick up my niece from school. It starts with the idle hunting **** again. I rev the car. Put it back in drive and it stops. Then when I get home and put it in park the problem disappears. The car loves to gaslight me. It's at least drivable and I've noticed that my fuel lasts a bit longer but the problem has been downgraded to a small once in a while gremlin. After a year I have yet to figure out why. I apologize for my late response. Recovering from surgery.
Typically the stock pump will not make more than 18 psi. Everyone seems to think more is better and install a TPI pump that can produce pressures >43 psi. It's the FPR that regulates the fuel pressure as it name implies. Perhaps you have the wrong spring in the FPR or maybe a restriction along the return side. The 20 psi will create a rich/over fueling condition...but I'm not sure if that would create the symptoms that you're describing. Click image
hi. it took a while but my mechanic put an adjustable regulator to get it in spec. From what i can recall it did not make a difference. I recently got a OTC monitor 2000 and the block lean multiplier is indicating a slightly rich condition but we are currently trying to figure that one out. Currently before the car broke down again today it was running somewhat ok after my mechanic replaced some faulty new fuel injectors and the ecm. Still acts up but I call it a compromise.
Have your mechanic check that. 
